DIGEST 2006 - Sabita

DIGEST 2006

Sabita Digest 

Published by the Southern African Bitumen Association 

5 Lonsdale Building 

Lonsdale Way 

Pinelands 7405 

South Africa 

Tel. +27 21 531 2718 

Fax. +27 21 531 2606 

email info@sabita.co.za 

www.sabita.co.za 

March 2007 

ISBN 978-1-874968-32-0 

Information from this publication may be reproduced 

provided the source is acknowledged 

Considerable effort has been taken to ensure the accuracy and 

reliability of the information contained in this publication. However, 

neither Sabita nor any of its members can accept any responsibility 

whatever for any loss, damage or injury resulting from the use or 

implementation of this information. 

The views and opinions expressed in this publication are those of the 

authors, and do not necessarily reflect the views of Sabita or any of 

its members. 

2

Mission 

Sabita’s plans and actions are consistent with good corporate 

citizenship to underpin its dealings with government, and to 

assist its members. 

Vision 

Sabita will: 

• advance best practice in southern Africa with due regard to 

worker health and safety, as well as the conservation of the 

environment; 

• provide education and training schemes to develop skills 

and competencies that are sustainable and aligned to 

national goals and frameworks; and 

• engage government to promote the social and economic 

value of road provision and efficient delivery by state road 

organisations. 

3

Contents 

Foreword . . . . . . . . . . . . . . . . . . . . . 7 

1. Valediction 

Local and international accolades mark retirement of 

Piet Myburgh . . . . . . . . . . . . . . . . . . . . 11 

2. Industry Overview 

Bitumen, gravel and the fuel price in South Africa . . . . . . . . 17 

Prof Don Ross 

Aggregate supply to the road construction sector . . . . . . . 28 

Alex Weideman 

Health and safety in the workplace . . . . . . . . . . . . 30 

Piet Myburgh 

3. Education and Training 

Updating best practice guidelines and documents . . . . . . . 39 

Trevor Distin 

SA's education system: A systematic overhaul is vital 

to sustainable skills acquisition . . . . . . . . . . . . . 45 

Prof Emile Horak 

Improving service delivery through appropriate 

road maintenance . . . . . . . . . . . . . . . . . . 61 

Mike Winfield 

SAT: 2006 activities generate a new vision of 

member service . . . . . . . . . . . . . . . . . . . 64 

John Onraët 

Flexible pavement engineering course to cater for 

industry needs . . . . . . . . . . . . . . . . . . . 67 

Les Sampson 

4

4. Innovation 

The use of steel slag aggregate in asphalt mixes . . . . . . . 73 

Hugh Thompson, Michael Bouwmeester 

In search of sustainable pavement solutions . . . . . . . . . 82 

Prof Kim Jenkins, Dr Fritz Jooste 

Overcoming temperature and time constraints 

using FT wax . . . . . . . . . . . . . . . . . . . . 88 

Francois Bornmann, Robbie Hiley, Stefan Strydom 

Advantages of SA's new single pass surface dressing machine . . 96 

Deon Pagel 

Innovative design methods for HMA in Gauteng . . . . . . . 102 

Derick Pretorius, Herman Marais 

Forensic investigation into premature distress in asphalt . . . . 111 

Elzbieta Sadzik 

5. Best Practice 

Old habits die hard ... especially in Cape Town . . . . . . . 119 

Julian Wise 

Disposal of penetration grade bitumen in South Africa . . . . . 126 

Mannie Levin 

Bond and tack coats to improve total 

structural integrity . . . . . . . . . . . . . . . . . 130 

Kobus Louw 

A performance classification system for SA: Quo Vadis? . . . . 138 

Prof Kim Jenkins 

The use of modified binders in road construction in SA . . . . . 143 

Dennis Rossmann 

Developments in seal design . . . . . . . . . . . . . . 147 

Gerrie van Zyl 

The influence of weather on prime applications . . . . . . . 150 

Johan Muller 

The development of a Road Transport Management System 

in SA . . . . . . . . . . . . . . . . . . . . . . 159 

Paul Nordengen 

Accreditation of thin bituminous surfacings in SA . . . . . . . 166 

John Odhiambo 

5

Foreword 

We are proud to bring you the 2007 digest publication. Great effort has 

been made to ensure that we cover a wide spectrum of topical and 

relevant issues, ranging from the latest developments in product 

technology to socio-economic issues which all have a bearing on the 

design and use of bituminous materials. This is an industry publication 

supported by local practitioners, and we are very grateful for the 

contributions made by those authors who have generously shared their 

time, knowledge and expertise. 

The intention of the Digest has always been to offer practitioners a 

vehicle through which they can provide an insight into new 

developments which could impact and shape the future of our industry. 

We trust that we have achieved this and that readers will gain a new 

understanding of the current status of our industry, and be encouraged 

to embrace innovation and implement new developments within your 

own organisations. 

The construction industry in South Africa is experiencing unprecedented 

growth after many years of under spending on infrastructure provision 

and preservation. This changed scenario presents a new set of 

challenges to our resource base, with a resultant increase in demand for 

skills and materials. Some of the articles written provide insight into 

these problems, and a vision of how some of the challenges are being 

addressed. For ease of reading the articles have been grouped into four 

sections namely: Industry Overview, Education and Training, 

Innovation and lastly Best Practice. 

We trust that you will enjoy reading this edition of the Digest and find it 

as enlightening and interesting as previous editions. 

Trevor Distin 

CEO 

Sabita 

7

1 

Valediction

Local and international 

accolades mark retirement of 

Piet Myburgh 

Piet Myburgh, internationally 

acknowledged 

as an authoritative and 

influential leader in bituminous 

technology in the southern 

hemisphere, retired as 

executive director of the 

association in September 

2006, after more than two 

decades of distinguished 

service. 

Myburgh took office as executive 

director of Sabita in October 1981, 

when the association was just 

emerging from its fledgling years. 

He leaves behind him a body 

which today stands alongside its 

sister bodies throughout the world 

as an equal. He will, however, 

continue to offer his knowledge 

and expertise to Sabita in a 

consultant capacity. 

His retirement was officially 

marked at a gathering of current 

and former Sabita councillors in 

Cape Town, where incumbent 

chairman Phillip Hechter paid 

tribute to Myburgh's contribution 

to the asphalt sector in particular, 

and to the southern African region 

in general. 

"While never losing sight of 

Sabita's primary obligation to 

promote the interests of its 

members, Myburgh built a deeper 

and broader agenda into his 

leadership, ensuring that the 

asphalt sector maintained its 

Piet Myburgh was awarded life 

membership of Sabita at his 

retirement function in September 2006 

pivotal role in the social and 

economic development of the 

southern African region,” Hechter 

said. 

"In doing so, he earned international 

respect as a thorough 

strategist, whose technical 

expertise, and comprehensive 

understanding of the political and 

economic changes taking place 

during his tenure, fostered the 

evolution of a healthy, robust and 

flourishing asphalt sector. 

As an engineer for the Cape 

Provincial Roads Department for 

17 years, Myburgh developed a 

unique broad-picture understanding 

of the technological 

demands of a good road network, 

the importance of its maintenance 

and management, and of the 

importance of such a network to 

11

economic growth. In addition to 

structural design of road 

pavements and the formulation of 

laboratory testing specifications, 

he was responsible for the 

development and implementation 

of judgment of compliance 

schemes based on probability 

theory, the conception and 

implementation of a pavement 

management system for the entire 

trunk route system for the Cape 

Province, and identifying research 

needs in the field of pavement 

engineering. 

This experience laid 

the groundwork for 

an unequalled 

overview of the 

symbiotic and 

integrated 

relationship between 

the bituminous 

products industry and 

the road 

infrastructure system 

it serves. His 

appointment brief 

was comprehensive 

and laid the foundation for 

Sabita's expansion into new 

strategic territories that would 

expand the association's pivotal 

role in the growth and 

development of South Africa 's 

bituminous products sector. 

In 1984 Sabita took the helm as 

the secretariat for CAPSA, which 

was launched in 1969 to satisfy 

the unique technological, 

economic and social demands of 

the southern African region. Under 

Myburgh's guidance CAPSA rapidly 

attained international stature, 

attracting global authorities on 

every aspect of blacktop pavement 

engineering, including technology 

development, infrastructure 

management, human resource 

provision, and the safety of 

workers and the environment. 

The evolution of CAPSA over this 

period facilitated the crosspollination 

of local and 

international technology, fostering 

the emergence of a knowledgeable 

industry able to match international 

standards of 

infrastructure design and 

construction. 

... an unequalled 

overview of 

the relationship 

between the 

bituminous 

products industry 

and the road 

infrastructure 

system it serves. 

CAPSA remains 

pivotal to Sabita's 

far wider focus on 

the transfer of 

knowledge at all 

levels. To meet 

this need Myburgh 

motivated the 

establishment of 

the Asphalt 

Academy (AsAc) 

in 2001, and the 

academy's registration 

in 2002 

initiated the evolution of South 

Africa most authoritative focus for 

the education and training needs 

of the bituminous products sector. 

Providing a wide range of services 

from courses and workshops to 

the publication of best practice 

guidelines, AsAc, which took over 

the CAPSA secretariat in 2004, has 

established itself as an integral 

arm of the industry. 

Further focussing on the transfer 

of knowledge, Myburgh was also a 

driving force in the publication of 

Sabita's widely respected 

technical manual/guideline series 

12

and audio-visual training aids, and 

was instrumental in the launching 

of the Road Pavements Forum 

(RPF) in 2001 to replace the 

Bituminous Materials Liaison 

Committee (BMLC). 

AREST 

Sabita's Asphalt Research Strategy 

(AREST) programme, which has 

evolved through four separate 

phases, was initiated by Myburgh 

in 1988, in association with the 

CSIR. Established to 

determine the asphalt 

research needs of 

both the public and 

private sectors on a 

joint and interactive 

basis, the AREST 

Task Force was, and 

remains, Myburgh's 

brainchild, and has 

delivered significant 

benefits in the form 

of greater efficiency 

in establishing and 

maintaining a 

cost-effective road 

network on the sub-continent. 

He was also responsible for 

establishing the bituminous 

products industry's most 

prestigious and sought-after 

incentive award, the Sabita 

Excellence Award, which is now 

presented annually. The first such 

award was made in 1988. 

He also initiated social 

development programmes such as 

the Councillor Empowerment 

Programme to promote 

infrastructure delivery at local 

government level, Sabita's 

Infrastructure Development 

Assessment Programme (SIDAP) 

under Professor Don Ross to 

develop a more productive method 

for evaluating rural road needs 

and to foster a closer synergy 

between blacktop engineering and 

economic priorities. He also 

directed the formation of Sabita's 

Centre for Occupational Safety, 

Health and Environmental 

Conservation (COSHEC) to 

facilitate the implementation of 

global standards of worker safety 

and environmental preservation. 

Throughout his 

tenure with Sabita 

Myburgh flew the 

Sabita flag at 

international 

conferences, 

keeping up with 

international 

developments and 

setting up 

long-standing 

associations with 

world leaders in 

bituminous 

products 

engineering. These remain in 

force, and have proved invaluable 

in ensuring the maintenance of 

global standards in South Africa's 

roads industry. 

Myburgh earned 

international 

respect as a 

thorough 

strategist, and 

fostered the 

evolution of a 

robust asphalt 

sector 

Contributions 

Hechter noted that recognition of 

Myburgh's contributions have been 

plentiful over the years, including 

two made at the celebration of 

Sabita's 25 th anniversary during 

CAPSA'04 at Sun City. Guest 

speaker Professor Steve Brown of 

Nottingham University said Sabita 

was able to stand alongside NAPA, 

EAPA, AAPA and Eurobitume as 

13

one of the world leading trade 

organisations in the field of flexible 

pavement engineering. 

He quoted from Brown address: 

"While Sabita's success is 

undoubtedly the result of a team 

effort, I must nevertheless pay 

tribute to one person whose 

steady hand on the tiller has been 

a vital ingredient in its success, a 

man who has provided continuity 

of leadership through difficult 

times. I refer, of course, to Piet 

Myburgh, who has appreciated 

both the technical and socioeconomic 

requirements of Sabita 

members, and has led your 

organisation with distinction." 

In a message of congratulation at 

the same function Ray Farrelly, 

chief executive officer of AAPA, 

said his organisation, “and indeed 

the world asphalt community, 

has benefited from the friendship 

and cooperation afforded by 

Sabita, by Piet Myburgh, and by 

the many others who have been 

part of Sabita over its 25-year 

journey." 

Myburgh's ongoing association 

with Sabita will include involvement 

in CAPSA'07, during which 

he will act as HSE session 

chairman and provide general 

management inputs. He will 

also review reports and manage 

inputs for existing technology 

development projects i.e. bitumen 

stabilised materials, hot mix 

asphalt wearing courses and HiMA 

trial sections, and will assist with 

updating existing Sabita manuals 

and writing articles for publications 

such as the Sabita Digest, Asphalt 

News and trade publications. 

14

2 

Industry 

Overview

Choosing road surfaces: 

Bitumen, gravel and the fuel 

price in South Africa 

Don Ross 

Professor, School of Economics 

University of Cape Town 

and University of Alabama 

Four fifths of SA’s roads 

(ex clud ing ac cess roads) 

are un sur faced. While this 

is not high by gen eral Af ri can 

stan dards, it is more than we 

find in coun tries with per 

capita GDPs sim i lar to ours. 

There are strong economic 

reasons for thinking that many of 

these roads should be upgraded to 

a bituminous pavement, at least 

among those made with gravel 

rather than in situ soil. The same 

reasons argue against building 

new roads according to principles 

that preserve the current ratio of 

bitumen to gravel, or tip it further 

in favour of gravel. Simply put, a 

higher proportion of new roads we 

lay down should be bitumensurfaced. 

This remains true despite 

significant increases in the price of 

bitumen, driven by the general 

spike in the cost of petroleum 

products, since early 2005. 

Certainly, these increases have 

stressed road budgets. The 

Gauteng Department of Public 

Transport, Roads and Works 

reported in 2005 that the cost of 

upgrading a gravel road to a low 

volume sealed road had increased 

by 67% since 2004, and the cost 

of upgrading to a standard 

surfaced road had increased by 

48% in the same period. This 

obviously implies that fewer roads 

can be upgraded or built from 

scratch without increased budget 

allocations, or until substantial 

new efficiencies can somehow be 

found. 

Paved vs gravel roads 

However, this obvious point should 

not be confused, as it often is, 

with the idea that construction and 

maintenance of paved roads has 

become significantly more 

expensive relative to properly 

maintained gravel roads. It is 

often assumed that because 

bitumen is a petroleum product, it 

must inevitably become a 

relatively worse option compared 

to gravel and cement when the 

world oil price is elevated. 

This reasoning leads to the 

conclusion that the proportion of 

17

unsurfaced roads we should 

upgrade and the proportion of new 

surfaced roads – as opposed to 

the totals that can be afforded 

from a fixed budget – should both 

be reduced from what they 

otherwise would be. 

In this article, I will explain why 

this hasty reasoning is mistaken 

from an economic point of view. 

If we slow the pace of road 

construction and upgrading as a 

response to more expensive fuel, 

this should mainly mean fewer 

gravel roads rather than fewer 

sur faced ones. (Note that re duc ing 

main te nance out lays on ex ist ing 

roads of ei ther type to save money 

would be self-de feat ing, since 

de fer ring this ex pen di ture 

in creases to tal costs, and the 

world price of fuel is not ex pected 

to de cline soon enough, if it ever 

will, to offset this fact.) 

Around the world, a standing 

supposition prevailed for many 

years that urban streets and 

provincial and national highways 

should be paved, and that the 

default materials for all other 

roads should be soil and gravel. 

Gradually over the past decade or 

two, however, a more 

sophisticated understanding of the 

value of infrastructure assets has 

overturned the traditional view. 

Before turning to the issue of the 

impact of fuel price increases, I 

will review the economic 

arguments for paving roads at 

lower levels of expected traffic 

volume than was once generally 

accepted. 

The basic business of economics is 

opportunity-cost calculation. 

Whenever a decision or policy 

leads to a stream of benefits and 

costs, we can attempt to evaluate 

it in terms of other possible 

streams we could have had 

instead if we’d made an 

alternative decision about how to 

dispose of our resources (including 

money, but also time and 

administrative energy). 

Thus, in considering the relative 

values of bitumen and gravel 

roads, we compare the costs and 

benefits of one type of road with 

an estimate of those we would 

have if we’d invested the same 

money, materials and planning in 

a road of the other type. 

Shadow pricing 

In the case of public infrastructure, 

benefits accrue over 

some period of time. If periodic 

maintenance of an asset is 

required, as with roads, then the 

same is true for some portion of 

the costs. The moment we set out 

to estimate opportunity costs over 

time, we must discount future 

values by the difference we attach 

between having the benefits or 

paying the costs now and 

deferring them. 

A com mon ap proach where money 

is con cerned is to set the dis count 

rate by ref er ence to the dif fer ence 

be tween the in ter est rate earned 

by a safe fi nan cial as set and the 

ex pected me dium-term rate of 

inflation. 

In SA it is currently customary to 

benchmark this at 8%. There are 

then two ways (which should 

agree with one another) in which 

18

we can economically test a 

possible investment: 

• The discount rate captures 

the opportunity cost of 

capital. In a sound 

investment, this must be less 

than the discount rate at 

which the present value of 

benefits and costs are equal, 

i.e. the internal rate of return 

(IRR). 

• We subtract the discounted 

costs from the discounted 

benefits so as to 

estimate the net 

present value 

(NPV) of the 

contemplated 

investment. This 

is the most 

direct way of 

comparing two 

types or 

instances of 

asset, such as a 

gravel road and 

a paved road: 

which has the 

higher NPV? It is 

immediately obvious that this 

form of comparison must be 

highly sensitive to the period 

of time over which we choose 

to estimate costs and 

benefits. One asset might pile 

up costs earlier than another 

but then deliver a better ratio 

of benefits to costs at later 

stages. How many of these 

later stages are factored into 

the calculation of NPV will 

then crucially influence the 

conclusion of our comparison. 

The key to effective economic 

analysis of any investment 

decision is finding a way to 

account for all consequences that 

have value to people or impose 

costs on them, even where the 

values and costs in question don’t 

have prices assigned to them 

directly by markets. Such 

non-traded cost and benefit 

streams must be assigned 

so-called ‘shadow prices’, that is, 

monetary amounts people appear 

willing to pay to avoid the costs 

and acquire the benefits. 

The key to 

effective economic 

analysis ... is 

finding a way to 

account for all 

consequences that 

have value to 

people or impose 

costs on them 

For example, if someone whose 

time can be sold 

on the consulting 

market for R1,000 

per hour spends 

two hours per 

month polishing 

their car, we can 

shadow price the 

value of a shiny 

car to that person 

at R24,000 per 

year. 

Bearing in mind 

that surfaced 

roads are 

relatively costly to build but 

relatively cheaper to maintain than 

gravel roads, we can identify the 

two general factors that have 

mainly contributed to overestimations 

of the economic value 

of gravel roads as compared to 

paved ones. The first is failure to 

consider long enough periods in 

calculating NPVs, or implicitly 

assuming too steep a discount 

rate (which amounts to the same 

thing). The second is failure to 

incorporate shadow prices for a 

range of non-traded benefits that 

flow from paved but not from 

gravel roads, or flow from gravel 

roads only to a lesser extent. 

19

These two issues are directly 

related: most of the important 

shadow-priced benefits from 

pavements accrue gradually. 

Before turning to these, however, 

let us start with costs. In southern 

Africa the construction cost of a 

kilometre of surfaced road with a 

regular chip seal is, on average, 

about 2.4 times the cost of 

building a properly engineered 

gravel road. Maintenance of a 

full-scale paved road constructed 

with hot mix asphalt costs, on 

average, 1.9% per year of initial 

construction costs until the point 

at which replenishment of the 

wearing course is necessary. 

Maintenance costs/km 

Maintenance of a gravel road 

costs, on average, 27% of initial 

construction costs until the point 

at which regravelling is necessary. 

These averages conceal the 

different effects of traffic volumes 

on the two types of road. A recent 

study in the US state of Minnesota 

found that gravel road 

maintenance costs per kilometre 

rise significantly at two thresholds: 

by 9% at an average annual daily 

traffic (AADT) rate of 50, and by 

30% at an AADT of 200. This is 

also the point at which gravel 

maintenance costs shoot 

dramatically past bitumen 

maintenance costs, with the gap 

thereafter widening steadily with 

AADT. 

Gravel roads must be regravelled 

on a shorter cycle than that 

associated with bitumen road 

resurfacing. This has a double 

effect on NPV comparisons: first, if 

we choose a long enough period it 

will include more regravelings than 

bitumen resurfacings, and, 

second, we will calculate the cost 

of the first regravelling operation 

in less steeply discounted Rand 

because it arises closer to the 

present. 

In southern Africa, bitumen 

resurfacing is half as costly on 

average as regravelling if roads 

are adequately maintained during 

the intervals. The fact that this 

smaller number gets multiplied by 

a smaller discount factor because 

of the earlier date to regravel adds 

to the strength of the relative case 

for bitumen. 

Nevertheless, use of the proportional 

relations above as the sole 

basis for trying to determine when 

a paved road is more economically 

efficient than a gravel road 

produces a relatively conservative 

threshold for upgrading. 

Differences stemming from AADT 

rates dominate all other factors on 

this skimpy information base. 

Conservative 

As a result, one would conclude 

that paving is only justified where 

AADT is expected to pass 200. 

Even adopting this conservative 

number would lead to upgrading, 

if budget allowed, of about 40% of 

current gravel road kilometres in 

Gauteng, for instance. (Gauteng is 

not claimed to be representative. 

Its large population pushes up its 

AADT levels compared to other 

provinces). On the other hand, its 

smaller distances push down its 

relative proportion of inherited, 

and possibly inefficient, unpaved 

20

oads. These considerations 

influence the optimal upgrading 

quotient in opposite directions, but 

there is no reason to suppose that 

they neatly cancel each other out.) 

of economic analysis. Let us now 

consider the shadow-priced 

benefits of road surfacing that 

should also be factored into 

evaluation. 

In any case, this conservative 

conclusion arises only prior to 

considering other relevant benefits 

of paved surfaces and costs of 

gravel ones. Before we turn to the 

domains where shadow pricing is 

concerned, one direct financial 

cost factor, which can’t yet be 

quantified because it is speculative 

but will turn up on public books as 

a market price rather than a 

shadow price, must be taken into 

account. This is that new gravel is 

becoming scarce in SA, so its price 

is sure to rise. 

Municipalities are no 

longer allowed to 

open new pits without 

performing 

environmental impact 

assessments, which 

are beyond the 

resource capacity of 

most rural 

authorities. In 

addition, in many 

in stances in south ern 

Af rica, op ti mal 

materials for gravel 

roads are con cen trated un der 

ar a ble land that has higher 

opportunity value as farmland 

than as gravel. Thus, on the ba sis 

of con struc tion and main te nance 

costs alone, we should ex pect the 

thresh old for sur fac ing, what ever 

ad di tional con sid er ations we use 

to determine it, to drop in SA. 

However, as noted, accounting for 

these costs is only the beginning 

Municipalities 

are no longer 

allowed to open 

new pits without 

performing 

environmental 

impact 

assessments 

• Because of the dust they 

spread onto crops, wildlife 

and people, gravel roads 

impose heavier 

environmental costs than 

surfaced ones. Dust causes 

allergies and respiratory 

illness, especially in small 

children. People must clean 

their homes, businesses and 

vehicles more often in dusty 

conditions, and this is not a 

cost that should be ignored 

simply because it is not borne 

by the state. It 

is, after all, still 

borne by the 

country on the 

dimension that 

ultimately 

counts for 

most, viz., 

reduced 

productivity. 

Even seemingly 

trivial expenses 

can produce 

high overall 

costs when 

multiplied by 

enough people and hours in 

calculating aggregate shadow 

prices. To my knowledge, no 

one has ever tried to 

estimate the costs of road 

dust in any jurisdiction. The 

task would be quite 

demanding. It is surely worth 

doing, however, because the 

resulting magnitude might be 

surprising to many, and thus 

might in turn help people not 

21

to forget a hidden cost of 

gravel roads; 

• Rougher road surfaces 

increase vehicle operating 

costs, especially fuel use and 

tyre wear. Fuel use premiums 

on gravel roads are especially 

noteworthy if one of the 

considerations leading some 

people to worry about 

bitumen use is its upward 

influence on our consumption 

of petroleum products. A 

1991 CSIR study estimates 

that equivalent traffic 

volumes burn, on average, 

6% to 7% more fuel on 

gravel roads than on paved 

ones. Though this already 

represents a very substantial 

cost externality for gravel, 

Namibia’s Klaus Dierks 

es ti mates a higher fig ure of 

20%. This partly re flects 

Dierks’s re stric tion to very 

low-qual ity gravel roads. 

How ever, the shadow price 

here is clearly high on any 

ac count. Us ing South Af ri can 

data, Dierks summarises 

overall extra vehicle 

op er at ing cost dif fer ences on 

me dium-grade gravel roads 

(IRI = 8) as com pared to 

me dium-grade sur faced roads 

(IRI = 4) at a low end of 

19% for buses and 27.5% for 

me dium-weight trucks. His 

over all con clu sion, based on a 

mix of Namibian and South 

Af ri can data, is that merely 

factoring vehicle operating 

costs into the com par a tive 

economic evaluation of road 

types re duces the re gional 

thresh old AADT for sur fac ing 

a gravel road to be tween 120 

and 160. (On his cal cu la tion, 

up grad ing to full as phalt 

pave ment does not move the 

thresh old from my ear lier 

es ti ma tion of 200.) If the 

thresh old of 120 were 

adopted in Gauteng, this 

would re sult in 50% of gravel 

road kilometres being 

regarded as warranting 

upgrade; 

Safer roads 

• Paved roads are safer than 

gravel roads because on 

paved surfaces vehicles can 

brake to faster stops from 

equivalent speeds and are 

less disposed to skidding. 

According to the Caterpillar 

Performance Handbook, the 

coefficient of traction (the 

ratio of horizontal force that 

would cause tyres to move to 

the vertical force on the tyre) 

for rubber tyres on a surfaced 

road is 0.90, as opposed to 

0.36 on unsealed gravel. This 

is offset somewhat by the 

fact that vehicles tend to 

travel faster on surfaced 

roads. However, accident 

data save us from having to 

speculate about the relative 

strengths of these countervailing 

influences. First, a 

1998 study by CSIR 

Transportek concludes that 

road surface conditions 

contribute to about 8.6% of 

all accidents in SA, and that 

surface improvements would 

prevent 10% of these 

altogether – so, 0.86% of the 

total. The accident rate per 

million vehicle kilometres on 

gravel roads is more than 

22

double that for two-lane 

surfaced roads, and the 

composition of fatalities 

among accidents on gravel 

(10.9%) is higher than on 

2-lane paved roads (7.8%), 

and much higher than on 

full-speed freeways (3.2%). 

Thus effects of differences in 

vehicle control strongly 

appear to swamp differences 

in driving speed where 

accident harm is concerned; 

• Gravel roads 

cannot, like 

bituminous ones, 

be constructed 

and maintained 

entirely using 

small equipment 

that can be 

operated by 

unskilled people; 

thus they fail to take into 

account SA’s abundance of 

underutilised labour, and are 

less effective at developing 

human capital in small 

contractors. National 

Government’s Extended 

Public Works Programme 

(EPWP) mandates that 

wherever labour-intensive 

methods can be deployed for 

the same budget outlay as 

capital-intensive methods, 

the former should be 

favoured. In fact this is too 

conservative, using an 

accounting measure of value 

where an economic measure 

would be more appropriate. 

Use of small contractors in 

road construction and 

maintenance builds human 

capital in the form of 

management, tendering and 

investment skills, with the 

acquisition of manually 

operated surfacing equipment 

an additional benefit. Since 

such capital is an economic 

asset with future multipliers, 

we should not implicitly set 

our willingness to invest in it 

at zero, as the EPWP 

presently does. 

It is unfortunately not possible 

here to attempt a quantitative 

estimate of the 

human capital 

investment value 

accruing to 

surfaced road 

construction and 

maintenance over 

gravel road 


maintenance. The 

issue has been 

confused in many discussions by 

benchmarking targets of ‘numbers 

of jobs’. 

.... capital is 

an economic 

asset with 

future 

multipliers 

Unlike human capital, ‘jobs’ are 

not assets since they are functions 

of overall productivity in the 

economy, are not fixed in extent, 

and do not have opportunity costs 

in the strict sense. 

Over the coming year, I and my 

graduate students at UCT hope to 

make progress against this 

confusion and produce a first 

quantitative estimate of the 

potential value in human capital 

creation of labour-intensive 

roadwork. In the meantime, we 

must be content with noting that 

whatever effect this has on the 

shadow price of gravel, the 

direction of the influence is clear 

and must further reduce the 

23

threshold for paving from the 

160/120 benchmark arrived at 

above. 

Similar remarks are in order 

concerning the other 

shadow-priceable factors 

discussed above and not yet 

quantitatively estimated in a 

model, viz., environmental 

impacts and safety. We saw earlier 

that the previous benchmark 

would direct us to upgrade 50% of 

gravel road kilometres in Gauteng. 

Consideration of the factors 

awaiting shadow pricing must then 

increase this already ambitious 

threshold, probably substantially. 

The influence of the fuel 

price 

Now that the factors affecting the 

relative economic values of paved 

and gravel roads have been 

identified, we can consider the 

relevance of fuel price increases to 

the balance of these factors. 

For most of the past six years, the 

price of gravel has risen faster 

than real in fla tion in SA, while 

bi tu men price in creases have been 

sub-in fla tion ary. How ever, 

bi tu men prices be gan ris ing faster 

than in fla tion about one year ago. 

Fig ures 1 and 2, com piled from 

data re leased by Sta tis tics SA, 

show these relationships: 

Suppose – as may or may not be 

the case – that 2005 is the first 

year in a secular trend with 

respect to these price 

relationships. This tells us nothing 

about whether the change in 

relative prices is enough to 

significantly offset the 

considerations raised above 

favouring increase in the 

proportion of surfaced roads. 

Several considerations suggest 

that it is not. 

Figure 1 (Source StatsSA) 

First, the 

arguments 

presented 

above 

emphasise 

that gravel’s 

relative costs 

tend to be 

hidden unless 

IRR, NPV and 

opportunity 

cost are 

calculated 

over an 

appropriately 

extended 

time period. 

If we 

responded to 

the 2005/6 

24

elative 

fluctuation by 

increasing our 

proportion of 

gravel used, 

at a point 

where the 

supply of 

domestic 

gravel is 

facing new 

constraints, 

this can only 

push up the 

expected cost 

of gravel. 

Secondly – 

and much 

more 

importantly – 

basic 

materials are far from the largest 

cost component of either surfaced 

or gravel roads. In the case of 

bitumen roads, costs of labour, 

plant, investigation, design, road 

marking, signage and other inputs 

make up a minimum of 75% of 

total construction and 

maintenance costs. 

Labour intensive methods 

With the exception of plant these 

additional inputs are mainly 

domestically produced – and to 

the extent that we increase 

emphasis on labour-intensive 

methods, machinery can be 

increasingly domestically sourced 

as well. By contrast, the largest 

cost component by far in 

construction and maintenance of 

gravel roads is haulage associated 

with the replacement of lost 

wearing course gravel. Gravel is 

heavy. It is most often carried in 

Figure 2 (Source StatsSA) 

trucks. Trucks run on petroleum 

(diesel) fuel. This expenditure, 

unlike increased expenditure on 

bitumen, occurs beyond the first 

year of a road project. Thus the 

proportional impact of rising fuel 

prices on road construction costs 

goes steadily upward for gravel 

relative to bitumen as time 

horizons are extended. To the 

extent that rising fuel prices are 

expected to be a negative external 

shock on road budgets, their 

proportionate impact is greater 

than on surfaced road prices given 

the use of the discount rate 

employed for most public 

investment purposes. 

Third, because the proportion of 

gravel road cost inflators (diesel 

fuel and heavy machinery) that 

must be imported are higher than 

for surfaced roads, factoring 

exchange rate risks into 

comparative NPV calculations also 

25

lowers the optimal proportion of 

gravel. 

For maintenance of SA’s current 

extent of gravel roads, we require 

about 30 million cubic metres of 

gravel to be hauled each year. At 

current distances between borrow 

pits, this is costing about 30 

million litres of fuel. An additional 

10 million litres of fuel is used for 

blading by motor graders. This 

amounts to about 0.1% of total SA 

diesel fuel consumption. These 

figures must be expected to rise 

faster than the fuel price if our 

overall use of gravel for roads 

increases. 

