DIGEST 2006 - Sabita

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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
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DIGEST 2006
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Mission Sabita’s plans and action
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4. Innovation The use of steel slag
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1 Valediction
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economic growth. In addition to str
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one of the world leading trade orga
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Choosing road surfaces: Bitumen, gr
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we can economically test a possible
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oads. These considerations influenc
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double that for two-lane surfaced r
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elative fluctuation by increasing o
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Optimising resource utilisation: Ag
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COSHEC in 2007: Health and safety i
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designed to assist road authorities
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• Obtain endorsement and commitme
Page 32 and 33: • institution of Sabita safety tr
Page 34 and 35: Towards an informed industry: Updat
Page 36 and 37: versions of some of Sabita’s earl
Page 38 and 39: from texture treatments to overlays
Page 40 and 41: South Africa's education system: A
Page 42 and 43: environment and red tape on small a
Page 44 and 45: Figure 2. Matric result trends the
Page 46 and 47: professional work, within the conte
Page 48 and 49: Assessing Teachers are often unclea
Page 50 and 51: 3 HG learners in a class of 40 SG).
Page 52 and 53: The following observations may be m
Page 54: documented successful maths and sci
Page 57 and 58: public awareness programme to illus
Page 59 and 60: Surge in SAT's knowledge transfer a
Page 61 and 62: organisation. With the improvement
Page 63 and 64: accomplished through self-study. Th
Page 65 and 66: 4 Innovation
Page 67 and 68: calcium oxide is not fully hydrated
Page 69 and 70: oad construction. As mentioned prev
Page 71 and 72: M ix type Coars e continuous Coarse
Page 73: Conclusions From the results presen
Page 76 and 77: itumen emulsion or foamed bitumen,
Page 78 and 79: operations, as well as to advance a
Page 81: Fischer-Tropsch wax bitumen modifie
Page 85 and 86: Figure 3: Layer temperature profile
Page 87 and 88: easily formed and shaped where nece
Page 89 and 90: Achieving cost-efficiency through t
Page 91 and 92: Graded stone seals The seals that a
Page 93: Figure 6 illustrates how the stone
Page 96 and 97: decided rather to use the old TRH8
Page 98 and 99: ecommendations (R69/97 for bitumino
Page 100 and 101: compositional fractions (See Table
Page 102 and 103: PRADO analysis. Large quantities of
Page 104 and 105: HMA research programme: Forensic in
Page 106 and 107: Conclusions The following conclusio
Page 108 and 109: test programme, will seek to develo
Page 111 and 112: Out of the box thoughts on traditio
Page 113 and 114: Or more appropriately, a lone thar
Page 115 and 116: seal, and everybody's happy! Or wer
Page 118 and 119: The status quo on landfill sites: D
Page 120: In August 2004 a status quo report
Page 123 and 124: Bond coats Bond coats were first us
Page 125 and 126: peak value of 1,2 J/cm 2 . Typical
Page 127 and 128: promote the breaking of the emulsio
Page 130 and 131: Bitumen stabilised materials: A per
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Figure 2: DSR testing at comparativ
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Revision of Technical Guideline 1 (
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º introducing upper limits on some
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void loss due to embedment and aggr
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Alternatives to coal tar products:
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you don’t measure” might have b
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gradually increased from approximat
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Conclusions MC 30 cutback bitumen
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Towards industry self-regulation: T
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Figure 2: Accidents involving heavy
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RTMS standards for transport operat
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operators as part of their quality
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• System installation i.e. applic
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Notes 169
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Advertiser Index Advertiser Page Co
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Sabita Video Training Aids Video se
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Associate Members Africon Engineeri
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DIGEST 2006 - Sabita

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