Applied Sciences Article  
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)  
[PERSON],*C, [PERSON] vd [PERSON]. [PERSON] and [PERSON]  
Department of Civil Engineering, University of Pretoria, Pretoria 0002, South Africa; [EMAIL_ADDRESS]  
Jordaan Professional Services (Pty) Ltd., Pretoria 0002, South Africa  
Department of Civil Engineering & School of Engineering, University of Pretoria, Pretoria 0002, South Africa  
[PERSON]SS]  
Correspondence: [EMAIL_ADDRESS]; Tel.: +27.824164945  
Factured Application: The surfacing layer on roads plays an essential role in the future performance of the road structure. In many traditional design approaches, the surfacing is also the most expensive part of the road pavement structure. It is directly exposed to the traffic loading as well as to often, harsh environmental conditions. The performance of the surfacing is highly dependent on the characteristics of the binder used and the interaction of the surfacing with the environment and the rest of the pavement structure. New-age nanotechnologies enable engineers to use modify binders to substantially improve the performance of surfacings and reduce the thicknesses thereof without compromising the integrity of the road structure as a whole. The optimisation of binder characteristics using applicable thin (chip seal) surfacings can contribute substantially to a reduction in road unit costs.  
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 archacic 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--3 rd 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; pavement engineering; chip seal surfacings; Cape seals; new-age modified emulsion (NME) stabilisation; anionic new-age modified emulsion slurries; modified binders; Sasobit-M(r) modified binders; accelerated pavement testing (APT); MMLS3