Environmental issues 

As environmental considerations 

reduce the acceptability of opening 

new borrow pits, as opposed to 

increasing the sizes of a reduced 

number of pits, average haulage 

distances must increase. Data 

collected from South-East Asia 

indicate that for every additional 

10 km. that gravel must be 

hauled, costs increase by $2 per 

cubic metre. 

By contrast, since the majority of 

inputs to a bitumen road are not 

imported, then to the extent that 

SA’s pavement materials inflation 

is driven by world prices, overall 

costs of surfaced roads should be 

expected to be sub-inflationary. 

These considerations can hardly 

be said to show anything decisive 

at this point. They surely should, 

however, block any casual 

suggestion that high fuel prices 

should imply more gravel roads 

pending completion and testing of 

a full quantitative estimation of 

input-output functions in SA’s road 

industry. 

The arguments mustered here 

suggest that were we to respond 

to the increased fuel price by 

reducing our use of bitumen for 

roads in favour of gravel, we 

would likely find that after 7-10 

years we had reduced rather than 

enhanced the overall efficiency of 

our road network compared to 

what we could have had for the 

same net investment. 

While it is true that we cannot 

build or maintain as many 

kilometres of roads per Rand as 

earlier in the decade (at least, 

given current productivity), it is 

probably not true that if budgets 

are not increased and 

retrenchments are made these 

should first be applied to new 

surfaced road construction or to 

upgrades from gravel. Rather, the 

opposite is more likely. 

By early 2008, we aim to have 

produced an economic model in 

which these speculations can be 

rigorously tested. 

 

26

Optimising resource utilisation: 

Aggregate supply to the road 

construction sector 

Alex Weideman 

Product Technical Manager 

Holcim SA (Pty) Ltd 

Wideranging questions 

have been raised 

about the ability of the 

aggregate industry to meet 

increased demand in the road 

construction industry – 

questions which cannot be 

examined without reflecting on 

the past. 

The aggregate industry is part of 

the construction industry, which 

went through a long period of low 

demand, starting in the mid 

eighties. This caused 

a number of plants to 

be shut down or 

mothballed, and 

others were forced to 

rationalise if they 

were to stay in 

business, and 

minimal investment 

in existing and new 

plants took place. 

With the sudden 

unprecedented 

growth in the market over the last 

two years, shortages in certain 

products have been experienced. 

Admittedly, there has been a lot of 

talk about the shortfall of material 

supply, and the aggregate 

industry has invested significant 

funds in recent years in the 

refurbishment and upgrading of 

existing plants. In addition, a large 

number of mobile plants that could 

help alleviate the shortage of 

materials have been imported, but 

there are concerns that some of 

these plants may be used in 

non-regulated mining areas. 

Rest assured, the 

aggregate 

industry does 

have more than 

enough reserves 

to cope with the 

increased 

demand. Most 

commercial 

operations have at 

least a 10-year 

mining plan. In 

the short-term 

certain operators might have to 

invest in their quarries to open the 

mine up for good quality material, 

but no shortage should be 

experienced. 

The aggregate 

industry has 

more than 

enough reserves 

to cope with 

the increased 

demand 

28

It is interesting to note that road 

surface material has higher 

specification requirements when 

compared with the balance of 

construction industry products, 

and that it makes up only a small 

percentage of the total aggregate 

market demand. Not all sources of 

aggregate type are thus suitable 

for use as road surfacing stone. 

Specifications 

Quarries that produce to these 

specifications invest in technical 

expertise, screening and crushing 

equipment, and put a great deal of 

effort into complying with these 

specifications. The day-to-day 

production of standard stone 

products does not always comply 

with the stringent road surfacing 

specification, and it is usually 

necessary for this material to 

undergo additional screening and 

crushing if it is to comply. 

The remainder of the material 

screened off during this process 

often does not fall within any 

specification which results in 

aggregate suppliers generating 

“waste stockpiles” that are difficult 

to market. 

In addition, production yield of the 

aggregate sizes required for road 

surfacing are often the slowest to 

come off the plant. The demand 

on road surfacing contracts 

usually arises over a very short 

peak period in the year, which 

could cause suppliers to over 

commit to orders, resulting in a 

shortage of material during the 

contract. Fortunately, with the 

latest crushing technology, it has 

become easier to produce to these 

specifications. However not all 

aggregate producers are in a 

position to upgrade their plants to 

this standard. 

It is important to stress that 

aggregate producers are working 

very hard to produce to these 

standards and trying their level 

best to keep up with the current 

demand. This objective would be 

more easily achieved if specifiers 

of road stone material were more 

sensitive to the realities of what 

can be delivered from a crushing 

plant. Without this kind of mutual 

understanding, shortages in 

specific sizes are inevitable. 

Specifiers and suppliers need to 

work together to avoid this 

problem becoming a reality, and 

engineers are encouraged to 

ascertain from the quarries what 

aggregates are available before 

deciding on the type of surfacing 

to be used in their design. 

Optimisation 

This would lead to better 

optimisation of the stone yield 

from the quarry, and thereby 

reduce the generation of unusable 

materials. In the event of wanting 

to utilise high performance 

surfacings it is imperative that 

the engineer predetermines what 

the inherent properties of the 

local aggregates are in terms of 

key performance parameters 

such as polished stone value (PSV) 

and the quarry’s ability to produce 

the required average least 

dimension (ALD). The latter 

information is crucial to ensure 

that the industry continues to 

provide sustainable best value 

products to our clients. 

29

COSHEC in 2007: 

Health and safety in the 

workplace – walking the talk 

Piet Myburgh 

The year 2007 will see a 

renewed commitment on 

the part of Sabita to a 

comprehensive business plan 

to advance global best practice 

in health, safety and 

environmental conservation 

(HSE) in South Africa. Tangible 

outputs have and will continue 

to be pursued to advance and 

support members’ initiatives to 

implement these HSE norms. 

Thus, ultimately, Sabita will 

represent a membership that is 

informed on current global best 

practice and future developments 

that impact on SA, a membership 

that voluntarily adopts methods 

and procedures compliant with 

global norms, leading to an ethos 

of self-regulation within the 

industry. 

Crucial to the attainment of this 

goal in the medium term is the 

institution of safety performance 

assessment schemes and, 

subsequently, award programmes 

that publicly acknowledge those 

members who commit to the 

principles of corporate 

responsibility to their employees 

and the environment. 

Commitment 

This year saw a significant 

increase in the dedicated funding 

of the business plan formulated 

within the context of the COSHEC 

strategic cluster, with the backing 

of the sponsor members (the oil 

companies). This enhanced 

resource will enable Sabita to 

launch an industry drive congruent 

with the oil companies’ commitment 

to putting profitability 

side-by-side with obligations to 

worker wellness and sustainable 

practice that protects the fragile 

environment. 

Key to the execution of the plan is 

to give downstream industry every 

encouragement and assistance to 

adopt triple bottom line policies 

that include: 

• the development of training 

material and programmes 

focusing on safety in the 

workplace; and 

30

• the establishment of 

processes and activities 

aimed at bringing global best 

practice to their doorstep. 

Consistent with a shift in emphasis 

from operational objectives in the 

past to strategic objectives in the 

future, Sabita will canvass 

members’ representatives at 

management level to serve on the 

COSHEC strategic cluster focus 

group. In such a manner the 

knowledge, experience and 

leadership capacity within the 

industry will be mobilised to give 

impetus to the execution of the 

plan. 

Business plan 

The scope of the activities of the 

COSHEC business plan is 

comprehensive, and covers all 

products and services normally 

provided by the bituminous 

product industry. Thus, in the case 

of the handling of bituminous 

binders, it is envisaged that all the 

following phases of handling will 

be taken into account in the 

development of appropriate codes 

of practice and training 

programmes: 

• Loading of product at 

refineries or depots; 

• Transportation, particularly 

by road; 

• Off-loading at storage 

facilities at secondary 

industry establishments; 

• Storage and handling at 

manufacturing site, factory or 

construction site; 

• On-processing or value 

addition operations e.g. 

emulsification, modification; 

• Waste management when 

disposing of surplus product. 

The scope of workplace activities 

associated with the services 

provided by the bituminous 

product industry will include: 

• Binder application to the road 

by spraying as well as 

chipping operations; 

• Hot mix and cold mix asphalt 

manufacture; 

• Transporting of asphalt; 

• Application i.e. paving and 

compaction; 

• Milling; 

• Crack sealing; 

• Sampling and laboratory 

testing; 

• Traffic accommodation during 

construction, maintenance 

and rehabilitation operations; 

• General site hygiene; 

• Waste management i.e. the 

disposal of excess asphalt or 

milled materials. 

Global standards 

As part of its goal to advance the 

level of awareness of global norms 

and standards through the 

dissemination of best practice, an 

initiative aimed at promoting the 

discontinuation of the use of coal 

tar products in road construction 

was launched recently with the 

publication of Sabita Manual 26 – 

Interim guidelines for primes and 

stone precoating fluids. 

Including input from the Society 

for Asphalt Technology (SAT) 

following a series of seminars held 

nationally, the guideline highlights 

conventional wisdom on alternatives 

to coal tar products, and is 

31

designed to assist road authorities 

in the selection of proven 

substitutes for carcinogenic and 

environmentally aggressive coal 

tar products. The guideline focuses 

on priming granular bases and 

precoating surfacing stone, and is 

intended to serve as an interim 

guideline until documents such as 

the outdated TRH1: Prime coats 

and bituminous curing membranes 

(1986) have been updated. 

Despite Sabita’s 

wide-ranging 

awareness campaign, 

and the lead taken by 

the South African 

National Roads 

Agency Limited 

(SANRAL), the 

Provincial Council 

Western Cape and 

the Gauteng 

Department of Public 

Transport, Roads and 

Works, none of South 

Africa’s 248 municipalities nor any 

of the six metropolitan councils 

have yet undertaken to prohibit 

the use of coal tar products in 

their road infrastructure projects. 

This is a problem demanding 

incisive action, as it is 

inconceivable that professional 

engineers should continue to allow 

environmentally harmful and 

unhealthy products to be specified 

for road construction when there 

is widespread substitution of this 

product with alternatives that are 

less harmful to workers or the 

environment. 

Another initiative to advance the 

introduction of global norms and 

standards in South Africa is the 

introduction of the first plenary 

session, Health, Safety and the 

Environment (HSE), at CAPSA’07 

this year. This session, convened 

within the context of the COSHEC 

business plan, will have 

distinguished speakers from 

Europe and the USA presenting 

up-to-date papers on topics 

covering legislation on the 

registration, evaluation and 

assessment of chemical 

substances, the 

challenges faced 

and dealt with by 

the asphalt 

industry in both 

Europe and the 

USA to meet the 

needs of society in 

respect of HSE, 

and future 

industrial trends 

to ensure that 

processes are 

sustainable and 

appropriate to 

reduced reliance on nonrenewable 

energy resources. 

No 

municipalities 

have yet 

undertaken 

to prohibit 

the use of 

coal tar 

products 

Workplace safety 

To mitigate employee exposure to 

injury or ill-health arising from the 

handling of bituminous products, 

Sabita recently launched a 

bitumen safety course, which 

kicked off in June 2006 when 25 

employees from member 

companies took part in the BitSafe 

train-the-trainers courses in 

Stellenbosch, Johannesburg and 

Durban. These trainers will now 

head up comprehensive training 

courses at their own companies to 

entrench awareness of the hazards 

associated with the handling of 

bituminous binders, and to 

32

mitigate the risks of exposure to 

these hazards. 

The modular format of the course 

facilitates training while limiting 

impact on production, and the 

intention is that all employees 

involved with the handling of 

bitumen throughout the supply 

chain should complete all 13 

modules within a two-year period. 

The course and its associated 

awareness-building function is 

supported with the design and 

publication of a series of safety 

posters which are now being 

issued free of charge to Sabita 

members. These posters are 

designed to be displayed in areas 

most frequently encountered by 

workers engaged in the relevant 

activities by encouraging workers 

to protect themselves against 

injury by wearing of Personal 

Protective Equipment (PPE). 

Academy certificate on completion 

of the course. 

Guidelines 

Started in 2006 and currently 

underway are steps to revise 

Sabita Manual 23 – Bitumen 

hauliers’ code: guidelines for 

loading bitumen at refineries. It is 

common cause that the relevance 

and comprehensiveness of this 

publication have been overtaken 

by time, and hence a project was 

launched to correct this situation. 

The purpose of the project is to 

compile a nationally accepted code 

of practice for loading bitumen at 

refineries, and the following steps 

will be followed towards this goal: 

Trainers will have the support of 

training aids such as DVDs, 

training manuals, prepared slide 

presentations and posters. 

Trainees will be assessed at the 

conclusion of each module, and 

will receive a joint Sabita/Asphalt 

Bitumen safety posters 

Sabita's BitSafe DVD 

• Identify shortcomings of the 

current haulier code; 

• Liaise with marketers/refiners 

to supplement content; 

• Revise and procure 

agreement; 

• Liaise with transport 

industry; 

• Collate comments and revise 

accordingly; 

33

• Obtain endorsement and 

commitment from refiners; 

• Publish and market. 

The project has now reached 

Phase 2, and visits to all refineries 

are underway to elicit concerns 

and proposals for a uniform code 

of entry, loading and exit of bulk 

bitumen haulers at refineries in 

South Africa. 

Review 

A review of the 

current document 

points to a number of 

issues that would 

need to be addressed 

in preparation of the 

proposed review. 

Some of the principal 

ones are listed below: 

• The current 

document relies 

on the willing 

compliance of 

Sabita members 

and hauliers for 

its successful implementation. 

This somewhat 

indulgent approach is not 

what is envisaged in the 

COSHEC business plan, and 

consequently it is likely that 

the title of the new document 

will be: A national code of 

practice for loading bitumen 

at refineries in SA, with the 

content phrased accordingly. 

It is envisaged that the 

preface to the document will 

carry an endorsement by all 

primary producers (i.e. 

marketers and refineries) and 

an undertaking to enforce the 

content at their loading sites; 

The aim is 

to adopt 

a single 

(minimum) 

national 

standard code 

to address safety 

and environmental 

issues 

• The current document admits 

to variance of standards 

and/or procedures at 

refineries. The aim is to adopt 

a single (minimum) national 

standard code that 

adequately addresses safety 

and environmental issues. 

Should any particular refinery 

have additional requirements, 

these can be dealt with in an 

appendix (or the Sabita 

website) that 

can be 

amended from 

time to time. 

Operations 

Operational 

aspects that will 

be covered 

comprehensively 

are: 

• Entry 

procedures; 

• The vehicle 

(roadworthy 

certificates, pre-load 

inspection, dangerous goods 

placards, orange box etc); 

• The driver (Medical fitness EC 

license and PrDP(DG) 

qualifications and declaration 

of compliance etc.); 

• Requisite documentation 

(uplift documentation, 

dangerous goods declarations 

etc., MSDS); 

• Required loading procedures 

to be followed by the haulier 

driver and assistant as well 

as refinery staff; 

• Departure procedures. 

Since publication of the current 

document in 2000, attitudes and 

34

policies with regard to HSE have 

changed significantly, and refinery 

standards and requirements for 

load upliftment have converged. 

As a result the content of the 

manual will be substantially 

amended during the revision. 

Cognisance will also be taken of 

Sabita Manual 25: Quality 

management in the handling and 

transport of bituminous binders, 

which contains a 

wealth of 

information that 

needs to be 

incorporated in 

the proposed 

code. 

Ultimately it may 

be necessary to 

compile a 

comprehensive 

document 

covering the 

attainment of both 

the safety and 

quality standards 

in the handling of 

bitumen from 

refinery to 

site/depot. This 

will obviate the obvious pitfalls of 

duplication and discrepancies, and 

those associated with periodic 

updates. 

Safety file 

Sabita has compiled a Safety File 

to assist those members involved 

in the construction of bituminous 

surfacings and layer works in the 

compilation of a Contract Safety 

File as stipulated in the OHS act. 

The main section of the guide 

recommends risk assessment and 

safe work procedures for a range 

of operations and plant directly 

Sabita's guide for in-service 

safety training 

related to the handling of 

bituminous materials. Examples 

are also given of a typical safety 

management structure and the 

appointment and responsibilities of 

safety management positions in 

terms of the OHS Act. This 

document has been published in 

the Members Only section of the 

Sabita website for editing by our 

members as they see fit. 

Waste disposal 

A full report on the 

current status of 

public-private 

sector interaction to 

facilitate the 

permitting of sites 

for the disposal of 

surplus bitumen can 

be found on Page 

126). 

Member 

participation 

Ultimately, COSHEC 

will succeed in its 

goal if its vision “...to incentivise 

members to adopt a culture of 

corporate responsibility in respect 

of sustainable work practices, 

worker safety and environmental 

protection” materialises through 

voluntary participation. 

Fundamental to achieving this goal 

is the establishment of a reference 

framework or criteria for the 

assessment of members’ 

performance which, as a first step, 

can be measured against simple 

criteria such as: 

• a commitment to the non-use 

of coal tar products; 

35

• institution of Sabita safety 

training programmes; 

• disposal of surplus bitumen to 

approved landfill sites only; 

• acceptance only of bitumen 

consignments that have been 

loaded in accordance with 

refinery safety requirements; 

and 

• submission of incident reports 

for incorporation into a 

national incident database for 

establishing a national 

industry benchmark. 

Eventually members’ performance 

will be assessed against national 

norms and compliance with 

legislation relevant to their 

industrial operations. It is 

envisaged that members 

performing well against criteria 

currently being developed should 

be appropriately rewarded through 

a prestigious annual industry 

award scheme. 

Such members will in themselves 

become the industry beacons, for 

others to emulate on the 

ascendant road to achieving 

profitability through safe and 

responsible means. 

 

36

3 

Education 

and 

Training

Towards an informed industry: 

Updating best practice 

guidelines and documents 

Trevor Distin 

Chief Executive Officer 

Sabita 

Notwithstanding various 

approaches to the 

National Department of 

Transport (NDoT) by both 

Sabita and the Road 

Pavements Forum, culminating 

in a briefing by Sabita of the 

Minister of Transport, Jeff 

Radebe in November 2005, 

national documents that are 

supposed to reflect best 

practice for the design, 

construction and maintenance 

of roads continue to languish 

in a state of obsolescence. 

This inability on the part of NDoT 

to respond to a well articulated 

national need could possibly be 

ascribed to the irreversible 

migration of institutional 

knowledge to the SA National 

Roads Agency Ltd (SANRAL) when 

that body was established in 1998. 

Sabita has always held the view 

that these documents, such as the 

series of Technical Recommendations 

for Highways (TRH), and 

Technical Methods for Highways 

(TMH) and national specifications, 

form the basis of sound 

engineering practice aimed at the 

optimal provision and maintenance 

of our road network. A further 

benefit is that these documents 

can provide an essential 

springboard for new entrants into 

the roads industry, whereby they 

can avail themselves of the 

benefits of decades of experience 

and achievement in the roads 

industry. 

Incisive action 

Given the crucial role of up-todate 

codes of practice and 

specifications in ensuring the 

sustainability of the road building 

industry and to stem the erosion 

of skills from the various road 

authorities at both provincial and 

municipal levels, incisive corrective 

action needs to be taken by 

appropriate industry sectors to 

redress the shortcomings. 

Sabita has responded to this need 

by significantly increasing its 

investment in technology 

development in the bituminous 

39

product sector, an initiative 

designed to ensure that a well 

informed bituminous materials 

industry is sustained through the 

systematic publication of updated 

and current best practice 

guidelines. 

Standard test methods 

The standard test methods for 

road building materials are 

contained in TMH 1, which was 

last updated in 1986. Many of 

these methods are 

now outdated and 

need to be 

reviewed. The 

Materials Testing 

Committee of COTO 

is currently 

reviewing selected 

TMH 1 test methods 

to bring them into 

line with legislated 

accredited system 

requirements. The 

revised test 

methods will 

therefore be rewritten and 

published as national standards 

under the auspices of the SABS. 

Sabita has agreed to finance the 

revision of the test methods 

pertaining to bituminous products. 

This will be a mammoth task, but 

a vital one if we want to ensure 

that reliable and accurate test 

methods are in place to measure 

and control the quality of our 

products. This initiative has the 

strong support of Sabita’s 

membership, as it allows the 

private sector to have direct input 

into the review process under 

SABS from which they were 

previously excluded. 

Sabita has 

responded to 

industry needs by 

significantly 

increasing its 

investment in 

technology 

development 

During the course of 2007 the 

asphalt test methods will be 

revised, and Dave Wright of 

Ninham Shand (Pty) Ltd has been 

appointed to facilitate the process 

between industry and SABS. 

Thereafter we intend to 

standardise the modified binder 

test methods which are currently 

contained in the Asphalt 

Academy’s (AsAc) TG1 document. 

Fortunately the test methods 

specified in SABS specifications for 

penetration bitumen, cutback 

bitumen and 

bitumen emulsions 

are based on 

international test 

methods such as 

ASTM, which are 

regularly reviewed 

and therefore 

up-to-date. 

Best practice 

guidelines 

Over the years 

Sabita has been 

committed to the publication of 

best practice guidelines to keep 

the industry at large informed on 

new developments in bituminous 

product technology, and to 

consolidate best practice. Many of 

these publications are being 

overtaken by new technology, 

products and procedures, and are 

in need of review. This review 

process will include an increased 

focus on the safe handling aspects 

of bituminous products and the 

impact of their usage on the 

environment. 

The medium of technology 

transfer has also evolved from 

hard (printed) to electronic 

format. However, electronic 

40

versions of some of Sabita’s earlier 

manuals do not exist. Sabita has 

recognised this and will be 

updating selected manuals and 

also re-shooting its video testing 

series onto DVD format. These 

efforts have received a further 

boost from CAPSA, 

which has allocated a 

portion of its surplus 

funds towards the 

updating of Sabita 

manuals and audio 

visual aids. Below is a 

summary of the current 

status of the review 

process now underway 

on selected Sabita 

manuals and audio 

visuals: 

Manual 2 – Bituminous 

binders for road 


maintenance: The 

fourth edition of this 

manual is currently under review 

and has been expanded to 

incorporate information on the 

constitution and rheology of 

bitumen. The manual contains 

updated information on 

specifications, testing 

and HSE issues for 

binders. 

Manual 5 – Guidelines 

for the manufacture 

and construction of hot 

mix asphalt: An expert 

group has been 

appointed to review the 

contents of the manual 

with the purpose of 

incorporating the latest 

developments in HMA 

manufacture and 

Manual 2: Bituminous 

binders for road 


maintenance. 

Manual 22: Hot mix 

paving in adverse 

weather 

paving into the second edition. 

Manual 10 – Appropriate 

standards for bituminous 

surfacings: An inception study has 

been done to determine the scope 

of work required to update this 

manual. A proposal is 

being considered to 

finance further research 

into incorporating latest 

developments on 

labour based 

techniques for the 


maintenance of low 

volume roads. 

Manual 16 – Economic 

analysis of short term 

rehabilitation (REACT): 

A decision has been 

taken to finance the 

upgrading of the 

original REACT program 

from a DOS to Windows 

operating system, ultimately for 

incorporation into the revised 

TRH12 which is being funded by 

SANRAL. This software is a vital 

tool for analysing the impact of 

timely pavement maintenance and 

rehabilitation at a 

project level. 

Manual 19 – Technical 

guidelines for the 

specification and design 

of bitumen rubber 

asphalt wearing 

courses: The second 

edition has already 

been reviewed and is 

awaiting finalisation of 

the TG1 specification 

for bitumen rubber 

binders before going to 

print. 

41

Manual 22 – Hot mix paving in 

adverse weather: This manual has 

already been revised and the 

second edition was published in 

August 2006. The first edition has 

been expanded to capture broader 

experiences outside the Western 

Cape and to formulate practical 

recommendations for paving in a 

wide range of conditions applicable 

to the southern African 

environment. 

Manual 23 – Bitumen haulier’s 

code: This manual will be reviewed 

with the intent to develop a 

standard practice for loading 

bitumen at refineries. It will be 

expanded to incorporate, inter 

alia, driver training and vehicle 

requirements to facilitate 

improved safety awareness. This 

initiative will be funded out of the 

dedicated COSHEC budget for 

HSE. 

Manual 26 – Interim guidelines for 

primes and stone precoating 

fluids: This manual serves as a 

guideline to capture best practice 

in the replacement of coal tar 

based products for 

priming bases and 

precoating road 

surfacing stone. This 

new publication was 

distributed in 

November 2006 and its 

purpose is to assist 

road authorities with 

the selection of proven 

alternative products 

and processes. This 

publication was also 

financed out of the 

dedicated COSHEC 

budget for HSE. 

Video series 

Sabita has 15 videos covering the 

testing of penetration bitumen, 

bitumen emulsion, bitumen rubber 

and hot mix asphalt. The plan is to 

begin by filming the penetration, 

cutback and emulsions tests, as 

these are based on international 

test methods, and to film the 

asphalt and modified binder tests 

only once these have been 

reformatted under SANS. 

New manuals 

Sabita's commitment to an 

informed industry is not limited to 

only updating existing publications, 

but also to identify gaps in 

the coverage of best practice and 

to fill these. To this end three new 

manuals have been identified for 

publication in the near future. 

They are: 

Manual 26: Interim 

guidelines for primes 

and stone precoating 

fluids 

Manual 27 – Design and use of 

slurry seals: A request was tabled 

at the November 2006 Road 

Pavements Forum (RPF) for the 

industry to capture best 

practice in the design 

and use of slurry. Some 

information is 

contained in the 

current TRH3 document 

on the design of seals, 

but the intention is to 

remove this information 

from the new TRH3. 

The new document will 

present correct 

techniques and 

procedures for the 

design and application 

of slurry in a wider 

range of applications 

42

from texture treatments to 

overlays, slurry bound Macadams, 

Cape Seals, microsurfacing and rut 

filling. 

Manual 28 –Acceptance criteria for 

the design and use of thin layer 

asphalt (ACTLA): The purpose of 

this manual is to encapsulate the 

findings from research carried out 

on developing protocols for the 

design and quality control of thin 

layer asphalt wearing courses. It 

is aimed at the use of 

thin layer HMA on low 

volume roads such as 

those in residential 

areas, where the 

environmental 

conditions differ from 

those of highways. 

Manual 29 – 

Certification of binder 

distributors: A draft 

guideline, intended to 

replace TRH1 has been compiled 

on the requirements for certifying 

a binder distributor for spraying 

binders to. The publication of this 

manual, replacing TRH 1, will take 

place as soon as the new binder 

calibration system involving the 

outsourcing of the certification 

process to a third party is 

implemented by the provinces. 

Dissemination 

The intention is that all these new 

manuals will be available on the 

Sabita website, www.sabita.co.za 

in PDF format at no cost. Similarly 

the electronic copies of these 

manuals will be placed on CDs for 

distribution at no cost to 

Students' CD 

engineering students at 

universities and universities of 

technology. Hard copies will still 

be printed and sold to cover 

publication costs. 

All these efforts in updating best 

practice publications are aimed at 

partnering with government and 

assisting, where, possible, with 

the transfer of knowledge to new 

entrants into the industry. Our 

efforts are further augmented 

through our 

association with the 

Asphalt Academy 

(AsAc) and the Society 

for Asphalt Technology 

(SAT). Both AsAc and 

SAT are instrumental 

in disseminating 

information through 

seminars and 

workshops. AsAc's 

training courses are 

aimed at educating 

practitioners on the latest 

technology in the blacktop 

industry, while SAT hosts 

workshops where information is 

shared and debated with its 

members on new technological 

developments. 

AsAc also captures best practice 

through the publication of 

manuals, known as Technical 

Guidelines (TG), which have the 

wider input of all stakeholders in 

the roads industry. The RPF Task 

Group on modified binders is 

currently reviewing the technical 

guidelines on The use of modified 

bituminous binders in road 

construction (TG1) and the second 

edition is expected to be published 

in April. 

43

Conclusion 

There is much concern in the 

industry about the lack of 

commitment from Central 

Government for the NDoT to take 

custodianship of updating national 

standards and codes of practice 

for road building materials. Sabita 

is very much committed to 

ensuring that those documents, 

which have an major influence on 

the performance of bituminous 

products, are up to date and 

reflect current best practice. Every 

effort will be made to achieve this 

objective, and we welcome the 

opportunity of partnering with 

road authorities and agencies in 

our endeavours to ensure that our 

technology remains competitive, 

and that we have a well informed 

industry. 

44

South Africa's education system: 

A systemic overhaul is vital to 

sustainable skills acquisition 

Emile Horak 

Professor and Head of Department 

of Civil Engineering 

and Biosystems Engineering 

University of Pretoria 

One of the realisations 

South Africa has 

experienced since 1994 

is that the welcome to the 

international scene had a 

sweet as well as a bitter side. 

The sweet side was the 

obvious miracle of democracy 

and all it brought to all our 

people. The down-side of 

democracy is that it also 

brings international 

competitiveness to your door, 

together with a lot of bitter 

lessons. 

Michael Porter (1990) studied the 

international competitiveness of 

nations, and he found that the 

quality of education, and 

particularly that in science, maths 

and technology, is one of the main 

underlying factors influencing the 

success of a nation in such a 

globally competitive situation. 

Lawless (2005), in her study on 

trends and figures in the civil 

engineering profession in South 

Africa, showed that for both 

medical and all engineering 

professionals in SA, the ratio of 

population to professionals was 

between 2000-2500:1 while for 

first world countries it ranges 

between 100-500:1. This disparity 

in benchmarking with the 

developed world can be further 

verified in Figure 1 (see following 

page), which shows the results of 

a recent study (Fricke et al, 2006) 

of the ratio of persons of the 

24-year old population per country 

qualified in Science and 

Engineering (S&E). 

This clearly shows that South 

Africa is not even the leader in 

Africa, and extremely weak when 

benchmarked against Japan, the 

UK or the Nordic countries. The 

use of 24-year olds also implies a 

longer term impact, as it is 

persons of that age, with the right 

skills and qualifications, who will 

sustain any competitive position 

over the next 10 to 15 years. 

The recent economic growth in SA 

has been spectacular by all 

standards, but the realisation that 

sustainability may become an 

45

Figure 1. International benchmarking of science and engineering populations 

issue has also grown in government 

circles. Government has put 

forward a R372-billion five-year 

public infrastructure investment 

programme to address this 

sustainability problem. This 

investment is seen as key for 

driving higher levels of economic 

growth required to achieve South 

Africa’s broader aim of halving 

poverty and unemployment by 

2014 (Le Roux, 2006). The 

shortage of suitably qualified 

technical people has been 

identified as the most important 

obstacle to the sustainability of 

the government’s economic 

miracle over the longer term, and 

also to the implementation of its 

public infrastructure investment 

plan. 

The Accelerated and Shared 

Growth Initiative for South Africa 

(ASGISA) developed by 

government identified six binding 

constraints which must be 

overcome. “Besides the shortage 

of suitably skilled labour, these 

constraints entail the volatility and 

level of the currency; the cost, 

efficiency and capacity of the 

national logistics system; barriers 

to entry, limits to competition and 

limited new investment 

opportunities; the regulatory 

46

environment and red tape on 

small and medium–sized 

businesses; and deficiencies in 

State organisation, capacity and 

leadership” (Le Roux, 2006). 

The Joint Initiative on Priority 

Skills Acquisition (JIPSA) has 

subsequently been launched to 

counter the skills 

dearth of engineers, 

artisans and other 

technically skilled 

people who will be 

essential in making 

ASGISA work. 

JIPSA was launched 

on March 27 2006 

by Deputy President 

Phumzile 

Mlambo-Ngcuka as 

a multi-stakeholder 

group in which 

government, 

business and labour 

have joined forces 

to fast-track the provision of 

priority skills for accelerated and 

shared growth. 

These include high-level, 

world-class engineering and 

planning skills for core network 

industries, such as transport, 

communications and energy. 

Other critical skills on the list are: 

• city, urban and regional 

planning and engineering 

skills; 

• artisan and technical skills, 

particularly, those needed for 

infrastructure development; 

• management and planning in 

education, health and 

municipalities; 

JIPSA targets call 

for engineering 

graduates to 

increase by 1000 

per year; 

technologists by 

300 per year; and 

artisans by 15 000 

to 20 000 

per year 

• teacher training for 

mathematics, science, 

information and 

communication technology 

(ICT); and 

• language competence in 

public education. (Le Roux, 

2006). 

JIPSA has 

subsequently set 

“rough” targets for 

South Africa’s 

universities and 

universities of 

technology. They 

must increase the 

number of 

engineering 

graduates by a total 

of 1000 graduates 

per year. Secondly, 

the country’s 

universities of 

technology must 

increase the 

number of 

technologists they produce by 300 

a year. Thirdly the number of 

qualifying artisans must be 

increased to between 15 000 and 

20 000 a year. (Le Roux, 2006). 

An amount of R48 million has 

immediately been made available 

to give support to engineering 

faculties to achieve these targets. 

