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.
