Green Economy Journal Issue 48

WASTE
WASTE
THE ROAD TO
SUSTAINABILITY
The use of waste materials in
South African road construction
The Council for Scientific and Industrial Research has recently been
involved in several new research initiatives geared towards providing
alternative waste material products, specifically to be used by the
asphalt pavement industry in South Africa.
The research focus of the CSIR has been centred around creating
a more inclusive and sustainable approach to future road
construction, particularly through increasing the potential for job
creation, increasing economic benefits, producing better performing
roads and trying to resolve South Africa’s environmental challenges.
One of the CSIR’s recent successes has been around the adoption of
locally produced waste alternatives (opposed to importing costly
conventional road and waste products).
CASE STUDY ON THE SUSTAINABLE USE
OF RECYCLED TYRES
Construction of a road section in Roodepoort, Gauteng
In 2019, the CSIR in collaboration with Much Asphalt (Pty) Ltd successfully
constructed a road trial section in Roodepoort using locally available
micro-fillers and recycled tyres. The project came to fruition when both
products under development were successfully paved into a controlled
road trial section, after a year of combined laboratory development and
rigorous evaluation.
The 200m long trial section includes a 60mm modified enrobés à
module élevé (EME) base layer and a 40mm modified bitumen-rubber
asphalt layer that was constructed over a cleaned gravel base. This layer
was treated with a SS60 tack-coat prior to paving. The location of the
trial section specifically allows for continual performance monitoring,
which includes up-to-date details on the distribution and volume of
traffic that moves across the section.
Georges Mturi, CSIR’s project manager speaking on the success
of the project: “During both the development and trial phase, several
performance characteristics were evaluated as predictors of in-situ
performance, which served as the baseline for the performance
evaluation that were set to run on a three-month basis for a period of
one year after construction.” In this regard, he adds “The evaluations
and visual inspections have shown that after nine months of traffic and
environmental exposure, the layers are performing as expected.”
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Construction of road trial section made
from recycled tyres.
To date, no edge breaking is present where heavy vehicles are moving
onto and off the surfacing, no permanent deformation is present on the
surfacing (particularly at stopping locations and where regular vehicle
turning takes place) and, lastly, there are no signs of any deflection or
temperature-induced crack formations taking place.
Joanne Muller, regional laboratory manager at Much Asphalt says, “The
developed and trialled technologies aimed at improving the performance
properties of standard 10/20 based EME, while also acting as a viable
replacement product for standard styrene-butadiene styrene (SBS)
modified A-E2 binder, without detracting from pavement performance.
These are deemed effective as they can assist industry practitioners in
their endeavour to provide long-lasting pavements to society.”
Overall, the project is aimed at assisting bitumen users, asphalt
manufacturers and other intermediary bitumen suppliers. It is expected
that the technology will enable the correction of poor bitumen to
pass performance specifications. Additionally, the technology may
also improve the performance of standard bitumen from one grade to
another, especially in the event of national bitumen shortages. It is also
important to highlight that a major benefit of this invention would be an
increase in the recycling rates of waste tyres in South Africa, which will
ultimately lead to better-performing roads and a greener environment.
CASE STUDY ON THE USE OF WASTE PLASTIC
Construction of road sections on Road P159/1 (R80) in City of Tshwane, Gauteng
The CSIR, along with the Department of Science and Innovation (DSI),
as well as the plastics and roads industry, have recently worked on a
demonstration project in South Africa to evaluate the feasibility of using
waste plastic in road construction. The project aimed to identify lowvalue
plastic types and evaluate their potential usage in asphalt road
surfacing in accordance with South African road design standards and
environmental conditions.
The culmination point for the project was the construction of
Gauteng’s first “waste plastic” road trial section, currently located on
Construction of road trial section
made from waste plastic.
the R80. This trial section was used by the CSIR’s Smart Mobility Cluster
for proof-testing plastic-road technology in South Africa. The CSIR
has to date successfully completed a full-scale research investigation
and laboratory programme that was validated through Heavy Vehicle
Simulator (HVS) testing.
The project’s sponsors and key stakeholders from the DSI, Roadmac
Surfacing (Pty) Ltd (Raubex Group) and Much Asphalt were crucial in
supporting the CSIR’s project team throughout construction.
Although technical findings from the project are still currently being
published, the CSIR’s project team stated: “The project has successfully
showed potential in using specified waste plastic materials to design
rut resistant asphalt mixes without compromising on other asphalt
performance requirements. The approach requires the adoption of
necessary criteria to establish a consistent source of waste plastic.”
The research project highlights the need to understand the
mechanism that improves rut resistance to ensure that this benefit
is realised through controlling performance criteria and handling of
the asphalt mix. The research identified requirements for measuring
additional asphalt properties that would quantify the contribution of
the asphalt layer to safety, health and environmental sustainability.
Project team included: Georges AJ Mturi, Johan S O’Connell, Imraan
Akhalwaya, Theresa George, Vincent O Ojijo, Tladi Mofokeng, Nonzwakazi
Ncolosi, Michandre Smit and Linda Godfrey.
The end of the road
Feedback from these case studies is aimed at encouraging government
and road industry stakeholders to adopt the use of waste materials for
environmental benefits, as well as for the improved performance of road
surfaces. The technologies will require the development of application
guidelines to promote a better understanding of the suitability of waste
materials for road projects and therefore lower the risk of premature
failure of roads.
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