Unfortunately “correcting 

formulas” used in the past 

prevailed in the current funding 

allocation to universities, resulting 

in institutions like the University of 

Stellenbosch receiving nothing 

because their student demographics 

are not satisfactory. This 

tendency to persist with political 

adjustment motives ignores the 

reality of the limited capacities at 

47

these universities, even if they are 

politically corrected, and seems to 

misjudge the problem definition. 

Even though the Deputy President 

has frequently noted that JIPSA 

should not be seen as a “silver 

bullet” it seems that there is some 

confusion with the just in time 

(JIT) concept. There seems to be a 

lack of understanding that such 

targets cannot be set or produced 

without understanding the system 

that must be in place to support 

such outcomes. 

The systemic nature of the defects 

in the education system 

underlying the ambitious targets 

set by JIPSA is 

either ignored, or 

suffers from the 

typical South 

African political 

attitude – which is 

to issue decrees 

and presume the 

problem is thus 

solved. JIPSA 

seems ignorant of 

the bigger picture of 

the current 

aggressive 

international 

competition for the 

same scarce technical skills. With 

the best of nationalistic intentions, 

like the “welcome home 

revolution”, there may not even 

be short term gains of possibly 

attracting some of the “drained 

brains”. There is a systemic 

problem in the education system 

in South Africa which is at the 

bottom of the skills development 

pyramid, and this needs to be 

recognised and addressed before 

There is a systemic 

problem in the 

education system 

in South Africa.... 

which must be 

addressed before 

there will be any 

sustainable skills 

development 

there will be any real sustainable 

skills development. 

This paper will concentrate on the 

systemic problems in the 

education system by unpacking 

experience gained from a 

successful maths and science 

outreach program to 

disadvantaged schools over the 

past 3 to 4 years. It will also show 

that these problems would need to 

be addressed in a systematic 

fashion and that longer term goals 

will have to be set and not just 

short term politically motivated 

social engineering goals. 

Root of the problem 

Applying the Pareto 

principle to the 

factors identified by 

ASGISA, it is 

evident that the 

root of the problem 

is the consistently 

low number of 

learners with maths 

and science at 

school level. This is 

clearly also 

confirmation of the 

factors already 

identified by Porter 

(1990). National 

South African matriculation figures 

show that the number of 

matriculants has steadily declined 

from about 550 000 in 1998 to 

about 450 000 in 2003 as shown 

in Figure 2. Even though this trend 

has bottomed out, the further 

proportional aspects, such as 

those passing with exemption, are 

still disturbingly low. 

Approximately 12% of these 

matric entrants wrote maths on 

48

Figure 2. Matric result trends 

the standard grade while only 4% 

wrote maths on the higher grade. 

The same disturbing trends were 

observed for science matric 

results. The Third International 

Mathematics and Science Study 

(TIMSS) in 1994/1995 and 

TIMSS-R (repeat survey in 1999) 

confirmed that South African 

learners are consistently weak in 

maths and science at the Grade 8 

level, compared with the other 

international participants. (Howie, 

1999 and 2002). A media release 

by the HSRC (December 2004) on 

results of the TIMSS 2003 study 

stated “Comparison with TIMSS 

1999 indicates there was no 

significant difference in 

mathematics and science scores in 

this period”. 

This international benchmarking 

exercise is used even by 

developed countries, like the USA, 

as a strong indicator and tool to 

locate problems in their education 

system (Horak and Fricke, 2002). 

In the case of SA, the consistently 

low performance clearly points to 

systemic problems in the 

education system. Among the 

many factors contributing to the 

low performance of these learners 

is the negative attitude and lack of 

competence of teachers: “On the 

whole, about half of the teachers 

reported feeling ill-prepared to 

teach the content of either 

mathematics or science curricula. 

There appears to be few teachers 

with significant experience and a 

relatively small percentage have 

university level qualifications” 

(Howie, 1999). 

Whilst there are many other 

interventions attempting to 

address these or similar issues, 

many of them tend to be 

49

“quick-fix” solutions, offering 

support rendered to learners 

already in their matric year. These 

interventions cannot bring about 

real sustainable change, and often 

cannot initiate deep change as the 

learners’ foundations are already 

poor or they have already been 

committed to maths and science 

study on the standard grade. In 

addition, although the combined 

affect of numerous intervention 

strategies in education have 

brought about generally improved 

pass and matriculation exemption 

rates, the number of learners 

writing maths in matric has 

decreased, and while the 

percentage of learners passing on 

the Standard Grade has increased, 

this percentage has remained at 

between 4% and 5% for Higher 

Grade learners. 

(Taylor, Muller & 

Vinjevold, 2003, 

12). 

Teacher 

Mentorship 

Programme 

(TMP) 

Anecdotal evidence 

indicates that 

mathematics 

teachers promote 

standard grade mathematics as it 

has a higher pass rate potential 

and higher symbol potential than 

higher grade mathematics. This 

relates to the way in which their 

performance is being measured, 

too. Parents are often also 

ignorant about the longer term 

implications for career choices. 

(Fricke and Horak, 2006). 

The TMP has 

highlighted 

teachers' 

utter confusion 

with the 

Outcomes Based 

Education 

(OBE) system 

The maths and science teachers 

were identified by the University of 

Pretoria as the most cost effective 

area of involvement for the 

engineering industry in improving 

the numbers and quality of maths 

and science learners (Horak, 2003 

and Horak and Fricke, 2004). To 

address the maths and science 

crisis, a pilot project was started in 

2004 in five disadvantaged schools 

concentrating on teacher support 

and capacity building. 

The Teacher Mentorship 

Programme (TMP) involves 

individual mentoring of teachers of 

mathematics and science in grade 

8 to 12, during timetabled free 

periods in school time, by 

experienced mentor teachers on 

the school premises. Such 

interventions are 

designed to take 

place once in every 

7-day cycle for at 

least a 3 year 

period to ensure 

sustainability. 

Working 

conditions 

Research and 

experience have 

shown that short 

courses and 

workshops away from their own 

work environment proliferate, but 

have limited lasting effect as it 

often ignores the reality of the 

teachers’ working conditions and 

the problems they face (Fricke et 

al, 2006). This on-site involvement 

is therefore to ensure 

teachers are empowered to 

address all aspects of their 

50

professional work, within the 

context of their work environment. 

The teacher mentoring in this 

initiative is supported by a 

comprehensive programme, for 

both teachers and learners, of 

exposure to Science, Technology, 

Engineering and Maths (STEM) 

and awareness of careers in the 

STEM industry (Horak and Fricke, 

2004). A particular objective is 

the improved qualifications of the 

matriculants, in the hope that 

many more of them will enter the 

engineering fields. In the rest of 

this paper the observations from 

this TMP intervention will be 

described to illustrate the full 

impact and implication on the total 

system of skills development 

which it must feed into (Fricke et 

al, 2006 and Fricke/Horak, 2006). 

Even though these observations 

may appear to be highlighting 

negative aspects, it is designed to 

confirm the systemic nature of the 

problem and many of the 

problems have seen improvement 

in the last twenty months. 

In general, the experiences with 

teachers during the first year of 

TMP implementation has 

highlighted their (Howie, 2002), 

utter confusion with the outcomes 

based education (OBE) 

methodology introduced in recent 

years, and general incompetence 

in the various forms of 

assessment. 

Qualifications 

Consider the qualifications of the 

teachers at five TMP secondary 

schools 2004 as shown in Table 1: 

Total number of 

teachers 

Qualified to teach at 

primary school level 

Qualified to teach at 

secondary school level 

50 16 34 

Table 1: Teacher qualifications 

The TMP project has been running 

for 22 months in five schools, and 

there are many positive indicators 

of progress. However, the 

following observations, made at 

the start of TMP interaction with 

the schools, indicate that there are 

systemic problems in the schools 

which impact on the maths and 

science achievements of learners. 

Some of these comments are 

based on personal observations, 

but external audits done by 

education experts were also used 

to provide a more objective view. 

However, this number of teachers 

at the secondary school level must 

be looked at in more detail. 

Experience and observation 

(Howie, 2002) has shown that 

these teachers are NOT qualified 

for the post they are in, and this is 

partly because: 

• Many are not teaching the 

subject for which they 

obtained their qualifications; 

• Most received diplomas at 

teaching colleges which were 

51

phased out subsequent to the 

change of government in 

1994, and in many cases the 

quality or standard of the 

diplomas is questionable; 

• Some of the teachers last 

studied the subject that they 

are teaching during their own 

school years. 

These have the following 

consequences: 

• Lack of subject content 

knowledge and confidence 

leading to incorrect teaching; 

• Lack of appreciation of the 

need for sequencing of 

teaching content, leading to a 

lack of structure and 

planning; 

• An inability to explore 

concepts with learners, as the 

teachers do not understand 

the concepts themselves. 

Teachers’ skills 

In the recent analysis of nationwide 

surveys amongst learners in 

the Numbers and Needs study by 

Lawless (2005), it was found that 

learners reported that they are 

being taught by: 

• Under-qualified teachers; 

• Teachers who do not 

complete the syllabus; 

• Teachers who cannot give 

adequate explanations; 

• Teachers who do not mark or 

check their work. 

A deeper analysis of these aspects 

at the TMP schools confirms the 

following points: 

• Syllabus completion/ 

teaching pace: No proper 

planning takes place, hence 

the teaching pace is often far 

too slow, leading to syllabi 

not being completed. In an 

anonymous questionnaire, 

32% teachers said that they 

would bring the learners in 

during the holidays to 

complete the syllabus, rather 

than pace themselves to 

complete it during term time; 

• Focus on seniors: Many 

teachers do not see the 

importance of getting the 

younger learners to finish the 

syllabus to provide the 

knowledge base for the 

future; 

• Minimal use of teaching 

time: An estimate based on 

on-site observations by the 

mentors show that learners 

receive only about 35% of 

the allocated period time; 

• Teaching style: Teachers 

are not generally interactive 

with learners, nor 

stimulating, possibly because 

they have no confidence with 

the material. Teacher talk 

dominates most of the 

classroom time; 

• Homework: Teachers do not 

give enough homework and 

are unable to enforce it being 

done; 

• Science laboratory 

practicals: most teachers 

have never done laboratory 

work themselves, either at 

school or at college, and 

therefore they do not conduct 

experiments at school. 

52

Assessing 

Teachers are often unclear on how 

to assess and cannot differentiate 

between different types of 

assessment. As a result of poor 

English proficiency, they struggle 

in setting assessments in which 

learners understand what they are 

required to do. Their 

administration of assessments is 

also poor, often not adhering to 

specific departmental criteria. 

Exam papers are generally poorly 

balanced, with repetition and poor 

mark allocation. They do not cover 

the correct material and questions 

are not of the correct standard. 

Teachers are not capable of 

moderating each other’s papers. 

Heads of Department are not able 

to judge the standard of others’ 

papers, as they often do not know 

the syllabus. 

Knowledge transfer 

problems 

Other factors affecting knowledge 

transfer include: 

• Class discipline: is not a 

problem, but many learners 

are not punctual; 

• Learners’ work discipline: 

Teachers feel they are 

powerless with learners, 

therefore seldom discipline 

them or enforce work; 

• Invigilation: There is little 

teacher control during the 

exams. 

• Organisation and Resources: 

General organisation and 

control of textbooks and 

resources is exceptionally 

poor (teachers and 

management alike); 

• Use of media: Many teachers 

do not know how to utilise 

the media resources, if the 

schools have them; 

• Utilisation of laboratories: 

Very few educators conduct 

experiments during the term; 

they either cannot perform 

them, or a suitable 

laboratory is not available; 

• Computer facilities: Some of 

the schools actually have 

computer rooms, but they 

are generally unused. 

Support and operational 

issues are often overlooked 

when donors open these 

facilities. 

Teachers were asked to evaluate 

themselves on six items, and 

these were compared with the 

mentors’ evaluations of them. Of a 

total of 174 items, teachers 

evaluated their abilities as higher 

than the mentors’ evaluations on 

93 counts, and this self-rating was 

frequently two points (on a 5-point 

scale) higher than that of the 

mentors. The indication here is 

that the teachers have a poor 

frame of reference by which they 

judge themselves and their own 

teaching practise. 

Attitudes 

• Teachers show no sense of 

urgency dictating their 

general approach to 

teaching: they showed 

enormous time wastage in 

terms of actual teaching time 

(teachers miss periods to 

smoke, mark during periods, 

are slow in getting going, and 

53

generally mismanage the 

period time; they take far 

more leave than allowed and 

there are no effective 

controls); 

• Teachers often do not 

indicate a passion or concern 

for the learners, or a feeling 

of responsibility for the 

learners’ success or failure, 

but are functional in their 

tasks; 

• Teachers generally have a 

poor work ethic during the 

term (they do not have the 

will or inclination to work 

hard); yet they may go to 

school in the 

holidays to 

give classes in 

an attempt to 

complete the 

syllabus. They 

show little 

willingness to 

undertake 

extra-mural 

activities to 

broaden the 

learners’ 

experience, 

e.g. participate 

in expos, 

science fairs 

and competitions. 

• Teachers have a desire for 

material or information, but 

do not bother to seek it out. 

• Many teachers hide behind 

other issues to explain poor 

results, e.g. timetable 

problems and lack of 

resources. 

Department heads 

The heads of department of maths 

and science are frequently biology 

Heads of 

department .... 

feel they do 

not have 

authority over 

staff, and that 

they are 

powerless to 

control teachers 

teachers, who struggle to give 

didactic support to the teachers, 

and are often not particularly 

interested in the maths and 

science departments. They 

frequently feel that they do not 

have authority over staff, and feel 

powerless; therefore they do not 

monitor or control teachers and 

their progress. 

Very few subject meetings were 

held, and there was little 

collaboration between teachers. 

There is often only one teacher 

per grade level, which allows that 

teacher to lag behind and not 

complete the 

syllabus as there is 

no monitoring or 

observation taking 

place. 

Learners and 

school 

experience 

• Higher Grade 

and Standard 

Grade issues: All 

learners are 

taught on the 

Standard Grade 

(SG) throughout school. 

Recently the TMP schools 

have started (misguidedly) 

allowing some learners to 

study maths and/or science 

on the Higher Grade (HG) in 

grade 12 (approximately 10 

to 15% of matriculants), 

even though the subject has 

only been taught on the SG 

in previous years. However, 

the few HG students are not 

taught HG work in class (due 

to the fact that there may be 

54

3 HG learners in a class of 40 

SG). Instead, they receive 

tuition in the afternoons once 

a week, or self-study. 

• Homework: Learners receive 

very little homework and 

therefore get little 

opportunity to reinforce work 

done in class. Even so, 

learners make little attempt 

to do their homework; 

• Exams: Learners are not 

given their exam timetables 

in good time for planning, so 

they are unable to set up a 

study programme/timetable; 

matrics stay at home after 

prelims, and few return for 

revision; 

• School situation: Class sizes 

range from 40 to 70 per 

class, often exceeding the 

classroom capacity; there are 

no functional libraries, and 

laboratories are inadequate 

or not used for science. 

Resources and discipline 

Textbooks, desperately needed by 

teachers, are generally in very 

short supply, and often not 

brought to school by learners. 

Most learners do not have 

calculators and mathematics 

construction sets, making it very 

difficult to teach the syllabus 

sections requiring these. 

Science and maths learners in 

particular do not see the relevance 

of science and maths in their lives, 

and are therefore unmotivated. 

Many learners do not go to class, 

or are late for class; most do not 

do their homework, and teachers 

feel powerless to deal with any 

indiscipline. 

Learners in general are not 

prepared in any way for school 

and what it means, and such 

negative issues with the learners 

also contribute to the lack of 

Figure 3. Impact of English proficiency on learner performance in maths 

(Lawless, 2005) 

55

enthusiasm and commitment on 

the part of the teachers. 

Language Issues 

obviously have an impact on their 

maths and science performance, 

since they are required to write all 

assessments in English. 

A dominant problem at the schools 

is the issue of language (Howie, 

2002). Lawless (2005) also 

surveyed this issue on a national 

scale and showed very clearly that 

there is a definite relation between 

English proficiency, as measured 

in grade 12 symbols, and maths 

symbols. This is shown in Figure 3 

where learner matric performance 

is expressed in terms of their 

matric symbol in English as first 

language as well as second 

language. 

It was found that 

none of the 

teachers nor any 

or the learners at 

the TMP schools 

had English as 

their first 

language, and yet 

the language of 

instruction and 

assessment is 

English. In fact, 

Grade 

in many cases the teachers’ 

English is so poor that they teach 

in the vernacular, further 

decreasing the learners’ chance of 

mastering the language. The 

written tasks set by the teachers 

are, in addition, frequently so 

poorly set out and explained that 

the learners do not understand 

what is required of them. 

Informal research was undertaken 

to assess the extent of the 

language problem, using sample 

groups of learners. Their English 

proficiency levels were tested, as 

this language proficiency will 

As a benchmark or reference for 

the English proficiency test results 

at the TMP schools, their results 

were compared with those of 

similar sample groups of learners 

at two other Tshwane schools 

(both government co-educational 

schools): 

• An English-medium school 

where most of the learners 

speak English as their home 

language, and write exams in 

Benchmark schools 

B1 (English) 

B2 (Mother 

language) 

TMP schools 

Grade averages 

8 39 38.5 21.5 

9 48 37 22 

10 62 43 24 

11 58 46 24 

Table 2: English Proficiency test results (all marks are 

percentages) 

English (B1 in the table 

below); 

• A school where most of the 

learners speak English as 

their second language but 

write exams in their home 

language (B2 in the table 

below). 

TMP schools are discussed as a 

group as they show consistent 

results. In all of these schools the 

learners speak English as a 

second, third or fourth language, 

but they must do all their learning 

and assessment in English. 

56

The following observations may be 

made: 

• Based on the norms expected 

per grade, no learner in the 

test samples at any of the 

TMP schools has an English 

language proficiency even 

equal to that of a grade 7 

learner; 

• While the benchmark schools 

show a trend indicating an 

increase in marks as the 

learner progresses through 

the school to higher grades, 

this is not seen at the TMP 

schools, despite the fact that 

all learners attend English 

lessons daily. 

Learners’ 

achievements in 

maths and science 

assessment will 

certainly be 

negatively affected 

as their 

understanding of 

their questions will 

be very poor, and 

they will not be able 

to express their 

answers in English. 

Although the impact 

on their maths and 

science assessment marks cannot 

be quantified, it could be assumed 

that these marks would, as a 

consequence, be at least a symbol 

lower than the mark that would be 

a realistic evaluation of their 

actual maths and science 

knowledge. 

School management 

issues 

The following observations were 

made regarding the school 

Learners do 

not see 

opportunity for 

themselves 

to work in 

the fields of 

mathematics 

and science 

management as it impacts on the 

maths and science outreach 

efficiency of TMP. It is 

acknowledged that it may be 

tainted with subjective opinion, 

but other audits confirm these 

observations (Fricke et al, 2006) 

• Principals do not use their 

authority to insist on certain 

teaching practices, do not 

monitor individuals or 

departments, and do not 

have overall school control; 

• Lack of system and 

organisation at every level 

affects teaching across the 

board, e.g. compiling 

timetables, poor timing of 

periods and inadequate 

teacher 

management; 

• Climate of 

learning: The 

school 

atmosphere is 

not a formal 

learning one. 

There are regular 

social days 

(spring day, 

beauty pageants) 

in which teachers 

do not teach so 

many learners do 

not attend school; 

• Shortage of funds: As a result 

of funding shortages learners 

do not receive nearly 

sufficient photocopied 

material, there is sometimes 

no electricity, and learners 

cannot be sent on excursions. 

This is partly due to parents’ 

non-payment of school fees. 

• Inadequate vocational 

guidance: teachers are 

unable to motivate and 

inform the learners. Most of 

57

these township schools do 

not receive the attention of 

representatives from the 

tertiary institutions because 

the latter prioritise those 

schools which are more 

successful; as a result 

learners most in need of 

motivation do not receive 

such incentives. 

STEM exposure 

(a) Learners: Learners in general 

have no goals for the future, and 

particularly do not see opportunity 

for themselves to work in the 

fields of maths and science. They 

have received little exposure to 

Science, 

Technology, 

Engineering and 

Mathematics (STEM) 

and are unaware of 

careers that might 

be open to them in 

these fields. They 

also tend to think of 

these vocations as 

unattainable for 

black children of 

poor financial 

means. 

(b) Teachers: Teachers do not 

know what is involved in the 

various careers, and therefore 

cannot advise their learners. With 

the change in curriculum (FET in 

2006) teachers do not know how 

to advise learners in terms of 

subject choice e.g. whether to 

study maths or maths literacy. 

Conclusion 

There are therefore several factors 

that must be addressed 

It is unproductive 

to concentrate 

on the output side 

while ignoring 

the larger 

problem on the 

input side 

simultaneously while mentoring 

the teachers in an education 

support programme at schools. 

It is of little worth to improve a 

teacher’s skills if that teacher 

faces learners who are negative, 

bored or unmotivated, and do not 

see the value of the subject that 

the teacher is trying to teach. 

Thus it is important to cover all 

teacher aspects, as well as trying 

to assist with improving general 

school problems, and supporting 

the learners academically and in 

terms of their motivation. 

Social engineering projects, such 

as JIPSA, also function within a 

system. Therefore 

one cannot only 

concentrate on the 

output side and 

ignore the larger 

problem on the 

input side. It seems 

that the current 

JIPSA 

implementation is 

suffering from a 

naïve short term 

vision and lack of 

appreciation of 

system functionality. 

There seem to be clear indications 

that short term targets tend to be 

set in isolation, with political intent, 

ignoring the realities of the bigger 

picture. The result is that the JIT 

principle is applied without 

understanding that scarce technical 

skills depend on the availability of 

very basic maths and science skills 

at school level. This paper has 

shown that the education system is 

terminally flawed and in need of a 

systemic overhaul. A well 

58

documented successful maths and 

science outreach programme used 

to unpack the underlying systemic 

problems clearly shows that no 

amount of tinkering with the 

existing system will ever produce 

the desired results, and no 

treatment of symptoms will help. 

What is needed is an appreciation 

of the underlying problems in the 

total education system which will 

take more than politically 

expedient statements and decrees 

to be effective. The final conclusion 

therefore is that the JIPSA initiative 

is therefore not just in time, but 

just out of time! 

 

References 

I. Fricke, E. Horak, L. Meyer and N. van 

Lingen (2006): Lessons from a 

mathematics and science intervention 

programme in Tshwane township schools. 

Centre for Research on Engineering 

Education (CREE) Conference. September 

2006, University of Pretoria, Pretoria, 

South Africa. 

I. Fricke, E. Horak (2006): Observations 

from an intervention programme in 

secondary township schools in the Tshwane 

area to address the maths and science 

crisis. Paper submitted for publication to 

the South African Journal of Higher 

Education (SAJHE). Pretoria, South Africa. 

E. Horak (2003): Developing the small 

school pool for engineering in South Africa. 

Proceedings of the 7 th Baltic Region 

Seminar on Engineering Education, UICEE 

series with UNESCO support, St 

Petersburg, Russia, September 2003. 

I. Fricke, E. Horak (2004): Building 

Capacity by mentoring Mathematics and 

Science Teachers. Paper accepted and 

presented at the 7 th Conference on Asphalt 

Pavements for Southern Africa, 2004, Sun 

City, South Africa. 

S. Howie (1999): Report on Science and 

Technology Centres in South Africa. Human 

Sciences Research Council. Pretoria 1999. 

S. Howie (2002): English proficiency and 

contextual factors influencing mathematics 

achievement of secondary school pupils in 

South Africa. PhD Thesis, University of 

Twente, Netherland, 2002. 

A. Lawless (2005): Numbers & Needs: 

Addressing imbalances in the civil 

engineering profession. South African 

Institution of Civil Engineering, September 

2005. 

H. Le Roux (2006): Brain gain. 

Engineering News, 15-21 September 2006. 

M. Mangena (2004): Speech presented at 

CSIR Conference Centre. Minister of 

Science and Technology, CSIR Conference 

Centre, April 2004. 

National Strategy for Mathematics, 

Science and Technology Education 

(2004): Creating Tomorrow’s Stars Today. 

Implementation Plan 2005 – 2009, 

Department of Education Document, 2004 

M. Porter (1990): The competitive 

advantage of nations. Macmillan Press, 

1990, New York, United States Of America. 

Sunday Times Newspaper, 2 January 2005. 

N. Taylor, J. Muller and P. Vinjevold 

(2003): Getting Schools Working. 

Research and Systemic School Reform in 

South Africa. Pearson Education, South 

Africa. 

HSRC Media release, Internet, 

www.hsrc.ac.za/media/2004/12/20041214 

59

Sabita's Local Councillor Programme: 

Improving service delivery 

through appropriate road 

maintenance 

Mike Winfield 

Director 

Zebra Bituminous Surfacings cc 

From 1997 to 1998 Sabita 

ran an extremely 

successful empowerment 

programme for municipalities 

known as the Local Councillor 

Empowerment Programme 

(LCEP). The objective of this 

initiative was to expose newly 

elected councillors to the 

importance of roads 

for improving 

service delivery, and 

their role in the 

management and 

implementation of 

road provision. 

Over a two-year period 

close to 100 

workshops were 

conducted in the 

KwaZulu-Natal, 

Western Cape and 

Gauteng provinces, 

with just over 1000 

councillors and officials 

participating. 

These workshops, 

conducted shortly after 

the elections of 1994, 

Sabita’s LCEP booklet 

on the need to 

maintain roads 

provided the first opportunity for 

many of the local councillors to be 

involved in the decision making 

process associated with the 

allocation of budgets and the 

management of infrastructure 

within a local authority. Much of 

the success of the workshops was 

the result of the skilled facilitation 

provided by Sabita 

members, and the 

emphasis on the 

importance of roads in 

service delivery. 

Members in turn were 

also sensitised to the 

needs of the 

communities in which 

they operated, enabling 

them to optimise their 

spectrum of services 

and products 

accordingly. 

Public awareness 

campaign 

In 2002 the format for 

the LCEP was changed 

from that of facilitation 

based workshops to a 

61

public awareness programme to 

illustrate the benefits of good 

roads to the social and economic 

development of previously 

disadvantaged communities. The 

programme included bus tours to 

the townships of Soweto in 

Johannesburg and Khayelitsha in 

Cape Town for councillors, officials 

and media personnel, who were 

able to view at first hand the 

effects of roads on the social and 

economic development of those 

areas. 

These tours clearly illustrated to 

all participants the 

benefits that accrue 

to the community 

from a good road 

infrastructure in 

comparison to areas 

where there was a 

lack of good roads. 

In a report back 

session, 85% of 

councillors 

recognised the need 

for road 

maintenance 

expenditure to 

receive a higher 

priority than direct 

social spending e.g. 

housing and 

schools. With the new 

understanding that roads should 

be seen as the “arteries of a 

nation”, the councillors rated 42% 

of our roads as being “in a poor 

condition”. It became clear that 

the fundamental message of how 

a well maintained road 

infrastructure impacts positively 

on our society was clearly gaining 

acceptance. 

85% of councillors 

recognised 

the need for 

road maintenance 

expenditure 

to receive a 

higher priority 

than direct 

social 

spending 

Improved in service 

delivery 

South Africa has recently entered 

the third election period for local 

councillors since the 

democratisation of South Africa. 

While the role of the councillors 

has not changed, Sabita 

recognised that there was a 

pressing need to improve the 

communication process between 

councillors and appointed officials 

if the backlog in maintaining our 

ageing road infrastructure was to 

be adequately tackled. This 

understanding has 

been highlighted by 

the reduction in 

focus and spending 

on routine road 

maintenance in 

many local 

authorities. 

With this in mind 

Sabita proposes to 

run a revised series 

of seminars under 

the banner, 

“Improving service 

delivery through 

appropriate road 

maintenance”. It is 

intended that a broader cross 

section of appointed officials and 

elected councillors will be 

represented at these seminars, 

including staff from the financial 

and the technical departments. 

It is important therefore that these 

seminars should not be highly 

technical, but should focus on the 

importance of asset preservation. 

This approach augments and 

supports government’s growth 

62

strategies as promulgated by the 

ASGISA objectives. 

The proposed seminar will focus 

on three main areas: 

• The requirements of the 

Municipal Finance 

Management Act (MFMA), 

which requires that local 

authorities report annually on 

their fixed assets including 

roads. These reports are 

required to indicate the level 

of depreciation or 

appreciation of these assets; 

• The second focus area is to 

highlight the actual status of 

the road network in the 

region where the workshop is 

being conducted; 

• The third focus area will give 

a brief overview of best 

practice and solutions to 

ensure a well-maintained 

municipal road network. 

The seminars will conclude with a 

panel discussion in which 

delegates may express their views 

and chart a way forward. 

The first seminar is scheduled to 

be held in the Western Cape on 15 

March 2007. Based on the 

experience gained at this seminar, 

further seminars will be hosted in 

other regions. Sabita has 

commissioned a public relations 

company to assist with the 

marketing of these seminars to 

maximise the attendance of the 

local councillors and to ensure that 

they are not intimidated by the 

technical aspects of the seminars. 

SALGA Endorsement 

Sabita is also seeking the 

endorsement of the seminars by 

South African Local Government 

Association (SALGA) to help in 

motivating the hosting of seminars 

in other provinces. 

To build on one of the key success 

factors in the implementation of 

the previous LCEP, the intention is 

to optimise the involvement of 

Sabita members. Sabita members 

operating in an area where 

seminars are to be conducted will 

be invited to set up small 

exhibition stands or display their 

equipment. This strategy will 

provide Sabita members with an 

opportunity to display their 

particular areas of service in the 

urban road maintenance arena, 

and to interact with municipal 

officials and councillors in an 

environment of learning and 

empowerment. 

To reduce the time in preparing 

for the successive seminars, it is 

intended that the contents of each 

presentation be packaged in a way 

that ensures ease of 

communication. Sabita has 

prepared an informative 

non-technical hand out on the 

importance of maintaining a 

surfaced road network that may 

be used as reference material by 

the delegates. 

Any organisation or person 

wishing to conduct a seminar in 

their region should telephone 

Trevor Distin at 021-531 2718, or 

make contact by email through 

info@sabita.co.za. 

63

Surge in SAT's knowledge transfer activities: 

2006 activities generate a new 

vision of member service 

John Onraët 

President 

Society for Asphalt Technology 

While the asphalt 

industry benefitted 

from the strong 

growth in the construction 

economy in 2006, SAT’s 

leadership is committed to 

ensuring that the same growth 

impacts positively on the 

Society in new and innovative 

ways. But firstly let us reflect a 

while on the past year, during 

which some really good things 

happened. 

As a Society for individuals, it is 

incumbent on all regional officers 

to ensure that there is adequate 

delivery to members in their 

areas. This has not really been to 

our satisfaction in the past, and 

there is now strong motivation and 

intent to turn this around. 

I am pleased to report that the 

regions, under the chairmanship of 

Basil Jonsson (Central), Craig 

Bradley (Eastern) and Graeme 

McGregor (Southern), experienced 

a surge in activity during 2006, 

and their good work deserves the 

proper recognition. 

Some examples are: 

• The Eastern, Southern and 

Central regions all convened 

well attended workshops on 

the latest European trends in 

warm asphalt technology; 

• All regions took part in the 

Sabita road show arranged to 

highlight industry efforts to 

phase out the use of coal tar 

products; 

Craig Bradley, 

Chairman, Eastern 

Region 

Basil Jonsson, 

Chairman, Central 

Region 

Graeme McGregor, 

Chairman, Southern 

Region 

64

• The Eastern Region held a 

highly successful seminar on 

the interpretation of asphalt 

test results, as well as the 

use of the Bailey Method as a 

means of determining 

behavioral aspects of 

aggregate as part of an HMA 

design. Another seminar was 

held in this region to discuss 

the pros and cons of asphalt 

reinforcement; 

• The Southern and Eastern 

regions held 

technology 

exchange 

feed-back 

sessions where 

various 

delegates to 

the ICAP 

conference in 

Canada shared 

their new 

knowledge and 

experiences; 

• The Southern 

and Central 

regions held 

successful, 

well attended 

workshops on 

the current status of Ultra 

Thin Friction Courses. 

Although individuals from the 

client body sector (both members 

and non-members) do often 

attend SAT functions, we would 

like to see attendance numbers 

increase in future. SAT provides 

excellent networking opportunities 

and is an ideal discussion forum 

for all individual role players in the 

industry. The council will 

proactively be encouraging local 

authorities to support their staff in 

attending future meetings. 

Our aim is to 

develop and 

enhance our status 

as a Learned 

Society and to 

position SAT 

locally and 

internationally 

as a reputable 

organisation 

It is pleasing to note the improved 

attendance at seminars in the 

Central Region, which recorded 

the highest number of delegates. 

