Evaluation of Cost-Effective Modified Binder Thin Chip and Cape Seal Surfacings on an Anionic Nano-Modified Emulsion (NME)-Stabilised Base Layer Using Accelerated Pavement Testing (APT)

Abstract

Emulsion stabilisation of base layers surfaced with chip seals often proves problematic, with chips punching into the base and early distress. This can be aggravated by the use of modified binders that restricts the evaporation of moisture from pavement layers. The introduction of new-age (nano)-modified emulsion (NME) stabilisation has the advantage that water is chemically repelled from the stabilised layer, resulting in an accelerated development of strength. A need was identified to evaluate the early-life performance of selected chip and Cape seals, together with identified modified binders on anionic NME-stabilised base layers constructed with materials traditionally classified as unsuitable, using archaic empirically derived tests. Three different chip seal surfacings with unconventional modified binders were constructed and evaluated using accelerated pavement testing (APT) with the Model Mobile Load Simulator—3rd model (MMLS3). The objectives of the experimental design and testing were to evaluate the binder performance, chip seal performance in terms of early loss of chips before chip orientation, punching of the chips into the anionic NME-stabilised base and deformation characteristics of a Cape seal that was hand-laid using an anionic NME slurry without any cement filler. It was shown that that chip seal surfacings can be used at low risk, on a base layer containing materials with fines exceeding 22%. The selection of specific modified binders can reduce risks associated with chip seal surfacings, which can impact construction limitations. The recommended use of elastomer-modified binders on newly constructed or rehabilitated layers, resulting in moisture entrapment, needs to be reconsidered.

Nanotechnology Incorporation into Road Pavement Design Based on Scientific Principles of Materials Chemistry and Engineering Physics Using New-Age (Nano) Modified Emulsion (NME) Stabilisation/Enhancement of Granular Materials

“…For comparisons with the traditional recommended designs, typical designs are compared in Figure 27. The work performed on the evaluation of thin chip seals, especially that performed on a Cape seal with a variation of modified binders, has confirmed the potential use of this thin surfacing as a protective surfacing layer for roads carrying relatively high traffic loadings on base and sub-base layers stabilised with a material compatible stabilising agent (with deformation characteristics comparable to that of asphalt surfacings specified for highways) [49].…”

“…Hence, these pavements will be very suitable in an environment where law-enforcement in terms of over-loading is a scarcity or non-existent. Lifecycle cost analyses [51] on a number of projects have shown initial material cost savings of 30 to 50 per cent, with additional savings in construction time and considerable savings in possible periodic maintenance over the design period [25,26,49].…”

Nanotechnology Incorporation into Road Pavement Design based on Scientific Principles of Materials Chemistry and Engineering Physics

“…For comparisons with traditional designs recommended, typical designs are compared in Figure 27. Work done on the evaluation of thin chip seals, especially that done on a Cape seal with a variation of modified binders, has confirmed the potential use of this thin surfacing as a protective surfacing layer for roads carrying relatively high traffic loadings on base and subbase layers stabilised with a material compatible stabilising agent (with deformation characteristics comparable to that of asphalt surfacings specified for highways) [49].…”

Constructability of Road Pavement Layers Using New-Age (Nano) Modified Emulsion (NME) Stabilisation of Naturally Available Granular Materials in Roads Varying from Highways to Local Access Roads

“…In combination with fundamental concepts in terms of practical pavement engineering, such as Unconfined Compressive Strength (UCS) and Indirect Tensile Strength (ITS), to evaluate the suitability of the use of stabilised granular materials in road pavement layers, nanotechnology advantages may be met with resistance in practice by traditionalists unfamiliar with these material evaluation techniques. In such cases, the fact that the stabilised granular material design method is based on fundamental scientific principles [2,3,4,5,6,7,8], been evaluated and proven in National Research and University laboratories [4,9,10], evaluated in practice through Accelerated Pavement Testing (APT) [11,12,13] and implemented on several roads in southern Africa [14] may have little effect on the construction industry.…”

“…No technology is without risks. However, a rigorous process of risk assessment and the development of a scientifically based material design method [8], laboratory evaluations [4,9,10] and full-sale APT loading assessments [11,12,13], allowed for design risks to be identified and as far as possible, to be addressed in practice. However, contractors often experience unforeseen risks, many of which can be prevented or limited through the timeous identification thereof and the demonstration of the consequences and possible solutions to construction problems through practical examples.…”