While the asphalt industry in KZN 

is simmering down somewhat 

compared with the rest of the 

country, it is encouraging to note 

the ever-increasing number of 

emerging consultants and 

contractors who are attending SAT 

seminars. This will now become a 

key focus area of 

SAT and all 

practitioners 

involved with the 

emerging contractor 

and consultant 

market are urged to 

encourage them to 

attend seminars 

and eventually join 

as members of the 

Society. 

Most importantly, I 

can proudly 

announce that SAT 

is now financially 

secure and healthy, 

and our financial 

woes are thankfully a thing of the 

past, due mainly to concerted 

efforts by the Council (more 

especially the regional 

chairpersons). 

However, this does not entitle us 

to relax or to rest on our laurels. 

We now have the opportunity to 

grow the Society and improve on 

our current success. 

Our aim is to develop and enhance 

our status as a Learned Society 

and to position SAT locally and 

internationally as a reputable 

65

organisation. With the 

improvement in our financial 

situation, the Council is now in a 

stronger position than ever to 

deliver improved services to our 

members. 

Priority will be given to the 

following issues in the year to 

come, although the list is not 

exhaustive: 

• There will be further rationalisation 

and streamlining of 

our accounting and 

administration functions; 

• There will be a concerted 

drive to enhance the delivery 

of technology exchange 

amongst our members, with 

improved quality of seminars 

and workshops, and more 

connectivity with overseas 

specialists; 

• In the process of streamlining 

of our administration, a 

members’ newsletter will be 

produced; 

• SAT will have an opportunity 

to heighten our profile at 

both CAPSA 2007 and at the 

Road Pavements Forum; 

• Closer ties and cooperation 

with other important industry 

bodies, such as Sabita, AsAc, 

ASPASA, SAFCEC, IMESA, is 

seen as a priority; 

• There will be continuous 

improvement of our website, 

and members will have the 

opportunity to coerce their 

employers to advertise or 

sponsor pages; 

• We will keep members 

abreast of industry 

occurrences overseas, 

reporting back as they occur; 

• We will maintain a positive 

state of our financial health 

to create and deliver value 

to our members; 

• The allocation of CPD points 

is under investigation and will 

be available to members; 

• Regional chairpersons will be 

encouraged to find new 

members. 

In closing I would like to thank all 

Council members who have put in 

“sweat equity” into ensuring the 

continuation of the Society. I know 

it is all voluntary and may this 

positive spirit continue. 

66

AsAc activities focus on CPD: 

Flexible pavement engineering 

course to cater for industry 

needs 

Les Sampson 

CEO 

The Asphalt Academy Trust 

After six years of 

operations during which 

more than 3 750 

delegates attended 98 

educational events organised 

by AsAc, the academy is now 

poised to make a major 

contribution to continuing 

professional development 

(CPD) and personal growth 

through the presentation of a 

comprehensive course on 

Flexible Pavement Engineering 

The first course is scheduled for 

presentation from March 2007 to 

May 2008 in Pretoria, in 

association with the Continued 

Education Section of the University 

of Pretoria. 

The development of this course is 

an exciting new initiative 

instigated during the 2005/06 in 

response to an industry needs 

survey undertaken by the CSIR on 

behalf of the Asphalt Academy. 

The survey reported that road 

authorities, consulting engineers 

and other practitioners had raised 

concerns about the lack of 

pavement engineering knowledge 

displayed by recently graduated 

civil engineers, technicians and 

technologists. In the past, this 

shortcoming has forced employers 

to deploy significant resources 

over several years to ensure that 

young engineers had the 

necessary know-how to carry out 

their duties effectively. 

There were several motivating 

factors for the development and 

presentation of such a course. 

Although various institutions offer 

similar courses either on demand 

or as part of a continuing 

education programme, most of 

these are infrequently available, 

and often have insufficient 

practical content. 

Various tertiary institutions offer 

semester block courses on 

Transportation Engineering or 

Urban Engineering either as a part 

of a postgraduate qualification, or 

simply for individuals to gain 

further information. However, 

actual lecture time is relatively 

limited, requiring that a large 

amount of the learning be 

67

accomplished through self-study. 

The consequence is that several 

years pass before a newly 

graduated engineer has sufficient 

knowledge to fully contribute to 

his/her firm’s workload. 

In response to the industry needs, 

the extensive and flexible 

curriculum is structured into seven 

modules involving 11 weeks of 

classroom study over a 14 month 

period, supplemented by project 

work in the learner’s home office. 

Participants who 

successfully 

complete the course 

will gain credits 

towards a 

postgraduate 

qualification where 

required. Credits 

towards 

professional 

registration are also 

being discussed 

with the relevant 

authorities. 

An integral part of the course 

structure is to guide the learner 

through the inception, design and 

construction of both a new road 

and a rehabilitation project. The 

project assignments will be 

consistent to all the modules, with 

written and oral submissions to 

encourage the students to apply 

the theoretical knowledge gained 

through lectures to actual 

projects. At the end of the course, 

students will be required to submit 

a final oral project report 

supplemented by an extensive 

project file for assessment. 

Participants who 

successfully 

complete the 

course will 

gain credits 

towards a 

postgraduate 

qualification 

Other ad hoc initiatives 

undertaken during recent years in 

response to industry needs have 

been the presentation of the 

Quality Management of Bitumen 

course in 2005, which will 

hopefully be repeated on request 

during 2007/08, and Achieving 

Volumetrics and Compactability 

using the Bailey Method during 

November 2006. An international 

lecture and workshop on 

Acceptance Control and Quality 

Assurance of HMA is also 

scheduled for 

February 2007. 

In addition, the 

following regular 

courses will still be 

offered on a 

regional basis: 

• Introduction to 

bituminous 

products; 

• Application and 

construction of 

surfacing seals; 

• Design of surfacing seals; 

• Manufacture, application and 

construction of hot mix 

asphalt; 

• Design of hot mix asphalt 

(including the application of 

the Bailey Method; 

• Compaction of hot mix 

asphalt (in conjunction with 

SARF). 

To ensure that best practice 

manuals currently published by 

AsAc are relevant to current 

technology, TG1 – The Use of 

Modified Bituminous Binders in 

Road Construction is being 

upgraded and revised by an 

industry task group for distribution 

68

in the first half of 2007. TG2 – The 

Design and Use of Foamed 

Bitumen Treated Materials will be 

replaced in 2008 by a Bitumen 

Stabilisation manual incorporating 

foamed bitumen and emulsion 

treatment of materials. This 

document will be finalised on 

completion of the research 

currently being sponsored by 

Sabita and the Gauteng 

Department of Public Transport, 

Roads and Works. 

The full AsAc course schedule for 

2007/08, including detailed 

information on the courses, dates, 

regional location and costs, is 

available on the AsAc website at 

http://asphaltacademy.co.za. The 

website also offers an on-line 

registration facility. 

 

69

4 

Innovation

A viable alternative to natural aggregates: 

The use of steel slag aggregate 

in asphalt mixes 

Hugh Thompson 

Director 

WSP SA Civil and 

Structural Engineers 

(Pty) Ltd 

Michael Bouwmeester 

Associate 

WSP SA Civil and Structural 

Engineers (Pty) Ltd 

Far from being a waste 

product of the steel 

production process, steel 

slag is a high quality resource 

for use as an aggregate in road 

construction, and as such it 

should be seriously considered 

as a viable alternative 

aggregate in hot mix asphalt. 

Due to the changes in traffic 

loading spectra and higher road 

surface temperatures being 

experienced in South Africa, 

numerous investigations have 

been undertaken to assess the 

properties of asphalt mixes to 

improve durability, and resistance 

to fatigue fracture and 

deformation. One such 

investigation examines the use of 

steel slag as an aggregate in 

asphalt mixtures. 

As a result of increasing focus on 

the environmental requirements 

for the acceptable disposal of 

waste slag, as well the 

considerable strain on the already 

limited number of aggregate 

resources, steel slag is being 

increasingly considered as an 

alternative to natural aggregates 

in the road construction industry. 

Slag production 

Steel slag is produced during the 

separation of molten steel from 

impurities in steel-making 

furnaces, and is composed of 

calcium silicates together with 

oxides and compounds of iron, 

manganese, alumina and other 

trace elements. 

Free lime and magnesium oxides 

that have not reacted with the 

silicate structures can hydrate and 

expand in humid environments, 

which is precisely what happens 

with steel. Consequently, slag 

aggregates exhibit a tendency to 

expand. Volume changes of up to 

10% or more, attributable to the 

hydration of calcium and 

magnesium oxides, can cause 

difficulties. 

For this reason it is important that 

further weathering of the steel 

slag takes place to cause the free 

calcium oxide to hydrate. If the 

73

calcium oxide is not fully hydrated, 

the presence of water can cause 

hydration and the further breaking 

down of the aggregate. In a steel 

slag asphalt mix this is characterised 

by isolated white deposits of 

calcium carbonate, which is 

formed by the hydration and 

carbonation of free lime close to or 

at the surface of the aggregate. 

Consequently steel slag destined 

for use as an asphalt aggregate 

should be stockpiled outdoors for 

up to 18 months to expose the 

material to moisture, either from 

natural precipitation or the 

deliberate application of water, to 

ensure that potentially destructive 

hydration and its associated 

expansion takes place prior to its 

use as an aggregate in asphalt. 

The properties that have to be 

evaluated for the suitability of slag 

as an aggregate relate to the 

chemical, physical and mechanical 

nature of the material. Table 1 

gives indications of the typical 

properties of steel slag, dolerite 

and quartzite. 

Physical properties 

The unique properties of steel slag 

improve the performance 

characteristics of asphalt materials 

in a number of ways. These are 

discussed below. 

Density: Particle density of the 

steel slag aggregate compared to 

the dolerite and quartzite 

aggregates in Table 1 indicate that 

steel slag is a more dense and, 

hence, heavier material. The 

disadvantageous financial effect of 

this higher tonnage demand has to 

be offset by the price of steel slag 

aggregate compared to 

conventional aggregates to render 

mixes using steel slag 

economically viable. 

Property 

Steel slag 

13.2mm 

Steel slag 

9.5mm 

Steel slag 

-3.0mm 

Dolerite 

13.2mm 

Quartzite 

Free lime (%) 2.36 2.36 2.36 N/A N/A 

pH 12.8 13.1 13.1 8 5 

Particle density 

(kg/l) 3.239 3.188 3.319 3.069 2.7 

Water absorption 1.1 2.1 2.4 0.7 0.3 

Flakiness index 3.9 7.7 - 20 23 

Ten Percent Fines 

Value 

Wet 

Dry 

Aggregate 

crushing value 

Wet 

Dry 

Polished stone 

value 

460 

490 

7.3 

- 

460 

490 

7.3 

- 

- 315 

350 

- 

- 

13 

11 

236 

299 

20 

15 

63 63 63 52 55 

Table 1: Steel Slag, Dolerite and Quartzite Properties 

74

Water absorption: Steel slag is 

typically more absorbent than 

dolerite and quartzite, a property 

arising from the nature of the steel 

slag aggregate and the manner in 

which it is produced. This has the 

effect of higher binder absorption 

than would be expected of dolerite 

or quartzite. This is an important 

factor that needs to be considered 

in the evaluation of the mix 

design, especially when 

determining volumetric properties. 

Flakiness index: 

The flakiness index 

of the steel slag 

aggregate is 

markedly lower 

than that of dolerite 

and quartzite 

aggregates. The 

more cubical shape 

of the slag enables 

the formation of 

strong interlocking 

structures within 

the asphalt mixture, 

which exhibits high 

stiffness and 

excellent resistance 

to permanent 

deformation. 

Aggregate strength: The high 

Ten Percent Fines and the low 

Aggregate Crushing Value 

indicates the high density and 

crushing strength of the steel slag 

aggregate, properties which 

ensure substantial resistance to 

degradation under traffic loading. 

pH value: Steel slag, with a pH of 

between 8 and 11, has a strong 

affinity for bitumen and, therefore, 

displays a greater degree of binder 

retention. This is a very important 

The more 

cubical shape 

of the slag 

enables the 

formation 

of strong 

interlocking 

structures 

within the 

asphalt 

characteristic in relation to 

resistance to stripping and, 

consequently, long-term 

durability, and it makes steel slag 

an ideal aggregate for enhancing 

the life of asphalt mixtures. 

Polished stone value: A polished 

stone value of 63 for steel slag 

aggregate indicates a high 

resistance to the polishing of the 

aggregate surfaces under the 

action of traffic, which augurs well 

for providing a texture that 

promotes skid 

resistance. It is 

usual for an 

aggregate having a 

PSV in this range to 

have a poor 

abrasion value, as 

the resistance to 

polishing can be 

attributable to loss 

of particles or 

grains from the 

surface of the 

stone. Steel slag, 

however, also has 

excellent resistance 

to abrasion. This is 

an unusual 

combination of properties, making 

steel slag a safe and durable 

alternative to natural aggregates. 

Free Lime: The application of 

steel slag aggregates in road 

construction is only practical if 

there is sufficient volumetric 

stability – a property indicated by 

the presence of free lime. As 

indicated in Table 1, the free lime 

content of the steel slag aggregate 

tested is 2,36%. A maximum limit 

of 5% free lime is used as a 

criterion to evaluate whether an 

aggregate is suitable for use in 

75

oad construction. As mentioned 

previously, the weathering of the 

aggregate is of utmost importance 

to the stability of the aggregate, 

and is considered to be one of the 

most important aspects of raw 

materials handling. 

Steel slag asphalt mixes 

The objective of investigating steel 

slag asphalt mixtures was to 

produce a rut resistant asphalt for 

application where traffic loading is 

high, vehicle speeds low, and 

environmental conditions varying. 

Trial steel slag asphalt mixes were 

prepared for use during the N3 

Toll Concession (N3TC) routine 

maintenance contract between 

Heidelberg and Cedara. 

A mix design was completed using 

the steel slag as an aggregate, 

along with a filler to satisfy the 

-0,075mm grading limits. The 

grading specification used for the 

mix design was according to TRH8 

(Coarse). A 4% SBS modified 

binder was used to enhance the 

natural properties of the bitumen 

by making the binder more elastic 

at higher temperatures, which in 

turn enables the binder to 

withstand repeated traffic loading 

and reduces rutting potential. 

Results 

For the mix adopted, the 

specification required a stability 

within the range 8,0 kN – 18,0 kN. 

Test results indicated a stability in 

the region of 15,0 kN. This can in 

part be attributed to both the use 

of steel slag as an aggregate, and 

to the polymer modified binder. 

The higher stability indicated that 

the mix was ideally suited to the 

requirements of a deformation 

resistant asphalt surfacing. The 

maximum flow recorded at the 

various binder contents tested was 

4mm compared to the recommended 

range of 2 – 6mm. 

The Indirect Tensile Strength (ITS) 

of the mix is a measure of the 

stiffness of an asphalt mix i.e. how 

well it distributes loading to 

underlying layers. In the Interim 

guidelines for the design of hot 

mix asphalt in South Africa 2001, 

the minimum recommended 

stiffness for a surfacing mix is 

1000 kPa. The stiffness of the 

steel slag mix design reported, 

1280 kPa, is significantly higher 

than this minimum requirement. 

The above document also 

recommends a minimum Voids in 

Mineral Aggregate (VMA) of 

15,0%. Low VMA asphalt mixes 

tend to be sensitive to changes in 

binder content and create tender 

mixes that may be more inclined 

to rutting and bleeding. The 

minimum VMA recorded for the 

binder contents tested – 16,3% – 

exceeds the minimum requirement 

and is suited to a rut resistant and 

durable asphalt surfacing. 

To optimise void content to 

counter air and water permeability 

on the one hand, and fattiness and 

bleeding on the other, a target 

Voids in Mix (VIM) of 4% was 

adopted, as suggested by 

Superpave 2001. The reported 

results for the steel slag mix 

design, was very close to the 

optimum voids content of 4%, and 

the mix met the requirement for 

76

air permeability recommended in 

TRH8 (1987) which is less than 

1,0 x 10 6 cm 3 /second. 

The required Voids Filled with 

Binder (VFB) should lie between 

65% and 75% (Superpave 2001). 

The values of VFB obtained in the 

mix design are slightly on the high 

side, due to the high VMA, which, 

along with the voids in the mix, 

determine the VFB. 

Additional testing 

Gyratory Testing: This test gives 

an indication of the compactability 

of a mix, and reasonably simulates 

in-service compaction under 

traffic. From Table 2 it can be seen 

that the steel slag mix at various 

binder contents satisfies the 

gyratory testing requirements 

given in the Interim guidelines for 

the design of hot mix asphalt in 

South Africa 2001. 

(MMLS) apparatus. The results 

obtained can be seen in Table 3. 

These test results indicate that the 

steel slag asphalt displays 

somewhat better resistance to 

deformation than the Dolerite 

asphalt and SMA samples 

evaluated. 

Volume Expansion: As 

mentioned before, it is of utmost 

importance that the steel slag 

aggregate used for road construction 

is volumetrically stable. To 

evaluate the stability of steel slag 

aggregate once it has been 

subjected to weathering, volume 

expansion testing is undertaken as 

a quality control measure. Typically, 

the volume increase of the 

steel slag aggregate is dependent 

on time, and this behaviour, for all 

steel slag, is usually asymptotic, 

with a high rate of initial volume 

expansion decreasing with time to 

virtually zero. 

Percentage 

binder 

Voids @ 125 

gyrations 

Voids @ 300 

gyrations 

Design 

Specification 

4.7% 4.8% 4.9% 5.0% 5.1% Voids E80s 

5.1 4.9 4.8 4.3 5.4 Min 4.0 >10x10 6 

3.9 2.6 2.6 2.7 3.3 Min 2.5 >10x10 6 

Table 2: Gyratory Test Results 

The results indicate that the mix is 

not easily compacted under traffic, 

and is therefore considered to be a 

rut resistant mix which will 

perform well in service. 

Wheel Tracking Test: Cores of 

150mm diameter were removed 

from four locations for 

comparative testing using the 

Model Mobile Load Simulator 

Soluble Deleterious Material 

Test: Steel slag is further required 

to be tested for soluble deleterious 

materials.The required minimum 

according to SABS 1083 is 85%, 

and therefore the sample is 

considered to be acceptable. 

Grip Tester Friction 

Measurements: Grip Tester 

friction measurements were 

77

M ix type 

Coars e 

continuous 

Coarse 

continuous 

S MA fibre Coars e 

continuous 

S MA C ombinatio n Semi-ga p 

B inder type 

S B S 

S B S 

6 0/7 0 

S B S 

S B S S BS-60/7 0 60/7 0 

A ggregate S teel sla g D olerit e D olerit e D olerit e Q uartzit e 

Stee l 

s lag/ dolerit e 

M MLS3 dat a 

A ve. voids (%) 3 . 1 

3 . 3 

- 3 . 6 

7 . 2 

7. 2 

Ave. 

fter 

rut depth 

a 50 k 

r epetitions (mm ) 

Ave. 

core height 

(mm) 

Ave. rut depth 

a fter 100 k 

repetitions (mm) 

Quartzite 

1 .2 

- - 2 . 0 

2 . 5 

2. 2 

6 4 

3 3 

4 1 

4 1 

3 6 

9 5 

3 2 

1 .2 

1 . 3 

1 . 7 

1 . 8 

2 . 6 

2 . 9 

* 

Table 3: Comparative 

* Readings 

wheel tracking tests 

not available due to 

of different asphalt mixes 

excessive rutting 

78

undertaken on a trial section 

consisting of a 13,2mm single 

seal, with steel slag as an 

aggregate on the south bound 

lane and shoulder, and dolerite as 

an aggregate on the north bound 

lane and shoulder. The results are 

presented in Table 4. 

The results indicate that the steel 

slag aggregate provides a more 

skid resistant surface than the 

corresponding dolerite aggregate. 

Environmental 

considerations 

Today we have an obligation to 

consider the impact of our actions 

on the environment, especially 

with regard to preservation and 

sustainability. By using steel slag 

as an aggregate, the environment 

is reaping a two-fold benefit. The 

most obvious environmental 

advantage is the preservation of 

precious natural resources, and 

Carriageway Steel slag (southbound) Dolerite (northbound) 

Lane/position Shoulder Outer 

wheel 

path 

Inner 

wheel 

path 

Shoulder 

Outer 

wheel 

path 

Inner 

wheel 

path 

Ave. grip no. 0.62 0.62 0.71 0.56 0.59 0.59 

Std. dev. 0.0381 0.0355 0.0336 0.0171 0.0157 0.0164 

Minimum 0.50 0.51 0.56 0.52 0.50 0.53 

Maximum 0.77 0.75 0.79 0.62 0.62 0.62 

90 th percentile 0.58 0.59 0.68 0.55 0.57 0.56 

Table 4: Grip Tester Friction Measurements 

Performance 

As can be seen from the above 

testing, the steel slag asphalt mix 

complies with normal design 

criteria and indicates that this 

aggregate can be effectively used 

to improve the properties of an 

asphalt mix. 

Because site conditions may not 

always be emulated by laboratory 

testing, in-service assessment was 

carried out, and this has indicated 

that, to date, the performance of 

the mix on the road has been 

satisfactory, with no problem 

areas evident. 

another benefit is a reduced need 

to dispose of the material in 

landfill sites. 

There is however one negative 

perception associated with the use 

of steel slag aggregates, and this 

is the leaching of chemicals from 

the slag aggregate into the 

groundwater and resultant 

negative impacts on the 

environment. However, studies 

undertaken in Germany have 

shown that this leaching of 

chemical elements is insignificant 

in terms of environmental impact, 

and should not be considered an 

issue of concern in terms of 

environmental health and 

sustainability. 

79

Conclusions 

From the results presented, it can 

be seen that steel slag produces a 

high quality aggregate, which can 

yield a number of benefits in 

terms of improved skid resistance, 

resistance to permanent 

deformation and durability. Road 

owners, road users and the 

environment benefit from the use 

of steel slag as an aggregate in 

the road construction industry. 

Steel slag aggregate is indeed a 

valuable commodity to the road 

construction industry, and should 

be considered as a viable 

alternative aggregate in the road 

construction industry. 

 

References 

1. Asphalt Institute: Mix design methods 

for asphalt concrete and other hot mix 

types. MS-2. Sixth edition. 

2. Asphalt Institute: Superpave mix design, 

Superpave series No. 2 (SP-2). Third 

edition 2001. United States of America. 

3. Colarado Department of Transportation: 

Contract No. CMS 804-99. January 2001: 

Development of a new high performance 

asphalt mix for 1-70 through Greenwood 

Canyon. CTL/Thompson Inc. Colarado. 

4. Committee of State Road Authorities. 

TRH8:1987. Selection and design of hot 

mix asphalt surfacings for highways. South 

Africa. 

5. European conference on slags. Marseilles 

25-27 March 1988. Proceedings: The steel 

slags, characteristics and properties. Dr 

Ing. H Motz. 

6. Euroslag: Engineering of Slags, A 

Scientific and Technological Challenge. 2nd 

European Slag Conference. 9-11 October 

2001 Dusseldorf. Proceedings: Progress in 

the utilisation of steel slags in the UK. 

G.H.Thomas: Thomas Research Services 

Ltd. United Kingdom. 

7. Euroslag: Engineering of Slags, A 

Scientific and Technological Challenge. 2nd 

European Slag Conference. 9-11 October 

2001 Dusseldorf. Proceedings: EAF Slag in 

Aspahlt. N.Jones – Steelphalt. United 

Kingdom. 

8. Hot mix asphalt design Project. 

September 2001. Interim guidelines for the 

design of hot mix asphalt in South Africa. 

9.http://www.tfhrc.gov/hnr20/recycle/ 

waste/ssa3.htm 

10. http://www.tfhrc.gov/hnr20/recycle/ 

waste/ssa1.htm 

11. Ohio Department of Transportation. 

November 1993. Report No. 

FHWA/OH-94/004. Precipitate potential of 

highway subbase aggregates. J.D.Gupta 

and W.A Kneller. 

12. Oregon Department of Transportation. 

State Research Project #511. April 2000. 

Steel slag in hot mix asphalt concrete. Final 

report. L. Hunt and G.E. Boyle. 

13. Steelmaking Slag Technical Committee. 

1993. Steel Slag Aggregates Use in Hot Mix 

Asphalt Concrete. Final Report, prepared 

by John Emery Geotechnical Engineering 

Limited. USA. 

14. Transportation Research Board. 

National Cooperative Highway Research 

Programme, Synthesis of Highway Practice 

199. Recycling and use of waste materials 

and by-products in highway construction. 

R.J. Collins and S.K. Ciesielski, Washington 

DC 1994. 

15. United States of America. National 

Cooperative Highway Research Program 

Synthesis of Highway Practice 199, 

Transportation Research Board. 1994. 

Recycling and Use of Waste Materials and 

By-Products in Highway Construction. 

Collins, R. J. and S. K. Ciesielski. 

Washington DC. 

80

Bitumen stabilised materials: 

In search of sustainable 

pavement design solutions 

Kim Jenkins 

Professor 

SANRAL Chair 

University of Stellenbosch 

Dr Fritz Jooste 

Director 

Modelling and Analysis 

Systems (MAS) 

Over the past two 

decades many South 

African pavement 

engineers have become aware 

of mounting pressure to 

conserve the environment, 

coupled with a decreasing 

availability of crushed stone 

material. 

These two issues have prompted a 

radical 

re-assessment 

of the manner 

in which 

pavement 

design is being 

approached in 

South Africa. 

(G1 material in particular, as 

shown in Figure 1). However, in 

the face of decreasing availability 

of such material, engineers now 

have to improvise and recycle 

existing pavement layers, as 

opposed to simply importing new 

crushed stone material. 

The treatment of existing 

pavement layers with bituminous 

materials, either in the form of 

Traditionally, 

pavement 

design 

philosophy in 

South Africa 

was based to a 

large extent on 

the assumption 

of readily 

available and 

cost effective 

crushed stone 

Figure 1: Breakdown of some structure types in the TRH4 

(1996) catalogue for design traffic greater than 

3 msa, highlighting the strong reliance of current 

design guidelines on crushed stone 

82

itumen emulsion or foamed 

bitumen, offers a feasible and cost 

effective solution to the problem of 

providing sustainable pavement 

design solutions. However, this 

challenge is not without obstacles, 

and most significant of these is the 

lack of sound and practical 

guidelines to the design and use of 

bitumen stabilised materials. 

Structured experience 

Inadequate guidelines have 

resulted mainly from the lack of 

structured and documented 

experience related to the design, 

use and performance of bitumen 

emulsion and foamed bitumen 

materials. 

To address these issues, Sabita, in 

conjunction with the Gauteng 

Department of Public Transport, 

Roads and Works (GPTRW), 

initiated a project to develop 

updated guidelines on the design 

and use of Bituminous Stabilised 

Materials (BSM). 

This initiative aims to incorporate 

both emulsion and foamed 

bitumen materials in a single BSM 

guideline to promote rational 

materials selection and equitable 

competition between the two 

material types. This guideline will 

update the technology presented 

in current guidelines for these 

materials (e.g. TG2 – Interim 

Technical Guidelines: The design 

and use of foamed bitumen 

treated materials, Sabita Manual 

14: GEMS – The design and use of 

granular emulsion mixes, and 

Manual 21: ETB – The design and 

use of emulsion treated bases.) 

The Project 

The project to develop a guideline 

for the design and use of 

bituminous stabilised materials 

was initiated in early 2005. At the 

outset, it was recognised that the 

structural design and mix design 

elements of the existing guidelines 

required the most urgent and 

significant improvements. The 

project was therefore structured to 

address these two aspects in a 

comprehensive manner. Owing to 

the ambitious scope of the project, 

it was structured to allow 

execution in distinct phases, as 

shown in Figure 2. 

The mix design element of the 

project is being undertaken by 

Professor Kim Jenkins of the 

University of Stellenbosch, while 

the Structural Design element is 

being handled by Drs. Fritz Jooste 

and Fenella Long of Modelling and 

Analysis Systems (MAS). 

As shown in Figure 2, the second 

phase of the project is currently in 

progress, and the bulk of this work 

is scheduled for completion in 

early 2008, at which time the 

compilation of the guidelines will 

begin. 

Mix Design Developments 

The mix design component of this 

study aims to identify the 

inadequacies in current 

approaches to foamed bitumen 

and bitumen emulsion mix design 

procedures, and to explore 

laboratory test protocols and 

available laboratory test data for 

these materials that would provide 

83

Completed 

early 2006 

Phase 1: Inception study 

• Obtain available performance data on pavements 

incorporating bituminous stabilised materials (BSM); 

• Review existing tests and protocols related to mix design 

on BSM; 

• Formulate approach and detailed planning for Phase 2. 

in 

Currently 

progress 

Phase 2: Develop new methods as needed 

• Develop pavement design and materials classification 

methods based on LTPP and APT data; 

• Refine existing laboratory tests and develop new tests as 

needed to facilitate mix design and classification of BSM 

stability and flexibility. 

Completion 

in 2008 

Phase 3: Compile guidelines 

• Incorporate new methods and practices for Mix Design 

and Structural Design from Phase 2; 

• Review and expand sections related to construction, 

materials selection and composition; 

• Review and publish. 

Figure 2: Structure of the Project 

a more fundamental, reliable mix 

design method for cold mixes in 

general. 

The overall framework of TG2 was 

found to be well-founded but not 

comprehensive, and certain 

components to the mix design 

procedure were found to be 

lacking. In addition, this project 

aims to use more explicit mix 

design tests to classify the 

emulsion and foamed bitumen 

mixes for pavement design 

purposes. The mix design 

component of the study therefore 

has four main objectives: 

• Investigate the incorporation 

of triaxial testing into the mix 

design procedure. Shear 

parameters reliably define the 

performance properties of 

cold mixes, but standardised 

(simple) procedures need to 

be developed to meet the 

needs of both research and 

commercial laboratory 

84

operations, as well as to 

advance an understanding of 

the relationship between 

monotonic versus dynamic 

properties of cold mixtures; 

• Develop more realistic and 

reliable specimen preparation 

and conditioning protocols, 

especially with respect to 

compaction and curing. 

Cognisance needs to be taken 

of, for example, binder type, 

aggregate type and active 

filler content; 

• Identify a durability test for 

incorporation into the mix 

design procedure. In the 

broad sense, durability covers 

binder durability as well as 

mix durability (especially 

moisture damage). Current 

Tensile Strength Retained 

(TSR) tests in the ITS mode 

do not provide sufficiently 

reliable simulation of 

moisture damage; 

• Identify a reliable and robust 

classification system for 

emulsion and foamed 

bitumen treated materials 

that could be used for 

pavement design purposes. 

Although a unified system 

that would be generic for all 

cold mixes would be 

preferred, key differentiators 

may need to be incorporated 

to distinguish between the 

materials if this is not 

possible. 

Given the scope of these 

objectives, data on a wide range 

of mixes has already been 

gathered and synthesised in a 

database under several different 

headings, including mechanical 

testing (shear properties, resilient 

properties and permanent 

deformation), flexural testing 

(strain-at-break, flexural stiffness 

and fatigue), curing, durability 

(moisture susceptibility and binder 

ageing) and compaction. 

Laboratory and field research 

(using trial sections) will continue 

in 2007 to develop and calibrate 

revised and new procedures for 

the mix design of emulsion and 

foamed bitumen treated mixtures. 

Although some of the monitoring 

of field trials will continue through 

2008, by early in that year it is 

planned that sufficient findings will 

be available to incorporate into the 

new guideline. 

Structural design 

developments 

The aim of the structural design 

component of the project is to 

provide a practical, reliable and 

validated methodology for 

determining the structural capacity 

of pavements that incorporate 

bituminous stabilised layers. At 

the outset, it was recognised that 

such a method would require a 

significant knowledge base related 

to the construction and 

performance of pavements that 

incorporate BSM. A comprehensive 

search and analysis task is 

therefore being conducted to 

obtain and document data relating 

to the performance of BSM 

pavements under long term field 

loading conditions, as well as 

under Heavy Vehicle Simulator 

(HVS) testing. 

To date, the available construction 

and long term field performance 

information for 17 BSM pavement 

85

sections has been compiled and 

documented, with a further six 

sections under investigation. Data 

has also been obtained and 

summarised for seven BSM 

pavements that were tested with 

the HVS. These seven pavements 

provide a total of 22 configurations 

tested under different 

loading intensities. The combined 

performance database will be used 

to construct a knowledge base 

which will be used to calibrate and 

validate the pavement design 

method for BSM pavements. 

The structural design method will 

incorporate the best elements of 

mechanistic design, coupled with a 

strong empirical component that 

will be determined by the 

pavement performance database. 

The mechanistic 

design element will 

include a basic 

assessment to 

check that 

pavement balance 

and subgrade strain 

requirements are 

satisfied. Weaker 

elements of 

mechanistic design 

– such as the 

uncertainty 

associated with 

assumed layer stiffness – will be 

addressed through the use of a 

materials classification system 

which will provide detailed 

guidelines on how to classify 

materials based on indicator tests. 

The material classification 

assigned to different layers will 

then be used to obtain appropriate, 

predefined modular ratios 

for each layer, which in turn can 

be used to obtain realistic and 

situation-specific stiffnesses for 

each material class. 

Pilot test 

The aim is to 

provide a practical, 

reliable and 

validated 

methodology for 

determining 

structural capacity 

To date, the basic methodologies 

of the pavement design and 

materials classification systems 

have been completed. It is 

envisaged that a trial version of 

the design method will be pilottested 

during 2007. This testing 

will be performed by selected 

practitioners, and feedback will be 

used to refine the method for 

optimal accuracy and robustness. 

It should also be noted that, 

during 2006, the CSIR developed 

a long term research plan for an 

updated, 

generalised 

pavement design 

method for South 

Africa. 

This project was 

initiated by the 

South African 

National Roads 

Agency Ltd 

(SANRAL), and will 

address many of 

the deficiencies of 

the current mechanistic design 

method. 

Discussions will continue to ensure 

that the outcome of the structural 

design method for bitumen 

stabilised materials will 

complement the SANRAL initiative, 

which has a broader and longer 

term objective. 

 

86

Fischer-Tropsch wax bitumen modifier: 

Overcoming temperature and 

time constraints 

Francois Bornmann 

Marketing Manager 

Sasol Wax 

Robbie Hiley 


Sasol Wax Australia (Pty) Ltd 

Stefan Strydom 

Business Manager 

Sasol Wax 

Contractors in South 

Africa, Australia and 

elsewhere have achieved 

optimum pavement performance 

when mixing and placing 

hot and warm asphalt, even 

under conditions of inclement 

weather and extended time 

and haul distance, through the 

use of bitumen modified with 

Fischer-Tropsch wax. 

Wax modifiers (commonly referred 

to as Sasobit® or FT wax) are 

produced by Sasol Wax (a division 

of Sasol Chemical Industries Ltd.) 

using the Fischer-Tropsch catalytic 

process utilising natural gas. FT 

wax is fundamentally different 

from naturally occurring waxes in 

bitumen, in that it is inert to 

chemical and ultraviolet activation. 

It further combines a low melt 

viscosity with a reduction in 

penetration and an increased 

softening point of the modified 

binder. 

The physical and rheological 

properties of FT wax have a 

significant impact on those of the 

base binder at low modification 

levels. These are evident in the 

improved blending, compaction 

and ease of laying of the modified 

asphalt and the resultant 

performance characteristics of the 

pavement. 

Physical properties of 

FT wax 

Pure FT wax begins to crystallise 

above 100 0 C. However, practical 

experience has shown that asphalt 

mixes containing this modifier can 

be compacted at temperatures as 

low as 80 0 C, which seems to 

contradict the first statement. This 

raises the question of the 

mechanism of FT wax crystallisation 

in asphalt mixes, since this 

has a considerable influence on 

the minimum temperatures of 

88

asphalt paving and rolling, and its 

efficacy as a warm mix additive. 

A DSC (Differential Scanning 

Calorimetry) 1 investigation shows 

that the crystallisation onset 

temperature of the modifier in 

asphalt hot mixes depends on its 

concentration and on the cooling 

rate of the mat. Under realistic 

circumstances (3 % FT wax in the 

binder and 2°C/min cooling rate) it 

begins to crystallise around 85°C. 

This implies a viscosity reducing 

effect down to this temperature 

level. Constraints regarding the 

mix workability are not expected 

since the rolling of hot mix asphalt 

– and even of warm mix asphalt – 

is usually completed above 85°C. 

Figure 1: Influence of Sasobit on bitumen viscosity 

89

Viscosity 

The significant influence of FT wax 

on bitumen viscosity is shown in 

Figure 1. 

FT wax-modified asphalt exhibits 

the anomaly of increased 

resistance to permanent deformation 

in the service temperature 

range, while promoting workability 

through lower binder viscosity in 

the mixing/paving range of 

temperatures. 

The presence of a dense lattice of 

hydrocarbon wax crystals causes a 

restriction to flow of a “softening” 

binder mass at elevated 

temperature under the influence of 

heavy axle loads, while the melt 

characteristic of the wax is 

showing the same kinetic delay 

with a resultant higher melt point 

and no detrimental effect on 

binder viscosity. 

Physical properties of 

modified binder 

Increasing percentages of FT wax 

were added to 80/100 penetration 

grade bitumen to illustrate the 

effect on various binder 

properties. These are depicted in 

Figure 2. 

Both design engineers and 

contractors can use these effects 

to meet a particular desired 

outcome where, for instance, long 

haul distances, short road closure 

windows and poor weather 

conditions pose a threat to a high 

quality finished pavement. 

Case Studies 

The case studies below 

demonstrate how the unique 

properties of FT wax-modified 

asphalt can be utilised to 

overcome severe conditions of 

long hauls, narrow construction 

windows and low ambient 

temperatures to provide a durable 

pavement in the rehabilitation of 

highly trafficked roads 2,3 . 

Heavy traffic in major global cities 

now increasingly requires that 

routine maintenance of important 

arteries be carried out within a 

very short space of time 2 . Labour 

Figure 2: Effect of increasing Sasobit content 

90

intensive and time consuming 

projects such as deep patch 

maintenance are even more 

troublesome. 

A deep patch maintenance project 

in Sydney, Australia, required that 

a stretch of road pavement 67 

meters long, approximately 

400mm deep and 3 meters wide 

be removed, profiled and repaved 

in four layers within 9 hours — 

working at night, in the middle of 

winter. No rutting was to be 

observed the next morning or 

shortly thereafter as a result of 

elevated asphalt temperatures. 

The road carries a traffic loading of 

approximately 60 000 vehicles/ 

day, and road authority 

specifications on compaction, ride 

quality etc. had to be met. 

Project 

requirements 

The project 

requirements could 

only be achieved by 

producing and 

delivering “warm 

mix” asphalt to site, 

and laying it at 

considerably lower 

temperatures than 

normal. This was achieved by 

modifying the bitumen with FT 

wax at 1.5% of the binder 

content. 

The project started at 20h30 with 

the profiling and removing of the 

old asphalt and base layers. Once 

the area had been cleaned, 

200mm of stabilised base was 

compacted into the affected area 

and finished to ensure that exact 

levels were attained. This process 

No extraordinary 

precautions 

were taken 

during the 

paving or 

compaction 

processes 

lasted until approximately 00h30, 

by which time the ambient 

temperature had dropped to 10 0 C. 

Wind chill effects made workability 

and effective compaction even 

more difficult. 

The asphalt was to be laid in two 

base layers of 60mm each, and 

two wearing course layers of 

45mm each. The 60mm base 

layers were produced at 130 0 C, 

and the two top layers at 140 0 C. 

Paving of the first layer began at 

approximately 00h45. In addition 

to the low paving temperatures, 

the paver burners were also 

limited to 120 0 C to minimise 

introduction of any extra heat into 

the system. 

Temperature probes were inserted 

into the core of 

each asphalt layer 

to measure 

variations in the 

temperature of each 

mat throughout the 

whole process. The 

probes were placed 

in the middle of 

each layer (probe 1 

in the bottom and 4 

in the top layers) 

and not directly on 

top of each other to 

make sure that the wires were not 

cut during the rolling. The 

temperature increase is due to the 

subsequent layers being deposited 

on top of the underlying 

layers.The detailed temperature 

profiles in Figure 3 show the core 

start temperatures and the time 

frames taken to finish all four 

layers. 

91

Figure 3: Layer temperature profile 

In each case cores were taken 

immediately before the next layer 

was laid on top of it, and these 

were analysed specifically for 

compaction. During the whole 

process the paving temperatures 

in the back of the paver varied 

between 110 and 125 0 C. 

Construction of the pavement was 

finished at approximately 04h30 

(including the coring of the last 

layer), and the road was opened 

to traffic immediately. 

No extraordinary precautions were 

taken in the paving or compaction 

processes. No dragging of the 

paver or the appearance of a 

“bony” mix, typical of paving at 

these temperatures, was 

observed. There were also no 

problems experienced with hand 

raking of the edges of the top 

mat. Joints with the existing 

pavement were smooth and tight, 

and all building specifications were 

met. 

Long haul in NSW 

Broken Hill is a town close to the 

NSW border with South Australia, 

approximately 550 kilometres 

from Adelaide and 760 kilometres 

from Dubbo. There are no asphalt 

plants near Broken Hill, and if a 

minor or medium sized paving 

project is undertaken, asphalt 

must be trucked over these vast 

distances. This results in haulage 

times of up to 10 hours or more, 

depending on traffic conditions. 

The alternative is concrete paving 

which is not always an option due 

to unstable road substrates and 

heavy mining vehicles. 

Unless a mobile plant is used, the 

asphalt is normally heated up to 

inordinately high temperatures (as 

high as 185 0 C) and then is laid 

only during the very hot months – 

effectively December to January. 

Any small abnormality in the 

weather causes huge problems 

and the window for pavement 

construction or repair could shrink 

considerably. 

When the asphalt arrives on site it 

is often extremely difficult to work 

due to large heat loss suffered 

during transport. If there are any 

92

delays because of traffic diversion 

or pre-laying preparation of the 

road, the asphalt is often unusable 

when the time comes for it to be 

laid. The road authority frequently 

has to allow for losses of up to 

10% – even in the very warm 

months. 

The trial asphalt was 

manufactured with a 320 viscosity 

grade bitumen (similar to 

penetration grade 40/60), 

modified with 1.5% FT wax, and 

was loaded into the trucks at 

180 0 C. It was covered using a 

heat shield sheet laid over the top 

of the asphalt, together with three 

layers of carpet under-felt, and 

finally the usual tarpaulin covers. 

The first truck arrived at 

approximately 

10h30 after a 9.5 

hour drive. On 

arrival the asphalt 

temperatures at the 

side walls were as 

low as 112 0 C, while 

the surface and 

core temperatures 

were in the region 

of 130 0 C and 

160 0 C, respectively. 

Although the trial 

was planned for a 

very hot day it had rained the day 

before, and the ambient 

temperature was only 24 0 C in the 

morning. 

The road was profiled and cleaned, 

and paving then began as usual 

with a 25mm layer. During the 

laying operation the temperature 

of the asphalt dropped to 100 0 C 

on the sides of the paver (surface 

temperature), with the 

Total haulage 

times of up to 

12 hours 

before the 

asphalt could 

be loaded into 

the paver 

temperature in the middle being in 

the region of 135 0 C. The ambient 

temperature at this time was 

about 30 0 C. 

After the asphalt had been laid the 

edges were hand-worked to 

smooth them off, and a vibratory 

roller was used to compact the 

asphalt. Once the road had 

reached a surface temperature in 

the region of 65 0 C, a 17 ton 

pneumatic roller was used with a 

coverage of 6 passes to complete 

the compaction. The road surface 

temperature after finishing was 

approximately 45 0 C. After a few 

minutes the road was opened to 

traffic and the other half of the 

road was tackled. Total elapsed 

time from profiling until the road 

was opened to traffic was 2.75 

hours. 

The second truck 

carrying the next 

two loads of asphalt 

had been waiting 

for a few hours, 

resulting in a total 

transit time of 

approximately 12 

hours before the 

asphalt was loaded 

into the paver. This 

asphalt temperature 

in the truck had reached as low as 

100 0 C near the side walls, and was 

115 0 C and 135 0 C at the surface 

and core respectively. 

Construction proceeded as with 

the previous lane, and only a few 

lumps of asphalt (150 kg) were 

found to be unusable. 

In the cases mentioned above, the 

asphalt was laid as if in close 

proximity to the plant, and was 

93

easily formed and shaped where 

necessary. To date no problems 

have been noted with the 

pavement, and no subsequent 

rutting or movement of the 

asphalt has been observed. 

Also no “slumping” and bleeding of 

the mix in transit was observed as 

was normally the case with these 

long haulage paving projects. This 

feature resulted in real savings as 

bleeding would have damaged the 

insulating materials. 

It was evident that the road 

authority had widened the working 

window of asphalt in Broken Hill 

by another four months, which has 

“paved the way” for an extended 

programme next year. The trial 

was an outstanding 

success, with both 

the subcontractor 

and the road 

authority impressed 

by the performance 

of the FT 

wax-modified 

asphalt. 

Boral Asphalt noted 

that FT wax 

modification 

provides a practical 

and economical 

means of 

significantly 

increasing the range of products 

available from our regional asphalt 

plants, while still providing a 

quality product for the client. 

Durban freeways 

The addition of 

FT wax lowered 

the mixing and 

compaction 

temperature 

by 20 0 C more 

than would 

otherwise have 

been possible 

road closures. Work on the 

Southern Freeway Phase 2 and 3, 

as well as on the Western Freeway 

Phase 1 and 2, recently benefited 

from the use of FT wax modifier. 

The project team had great 

difficulties with thin surfacing work 

(25 mm wearing course) 

scheduled to be laid at night in 

conditions falling ambient 

temperatures as winter 

approached. It proved impossible 

to meet the asphalt specifications 

using the specified modified binder 

within the allowed construction 

window, as only day time work on 

Sundays produced satisfactory 

results. 

Penalties 

The impending 

penalties for delays 

prompted the 

supplier, National 

Asphalt, to use their 

extensive 

experience with FT 

wax to persuade the 

client to allow a trial 

section with this 

modifier. The 

results showed that 

work could be 

carried out at night and during 

winter time since the addition of 

FT wax lowered the mixing and 

compaction temperature by 20 0 C 

more than would have been 

possible using the specified 

modified asphalt. 

The Southern and Western 

Freeways of the Durban Metropolis 

both carry heavy traffic loads 

offering very little opportunity for 

The client approved the use of FT 

wax for the remainder of the 

projects. 

94

A total of 95 000 tons of FT 

wax-modified asphalt was laid 

without a single failure, working at 

night in adverse winter conditions 

and with minimal disruption of 

traffic. 

Storage stability 

It was noted by National Asphalt 

that FT wax modifier is easily 

blended and yields long storage 

stability. Due to the lower mixing 

temperatures required, energy 

savings were also realised, and an 

extended construction window was 

achieved as a result of the 

reduced temperature at which the 

desired compaction could be 

achieved. 

References 

1 – Dr. T. Butz: Laboratory 

report. Sasol Wax, 2006 

2 – Dawie Erasmus, Vela VKE: 

Night time rehabilitation of the 

Southern Freeway (M4) Durban – 

Civil Engineering, July 2005, Vol. 

13, No. 7, 3. 

3 – Ingenuity solves surfacing 

problem – Modern Asphalts, 

February 2006 

Acknowledgements 

The authors extend their gratitude 

to J Figueroa, S Yin and C Brady of 

the RTA NSW Australia, 

G.Hennessey, R.Crabb and 

J.Burton of Boral Asphalt, 

Australia, and to Wynand Nortje of 

National Asphalt, South Africa, for 

their valued input. 

 

95

Achieving cost-efficiency through technology: 

Advantages of SA's new single 

pass surface dressing machine 

Deon Pagel 


Tarfix (Pty) Ltd 

Sourcing and introducing 

appropriate and 

innovative solutions to 

the South African road 

industry is one of the 

hallmarks of industry 

leadership. The recent advent 

of a high tech, single 

pass, surface dressing 

machine by Tarfix (Pty) 

Ltd now offers a wide 

array of new possibilities 

in road surface seals. 

Figure 1 highlights the major 

technical differences between the 

two systems, of which the most 

notable is the variability in the 

time between the contact of the 

stone with the binder in the 

conventional system. 

Developed in France, and 

now used internationally, this 

new method of road 

surfacing allows for the 

simultaneous application of 

the binder and the aggregate 

in a single pass. In 

comparing this method with 

the traditional two pass 

system, it soon becomes 

very apparent that the latter 

has a number of inherent 

limitations which are 

overcome when using the 

single pass system. 

Figure 1 

96

Figure 2: The Chipsealer 61 unit with 3 500 l binder tank 

and behind it the 8.5m 3 stone hopper 

The Chipsealer units are fully 

imported from Secmair in France. 

The South African units boast the 

most advanced technology ever 

installed on this type of 

equipment, and includes three 

on-board computers, which control 

all aspects of the binder and 

aggregate application, as well as 

monitoring all the relevant 

physical environmental data (such 

as road temperature, air 

temperature, positioning etc.) 

and recording the application on 

video. 

In the international arena the use 

of the single pass system has had 

a major impact on the traditional 

sealing market, and specifically on 

the effectiveness of maintenance 

seals, leading to a zero pothole 

scenario. It is believed that the 

introduction of this equipment into 

the South African market will 

assist road owners to more 

effectively maintain their road 

networks and reduce annual 

maintenance costs. 

In addition the accurate spraying 

of the binder (temperature control 

of surface seals. 

and 

application 

rate) in 

accordance 

with 

specifications, 

(which is 

normally 

difficult to 

achieve in 

practical 

terms on 

site,) should 

greatly 

improve the 

effectiveness 

The use of visual imaging 

equipment and integrated 

computer controls on the new 

Secmair equipment offers road 

owners an alternative that was not 

previously available to them – i.e. 

the option of applying a low cost 

maintenance seal over just that 

portion of road that really needs 

treatment. 

Emulsion binders 

The units are designed to apply all 

types of binders, including 

modified binders, requiring an 

application temperature of up to 

170 0 C. International trends show 

that the future of these units lies 

with the application of emulsion 

and modified emulsion binders. 

The environmental and safety 

aspects associated with emulsions, 

together with the ease of 

application and the reduction in 

energy consumption (LP gas in 

particular), makes emulsions a 

very attractive option. 

97

Graded stone seals 

The seals that are being proposed 

as generic low cost holding actions 

on a road are typically made up of 

a modified emulsion binder, 

combined with a “slightly” graded 

stone aggregate, such as a 

combination of a 6.7 and 9.5mm 

stone, or even a 4.75 and 6.7mm 

stone. The graded effect of the 

stone aggregate, together with the 

Figure 3: Efficient use of graded stone and emulsion 

binder for sealing cracks 

low viscosity of the emulsion to fill 

the cracks, achieves a result that 

is not obtainable with conventional 

surfacing systems (see figure 3). 

Conventional seals 

Apart from their ability to apply 

graded stone seals, the machines 

can be used for any of the 

commonly known single or double 

seals using up to 19mm sized 

aggregates and conventional or 

modified binders. 

Since the arrival of their first unit 

two months ago, a range of seals 

totalling in excess of a 100,000 m 2 

have already been completed. 

These applications varied from 

emulsion single and double seals, 

(also using latex modified 

emulsions) on municipal road 

networks, as well as 80/100 

penetration grade double seals. 

While the on board computers 

control the binder temperature 

and maintain the application rates 

of binder and aggregates within 

tight tolerances, 

(while digitally 

recording the road 

condition before 

and after 

application), there 

are also a number 

of other practical 

aspects which 

make surfacing 

with these units 

advantageous 

vis-à-vis 

conventional 

chip-and-spray 

techniques, 

namely: 

• Minimal aggregate loss in the 

early life of the seal due to 

instantaneous application 

with the binder; 

• Cost-effective sealing of 

roads requiring remedial 

treatment on distressed areas 

only; 

• Reduced traffic disruption due 

to fewer construction vehicles 

on the work site; 

• More versatile and suitable 

for sealing restricted areas 

due to the high 

manoeuverability, for 

example at intersections; 

98

Figure 4: Maintenance seals can be applied 

selectively while the unit is driving over the road 

• Self contained and minimal 

site establishment, which 

facilitates a quick response 

times. 

Quality issues 

Very few people realise how 

quickly the temperature of a 

bituminous binder drops once it 

makes contact with the road 

surface. It is exactly this 

occurrence that puts the single 

pass system way ahead of the 

conventional or traditional two 

stage system in terms of 

quality. 

exact same binder – in 

this case only after an 

initial delay of 30 

seconds. It can clearly 

be seen that after 2 

minutes the ball has 

made far less contact 

with the binder. This 

illustrates the 

importance of 

obtaining the correct 

binder viscosity if good 

adhesion of the 

aggregate to the binder is to be 

achieved. 

The diagram also illustrates that 

the temperature of a binder, even 

if applied as hot as 170 0 C, will 

reach the ambient road 

temperature about two minutes 

after application. This clearly 

proves that any delays in the 

stone reaching the binder will 

definitely result in inferior 

adhesion, and very likely in 

stripping of the aggregate – a 

phenomenon often seen on our 

roads. 

Figure 5 illustrates 

how the ‘wetting’ of 

metal balls is 

affected when 

making contact with 

bitumen at different 

time delays. The ball 

at the top left is very 

clearly best 

submerged, just two 

minutes after making 

almost immediate 

contact with the 

binder, i.e. as per 

the single pass 

system. The ball top 

right was brought 

into contact with the 

Figure 5: How the ‘wetting’ of metal balls is affected when 

making contact with bitumen at different time delays. 

99

Figure 6 illustrates how 

the stone application 

immediately follows 

that of the binder. 

Production and 

logistics 

Production depends 

largely on the type of 

seal being constructed 

and on the site 

logistics, but can vary 

between 5,000 to 

13,000m 2 per day. The 

latter figure was 

achieved locally while 

constructing a single seal using an 

emulsion binder, but larger 

machines will be made available in 

time to come, and for those 

contractors who are interested in 

high production, there are units 

available that capable of up to 

75,000m 2 per day. 

The objective is, however, to 

concentrate on the maintenance 

seals for local authorities, and also 

to offer a service to any contractor 

who wants a seal of between 

5,000 and 30,000m 2 done in a 

Figure 6: Stone aggregate being applied one second 

after the binder application 

very short time, without having to 

engage in huge and cumbersome 

site establishment. 

The second surface dressing 

machine is expected to arrive in 

South Africa in February 2007, 

offering a new and unique service 

to the roads industry as a whole. 

For any enquiries please contact 

Deon Pagel at 011-708 4794, (cell 

083 306 9774) or on e-mail: 

deon@tarfix.co.za 

 

100

Focus on deformation resistance: 

Innovative design methods for 

HMA in Gauteng 

Herman Marais 

Technical Manager 

Much Asphalt (Pty) Ltd 

Gauteng 

Derick Pretorius 

Director 

Arcus Gibb (Pty) Ltd 

To secure the position of 

hot mix asphalt wearing 

course as a cost-effective 

road layer, a re-examination of 

design procedures is 

necessary, especially to ensure 

that mix components are 

balanced to resist to 

permanent deformation while 

not compromising the 

durability of the layers. 

Following a recent forensic study 

by CSIR Built Environment on 

behalf of the Gauteng Department 

of Public Transport, Roads and 

Works (GPTRW), it was evident 

that a cooperative effort involving 

client bodies, consultants and the 

asphalt industry should be 

launched to redress the issue of 

premature road distress, 

especially at busy intersections. 

Over and above the need to 

ensure that structural design 

procedures are sound and based 

on relevant traffic data, mix 

design procedures should exploit 

available technology to design 

high performance mixes 

consistently, and to incorporate 

these principles into the regularly 

used production mixes in Gauteng 

to ensure that optimal asphalt 

mixtures render satisfactory 

performance and meet clients’ 

expectations. 

Background 

The development of rut-resistant 

mixes goes back to 2003, when 

Arcus Gibb and Much Asphalt 

undertook a contract at the OR 

Tambo International Airport 

(ORTIA), and since then methods 

have been continuously improved. 

Initially it was planned to use 

quartzite aggregate, but due to 

large volume requirements for the 

combined runway and major 

taxiways contract it was decided 

to use dolerite, available in larger 

quantities. The high design traffic 

class and 50mm thickness of the 

overlay called for asphalt with 

slightly larger aggregate than the 

COLTO continuously graded 

(medium sized). With this grading 

being effectively a 26.5mm type 

suitable for asphalt base, it was 

102

decided rather to use the old TRH8 

coarse envelope (13mm nominal 

aggregate type). The first contract 

where the dolerite TRH8 coarse 

mix was used successfully was the 

ORTIA Echo taxiway contract. On 

the following ORTIA contract 

(Yankee taxiway) the grading 

adopted was slightly finer on the 

2.36mm sieve, which resulted in 

lower gyratory voids and higher 

MMLS3 rutting values. 

Subsequently, to ensure 

compliance with more stringent 

performance-related specifications, 

it was decided to revert 

back to the original Echo taxiway 

contract grading with only slight 

changes to optimise the mix. 

These included adjustments in the 

grading to maintain VMA values in 

the region of 16, which satisfy the 

rut criteria without causing binder 

starvation of the mix, i.e. maintaining 

a film thickness of 7.5µm. 

With the very high volume of work 

that had to be completed before 

the end of 2006, it was decided to 

prepare a quartzite design as a 

Performance required Fundamental mix property Simulation testing 

to confirm 

performance 

• Mix 1: Highly trafficked (>ES10) wearing course: 

• High rut resistance 

and durability; 

• Acceptable fatigue 

resistance; 

• Acceptable friction (no 

fattening/bleeding). 

• Grading to be a 13.2mm nominal 

aggregate, coarse graded type to 

ensure compactability; 2.36mm 

key compositional point to be set 

to ensure VMA target obtained; 

filler set to obtain a filler/binder 

(F/B) ratio of ≈ 1.3. The grading 

curve to be smooth to ensure 

compactability and prevent 

segregation; 

• % passing 0.075mm (filler) to be 

relatively high to stiffen mix (F/B 

≈ 1.3 – 1.45); 

• Adequate VMA to get enough 

binder in (for durability/fatigue) 

while still preventing closing up 

of the mix (i.e. Marshall voids = 

5.0 and terminal voids in SP 

gyratory >3%); 

• Binder penetration – 60/70 - 

40/50 Pen; 

• Film thickness > 7.5µm 

(minimum binder content of 

4.5%) 

• MMLS3 @ 50°C 

on briquette/field 

cores; 

• Mod Lottman; 

• 4 Pt beam fatigue 

test @ 200µm 

and 350µm; 

• Gyratory curve to 

300 gyrations. 

Mix 2: Highly trafficked (>ES10) wearing course for high shear intersection 

areas: 

• Very high rut 

resistance and 

durability; 

• Acceptable fatigue 

resistance; 

• Acceptable friction (no 

fattening/bleeding) 

• As above with binder type to be 

40/50 Pen. and F/B slightly 

higher (±1.40) with film 

thickness > 7µm 

Table 1: Fundamental Design Principals 

As above 

103

ackup wearing course in the 

event of dolerite aggregate 

becoming unavailable during the 

contract. It also provided the ideal 

opportunity to develop the mix 

with quartzite aggregate as part of 

the preparation of the GPTRW rut 

resistance mixes. 

Design methodology 

(a) Fundamental design 

methodology 

The fundamental principles of 

compositional and volumetric 

asphalt design 1) 2) 3) , as developed 

on various high performance 

pavement structures since 2001 

are shown in Table 1 and were 

used to obtain specific 

performance properties for these 

mixes. 

The compositional and volumetric 

design methodology adopted 

utilises the following processes to 

arrive at optional mixes in 

accordance with target 

performance requirements: 

• Best aggregate sources in 

terms of desired aggregate 

properties (e.g. shape, 

i.e.cubical to slightly flaky; 

hardness according to COLTO 

criteria; consistency) are 

used; 

• Initial grading is optimised for 

50mm thickness, starting 

with a selected or specified 

nominal aggregate size 

(13.2mm) and filler to yield 

filler/binder ratio in the 

region of 1.3, and the 

in-between points on the 

grading log curve smoothed. 

Also the fraction passing the 

2.36mm screen (primary 

control sieve) is set at a level 

that ensures a “coarse 

graded” mix more or less 

coinciding with the coarse 

boundary of the conventional 

grading envelope; 

• Aggregate proportioning is 

carried out to meet the target 

grading; 

• Marshall volumetric design is 

then carried out to check 

VMA, VIM and binder/film 

thickness relationships; 

• The proportion passing the 

2.36mm screen is then 

adjusted to modify the VMA 

until volumetric requirements 

are met. It was noted that a 

2.5% reduction in the 

percentage passing the 

2.36mm screen generally 

resulted in a 1% increase in 

VMA (at the same binder and 

filler contents); 

• VMA is then adjusted, until 

binder film thickness, VIM’s, 

and gyratory voids meet 

volumetric/compositional 

targets. The aim is always to 

arrive at a cost-effective mix, 

by adopting the minimum 

binder content (or VMA for 

that matter) that will satisfy 

durability and fatigue criteria; 

• Performance tests are then 

carried out followed, if 

necessary, by a process of 

iteration until performance 

criteria are met. 

(b) Verification with other mix 

design methodologies 

(i) PRADO 

The implementation of the Belgian 

Road Research Centre 

104

ecommendations (R69/97 for 

bituminous mix design) involves 

an analytical study prior to 

verification by mechanical testing. 

This analytical study is supported 

by a software package called 

PRADO (Programmes for Asphalt 

Mix Design and Optimisation). 

This method aims to achieve the 

best possible compromise between 

various (and sometimes 

conflicting) requirements such as 

dealing with both resistance to 

fatigue and rutting of the mix. In 

Volumetric and mastic 

evaluation of dolerite and 

quartzite mixes: 

Theoretical volumetric calculations 

using PRADO software were done 

for both the designs incorporating 

both dolerite and quartzite. The 

results of the volumetric analysis 

(estimating VIM, VMA and the 

filler/binder ratio - by both mass 

and volume – and the stiffening 

effect of the mastic) over a range 

of binder contents were calculated 

as follows: 

Dolerite 

Quartzite 

Binder content (%) 

4 

4.5 

5 

5.5 

4 

4.5 

5 

5.5 

Estimated VIM (%) 

PRADO 

7.7 

6.5 

5.3 

4.1 

6.2 

5.1 

4.0 

2.9 

VIM (%) laboratory 

7.7 

5.4 

4.0 

3.6 

6.8 

4.9 

3.2 

1.5 

Estimated VMA (%) 

PRADO 

VMA (%) laboratory 

Filler/binder ratio (by 

mass) 

Filler/binder ratio (by 

volume) 

T R&B increase (mastic vs 

binder) 

17.1 

17.5 

1.4 

0.49 

11.9 

17.1 

16.7 

1.24 

0.44 

10 

17.1 

16.5 

1.12 

0.39 

8.7 

17.1 

17.4 

1.02 

0.36 

7.7 

15.3 

15.7 

15.9 

0.60 

21.7 

15.3 

15.1 

1.41 

0.53 

17.4 

15.3 

14.7 

12.7 

0.48 

14.6 

15.3 

14.4 

1.16 

0.43 

12.5 

Table 2: PRADO Mix Design Estimates Versus Actual Volumes 

this approach, the stability of the 

mix can be ensured by making use 

of intergranular friction while 

avoiding overfilling the mineral 

skeleton with mastic (i.e. with 

filler and binder). This mastic 

should only fill part of the voids in 

the mineral aggregate and should 

also have the right consistency 

(i.e. the correct proportion of filler 

and binder). 

Dolerite aggregate evaluation 

results 

In general the estimated VIM and 

VMA values as predicted by 

PRADO are slightly higher than the 

values obtained in the laboratory. 

From Table 2 it can be seen that 

the increase in the Ring & Ball 

temperature of the mastic 

105

compared to the pure bitumen for 

the dolerite mix, falls below the 

recommended range of 12 – 16°C. 

This would imply that the mix is 

tender, soft and relative easy to 

place and compact, while 

resistance to permanent 

deformation during the service life 

might be reduced. The fatigue 

resistance, however, should be 

good. 

Quartzite aggregate evaluation 

results 

In general the estimated VIM and 

VMA values, as predicted with 

PRADO, are slightly higher than 

the actual values obtained. 

The increase in the ring and ball 

soft point temp (T R&B ) of the 

quartzite mix at the design binder 

content of 4.7% is 16.8ºC, which 

is above the upper recommended 

limit. This indicates that difficulties 

may arise with the compactability 

and workability of the mix. 

However, it may also have a 

positive effect on the deformation 

resistance of the mix provided 

durability is adequate and fatigue 

resistance within specifications. 

(ii) Bailey Method 

The Bailey Method of gradation 

evaluation focuses on the 

aggregate properties that affect 

the way aggregates fit together 

(or pack) in a confined space or 

volume (See Figure 1). To analyse 

the packing factors, the method 

defines four key principles that 

break down the overall combined 

aggregate blend into four distinct 

Figure 1: Bailey Method Mix Composition Principals 

106

compositional fractions (See Table 

4). Each fraction is then analysed 

for its contribution to the overall 

mix volumetrics. 

By comparing the size of particles 

that fit into the voids between the 

largest aggregate pieces, and the 

size of the largest aggregate 

pieces found in a fraction, ratios 

can be developed that are an 

indication of how well all the 

particles in the fraction fit together 

and what the mix characteristics 

will be like. The Bailey Method can 

be used to predict how changes in 

the factors that affect packing will 

change the resultant volumetrics, 

compactability and segregation 

potential of a particular mixture. 

See Table 3 for packing factors, 

which vary from mix to mix. 

• Principle 2: Evaluates the 

coarse fraction and how the 

particle sizes in the coarse 

fraction pack together, and 

how this influences the 

packing of the fine fraction. 

(The volume of voids in the 

coarse aggregate, course 

fraction compactability and 

segregation susceptibility are 

also appraised.); 


packing of the overall fine 

fraction in the combined 

blend; 


packing of the fine part of the 

fine fraction. 

All four principles of the Bailey 

Method are interactive and must 

be monitored for changes. If a 

Gradings 

Continuously graded 

Gap graded 

Compactive effort 

Type = static, impact, shearing 

Amount = field vs laboratory 

Strength 

Individual aggregate toughness 

Shape 

Flat and elongated 

Cubical or round 

Surface texture 

Smooth 

Rough 

Size 

Nominated max. particle size 

Table 3: Properties that influence mix packing and end compaction 

Principles of the Bailey 

Method: 

Four principles are adopted in the 

method: 

• Principle 1: Determines the 

break between coarse and 

fine aggregates. From this it 

is established which particles 

create voids and which ones 

fill them and which fraction 

(coarse or fine) is in control; 

gradation changes, then all four 

principals must be reviewed. 

Evaluation of Dolerite and 

Quartzite mixes with Bailey 

Method: 

The dolerite and quartzite mixes 

were evaluated with the four 

Bailey principles, and the results 

are given in Table 4. 

The dolerite mix, somewhere 

between coarse and fine (more 

107

coarse) graded, may be 

problematic as far as the Bailey 

Method is concerned, as the 

coarse and fine fractions could be 

struggling for control of the 

volumetric properties. The CA 

Ratio used is slightly higher than 

the upper acceptable limit 

suggested, which could indicate 

possible compaction problems in 

the field. The FA c ratio is within the 

acceptable limits, but the FA f ratio 

is slightly higher than the 

suggested upper limit which would 

indicate high mortar stiffness (as 

intended in the design for 

deformation resistance in the 

fundamental design methodology . 

This is contradictory to the PRADO 

analysis of the mix, which 

indicates a tender mix. Large 

quantities of this mix have been 

paved in Gauteng with no 

significant compaction problems 

(including various ORTIA 

applications over last three years). 

The quartzite mix is 

“coarse-graded” and the coarse 

aggregate is therefore in control of 

the volumetric properties. The CA 

ratio is higher than the upper 

acceptable limit suggested, which 

could indicate possible compaction 

problems in the field. The FA c ratio 

is within the acceptable limits, but 

the FA f ratio is higher than the 

suggested upper limit, which 

would indicate high mortar 

stiffness (as intended in the design 

to ensure good rut resistance). 

This is in agreement with the 

Ratio Principle Dolerite Quartzite Acceptable 

range 

CA Ratio 1 92.7 97.5

PRADO analysis. Large quantities 

of this mix have been placed at 

the ORTIA with no significant 

compaction problems; the 

compaction procedures were, 

however, thorough, with layer 

thickness at 40mm and above. 

(c) Verification with performance 

related properties (i.e. 

original mix specification) 

Various performance related 

properties were defined to ensure 

field performance requirements 

would be met. The results of the 

fine-tuned mixes to be used in the 

Gautrans Challenge are listed in 

Table 5. 

Field performance to date 

The dolerite alternative for the 

intersection mix (40/50 pen 

binder) was used in three airport 

pavement contracts over the past 

two to three years. Extracted field 

core values confirmed satisfactory 

field MMLS values at less than 1.6 

mm rutting, and conformance with 

all other performance criteria; field 

performance to date has been 

good, given the extremely 

aggressive taxiway traffic (i.e. 22 

ton wheel loading; 1 400 kPa tyre 

pressure). 

This design methodology and 

performance criteria were used on 

various projects in the Western 

Cape (N7 rehabilitation, M5 

Rehabilitation, Cape Town 

International Airport (CTIA) major 

taxiways rehabilitation, and in 

Gauteng area (various airport 

taxiway rehabilitation and roads 

projects). Assessment of these 

mixes, on all these pavements, 

indicated satisfactory performance 

Performance 

requirements 

Deformation 

resistance 

Test type and 

parameters 

used 

MMLS on 

briquettes at 

50 0 C dry (on 

cores) (mm) 

Average 

deformation per 

cycle in 2000 - 

3000 range of 

DCT (µ) 

Gyratory voids at 

300 repetitions 

(on a 5% 

Marshall VIMs 

volumetric 

setting 

Criteria set 

Mix 1 Mix 2 Mix 1: WC for 

highly trafficked 

roads 

Quartzite 

Performance value 

Mix 2: WC for 

highly trafficked 

intersection 

Dolerite Quartzite Dolerite 

80% 85 90 N/T 84 

Fatigue 

4 Pt beam 

fatigue (at 200 

micron strain): 

reps to failure 

>2 mil >2 mil To be 

tested 

To be 

tested 

4.3 

N/T 3.2 

million 

ITS (kPa) >1000 >1000 1 368 >1000 >1000 1222 

Table 5: Performance Simulation Properties (Criteria and test values obtained) 

109

testing results and very successful 

field performance to date. 

Experience with this mix design 

methodology goes back to CTIA 

taxiway mixes placed in 2001/2. 

To date an equivalent 300 000 x 

22-ton wheel loadings (1 400 kPa 

tyre pressures), or an equivalent 

of 250 million E80’s, was carried 

without any deformation or 

durability problems. 

Previously, the conventional 

“middle of envelope” mixes utilised 

at the Much plant at Benoni 

(before 2003) showed MMLS 

values of ±3 to 3.5mm rutting. 

After compositional modification in 

accordance with the fundamental 

design methodology utilised in this 

study, this was changed (as listed 

above) to high performance rut 

resistant mixes – however, it is 

still “binder-rich” (due to good 

VMA values in the region of 16%) 

and therefore still has good fatigue 

resistance and durability. 

A full scale APT evaluation of trail 

sections of these mixes is planned 

for mid 2007 and an update of 

these results can then be reported 

to the industry. 

 

References: 

1 

F.J. Pretorius, K.J. Jenkins, F. Hugo, 

D. Vietze: Innovative Asphalt Mix 

Design and Construction : Case studies on 

CTI Airport and Kromboom Parkway. 

Paper presented at the 21st ARRB and 11th 

REAAA Conference, Cairns, 

Australia, 2003 

2 

K.J. Jenkins, F.J. Pretorius, F. Hugo, 

R. Carr: Asphalt Mix Design for 

Cape Town International Airport using 

scaled APT and other selected tests. 

6th International RILEM Symposium on 

Performance Testing and Evaluation of 

Bituminous Materials, PTEBM’03, Zurich, 

Switzerland, 2003 

3 

F.J. Pretorius, J.E. Grobler, J. Onraët: 

Development of a Fit-for-Purpose Product 

Performance Specification System for 

Asphalt Mixes. Paper presented at 

CAPSA'04, Sun City, 

South Africa, September 2004 

110

HMA research programme: 

Forensic investigation into 

premature distress in asphalt 

Elzbieta Sadzik 

Materials Engineer 

Gauteng Department of Public Transport, Roads and Works 

As part of a drive by the 

Gauteng Department of 

Public Transport, Roads 

and Works (GPTRW) to 

re-examine a number of 

unresolved issues associated 

with hot mix asphalt, a project 

was launched not only to 

define these issues, but also to 

serve as a catalyst for 

solutions to be sought jointly 

by the asphalt industry and 

consulting engineers. 

The project incorporates forensic 

and laboratory studies to define 

and, ultimately, redress premature 

distress of hot mix asphalt. This 

initiative seeks to bring about a 

common understanding of the 

issues at stake, a systematic 

response through innovative 

designs, and an accelerated 

pavement testing programme 

(APT) to evaluate the various 

proposals and to develop 

standards for hot mix asphalt over 

a range of operating conditions. 

In the last few years several 

incidents of unsatisfactory 

performance of HMA have been 

encountered on provincial roads in 

Gauteng. The poor performance 

was manifested in excessive 

deformation, especially at 

intersections, and premature 

cracking. In many instances, the 

HMA design life reduced from 8-10 

years to 4-6 years. Consequently, 

the financial viability of HMA 

became questionable. 

Research 

The GPTRW commissioned the 

CSIR Built Environment to develop 

an HMA research programme not 

only to investigate the causes of 

this unsatisfactory performance, 

but also to address several other 

unresolved issues associated with 

HMA, including: 

• The need for reliable test 

procedures and acceptance 

criteria for the assessment of 

permanent deformation and 

fatigue; 

• The need for reliable test 

methods to assess the 

durability of HMA; and 

111

Figure 1: A typical example of deformation 

(Courtesy of CSIR) 

• The need to assess the 

implications of contact stress 

magnitudes and distributions 

on the performance of HMA. 

An HMA research programme was 

proposed consisting of: 

• Desk-top studies; 

• Forensic investigations; 

• Laboratory studies; and 

• Accelerated Pavement 

Testing (APT) involving both 

the HVS and the MMLS. 

Forensic investigation 

The forensic investigation was 

conducted in two phases, namely 

a preliminary and a detailed 

investigation. The purpose of the 

preliminary investigation was to: 

• Assess the quality of the mix 

designs in broad terms; 

• Identify the differentiating 

characteristics of good and 

poor performing sections; 

• Attempt to identify the 

causes of the failures; and 

• Identify sections for the 

detailed forensic study. 

The preliminary forensic study 

concluded that: 

• Mix design needed to be 

better aligned with the design 

environment; 

• More attention should be 

devoted to aggregate 

packing; 

• More rut resistant mixes 

should be selected for 

intersections; and 

• Design protocols for SMA 

needed to be developed 

and/or refined. 

The objectives of the detailed 

forensic investigation were to 

better understand the typical 

characteristics of good and poor 

performing HMA mixes, and to 

identify mix design aspects that 

require further study in the HMA 

project. 

Detailed investigations were 

conducted on several sections of 

the provincial road network which 

were classified as both good and 

poor performers. As part of these 

investigations, non-destructive 

testing, such as FWD deflections, 

Dynamic Cone Penetrometer and 

seismic testing, were conducted, 

as well as laboratory tests on 

cores extracted from the sections. 

The forensic investigation included 

a range of stone mastic asphalt 

(SMA) mixes, medium 

continuously graded mixes and a 

bitumen rubber continuously 

graded asphalt mix. 

112

Conclusions 

The following conclusions related 

to the mechanisms of failure were 

drawn: 

1. Permanent deformation: 

• lack of proper support from 

the underlying structural 

pavement layers or the 

existing asphalt layer(s); 

• lack of resistance to 

permanent deformation of 

the new asphalt overlay. 

2. Cracking: 

• premature 

ageing of the 

binder where 

the asphalt 

layers were 

found to be 

permeable; 

• stripping and 

disintegration 

of old/new 

asphalt layers 

resulting in a 

lack of support 

provided to the overlays. 

During the forensic investigation, 

it also became apparent that 

current procedures to ensure that 

only approved mixes materialised 

on site were not satisfactory and 

required urgent attention. The 

same applies to the recording of 

“as built” data. 

Recommendations related to the 

design and performance of asphalt 

overlays included the following: 

• The design of new asphalt 

overlays should meet the 

Forensic study: 

Mix design 

needs to be 

better aligned 

with the 

design 

environment 

demands of the site where it 

will be applied; 

• Designs should be based on 

reliable traffic loading 

information and not only on 

nominal traffic volumes; 

• There is a need to develop 

mixes that depend more on 

the stone skeletons and less 

on the binder stiffness for use 

on sites subjected to slow 

moving traffic such as at 

intersections; 

• More attention should be paid 

to the mechanisms of distress 

of the existing 

pavement. 

The following main 

recommendations 

were made as a 

result of the 

investigations: 

• Asphalt and 

structural 

designs need to 

be based on 

appropriate 

rehabilitation 

investigations; 

• SMA design procedures 

should be reviewed; 

• The Bailey Method should be 

validated for South African 

conditions and be used as an 

aid to optimise HMA 

aggregate packing 

characteristics and also as an 

aid to quality control. 

Aggregate packing 

As a part of a desk top study for 

the forensic investigation, an 

international literature study was 

conducted to identify new tools 

that could be used to improve the 

113

aggregate structure of asphalt 

mixes. Grading characteristics of 

HMA mixes investigated in the 

forensic study were analysed using 

the principles of the Bailey 

Method, as well as related 

techniques such as the Dominant 

Aggregate Size Range and the 

permeability characteristics of the 

mix. 

Based on the limited number of 

mixes studied, it would seem that 

these analysis techniques hold 

good potential for South Africa. 

Industry challenge 

The asphalt industry has accepted 

this challenge enthusiastically and 

has come up with several 

interesting designs, which will be 

evaluated as part of the HVS 

testing programme (see page 

102). The innovative asphalt 

mixes included the following: 

• Stone skeletal HMA used at 

airports; 

• High Modulus Asphalt; 

• HMA mix designed according 

to the Bailey Method; and 

• HMA mix manufactured with 

chrome slag aggregates. 

An intended APT study on durable, 

rut-resistant mixes submitted by 

industry in response to a challenge 

issued by GPTRW has been 

preceded by meetings held with 

representatives of Sabita members 

– asphalt suppliers, together with 

their advisers and contractors. At 

these meetings discussions 

centred on problems encountered 

in asphalt mix design, aggregate 

supply logistics, consistent 

production and quality 

management processes. 

A general conclusion was that the 

COLTO specification for aggregate 

grading of asphalt mixes may no 

longer predicate optimal aggregate 

packing given the current 

aggregate shapes, and that other 

methods e.g. Bailey or PRADO 

may be more beneficial. 

A key objective of this cooperative 

effort of GPTRW and industry is to 

encourage innovative thinking 

without being restricted by current 

specifications. 

Figure 2: HVS with climatic chamber 

testing a standard mix 

APT and laboratory study 

APT and LTPP studies have 

commenced on road P159/1 (R80) 

with the testing of a standard 

asphalt mix commonly used in 

Gauteng. These studies, which are 

linked to an extensive laboratory 

114

test programme, will seek to 

develop appropriate test protocols 

and acceptance criteria for the 

assessment of permanent 

deformation of hot mix asphalt. 

The standard mix was constructed 

in three different layer thicknesses 

– 25mm, 40mm and 60mm – and 

the APT testing will be performed 

at three different temperatures – 

40 0 C, 50 0 C and 

60 0 C, using three 

different loading 

conditions. Future 

tests will compare 

the optimised 

designs submitted 

by industry with the 

performance of 

these conventional 

“box standard” 

mixes. 

This approach will 

create a better 

understanding of 

the mechanisms 

associated with permanent 

deformation and will allow 

designers to consider site-specific 

conditions, such as climate, traffic 

loading and pavement structure, 

in their designs. 

This cooperative 

effort of GPTRW 

and industry 

is to encourage 

innovative thinking 

without being 

restricted 

by current 

specifications. 

As good performance comprises 

resistance to both rutting and 

cracking, as well as durability, all 

experimental mixes will be 

monitored over extended periods 

of time to assess all these 

performance characteristics. 

It is anticipated that the APT 

testing of the standard mix will be 

completed by July 2007, after 

which the results 

will be evaluated to 

formulate 

recommendations 

that will ensure 

improvements in 

both the design of 

asphalt, the design 

of rehabilitation 

actions, and quality 

management of hot 

mix asphalt. 

More information on 

the forensic testing 

can be found in the 

Summary Report: 

Forensic Investigation into the 

Performance of Hot Mix Asphalt 

no: CSIR/BE/IE/2006/0015/B 

by E. Denneman and E.J. van 

Assen. 

 

115

5 

Best 

Practice

Out of the box thoughts on traditional mixes: 

Old habits die hard – 

especially in Cape Town! 

Julian Wise 

Director 

Zebra Bituminous Surfacing cc 

I've been a Capetonian for 

more than 60 years and 

yes, it is a great place to 

live, work and play. I've been 

here so long, I could probably 

write a booklet entitled How to 

enjoy Cape Town without 

actually moving! 

But what is it about the place that 

makes us feel and act differently 

from other areas – perhaps the 

mountains and coast, the 

(unpredictable) weather, 

vineyards, sugarbirds, Tweede 

Nuwe Jaar, the noon-day gun, the 

laid-back attitude, the perception 

that civilisation stops at Sir 

Lowry's Pass and all those other 

strange traditions that give this 

city its great character. 

One of these that I find as exciting 

and enjoyable as visiting the 

dentist is paving the traditional 

SABS asphalt mix normally 

specified for residential roads. This 

is: 

• 25mm thick; 

• 13.2mm maximum size 

stone; 

• 5% bitumen 

(60/70 pen); 

• 4.5% voids in the mix. 

When only 25mm thick, the 

proportionally large size aggregate 

and voids in the mix value cause 

the mix to be: 

• more difficult to compact 

than need be; 

• more permeable, thus putting 

the asphalt and base at risk; 

• more difficult to get good 

surface finish with handwork. 

Another fact not usually realised is 

that the compaction window of a 

25mm mat can range from as low 

as: 

• 6 or 7 minutes on a cold, 

windy day; 

• only 13 or 14 minutes on a 

blinding hot, windless, 

summer day. 

Enough time for rolling in cold 

weather? Enough time for placing 

by hand, then rolling? 

I don't think so mate! 

119

But the traditionalists doggedly 

persist in specifying it for 

low-traffic roads and parking areas 

that: 

• do not lend themselves to 

production paving or rapid 

compaction; 

• have a fair amount of 

handwork; 

• have low quality base course 

(G3 to G5, laterite, crushed 

rubble, calcrete, all of 

variable quality), that is not 

finished to a high standard; 

• have actual asphalt; 

thicknesses that can easily 

range from 15 to 35mm. 

(Imagine the compaction 

window time for a 15mm 

thick area!). 

The tradition joyfully continues by 

making sure that most of these 

jobs are paved in winter, when as 

long as it is not raining, it's 

regarded as a good paving day! 

"The job HAS to be handed over 

tomorrow y'know", followed by the 

phrase that has supported the 

movies for a generation “Don't 

worry, everything will be OK". 

Ja well no fine 

And then the subtle assurance 

“I'm sure the Engineer will 

understand." 

They don't say what it is the 

Engineer will understand – it 

usually turns out to be only what 

the specification says! And when 

the core results come out, they all 

promptly forget about the 

pressure-cooker situation at the 

time. 

The result? Typical problems 

encountered are: 

• erratic and variable density, 

especially in winter; 

• excessive permeability; 

• erratic surface finish, 

particularly with handwork; 

• increased risk to the base 

from the above. 

The root cause of these problems? 

The mix design is not appropriate 

for the application and 25mm 

thickness. (It is suitable for 

production paving of a 40mm thick 

layer.) 

"Nonsense,” some of you will be 

saying, “I've been using this mix 

for 35 years, and can show you 

many roads that are still perfect." 

Ja well no fine! 

Granted, this mix is not a 

complete disaster, but: 

• specs have tightened – 95% 

Marshall has largely been 

replaced with 92% Rice; 

• 60/70 pen bitumen has 

replaced the 80/100 used 35 

years ago; 

• in my experience testing has 

become “more thorough” to 

put it politely. 

Certainly not every core will be a 

failure, but the more thoroughly 

you test this mix, the more 

failures you generally find. I too 

can name many roads and parking 

areas that have failed to some 

extent – failed in density and 

failed to last a reasonable lifespan. 

Am I a lone wolf howling in the 

wilderness? 

120

Or more appropriately, a lone thar 

bleating on the mountaintop? 

Sabita's August 2006 edition of 

Asphalt News has a short article 

on research done by NCAT (USA) 

on Lift Thickness versus Nominal 

Maximum Aggregate Size 

(t/NMAS). (NMAS = 1 size larger 

than the first sieve to retain more 

than 10%). This extensive 

research can be found on the 

following website: 

www.eng.auburn.edu/centre/ncat/ 

reports. 

The report says it all in these 

“deep and meaningfuls": 

• Mixes with larger maximum 

size aggregates have larger 

voids that are more likely to 

be inter-connected, resulting 

in higher permeability; 

• As density decreases, 

permeability increases; 

• As thickness decreases, 

permeability increases; 

• Therefore mats that are 

thicker, with higher 

density and smaller 

maximum size aggregate 

will be less permeable. 

Figure 1 is a chart from this 

research and shows the effect of 

t/NMAS on permeability. It is a 

trend curve for a variety of 

fine-graded mixes, and NCAT's 

recommendation is: 

t/NMAS should be at least 3:1 

(Note the “at least")! Our 

traditional mix is 1.9:1, which 

from Figure 1 indicates it may be 

60% more permeable than if it 

was 3:1. 

Oh dear, is our sacred cow in 

danger of becoming mincemeat? 

Figure 1 

121

The publication, Interim Guidelines 

for the Design of Hot Mix Asphalt 

in South Africa (prepared in 2001 

as part of the Hot Mix Asphalt 

Design Project launched in 2001 

by SANRAL, the CSIR and Sabita), 

supports this. A few extracts are: 

• Clause 2-16: Current 

specifications limit the 

maximum aggregate size to 

not more than half the 

compacted mat thickness. 

Designers should consider 

decreasing this limit; 

whenever conditions are 

anticipated in which 

compactibility or segregation 

might pose problems during 

construction; 

• Clause 2-18: Selection of 

maximum size aggregate i.e. 

9.5mm for 25mm thick mats; 

• Clause 4-8: Minimum voids in 

the mix for light traffic is 

3.5%. 

Impermeability 

What should be the main purpose 

of such a thin layer on low quality 

base in a heavy winter rainfall 

area? 

Impermeability for a start! 

Impermeability and good 

compaction go hand in hand. We 

don't want to pave thicker do we, 

that would be too much of a break 

in tradition. But we can easily 

design for higher density and low 

permeability. 

Design the mix for quick, easy 

compaction – remember the very 

short compaction window time. 

• Use a small maximum size 

aggregate; 

• Use a high bitumen content 

to provide good lubrication 

for compaction; 

• Target a low voids in the mix 

– light traffic will only 

marginally increase the 

construction density, so there 

is no risk of rutting or 

bleeding. 

What were the origins of this 

stubborn, ingrained tradition? Bob 

Kingdon tells a fascinating story. 

The construction of the freeway 

system in Cape Town in the 60's 

prompted the establishment of 

three production HMA plants. As 

freeway projects tailed off, the 

producers looked for alternative 

markets to keep their plants busy. 

Cracked windscreens 

In addition, the standard surfacing 

for residential roads then was a 

single seal. To allow immediate 

opening to traffic, chips were 

spread at a rate 1.2 times higher 

than was called for by the design. 

Result was a period of flying chips 

and cracked windscreens until the 

team came back to sweep up the 

excess. 

So the authorities were looking for 

an alternative, especially for the 

then emerging Michells Plain. 

The wearing course for the 

freeways had been approved and 

established – 40mm thick, 

13.2mm maximum size aggregate 

CCC mix. 

So just reduce the thickness to 

20mm to make it economical 

enough to compete with the single 

122

seal, and everybody's happy! Or 

were they? 

Bob remembers that this mix was 

made with 80/100-pen bitumen, 

and was paved on primed 

ferricrete. 

"It was not an unqualified failure,” 

he says ruefully, “but we had 

endless problems with achieving 

density." 

What's changed? 

OK, so now it's a nominal 25mm 

thick, but is mixed with a stiffer 

60/70-pen bitumen that needs 

more compactive effort to get 

density. 

More rolling takes longer ... so the 

mat must stay hotter for longer – 

but it doesn't, does it! 

Impermeability 

Carl van der Merwe (UWP) 

designed a mix for Khayelitsha 

residential roads about 10 years 

ago. His main priority was 

impermeability to guard against: 

• "grey” water damaging the 

asphalt and base; 

• flooding due to blocked storm 

water catchpits. 

The mix was basically a Colto Fine 

paved 25mm thick using: 

• 6.7mm maximum aggregate; 

• 6% bitumen; 

• 1.5 to 3% voids in the mix. 

"Oh horrors!” I hear some of you 

cry, “It will bleed, it will rut"... 

No it won't – the light traffic does 

not increase compaction over what 

is achieved at construction. Good 

compaction was achieved even 

doing handwork, and ten years 

later these roads are in really 

excellent condition. It was a good 

design and it worked. 

Brian Roussouw (Kayad), that 

singularly innovative engineer, 

designed his township mix 

because he was sick of the 

problems using the traditional mix. 

“I wanted a contractor-proof mix 

that could be adequately 

compacted and looks good even 

with handwork,” he said. 

Recommended mix 

His “Kayad” mix is classed as a 

9.5mm NMAS fine-graded mix. 

Again this mix compacts more 

easily and is less permeable than 

the traditional. 

If anyone is still reading and 

doesn't consider this article the 

demented ramblings of a biased, 

senile contractor, my 

recommended specification to 

ensure compactibility and low 

permeability for a 25mm thick 

mat, using Cape Town aggregates, 

is: 

• a sound base with a high 

quality, primed finish; 

• a tack coat; 

• a mix with 9.5mm max size 

stone; 

• 3 to 4% target voids in the 

mix; 

• bitumen content for this is 

usually 5.5 to 5.6%; 

• filler/binder ratio 1.1 to 1.2. 

The advantages are: 

123

• Fewer roller passes needed to 

achieve compaction; 

• Better and more consistent 

density; 

• Improved permeability and 

thus more base protection; 

• Less cold weather risk; 

• Better for handwork; 

• More durability and a longer 

life. 

The disadvantages are: 

• Suitable only for light traffic; 

• It costs more (due to higher 

bitumen content). OH 

HORRORS! 

BUT IT WORKS. So decide for 

yourself whether you can afford it 

or not. 

Now, let me get on to Cape Town's 

Colto Coarse wearing course, 

paved 40mm thick, but using a 

massive 26.5mm max size stone. 

When I bounced this mix design 

off Bill Pine of Bailey Method 

research fame, his reaction was 

“Ha, ha, ha, ha, ha. Good luck to 

them!" 

On second thoughts, maybe I've 

been confrontational enough for 

one year, so I will save it for next 

year's Digest. 


Julian Wise gratefully acknowledges 

the inputs of Bob Kingdon, 

Carl van der Merwe and Brian 

Roussouw. 

 

124

The status quo on landfill sites: 

Disposal of penetration grade 

bitumen in South Africa 

Dr Mannie Levin 

Geohydrologist 

Africon Engineering International (Pty) Ltd 

In 2002 Sabita undertook 

an evaluation study of the 

classification and disposal 

options for penetration grade 

bitumen in South Africa. 

Samples of penetration grade 

bitumens from the four refineries 

in South Africa, labelled, A to D, 

were analysed and evaluated 

according to the Department of 

Water Affairs and Forestry’s 

(DWAF) Minimum Requirements 

for the Handling, Classification and 

Disposal of Hazardous Waste, as 

published in 1998. The objectives 

were to classify the bitumens and 

to determine the type of landfill 

required for their disposal. 

The approach in the Minimum 

Requirements is essentially a Tier 

1 or primary assessment of the 

risk posed by the materials to the 

environment, but the report 

includes an assessment of some of 

the Tier 2 or waste and site 

specific risks. 

The analyses undertaken included 

a head or total analysis of each of 

the samples for organic 

components by gas chromatographic 

and HPLC methods, 

together with leaching of the 

samples using the Toxicity 

Characteristic Leaching Procedure 

(TCLP) of the US Environmental 

Protection Agency (EPA). The 

leach solutions were analysed for 

a wide range of inorganic and 

organic analytes. 

Classification 

The Minimum Requirements 

demand a primary classification of 

the cold bitumen according to 

SABS Code 0228; the four 

samples were non flammable, i.e. 

the flash point is 61 0 C; corrosive, 

i.e. the pH is >6 or

The total analysis of the bitumens 

showed that they contained small 

amounts of volatile aromatic 

hydrocarbons, notably the BETX 

compounds and trimethylbenzene 

isomers, plus low amounts of 

polycyclic aromatic hydrocarbons 

(PAHs) such as naphthalene, 

anthracene, phenanthrene and 

pyrene: none of the PAHs 

observed are classified as known 

human or animal carcinogens. 

provided the estimated 

environmental concentration is 

less that the acceptable risk limit 

of the species, in this case Pb. 

Therefore, all the penetration 

grade bitumens delisted for 

disposal to general waste sites and 

can be disposed to medium or 

large general waste landfills that 

have a leachate management 

system, i.e. GMB+ or GLB+. 

Traces of chloroform, bromodichloromethane 

and phthalate 

esters were also detected in some 

of the samples. Although these 

organic species were identified in 

the bitumen samples, only toluene 

was detected in the leach solutions 

– but at trace levels close to the 

detection limit of 1ppb. There are, 

therefore, no 

organic compounds 

leached from the 

samples that can 

have a significant 

impact on the 

environment. 

Two samples of the 

penetration grade 

bitumen, B and D, 

leached Pb at 

concentrations just 

above its acceptable 

risk limit of 0.10 

mg/l and, therefore 

formally classify as 

high hazard (HG2) wastes in terms 

of the Minimum Requirements. 

Samples A and C formally 

classified as non-hazardous in 

terms of the Minimum 

Requirements. Even though a 

waste formally classifies as 

hazardous it can be delisted for 

disposal to a general waste landfill 

There are no 

organic 

compounds 

leached from 

the samples 

that can have 

a significant 

impact on the 

environment. 

Final report 

The final report produced early in 

2003 proposed that application be 

made to DWAF for approval of the 

delisting of penetration grade 

bitumens and that this include a 

request also for disposal to GBsites 

because GB+ landfills are not 

available in many 

areas within a 

reasonable 

transport distance. 

In their reply 

received on the 9th 

June 2004 DWAF 

gave permission for 

bitumen waste to 

be considered 

delisted subject to 

the conditions that 

if any uncertainty 

exists about 

whether a specific 

material falls within 

the tested parameters, then 

further analysis and leachate tests 

may be required. The delisted 

material may only be disposed of 

on a permitted facility, after the 

Permit Holder has applied and 

received written permission from 

DWAF. 

127

In August 2004 a status quo 

report was produced on the 

available landfill sites that could be 

considered for the disposal of 

penetration grade bitumen. A 

register of available sites was 

obtained from DWAF, and it was 

concluded that a limited number of 

B+ sites exist in South Africa and 

B- sites will have to be considered. 

Sabita members were asked to 

indicate their choice for localities 

where sites should be available, 

and to provide an estimate of the 

disposal volume. Twenty five sites 

were selected, and letters were 

sent to these sites informing them 

of the delisting, and of the request 

from Sabita that they be permitted 

to receive delisted penetration 

grade bitumen. 

Poor response 

The response was poor, with only 

a few sites reacting to the request. 

Margate indicated that the 

estimated amount of bitumen 

waste at that site did not warrant 

the cost of permitting. East 

London indicated that their Second 

Creek site was closing down and 

was not available. Similarly, the 

George site closed down and 

cannot be considered. The good 

news was that Durban was 

considering permitting some sites 

and that Ekurhuleni Metropolitan 

Municipality permitted their 

Rietfontein Landfill Site. 

The new Environmental Act came 

into effect on 1 March 2006 and 

the responsibility for permitting 

landfill sites was transferred from 

DWAF to the Department of 

Environmental Affairs and Tourism 

(DEAT). Communication with 

DWAF and DEAT during this period 

did not produce any results on 

applications for permitting by any 

of the selected sites. A new letter 

was sent to the selected sites, now 

reduced to eighteen, informing 

them of the change and 

requesting them to submit new or 

resubmit applications (if submitted 

previously) to DEAT in Pretoria. 

The result was disappointing, as 

some letters were returned 

unopened because municipal sites 

closed and district municipalities 

had taken over and opened new 

sites. The register at DWAF was 

clearly outdated. A new effort was 

taken and each municipality and 

or district municipality contacted 

to find the authority and 

responsible person with whom to 

communicate. 

The sites were now reduced to just 

11, excluding any municipal or 

commercial H:H sites. Most people 

are positive regarding permitting, 

subject to fund availability and/or 

a final acceptance of the request 

by the Local Council. 

It is uncertain how long it will take 

before adequate facilities for 

disposal of penetration grade 

bitumen are available. IMIESA in 

its October issue published an 

item informing people of Sabita's 

efforts to promote all aspects of 

health, safety and environmental 

conservation in the South African 

bituminous products industry. The 

efforts of Sabita will however 

continue, and with the support of 

DWAF, DEAT and the local 

authorities, permitting should be 

finalised during the next year. 

128

Adequate layer bonding critical: 

Bond and tack coats to improve 

total structural integrity 

Kobus Louw 

Research and Development Manager 

Colas SA (Pty) Ltd 

Worldwide, the design 

and construction of 

long lasting asphalt 

pavements is becoming 

increasingly important as 

greater demands are placed on 

the performance of these 

asphalt layers. 

Adequate bonding between 

asphalt layers is critical if the 

completed structure is to behave 

as a single structural unit and 

provide adequate strength. If the 

layers are not properly bonded 

together, they will behave as 

independent thin layers. 

Generally, such individual layers 

are not designed to accommodate 

the stresses imposed by current 

traffic patterns. Damage due to 

fatigue and deformation proceeds 

at a faster rate when a proper 

bond has not been created, 

resulting in rapid deterioration of 

the pavement structure. 

Inadequate bonding can result in 

delamination, cracking, potholes 

and ingress of water into the 

pavement structure. 

Over-application of the tack coat 

can result in slippage of the 

asphalt layers due to the 

lubricating effect of the excess 

binder. 

Tack coats 

Tack coats have traditionally been 

used in South Africa for improving 

the adhesion of hot mix asphalt 

layers to the substrates on which 

they are placed. These mixes are 

usually placed at a thickness of 15 

– 60mm. Anionic stable mix 

emulsion diluted with equal 

quantities of water is commonly 

used for this purpose. The 

application rate specified in COLTO 

is 0,55 l/m 2 for a 30% binder 

content emulsion, leaving a net 

residual binder application of 

approximately 0,165 l/m 2 . The 

method of application is often with 

a hand sprayer, and the resulting 

spread rate and evenness of 

application usually leaves much to 

be desired and may be referred to 

as “a lick and promise”. Paving 

can only commence after the 

emulsion has “broken”. 

130

Bond coats 

Bond coats were first used with 

the introduction of the integrated 

paver/sprayers for application of 

Ultra Thin Friction Course (UTFC) 

asphalt in South Africa in 1999. 

These thin, open graded asphalt 

layers are placed at an average 

thickness of 18mm. The strains 

induced by traffic at the surface/ 

binder interface are much greater 

than the forces acting on the 

thicker asphalt layer/binder 

interfaces, and undiluted rapid 

setting cationic polymer modified 

emulsions are thus used for this 

purpose to ensure adequate bond 

strength at the interface. 

The thin asphalt 

surfacing layer and 

the bond coats are 

usually offered as 

an integral package 

by the applicators. 

The paving unit 

applies the binder 

uniformly using a 

calibrated, 

computer 

controlled, spraying 

system. In the case 

of simultaneous application, the 

free water in the emulsion bond 

coat foams when it comes into 

contact with the hot mix asphalt. 

The reduced viscosity of the 

foamed binder and its subsequent 

expansion allows the binder to 

penetrate more effectively into the 

existing substrate and overlying 

mix, thus creating an improved 

bond. 

Application rate of the bond coat 

varies typically between 0,4 – 0,6 

l/m 2 depending mainly on the 

Deformation 

proceeds 

at a faster 

rate when 

a proper bond 

has not been 

created 

substrate texture, leaving a 

residual modified binder 

application of 0,26 to 0,39 l/m 2 , 

which is considerably higher than 

the residual binder content used 

for the conventional, thicker 

asphalt lifts. The thicker residual 

binder layers also provide better 

waterproofing, as the thinner, 

open graded asphalt layers are 

more prone to allowing water 

infiltration compared to the 

conventional, dense layers. 

Specific requirements 

• High softening point of 

residual binder to prevent 

excessive migration into the 

open UTFC 

aggregate 

structure under 

traffic after 

paving; 

• Very rapid 

setting 

characteristics. 

The UTFC layer is 

very thin and 

rapidly cools 

down after 

paving. During 

the time interval 

when the mat is at a 

temperature in excess of 

100 0 C, most of the water in 

the emulsion should boil off. 

The emulsion should be 

sufficiently de-stabilised 

during this short period to 

prevent re-emulsification, 

which could occur if 

unexpected rain falls on the 

surface within the first few 

minutes after paving; 

• Despite the rapid setting 

characteristics required of a 

bond coat, the emulsion 

131

should also be stable enough 

to withstand repeated heating 

cycles during handling and 

the highly detrimental 

shearing action of the 

transfer and dosing pump on 

the paver. 

Benefits associated with the use of 

bond coats are: 

• Greater cohesive strengths; 

• Greater adhesion; 

• Improved waterproofing. 

Modified emulsions 

SBR modified bitumen emulsions 

(three phase emulsions) are 

commonly used worldwide as bond 

coats. In Europe and America, SBS 

modified bitumen emulsions (two 

phase emulsions) are growing in 

popularity for this type of 

application. These emulsions are 

not yet available in South Africa, 

due to the specialised equipment 

required in the manufacturing 

process. 

Evaluation 

(i) In Britain, bond coats are 

characterised in the Specification 

for Highway Works (SHW) by 

their Vialit Pendulum Peak Binder 

Cohesion value. The test involves 

the measurement of the cohesion 

of recovered emulsion binders 

over a range of temperatures to 

obtain a cohesion-vs-temperature 

relationship. A stainless steel 

cube with a surface area of exactly 

1 cm 2 is attached, using a 1mm 

thick film of the recovered binder, 

to another fixed cube of similar 

area. The energy required to 

dislodge the cube at various 

temperatures by a swinging 

pendulum arm is determined. 

Intermediate grades should have 

a minimum peak value of 1,0 

J/cm 2 while the high performance 

grades should have a minimum 

Figure 1 

132

peak value of 1,2 J/cm 2 . Typical 

results appear in Figure 1. 

(ii) Julian Wise and Derick 

Pretorius conducted tests in 2003 

to determine the shear force 

required to dislodge a UTFC layer 

from a continuously graded SABS 

mix. 

In summary the following 

procedures were conducted: 

• Base briquettes were 

prepared in Marshall moulds 

according to the SABS mix 

specification, and compacted 

to 88% and 90% respectively 

of Rice, and allowed to cool; 

• Bond coat applied on top of 

SABS mix, followed by UTFC, 

and compacted with 100 

blows on one side only; 

• Composite briquette pushed 

partly out of mould to expose 

joint; 

• Load applied with a CBR 

press to determine shear 

force. 

The effect of the bond coat 

application rate on the 

permeability of the SABS mix was 

also evaluated. The results are 

summarised in Table 1. 

Handling 

Unlike conventional tack coat 

emulsions, bond coat emulsions 

are very shear and temperature 

sensitive, and should be handled 

strictly in accordance to the 

method prescribed by the 

suppliers. These are generally 

latex modified emulsions, which 

are sensitive to pumping and 

heating. Excessive pumping 

and/or heating forms tough, 

irreversible deposits, which can 

block the very small nozzles used 

by the integrated paver/sprayers. 

This can often lead to extensive 

delays on site. Special care should 

thus be taken during loading, 

heating and transfer operations to 

prevent damage to the emulsion. 

Bond strength 

The bond between the overlaid 

material and the existing surface 

is a function of: 

• Application rate: the quantity 

of tack or bond coat required 

is a function of the surface 

texture of the overlaid 

surface. Rough, milled 

surfaces have a surface area 

approximately 30% larger 

Bond coat (l/m 2 ) 

Degree of 

compaction 

(% of Rice) 

Average 

Permeability 

l/hr 

Average 

Tangential 

Tension (kPa) 

0.4 88 1.3 853 

0.4 90 0.2 689 

0.7 88 2.6 831 

0.7 90 0.2 772 

1.01 88 0.4 882 

1.01 90 0 752 

Table 1 

133

than smoother surfaces, and 

the quantity of tack or bond 

coat required for optimum 

adhesion is thus also larger. 

Under application can lead to 

bond failure, while 

over-application can lead to 

slippage and bleeding in the 

case of UTFC. The migration 

of excess binder from the 

bond coat into the UTFC is 

the single greatest risk to the 

functional performance of the 

new layer. For example an 

over application of 0.1 l/m 2 of 

net binder which migrates 

into the UTFC can increase 

the binder content of a 4.5% 

binder content 

UTFC mix by 

0.35% and 

reduce the air 

voids by 3%!; 

• Surface 

texture: 

rougher 

surfaces will 

adhere better 

to the overlaid 

asphalt layer 

than smoother 

layers; 

• Type of binder: 

very thin 

layers generally require 

undiluted polymer modified 

emulsions for optimum 

adhesion due to the larger 

stresses to which these 

surfaces are subjected; 

• Uniformity of application of 

the tack/bond coat: where 

possible, these materials 

should be applied with a 

calibrated binder distributor 

or spraying system to ensure 

a uniform and accurate 

application rate. At least 90% 

An over 

application of 

0.1 l/m 2 of net 

binder which 

migrates into 

the UTFC can 

reduce the air 

voids by 3% 

of the surface should be 

evenly covered to prevent 

defects in the overlaid 

material; 

• Cleanliness of the existing 

surface – tack or bond coats 

will not adhere to dusty, dirty 

surfaces and will be picked up 

by site traffic, leaving areas 

with insufficient binder to 

ensure proper adhesion of 

the overlaid material; 

• Control of site traffic: site 

traffic should not be allowed 

onto tacked areas before the 

emulsion has broken. The 

unbroken emulsion will be 

picked up on the vehicle 

tyres, leaving 

areas with 

insufficient 

binder to ensure 

optimum 

adhesion. 

Properties 

Mostly, anionic 

stable grade 

emulsions 

conforming to the 

requirements of 

SANS 309 are 

diluted and used as 

tack coat emulsions during hot 

mix applications. In some 

instances cationic spray grade 

emulsions, conforming to SANS 

548, are also used in a diluted 

form. However most users are 

unaware of the fact that cationic 

spray grade emulsions almost 

always contain a certain 

percentage of hydrocarbon solvent 

(flux). As this type of emulsion is 

generally used for surface dressing 

operations, the hydrocarbon flux is 

added to soften the binder and 

134

promote the breaking of the 

emulsion. It also enhances early 

mosaic development of the stone 

matrix in a seal. 

The quantity of flux in cationic 

spray grade is varied on a 

seasonal basis, with the higher 

hydrocarbon levels being used 

during winter months. SABS 548 

specifies a maximum allowable 

flux level of 5% m/m of residual 

binder. Should cationic spray 

grade emulsion be used as a tack 

coat, the flux component will be 

trapped under the overlaid 

material. Although generally not a 

problem in most paving 

applications, the use of cationic 

spray grade emulsions should be 

avoided on high stress areas, due 

to possible problems with slippage 

or creeping of the asphalt layer. 

Anionic stable grade emulsions 

contain no hydrocarbon solvents 

and are thus preferable for tack 

coat applications. 

Typical properties 

No national specifications exist for 

bond coat emulsions. These 

emulsions are supplied by the 

manufacturers, who provide their 

own specifications. Typical 

properties used to classify a bond 

coat emulsion are: binder content, 

viscosity and residue on sieve 

values. Minimum softening point 

and elastic recovery values are 

specified on the residual binder 

after evaporation of the water 

phase. These properties should 

comply with the requirements of 

TG1’s SC-E1 grade modified 

emulsion for seals, except that the 

product must not contain any 

hydrocarbon fluxes. It is possible 

that the specifications for these 

emulsions will be included in the 

revised TG1 guideline to be 

published later this year. 

European developments 

A common problem associated 

with the use of tack coats is “pick 

up” of the broken emulsion 

residue under the wheels of the 

tipper trucks supplying the hot mix 

asphalt to the pavers. This 

effectively results in areas where 

little or no binder remains on the 

surface, which can result in 

slippage cracking or delamination 

of the asphalt layer. 

A new type of tack coat emulsion, 

such as the Colnet system 

registered in the name of Colas SA 

in France, has been developed in 

Europe, and is known as “clean 

emulsion”. Essentially a hard 

grade of bitumen is emulsified 

using specialised equipment, and 

the emulsion is applied with a 

specially adapted binder 

distributor using three spray bars. 

The first spray bar applies an 

adhesion agent to the existing 

surface, while the second, or main 

bar, applies the emulsion. The 

third spray bar applies a chemical 

“breaking agent” on the emulsion 

to destabilise the emulsion and 

induce chemical breaking. Paving 

can commence immediately after 

application of the emulsion and 

“pick-up” on the truck tyres does 

not occur (see Figure 2). This 

system allows paving work to 

proceed at night, with no delays 

being caused by slow breaking of 

the tack coat. 

135

Figure 2: “Pick-up” on truck tyres 

"Clean"emulsions 

During the developmental stage of 

the Colnet system, Colas in France 

performed comparative tests in 

the laboratory with conventional 

and “clean” emulsions to evaluate 

the development of the bond 

strength over time. The emulsion 

was applied in an even layer on 

aluminium trays and small glass 

cylinders were positioned on the 

emulsion layer. In the case of the 

“clean” emulsion, the breaking 

agent was 

first evenly 

sprayed over 

the emulsion 

layer before 

positioning 

the glass 

cylinders. The 

strain 

required to 

debond the 

cylinders was 

then 

determined 

over time 

(See Figure 

3). 

Conclusion 

Tack coats and bond 

coats are critical to the 

successful performance 

of hot mix asphalt 

surfacings. Although the 

design and construction 

of hot mix asphalt layers 

always receive detailed 

attention, the selection 

and application of tack 

and bond coats often do 

not receive the attention 

they deserve despite 

their influence on the overall 

performance of the new paved 

surface. Hand application of tack 

coat is still common practice in 

South Africa, but is forbidden in 

most developed countries. Should 

the use of calibrated binders 

distributors eventually become 

compulsory for the application of 

tack coats, the emulsion producers 

will have greater incentives to 

produce innovative binders for this 

market sector. 

 

Figure 3: Bond strength – Conventional vs “clean"emulsion 

136

Bitumen stabilised materials: 

A performance classification 

system for SA ... Quo Vadis? 

Kim Jenkins 

Professor 

SANRAL Chair 

University of Stellenbosch 

As part of its undertaking 

to develop a performance 

classification system for 

South African bitumen, the 

specific working group of the 

Road Pavements Forum (RPF) 

task group on binder 

specifications, has arranged 

for bitumen from all four local 

refineries to be tested for 

compliance with the SHRP 

SuperPave grading system. 

This testing was arranged by 

Professor Kim Jenkins, convenor of 

the working group, to be 

conducted at the University 

Wisconsin, Madison by members 

of the research group headed by 

Professor Hussain Bahia. 

In Nov 2003 the RPF Resolved that 

” the Bitumen Specifications 

Working Group be reconvened 

with the objective of reviewing the 

South African binder specifications 

relative to international trends of 

Performance Grading (PG). A 

precursor of the above review 

process was the fingerprinting of 

various South African crude source 

binders using the American PG 

System. Professor Bahia played a 

key role in the development and 

implementation of the SHRP 

binder grading system and, having 

had several years of involvement 

in South African binders, kindly 

agreed to assist in both the testing 

and the interpretation of the PG 

results. 

Fingerprinting 

In general, the test results 

confirmed that the bitumen, 

sampled from all four South 

African refineries for the 

fingerprinting, complies with 

specific grades of the SuperPave 

classification system. This is 

encouraging, and will lay a sound 

platform for developing 

performance related specifications 

in SA. The full range of low 

temperature tests were not 

conducted on the binders (e.g. the 

Direct Tension Test (DTT) was 

omitted) as these are not directly 

applicable to the in-service 

conditions encountered in the SA 

climate. However, some additional 

138

Figure 1. Figure 1. Bitumen grades sampled from 4 refineries for finger printing 

testing was incorporated in the 

project and is reported on. 

Strategy 

Fingerprint testing carried out at 

Madison covered the following: 

• Standard Dynamic Shear 

Rheometer (DSR) testing on: 

º Unaged binder (with 

repeats); 

º RTFOT aged; 

º Pressure Ageing Vessel 

(PAV) aged. 

• Additional DSR testing on two 

manufacturers of apparatuses 

at: 

º 0.1% strain versus 12% 

strain; 

º Different times of day 

(temperature control). 

• Bending Beam Rheometer 

(BBR). 

Standard DSR testing at 12% 

strain (ε), according to SHRP 

protocols, was carried out. In 

addition, the Shear Modulus G* 

versus Frequency was measured 

at 0.5% ε for bitumen from four 

SA refineries, as shown in Figure 

2. 

The DSR results show particularly 

good agreement between the 

measurements at different strain 

levels, verifying that the 12% ε is 

within the linear range of testing. 

This verifies that SHRP’s reasoning 

for adopting 12% ε as their 

standard protocol is sound and 

applicable to SA bitumen too. 

The SHRP SuperPave Grading 

System classifies a binder by 

defining the average 7-day 

maximum pavement design 

temperature (ºC) as well as the 

minimum pavement design 

139

Figure 2: DSR testing at comparative strain levels 

temperature (ºC) that the binder 

can reliably withstand. 

the SA binders from the four 

refineries tested yielded the 

following: 

Bitumen grade 40/50 60/70 80/100 150-200 

SHRP SuperPave 

Classification: 

Refinery A to D 

X PG64-16 PG58-22 X 

PG64-16 PG58-22 PG58-22 X 

PG64-16 PG64-22 PG58-16 PG52-22 

PG70-22 PG64-22 PG58-22 PG52-28 

Table 1: SA binder classification from fingerprinting July 2005 bitumen samples 

For example, PG 64 – 22 would be 

appropriate for use in asphalt in 

an area with an average 7-day 

maximum temperature of 64ºC 

and a minimum temperature of 

-22ºC. Based on the testing 

carried out at Madison a 

preliminary SHRP classification of 

While a cursory glance at the 

classification may indicate that 

eight grades are required for SA 

binders, the SA climate and the 

needs of the SA roads industry 

have not yet been considered. It is 

conceivable, for example, that the 

number of grades could be 

140

educed to, for example, four, if a 

single lower temperature is 

adopted. These issues, along with 

the temperature intervals of the 

classification system, will be 

debated by the RPF Binder 

Working Group. 

Temperature zones 

It is indeed encouraging to note 

that SA bitumen meets the 

standards adopted in the USA, 

especially the good low 

temperature classification; 

however, there is still some work 

to be done, including identifying 

appropriate temperature zones in 

SA and appropriate binder tests, 

especially the simulation of long 

term ageing. For this purpose, 

alternatives to the PAV such as the 

Belgian Rotating Cylinder Ageing 

Test (RCAT) and possibly a 

prolonged RTFOT, are under 

investigation. 

In addition, the different 

requirements of surface seals 

versus asphalt surfacing, need to 

be taken into account. The 

selection of critical binder test 

parameters and the identification 

of appropriate limits to reliably 

interpret susceptibility to, for 

example, permanent deformation 

or cracking, will also need be 

investigated. Zero Shear Viscosity 

has been recognised 

internationally as a critical 

property that could assist in 

identifying permanent 

deformation, and will need to be 

considered. 


The refineries are commended for 

supporting this study, as well as 

Prof. Bahia and his team for 

carrying out the testing at such a 

reasonable cost and for providing 

technical insights. We now have a 

snapshot of really useful 

rheological information to guide us 

with possible bitumen gradings. It 

does not stop here, however; 

research on applicable long-term 

ageing simulation tests and 

experimental (non-conventional) 

tests on the binders, will continue 

in the quest of a suitable system 

for South Africa. 

 

141

Revision of Technical Guideline 1 (TG 1): 

The use of modified binders in 

road construction in SA 

Dennis Rossmann 

Materials and Pavement Engineer 

SANRAL, Eastern Region 

The publication in 2001 of 

the Asphalt Academy’s 

(AsAc) TG 1 – Technical 

Guidelines: The use of 

modified binders in road 

construction, was a major step 

forward in providing a single 

generic industry guideline 

covering the use of modified 

binders in South Africa. 

The introduction of generic binder 

classes, which are “polymer blind” 

but required to conform to end 

product property limits appropriate 

to the specific application, were 

viewed by many practitioners at 

the time as being fairly “radical”. 

However, over time these generic 

classes have steadily gained 

acceptance to a point where 

specifiers, producers and users 

now generally feel entirely 

comfortable with the system. 

Review 

Over and above normal good 

practice of reviewing technical 

guidelines approximately every 

five years, the field of bitumen 

modification is internationally a 

very dynamic one. As a result, at 

the November 2005 meeting of 

the Road Pavements Forum a 

resolution was passed to 

reconvene the task group to 

review the 2001 edition of TG 1. 

This reconvened group consists of 

many who where members of the 

original task group, with 

representation from road 

authorities, researchers, 

consulting engineers and 

contractors, as well as both 

primary and secondary binder 

producers. AsAc is fulfilling the 

role of secretariat. 

The initial phase of the project 

consisted of critically reviewing the 

following issues: 

• Applicability of current binder 

classes; 

• Guidelines with respect to 

selection criteria; 

• Appropriateness of current 

test protocols; 


test limits; 

143

• International specifications/ 

trends etc. and their 

appropriateness for South 

Africa. 

From this initial process it became 

evident that the revision process 

could not just be confined to a 

limited updating exercise. Over 

and above identifying some of the 

existing criteria that required 

amendment, major additions to 

the document were required to 

provide additional guidance to 

practitioners, especially the newer 

entrants into the industry. 

Amendments 

Some of the more significant 

proposed changes to the existing 

document are detailed below: 

• Applicability of current 

classes: Even with the benefit 

of hindsight, the original 

decision to limit the number 

of modified binder classes 

was a good one. With the 

acceptance that the binder is 

but one component of the 

final product, the current 

trend internationally is to 

reduce the existing number 

of classes to a more 

manageable and pragmatic 

one. Notwithstanding the 

above however, it has to be 

accepted that, while 

elastomers (SBR, SBS & B-R) 

are still the most commonly 

used modifiers, other 

products such as plastomers 

(EVA), natural hydrocarbons 

and Fischer-Tropsch (FT) 

waxes are currently being 

more widely utilised. As such, 

the present binder 

classification matrix will be 

expanded where possible to 

include these products; 

• Specialised applications: With 

the increased use of modified 

binders in a variety of road 

applications, the guidelines 

will be expanded to 

incorporate these specialised 

binders, such as modified 

emulsions used in 

microsurfacing and bond 

coats for UTFC’s, and high 

modulus and fuel resistant 

binders used in hot mix 

asphalt; 


test protocols: While the 

existing test protocols and 

associated property limits are 

not fundamentally 

performance based, they 

have been derived from 

practical experience gained 

over some considerable time. 

It is envisaged that, while 

some of the current tests 

classified as “Report Only” 

will be removed, the test 

regime for the different 

classes will be consolidated. 

This is to ensure that we use 

the most appropriate 

measures, in which the 

binder is expected to perform 

in-service and during 

handling, to control the 

binder’s performance; 


product property limits: A 

number of amendments to 

the existing product property 

requirements have been 

identified, some of which are: 

º “tightening up” the 

allowable limits on some 

properties; 

144

º introducing upper limits on 

some properties, such as 

Softening Point ranges; 

º bringing some of the limits 

more in line with 

achievable production 

experience. 

• Selection criteria: This 

section is being significantly 

expanded to give more 

guidance with respect to 

selecting the most 

appropriate modified binder 

class for a given expected 

demand. Aspects such as 

associated construction, 

environmental and production 

constraints relative to a 

specific binder class will also 

be included; 

• Associated issues: aspects 

such as quality management 

during storage and handling, 

as well as HSE issues, are to 

be expanded to a greater 

degree. This is to ensure that 

the finished product, once it 

leaves the blending plant, is 

handled in a safe and 

appropriate manner and that 

it remains within the 

specification. 

Conclusion 

It is envisaged that the revised 

TG 1 document will be a significant 

improvement on the 2001 edition. 

With the ultimate goal of 

facilitating the specification of pure 

performance-based requirements 

still on the horizon (albeit ever 

closer), it is hoped that the 

document will reflect current best 

practice in South Africa and thus 

ensure optimal utilisation of these 

products. It is currently planned to 

release the second revision in the 

first half of 2007. 

 

Schematic of the three-dimensional SBS network. 

(Courtesy of Shell Bitumen) 

145

Revised TRH3 imminent: 

Developments in seal design 

Gerrie van Zyl 

Director 

PD Naidoo & Associates (Pty) Ltd 

The basic philosophy for 

the design of stone seals 

in South Africa was 

developed by F.M. Hansen in 

New Zealand during the mid 

1930s. The principle applied 

was to partially fill the 

available voids around 

aggregate particles to retain 

the stone on the road under 

traffic and expected climatic 

conditions. 

Road authorities in South Africa 

applied and adjusted this 

philosophy to suite their particular 

conditions to great success, the 

majority specifying the application 

rate for a given situation, based 

mainly on traffic and aggregate 

size. 

Initial efforts by the former 

Committee of State Road 

Authorities (CSRA) and the CSIR 

to develop a single design 

procedure for South African 

conditions were not successful, 

resulting in guideline documents 

incorporating a compendium of 

design methods. 

During the early 1980s polymer 

modified binders were introduced 

to South Africa, adding to the 

complexities of design. 

Although not without difficulties, 

the Committee of Local Transport 

Officials (COLTO) succeeded, to a 

large extent, in unifying the 

various design approaches and 

also in incorporating design 

guidelines for modified binders in 

the Technical Recommendations 

for Highways (TRH3, Draft 1998). 

By accepting that each road 

authority’s design provides an 

acceptable seal, the “Rational 

Design” approach, as developed 

by the CSIR and the Department 

of Transport, was adjusted to 

obtain a range of appropriate 

binder application rates. 

The adjusted “Rational Design” 

determines the minimum volume 

of binder to retain aggregate and 

the maximum volume to provide 

sufficient macro texture for skid 

resistance, taking into account the 

147

void loss due to embedment and 

aggregate wear due to traffic. 

Stone loss 

Feedback from practitioners 

indicated satisfaction with the 

guidelines provided for 

conventional bituminous binders. 

However, guidelines for the design 

of seals with modified binders 

were questioned, as stone loss 

often occurred on single seals and 

bleeding could be expected on 

double seals. 

The South African National Roads 

Agency Ltd (SANRAL) took the 

initiative to update and to improve 

the TRH3 (1998). The 2007 

version is expected to be available 

on both the SANRAL and NDoT 

websites by March 2007. 

seals using 

modified 

binders: The 

design method is 

now based on 

the conventional 

binder design 

with provision of 

one adjustment 

factor to cater 

for specific 

modified binders 

and traffic 

situations. Tables are 

provided to select appropriate 

adjustment factors; 

• Design of split application 

double seals: The use of the 

19/6,7 split application 

double seal (19,0 mm and 

two layers of 6,7 mm 

aggregate) has increased 

dramatically on high volume 

roads in South Africa. This 

seal is designed and 

constructed to create 

additional voids for the 

movement of the bituminous 

binder and has the ability to: 

º Accommodate reasonably 

soft existing surfaces as a 

result of bleeding; 

º Reduce rutting; 

º Reduce water spray behind 

large trucks. 

The document, 

already reviewed 

by experienced 

practitioners, 

includes revised or 

new guidelines and 

practical hints e.g.: 

• Design of 

both single 

and double 

148

S-E1 Adjustment 

Conventional to Modified Binder 

Traffic ELV Single Seal Double Seal Split application double seal 

< 5000 1.3 1.0 1.1 

5000 – 20 000 1.2 1.0 1.0 

> 20 000 1.1 1.0 1.0 

• Selection of appropriate 

binders to suite prevailing 

conditions: Specific attention 

is given to emulsions and 

rejuvenators; 

• Graded aggregate seals: 

Guidelines from experience in 

Botswana has been 

incorporated; 

• Geotextile seals: Provisional 

guidelines are based on 

experiences in South Africa, 

Namibia and Australia; 

• Precoated sand seals: 

Although considered to be the 

cheapest seal, excellent 

performance has been 

reported, even on relatively 

high volume roads; 

• Labour intensive seals: 

Additional guidelines on 

slurry-bound Macadam seals 

are provided; 

• Slurry seals: Additional 

information and references 

for design purposes are 

provided; 

• Practical minimum and 

maximum binder application 

rates: The theoretically 

modelled design curves have 

been adjusted to prevent 

unnecessarily high binder 

application rates or rates 

below the practical minimum; 

• Pre-design tests and 

interpretation of test results: 

Specific emphasis is placed 

on the “ball penetration” and 

“sand patch tests”; and 

• Reference is made to the 

latest companion documents 

e.g. Sabita manuals. 

Several courses are planned for 

2007 by the Asphalt Academy 

(AsAc) to introduce the latest 

recommendations on seal design 

and application. 

 

149

Alternatives to coal tar products: 

The influence of weather on 

prime applications 

Johan Muller 

Assistant Technical Manager 

Tosas (Pty) Ltd 

At the Conference on 

Asphalt Pavements for 

Southern Africa (CAPSA) 

2004, the decision was made, 

in line with global best 

practice, to discourage the use 

of coal tar products in road 

construction in South Africa. 

This decision resulted in Sasol 

CarboTar closing its operations in 

June 2006, which drastically 

reduced the availability of coal tar 

products in the market and left 

only one source of coal tar 

products, namely that from Mittal 

Steel. The result was a significant 

reduction in the range of prime 

products available for the road 

construction industry. 

In the second half of 2006, Sabita 

launched a series of seminars 

under the auspices of the Society 

for Asphalt Technology (SAT) in 

the Gauteng, KwaZulu Natal and 

Western Cape regions to promote 

the discontinuation of coal tar 

usage. The seminars were well 

attended and suppliers were given 

the opportunity to promote 

alternative products and 

techniques to coal tar for priming 

granular bases and precoating 

surfacing stone. 

Contractor problems 

Contractors complained that tar 

products such as RTL 1/4P, RTH 

1/4P and Sasol Quick Drying 

primes wetted and cured quicker 

in practice than cutback bitumen 

primes such as MC 30. 

Table 1 compares properties of the 

different materials. 

In general, it has been found that 

invert bitumen primes work better 

than cutback bitumen primes. 

Yet, despite the properties of the 

primes, other factors such as the 

density and type of base material, 

also create havoc for the 

contractor. The moisture content 

and temperature begin affecting 

the performance of the prime in 

the application, and the end result 

is an undesirable primed surface 

which causes delays in 

150

Properties Tar Prime Cutback bitumen 

prime 

Invert bitumen 

emulsion 

Water content 0% 0% < 20% 

Solvent type Polar Non-polar Non-polar 

Solvent Creosote-like Paraffin-like Paraffin-like 

Viscosity Low Highest Lower than 

cutback bitumen 

Table 1: Tar vs bitumen primes 

construction. Placing hot mix 

asphalt or a seal on a prime that 

has not penetrated into the base 

substrate raises the probability of 

problems appearing later during 

the life of the surfacing. 

Penetration 

The penetration and drying 

problems with primes are worse in 

winter and this led the technical 

team at Tosas to investigate 

various ways to overcome these 

problems. The fact that the 

viscosity of bituminous products 

increases at lower temperatures 

prompted the Tosas team to 

investigate ways of decreasing 

viscosity. The alternatives were: 

• Increase the percentage of 

cutter to reduce the viscosity: 

This is standard practice and 

all suppliers can make the 

alterations, formulating a 

non-SABS 308 product, 

(unfortunately at a cost to 

the client). For example: MC 

30 + 10% additional paraffin; 

• Change the solvent type: 

(This was also investigated 

and may prove to be a 

longer-term solution if the 

specifications for cutback 

products are amended); 

• Emulsify the cutback bitumen 

in water: i.e. normal 

‘oil-in-water’ as opposed to 

invert emulsion where the 

water is the discontinuous 

phase. (Although the 

viscosity is reduced, one can 

be fooled by false penetration 

– although the water and 

some of the solvent 

penetrate, the bitumen 

droplets are unable to do so, 

and coagulate on top to form 

a skin. A high concentration 

of soap is also required to 

emulsify the product, which 

has a water content of 

between 40 and 50%. This 

large proportion of free water 

reduces the net binder 

content dramatically, and the 

contractor would be better off 

spraying bitumen primes at 

30-40% below specified 

application for the same 

effect.); 

• Look at the effect of 

temperature. 

Temperature 

Everyone knows that it is colder in 

winter and warmer in summer, air 

temperatures are lower than the 

road temperatures as it is warmer 

in the direct sun than in the 

shade. 

The clever philosopher who once 

said: “You do not know that which 

151

you don’t measure” might have 

been looking over our shoulders, 

because we did not know how to 

quantify the effect of temperature, 

and an interesting exercise started 

as a result of various other 

research initiatives. 

Binder suppliers and appliers, as 

well as contractors, are normally 

at the mercy of the elements. If it 

is not too cold it is too wet, if it is 

not too wet it is too dry. By just 

using some proper engineering 

judgement, however, we can solve 

and prevent many problems we 

create for ourselves by not 

measuring temperature. We 

measure density and moisture and 

binder application, but we do not 

pay enough attention to road and 

air temperatures when priming is 

done. 

Geography 

The Gauteng Highveld is dry for 

the majority of the winter. The 

absence of rain makes winter an 

excellent time to do road 

construction, but overnight 

temperatures are sometimes very 

low and may cause problems, 

especially in seal and prime 

applications. 

We investigated the following: 

• Temperature variations 

during the course of a day; 

• Differences between air and 

road temperatures; 

• The effect of sun and shade 

on these temperatures; 

• Variation of these conditions 

from season to season. 

By knowing the answer to these 

factors we believed it would be 

possible to make the following 

judgements: 

• Will it be possible to prime; 

• At what time can the 

contractor start the priming 

operation; 

• At what time should the 

contractor stop the priming 

operation; 

• What will the effect of shade 

(or cloud cover) be on 

priming operations. 

Although this knowledge cannot 

guarantee success, it can surely 

minimise problems and 

unnecessary losses of time and 

money.The following assumptions 

were made: 

• Spring and autumn will be 

considered sensitive 

transition periods; 

• A gradual warm-up will occur 

in spring, and the reverse in 

autumn; 

• Winter is the most critical 

period; 

• Summer is generally not a 

problem in terms of 

temperatures but wind, cloud 

cover and rain can affect the 

temperatures. 

Observations 

Daily temperature variation 

It is interesting to note that the 

increase in temperature follows 

the same trend but temperatures 

vary significantly between air, 

road, sun and shade – see 

Figure 1. 

152

Figure 1: Daytime temperature profile for 11 August 2006 

August 2006, as monitored in the 

graph above, was cold and is still 

considered as winter in Gauteng. 

Although the road temperature 

was still increasing at 15h00 in the 

sun, the road temperature in the 

shade started to decrease at 

14h00 with the decrease in the air 

temperature. The road temperature 

differences were also the 

largest between sunny conditions 

and shady conditions. 

Air-road temperatures 

The road temperatures in the 

shade changed very little during 

the day and, depending on the 

overnight temperature, it 

Figure 2: Daytime temperature profile on 1 December 2006 

153

gradually increased from 

approximately 10 0 C in winter to 

more than 25 0 C in summer. When 

it was windy and cloudy, the air 

and road temperature in the sun 

dropped to the shade temperatures. 

Sun-shade temperatures 

The minimum-maximum ranges 

for the air and road temperatures 

in the shade were of the same 

magnitude, yet the air 

temperature was always higher 

than the road temperature in the 

shade in the morning. The road 

temperature gradually increased 

during the day and the air 

temperature usually peaked 

between 13h00 and 14h00, 

decreasing thereafter. The latter 

was true for the air temperature in 

the sun, but the road temperature 

in the sun peaked much higher 

and also earlier (around 12h00). 

The road temperature also 

dropped significantly faster in 

comparison with the air 

temperature, which was directly 

related to the amount of direct 

energy from the sun. 

The season, wind, cloud cover and 

time of the day all play a 

significant role on both the air and 

road temperatures. 

Shaded areas are affected more 

than sunny areas. Care should be 

taken when wind and rain are 

present. Then, even in the sunny 

areas, temperatures drop at an 

alarming rate. 

Wind, cloud and rain 

When the conditions become 

cloudier, the road temperature is 

affected more rapidly than the air 

temperature. When the cloud 

cover disappears, the road 

temperature also increases more 

Figure 3: Average temperature variation during October 2006 

154

Figure 4: Average temperature variation during November 2006 

quickly. The effects of sun and 

shade on temperatures is shown in 

Figure 3. 

This observation substantiates the 

fact that weather patterns may 

have a dramatic influence on the 

success of a prime application. 

Moist, windy and cloudy conditions 

can be detrimental in the 

successful application of prime. 

Figure 5: The effect of cloud cover on 23 August 2006 

155

Conclusions 

MC 30 cutback bitumen’s 

performance as a prime is, apart 

from granular base type and 

density, very dependent on 

temperature, since temperature 

has the most direct influence on 

its viscosity. The viscosity 

influences the ability of the 

product to penetrate the base 

material and any MC 30 cutback 

bitumen which does not penetrate 

in the first day will lie on top of 

the base for more than a week, if 

not more. 

There are a number of actions 

from suppliers which may in future 

solve some of the penetration and 

drying time of cutback bitumen 

primes. True invert bitumen 

emulsions will increase success 

rate, but be careful, conventional 

emulsions cannot be used as 

primes. 

From this study it is evident that 

temperature and other weather 

conditions will play a significant 

role in the success of prime 

applications. 

The following should be considered 

to ensure successful prime 

applications on site: 

• During winter and early 

spring, prime applications are 

more sensitive to climatic 

conditions regardless which 

prime is used; 

• It is preferable to dampen the 

base with water the night 

before to achieve the desired 

moisture content; 

• Surface tension may be 

broken with a light 

application of water on the 

day the prime product is to 

be sprayed; 

• Temperature must be 

measured on site and the 

road temperature must be 

Figure 6: The viscosity-temperature relationship for MC30 cutback bitumen 

156

etween 10 and 15°C and 

rising to give the prime the 

best chance to penetrate 

successfully; 

• Temperatures should be 

monitored from 12h00, and 

no prime should be applied 

after 14h00 if the road 

temperatures are falling 

below 15°C, as this will 

prevent optimum 

penetration. 

• In summer time, when the 

overnight temperatures are 

generally above 15°C, 

cognisance should be taken 

of shade, wind, cloud cover 

and rain conditions, as these 

may have a negative 

influence on the success of a 

prime application. 

Task team 

A resolution was passed at the 

November 2006 meeting of the 

Road Pavements Forum for Sabita 

to convene a task team to 

investigate the possible changes to 

the SANS 308 Specification for 

Cutback Bitumens to overcome 

problems with poor penetration 

and slow drying. 

Sabita has also issued a new 

publication as an interim guideline, 

Manual 26 – Interim guidelines for 

primes and stone precoating 

fluids, which identifies alternative 

products to coal tars for priming 

and stone precoating, and offers 

the practitioner valuable 

information. 

Although priming operations are 

considered to be simple, incorrect 

prime applications may come back 

to haunt the industry, and can 

manifest in the flushing of volatiles 

through hot mix application in the 

first summer after the construction, 

leaving binder-rich patches. 

In seal applications, it may soften 

the binders and lead to premature 

punching or bleeding where higher 

binder applications were specified, 

especially in single seals. 

Although the temperature 

information in this paper is site 

specific, it is intended to sensitise 

the engineers in the contractor 

and consultant fraternity. 


The author acknowledges the 

assistance of Denzil Sadler and 

Hannes Lambert (Technical 

Department, Tosas) and Jacques 

van Heerden (Sasol Technology, 

Fuel Research). 

 

157

Towards industry self-regulation: 

The development of a Road 

Transport Management System 

in South Africa 

Paul Nordengen 

Research Group Leader 

Network Asset Management Systems 

CSIR Built Environment 

Heavy vehicle overloading 

has been South Africa's 

nemesis for decades, 

despite efforts at more 

effective law enforcement. 

Overloading causes 

accelerated road deterioration 

and, together with inadequate 

vehicle maintenance, driver 

fatigue and poor driver health, 

contributes significantly to 

South Africa's poor road safety 

record. 

In July 2003, the forestry industry 

embarked on a dti/Forestry South 

Africa-funded project with the 

CSIR, National Productivity 

Institute (NPI) and Crickmay & 

Associates to introduce a 

self-regulation system, the Load 

Accreditation Programme (LAP) to 

address overloading, vehicle 

maintenance and driver wellness 

in the timber transport industry. 

The initiative was in line with the 

DoT's National Overload Control 

Strategy (NOCS) in which one of 

the recommended interventions 

was to explore the concept of 

self-regulation and to facilitate 

such an industry-led initiative to 

complement law enforcement. The 

NOCS identified the Australian 

National Heavy Vehicle 

Accreditation Scheme (NHVAS) as 

one that had a number of 

components appropriate to the 

South African situation. 

Background 

The successful implementation of 

LAP in the forestry industry – the 

extent of overloading in terms of 

number of heavy vehicles charged 

with overloading dropped by 40% 

over a two year period – led to 

various stakeholders identifying 

the need to establish a national 

LAP steering committee to expand 

the programme to other 

industries. A national LAP 

workshop was held in June 2004, 

during which issues such as the 

vision, mission, mandate, 

objectives, structure and terms of 

reference of the proposed 

committee were discussed and 

debated. Stakeholders and 

organisations represented at the 

workshop included the NDoT, 

159

SANRAL, Forestry South Africa 

(FSA), the Institute for 

Commercial Forestry Research 

(ICFR), SA Cane Growers 

(SACGA), Road Freight Association 

(RFA), NPI and CSIR. The first 

meeting of the national committee 

was held in July 2004 and one of 

the first tasks was to compile a 

national LAP strategy. 

During the next 12 months various 

industries were approached with a 

view to participating in the LAP 

initiative, and by the end of 2005, 

a number of these industries had 

indicated their willingness. These 

included the Chamber of Mines, 

Sabita, ASPASA, SARMA, SACGA 

and the pulp, paper and board 

industry (distinct from the timber 

industry). 

In November 2005, the national 

steering committee, which now 

included new blood, identified the 

need to revise the LAP strategy 

document, and in particular to 

consider the possibility of a name 

change, as it was felt that the 

name “Load Accreditation 

Programme” put too much 

emphasis on the aspect of 

vehicle overloading without 

recognising other important 

aspects such as vehicle 

maintenance, driver 

wellness and productivity. 

decided to rename the initiative 

the Road Transport Management 

System (RTMS), and a Technical 

Working Group was appointed with 

the task of drafting the new RTMS 

strategy. 

The RTMS five-year strategy was 

officially launched in October 2006 

(Transport month) and in the 

foreword the Minister of Transport, 

Mr Jeff Radebe states that “(The 

RTMS) is an industry driven 

process that complements 

government programmes aimed at 

promoting efficient road based 

operations, road infrastructure 

protection and road safety. I 

therefore commend the 

pro-activity shown by the 

leadership of this initiative, and 

have no doubt that it will lead to 

tremendous improvement in the 

performance of the logistics 

chain." 

Road closures due to accidents 

involving heavy vehicles have a 

negative impact on the total cost 

of logistics in South Africa, which 

In fact, the issue of the 

name of the project was 

first raised and debated at 

the initial national LAP 

workshop in June 2004, but 

at that stage it was decided 

to keep the name. After 

lengthy (and some heated!) 

debates, the committee 

Figure 1: An example of accelerated pavement 

deterioration caused by heavy vehicle 

overloading 

160

Figure 2: Accidents involving heavy 

vehicles often lead to road closures, in 

some cases causing long delays 

is almost double that of the USA 

and 50% more than Japan and 

Brazil (as a % of GDP). 

The RTMS 

• National Standards Auditors 

(accredited by SANAS); 

• Tools (manuals, templates, 

implementation guidelines); 

• Information portals (website, 

data sharing); 

• Recognition and concessions; 

• Promotion (brand promotion 

to create meaningful 

recognition among public and 

industry stakeholders); 

• Special projects (selected by 

the RTMS stakeholders and 

are aligned to RTMS 

objectives); 

• Research and technology 

innovation. 

Stakeholders 

The RTMS strategy identifies the 

following stakeholders: 

RTMS is an industry-led, voluntary 

self-regulation 

scheme that 

encourages 

consignees, 

consignors and 

transport operators 

engaged in the road 

logistics value chain 

to implement a 

vehicle management 

system that 

preserves road 

infrastructure, 

improves road safety 

and increases the 

productivity of the logistics value 

chain. (This scheme also supports 

the Department of Transport's 

National Freight Logistics 

Strategy.) 

The RTMS will offer support for 

implementation of the following 

components: 

The total cost of 

logistics in South 

Africa is almost 

double that of the 

USA and 50% 

more than Japan 

and Brazil (as a 

% of GDP) 

Value-chain: 

• Consignees, 


transport 

operators; 

• Organised 

business and 

industry 

associations; 

• Organised labour. 

Other 

Stakeholders: 

• Government 

(Department of 

Transport, the 

dti, Department 

of Science and Technology, 

provincial and local 

government, SANRAL, law 

enforcement agencies, etc); 

• Public sector institutions 

(standards generating bodies, 

productivity institutions, 

research institutions). 

161

RTMS Vision 2012 

RTMS will be a nationally recognised self-regulating scheme for 

heavy vehicle road transport, resulting in a safe, equitable and 

competitive heavy vehicle logistics value chain. 

RTMS MISSION 

To provide a national certification scheme (standards, auditors, 

manuals) and implementation support (information portals, 

recognition, technology transfer) for heavy vehicle road transport to 

consignees, consignors and transport operators, focusing on: 

• Load optimisation; 

• Driver wellness; 

• Vehicle maintenance; and 

• Productivity. 

Standards 

The national steering committee 

identified the need to develop the 

standards based on a phased 

approach, and the starting point 

chosen was the standard 

developed for the forestry 

industry. 

Once the SA RTMS national 

standards have been tried and 

tested, it is planned that these 

standards will be made available 

through the SABS for adoption as 

a harmonised SADC standard. The 

final phase would be to propose 

the standard as the basis for the 

development of an international 

ISO standard for road logistics. 

The proposed process is shown in 

Figure 3. 

Structure 

The proposed RTMS structure is 

shown in Figure 4. The National 

Steering Committee has been 

functional since July 2004, and a 

Technical Working Group was 

established in November 2005. 

There are currently three industry 

steering committees (forestry, 

mining and asphalt). 

To date there has also been strong 

participation and support from the 

NDoT, SANRAL and the 

KwaZulu-Natal DoT as well as 

various corporate sponsors and 

associations (FSA, ICFR, Chamber 

of Mines, Sabita, ASPASA, SARMA, 

RFA). 

Development process 

In August 2006 the SABS was 

approached to develop the RTMS 

as a national standard. Through a 

consultative process, it was 

162

RTMS standards for transport 

operators – Timber 

Time 

Now 

Certification 

Private 

Amended industry-wide standards for 

consignors, consignees and transport 

operators 

6 

months 

Private 

Develop new SANS for road 

logistics with SABS 

18 

months 

SANS 

Develop SADC harmonised 

standard 

3 

years 

SANS 

SADCSTAN 

Convene 

international 

ISO 

committee 

Develop ISO 

standard for 

road logistics 

5 – 6 

years 

ISO 

SANS 

SADCSTAN 

Figure 3: Envisaged evolutionary process for developing RTMS standards 

Government and corporate sponsors 

National Steering Committee 

Experts and 

special interest 

groups 

Project Manager 

Functional teams 

Technical working 

groups 

Industry steering 

committees 

Figure 4: Proposed RTMS structure 

163

decided to first publish the 

standards as a “Recommended 

Practice” (ARP 067), Part 1 being 

the recommended practice for 

operators. A SABS Technical 

Committee, STANSA TC181B: 

Road Transport Management 

Systems, was constituted in 

October 2006, and a Working 

Group appointed to transform the 

LAP standards developed by the 

CSIR for the forestry industry into 

an SANS Recommended Practice. 

• Tasks and responsibilities; 

• Records and documentation; 

and 

• Performance assessments. 

Templates will be provided as 

examples to assist operators in 

preparing for certification, which is 

achieved through a successful 

external audit by a 

SANAS-accredited auditor. 

Conclusions 

The ARP 067-1:2007 Part 1: 

Operator Requirements – Goods 

was published by Standards South 

Africa in February 2007, and the 

Working Group is currently 

preparing Parts 2 and 3 of RTMS 

standards for consignors and 

consignees. 

ARP 067 Part 1 sets minimum 

standards for road transport 

through ten rules as follows: 

• Maintenance of 

a haulage fleet 

inventory; 

• Assessment of 

the vehicle 

mass and 

dimensions 

before each 

laden trip; 

• Verification of 

the mass 

determination 

method; 

• Maintenance of 

vehicles in a 

road worthy 

condition; 

• Vehicle and load safety; 

• Management of driver 

wellness; 

• Training and education; 

Consignors and 

consignees will 

be required to 

assume far 

greater 

responsibility 

for the manner 

in which their 

goods are 

transported 

The RTMS is an industry-driven 

initiative in co-operation with 

government, which attempts to 

address issues such as 

overloading, load securement, 

vehicle maintenance, driver 

fatigue and driver health and their 

impacts on road deterioration, 

road safety and the cost of 

logistics. The pending legislation 

covering the responsibilities of 


consignees with 

regards heavy 

vehicle road 

transport will no 

doubt have a 

significant impact 

on the nature of 

road transport 

contracts. It is 

anticipated that 


consignees will in 

future be 

required to assume 

a far greater 

responsibility for 

the manner in 

which their goods 

are transported on the public road 

network. The RTMS is a tool that 

can be used by consignors, 

consignees and transport 

164

operators as part of their quality 

management systems to address 

the current problems in road 

transport, thereby demonstrating 

their commitment to corporate 

governance. 

 

References 

National Overload Control Strategy. 

Department of Transport, March 1994. 

S.V. Kekwick 2003. National Overload 

Control: Self-regulation of heavy vehicle 

loading. CSIR Transportek, Pretoria. 

Alternative Compliance: National Policy. 

National Road Transport Commission. 

1998. Australia. 

Mass Management Accreditation Guide. 

Roads and Traffic Authority. 2000. RTA, 

New South Wales, Australia. 

Maintenance Management Accreditation 

Guide. Queensland Transport. 2000. 

Australia. 

Forest Engineering Southern Africa, CSIR 

Transportek, National Productivity 

Institute, Crickmay & Associates. 2004. 

Load Accreditation Programme for the 

Transport Industry. CSIR Transportek, 

Pretoria. 

Road Transport Management System 

Five-Year Strategy 2006. NPI, Midrand, 

South Africa. 

Road Transport Management Systems: Part 

1: Operator Requirements – Goods. 

Standards South Africa. 2007. ARP 067-1, 

SABS, Pretoria. 

165

The role of Agrément in South Africa: 

Accreditation of thin bituminous 

surfacings in SA 

John Odhiambo 

Manager 

Agrément South Africa 

In late 2005, the Board of 

Agrément South Africa 

approved the Guideline 

Document for the Assessment 

and certification of thin 

bituminous surfacing systems 1 

developed by an industry task 

team 2 . This development 

follows the success of other 

initiatives to expand the range 

of road products Agrément 

South Africa is able to 

evaluate. 

These include, but are not limited 

to, the following: 

• bridge deck joints (criteria 

drawn up in 2001 – eight 

joints are currently certified 

including two elastomermodified 

bitumen plug 

expansion joints); 

• road additives (criteria drawn 

up in 2004 – no products 

certified to date); and 

• thin bituminous surfacings 

(also termed ultra-thin 

friction courses UTFC), 

defined as proprietary 

bituminous products with 

suitable properties to provide 

a wearing course that is laid 

at a nominal thickness of up 

to 40 mm and is 

predominantly intended as a 

functional layer. 

The approval of the guideline 

document has paved the way for 

manufacturers of non-standard 

proprietary UTFC’s to now have 

their products evaluated and 

certified as ‘fit-for-purpose’. One 

proactive manufacturer is in the 

final stages of evaluating his 

system which, once successfully 

completed, will result in 

certification. 

Seven stage process 

The assessment and certification 

process is undertaken in six 

stages, followed by monitoring, as 

follows: 

• Assessment of the applicant’s 

data; 

• Assessment of production 

control; 

• Laboratory testing; 

166

• System installation i.e. 

application; 

• System performance trial 

section (if required); 

• Certification; 

• Monitoring. 

1. Data assessment: The 

applicant’s data, which should 

include general information on the 

product, the product’s track 

record, available test data, 

process quality control, and the 

specific intended use of the 

product, forms the basis of the 

subsequent assessment if found to 

be acceptable. 

2. Production control: It is a 

requirement of Agrément South 

Africa that an approved and 

documented quality system, based 

on the requirements of ISO 9000, 

be in place to control both the 

manufacture of constituents and 

the application process of the thin 

bituminous surfacing system. 

3. Laboratory testing: Testing 

will be carried out, where 

necessary, to determine or 

confirm characteristics of materials 

and to gauge aspects of 

performance. 

Characteristics of materials are 

determined to confirm that 

materials submitted for evaluation 

fall within the agreed or specified 

ranges; test values are also used 

for subsequent quality monitoring 

purposes. 

4. System installation: System 

installation will be witnessed to 

help gauge the effectiveness of 

the quality system and the 

procedures for the application of 

the UTFC. Road tests will be 

carried out and relevant samples 

taken for laboratory testing in 

accordance with the test methods 

and procedures detailed in the 

approved guideline document. 

These guidelines also lay down, 

where applicable, required 

performance levels. 

Required levels of performance 

take into account the certification 

classification category and traffic 

loads for which the system is 

intended. 

5. System performance: A trial 

is required to assess the 

performance of the system over a 

period of time, and site 

performance tests will include: 

• Visual observation; 

• Texture depth; 

• Skid resistance; 

• Torque bond. 

Additional tests may be required 

depending on whether 

performance characteristics are 

claimed which are not covered by 

the above mentioned tests. 

6. Certification: Subject to a 

favourable assessment, Agrément 

South Africa will issue an 

Agrément certificate which will: 

• clearly define the system and 

state the uses for which the 

system has been assessed; 

• verify the system’s 

compliance with the Board’s 

performance criteria. 

The certificate will also clearly 

indicate conditions of certification 

and the Board may, at its 

167

discretion, impose limitations or 

requirements governing the use of 

the system. 

7. Monitoring: One of the most 

important conditions of 

certification imposed is that the 

certificate holder must participate 

in the Board’s ongoing quality 

assurance scheme. This entails 

quality surveillance of the 

certificate holder by the Agency of 

Agrément South Africa on an 

annual basis, followed by three 

yearly certificate reviews. 

Ongoing monitoring also facilitates 

the amendment to the 

performance criteria where this is 

found to be necessary. 

Conclusion 

Agrément offers the owners of 

proprietary UTFC’s a mechanism 

to expand the use of their 

products through increased 

acceptance of non-standard 

products. At the same time it also 

provides the road authority with 

assurance that the product has 

been certified for a given 

performance level, and that the 

quality during manufacture and 

application will be carried out in 

terms of an approved quality 

management system. The 

certification of UTFC will in the 

near future become mandatory on 

all South Africa National Roads 

Agency Ltd (SANRAL) contracts. 

1 

A copy of the Guideline Document: 

The Assessment and Certification of 

Thin Bituminous Surfacing Systems is 

available free of charge from 

Agrément South Africa’s website, 

www.agrement.co.za . 

2 The Board is grateful to the industry 

task team whose input facilitated the 

development of the guideline 

document. This team included: Mrs E 

Sadzik, Prof K Jenkins, Messrs M 

Henderson, P Myburgh, JP Nothnagel, 

P Olivier, D Pretorius, D Rossmann, G 

Swart, B Verhaeghe, M Winfield, and 

J Wise. 

168

Notes 

169

Author Index 

Author 

Page 

Bornmann, Francois . . . . . . . . . . . . . . . . . . . . . . 88 

Michael Bouwmeester . . . . . . . . . . . . . . . . . . . . . 73 

Distin, Trevor . . . . . . . . . . . . . . . . . . . . . . . . . 39 

Hiley, Robbie. . . . . . . . . . . . . . . . . . . . . . . . . . 88 

Horak, Emile . . . . . . . . . . . . . . . . . . . . . . . . . . 45 

Jenkins, Kim . . . . . . . . . . . . . . . . . . . . . . . 82, 138 

Jooste, Fritz . . . . . . . . . . . . . . . . . . . . . . . . . . 82 

Levin, Mannie. . . . . . . . . . . . . . . . . . . . . . . . . 126 

Louw, Kobus . . . . . . . . . . . . . . . . . . . . . . . . . 130 

Marais, Herman . . . . . . . . . . . . . . . . . . . . . . . 102 

Muller, Johan . . . . . . . . . . . . . . . . . . . . . . . . . 150 

Myburgh, Piet . . . . . . . . . . . . . . . . . . . . . . . . . 30 

Nordengen, Paul . . . . . . . . . . . . . . . . . . . . . . . 159 

Odhiambo, John . . . . . . . . . . . . . . . . . . . . . . . 166 

Onraët, John . . . . . . . . . . . . . . . . . . . . . . . . . . 64 

Pagel, Deon . . . . . . . . . . . . . . . . . . . . . . . . . . 96 

Pretorius, Derick . . . . . . . . . . . . . . . . . . . . . . . 102 

Ross, Don . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 

Rossmann, Dennis . . . . . . . . . . . . . . . . . . . . . . 143 

Sadzik, Elzbieta. . . . . . . . . . . . . . . . . . . . . . . . 111 

Sampson, Les . . . . . . . . . . . . . . . . . . . . . . . . . 67 

Strydom, Stefan . . . . . . . . . . . . . . . . . . . . . . . . 88 

Thompson, Hugh. . . . . . . . . . . . . . . . . . . . . . . . 73 

Van Zyl, Gerrie . . . . . . . . . . . . . . . . . . . . . . . . 147 

Weideman, Alex . . . . . . . . . . . . . . . . . . . . . . . . 28 

Winfield, Mike . . . . . . . . . . . . . . . . . . . . . . . . . 61 

Wise, Julian. . . . . . . . . . . . . . . . . . . . . . . . . . 119 

170

Advertiser Index 

Advertiser 

Page 

Colas SA (Pty ) Ltd . . . . . . . . . . . . . . . . . . . . . . 129 

Corporate Image Holdings (Pty) Ltd . . . . . . . . . . . . . 60 

Engen Petroleum Ltd . . . . . . . . . . . . . . . . . . . . . 137 

Holcim SA (Pty) Ltd . . . . . . . . . . . . . . . . . . . . . . 27 

Kaytech [a division of Kaymac (Pty) Ltd] . . . . . . . . . . 125 

More Asphalt . . . . . . . . . . . . . . . . . . . . . . . . . 158 

Much Asphalt (Pty) Ltd . . . . . . . . . . . . . . . . . . . . 81 

Sasol Wax (a division of SCI Ltd) . . . . . . . . . . . . . . . 87 

Spraypave . . . . . . . . . . . . . . . . . . . . . . . . . . 142 

Tarfix (Pty) Ltd . . . . . . . . . . . . . . . . . . . . . . . . 101 

Tosas (Pty) Ltd . . . . . . . . . . . . . . . . . . . . . . . . 146 

Zebra Bituminous Surfacings cc . . . . . . . . . . . . . . . 118 

171

Sabita Manuals 

Manual 1 Construction of bitumen rubber seals 

Manual 2 Bituminous products for road construction 

Manual 5 Manufacture and construction of hot mix asphalt 

Manual 7 SuperSurf: Economic Warrants for Surfacing 

Unpaved Roads 

Manual 8 Bitumen safety handbook 

Manual 9 Bituminous surfacings for temporary deviations 

Manual 10 Appropriate standards for bituminous surfacings 

Manual 11 Labour enhanced construction for bituminous surfacings 

Manual 12 Methods and procedures – Labour enhanced 

construction for bituminous surfacings 

Manual 13 LAMBS – The design and use of large aggregate 

mixes for bases 

Manual 14 GEMS – The design and use of granular emulsion mixes 

Manual 16 REACT – Economic analysis of short-term 

rehabilitation actions 

Manual 17 The design and use of porous asphalt mixes 

Manual 18 Appropriate standards for the use of sand asphalt 

Manual 19 Technical guidelines for bitumen-rubber asphalt 

Manual 20 Sealing of active cracks in road pavements 

Manual 21 ETB: The design and use of emulsion treated bases 

Manual 22 Hot mix paving in adverse weather 

Manual 23 Bitumen Haulier’s Code: guidelines for loading 

bitumen at refineries 

Manual 24 User guide for the design of hot mix asphalt 

Manual 25 Quallity management in the handling and transport 

of bituminous binders 

Manual 26 Interim guidelines for primes and stone precoating fluids 

Asphalt Academy publications 

TG1 

TG2 

Technical Guidelines: The use of modified binders in 

road construction 

Interim Technical Guidelines: The design and use of 

foamed bitumen treated materials 

Training Guides 

TRIP 

HMA 

HSE 

CEP 

— Technical Recommendations in Practice 

— Hot Mix Asphalt Training series 

— Health, Safety and Environmental Guidelines 

for bitumen and coal tar products 

— Councillor Empowerment Programme 

172

Sabita Video Training Aids 

Video series on testing of Bituminous Products 

Bitumen 

AV-1 

AV-2 

AV-3 

Penetration test / Softening point (ring and ball) 

Spot test / Rolling thin film oven test 

Brookfield viscosity / Ductility 

Bitumen Emulsion 

AV-4 

AV-5 

AV-6 

AV-7 

Hot mix Asphalt 

AV-8 

AV-9 

AV-I0 

AV-11 

AV-12 

Bitumen Rubber 

AV-13 

AV-14 

AV-15 

Sayboldt furol viscosity / Water content of emulsions 

Sedimentation value of emulsions / Residue on sieving 

Coagulation value with chippings / Coagulation value 

with Portland cement 

Binder content of slurry / Particle charge test 

Optimum binder content for asphalt 

Marshall test 

Binder content / Moisture content 

Static creep test / Immersion index 

Rice’s density and binder absorption/Bulk relative 

density and voids 

Ball penetration and resilience test / Dynamic viscosity 

Compression recovery / Flow test 

Bulk density of crumb rubber / Grading and loose fibre 

test of crumb rubber 

Video series on Blacktop Roads 

AV-22 

AV-23 

Black-top surfacing and repair (with Instructor Training 

Manual) 

Pavement surfacing and repairs for black-top roads 

Video series on Hot mix Asphalt 

AV-25 Manufacture 

AV-26 Paving 

AV-27 Compaction 

Health, Safety and 

Environmental Conservation 

AV-28 BitSafe – The safe handling of 

bitumen (DVD) 

For order information 

contact Sabita at: 

info@sabita.co.za 

173

Sabita Members 

Ordinary Members 

AJ Broom Road Products (Pty) Ltd 

Akasia Road Surfacing (Pty) Ltd 

Bitumen Construction Services (Pvt) Ltd 

Bitumen Supplies & Services (Pty) Ltd 

Black Top Holdings (Pty) Ltd 

BP SA (Pty) Ltd 

Brisk Asphalt Surfacing (Pty) Ltd 

Chevron South Africa (Pty) Ltd 

Colas SA (Pty) Ltd 

Engen Petroleum Ltd 

Javseal (Pty) Ltd 

Milling Techniks (Pty) Ltd 

More Asphalt 

Much Asphalt (Pty) Ltd 

Murray & Roberts Construction Ltd 

National Asphalt (Pty) Ltd 

Nikamandla Construction (Pty) Ltd 

Nyanga Roads (Pty) Ltd 

Phambili Road Surfacing (Pty) Ltd 

Polokwane Surfacing (Pty) Ltd 

Rand Roads (a division of Grinaker-LTA Ltd) 

Roadsmart (Pty) Ltd 

Sasol Oil (Pty) Ltd 

Shell SA Marketing (Pty) Ltd 

Spray Pave (Pty) Ltd 

Tarfix (Pty) Ltd 

Tarspray cc 

Tosas (Pty) Ltd 

Total SA (Pty) Ltd 

Van Wyk Tarmac cc 

Zebra Bituminous Surfacing cc 

174

Associate Members 

Africon Engineering International (Pty) Ltd 

Arcus Gibb (Pty) Ltd 

Asch Professional Services (Pty) Ltd 

BCP Engineers (Pty) Ltd 

BKS (Pty) Ltd 

Cape Peninsula University of Technology 

Dick King Lab Supplies (Pty) Ltd 

Entech Consultants (Pty) Ltd 

GMH/CPP Consulting Engineers (Pty) Ltd 

Goba (Pty) Ltd 

HHO Africa 

Holcim SA (Pty) Ltd 

Iliso Consulting (Pty) Ltd 

Jeffares and Green (Pty) Ltd 

Kaymac (Pty) Ltd t/a Kaytech 

Lafarge South Africa Ltd 

Lidwala Consulting Engineers (Pty) Ltd 

Ninham Shand (Pty) Ltd 

PD Naidoo and Associates (Pty) Ltd 

Rankin Engineering Consultants 

Sasol Technology Fuels Research 

Sasol Wax (a division of SCI) 

Siyenza Engineers cc 

Specialised Road Technologies (Pty) Ltd 

Stewart Scott International (Pty) Ltd 

Tshepega Engineering (Pty) Ltd 

Unitrans Fuel and Chemical (Pty) Ltd 

Vaal University of Technology 

Vela VKE Consulting Engineers (Pty) Ltd 

WSP SA Civil and Structural Engineers (Pty) Ltd 

Affiliate Members 

Beosumbar and Associates cc 

DMV Harrismith (Pty) Ltd 

MTTC (Pty) Ltd 

Salphalt (Pty) Ltd 

The Synthetic Latex Co (Pty) Ltd 

TPA Consulting cc 

175

Notes 

176

DIGEST 2006 - Sabita

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