Resistance
of asphalt mixtures to moisture damage is commonly known as
a function of interaction between asphalt and aggregate as they
are exposed to water. For many years, a number of research focused
on moisture damage have listed a number of important factors.
The mineralogical composition of aggregate and asphalt chemistry
is well known as an important factor in the susceptibility of
asphalt mixtures to moisture damage. However, the significance
of asphalt binder properties in affecting moisture damage has
not yet been widely investigated. In this study, the role of
binders in moisture damage is separated into adhesion and cohesion
properties. To measure the cohesion of asphalt, a method known
as tackiness test of asphalt using the Dynamic Shear Rheometer
(DSR) was employed. To measure the adhesion of asphalt to aggregate
surface, a modified pull-off test using the Pneumatic Adhesion
Tensile Tester (PATTI) was introduced.
b)
Specimen preparation for adhesion or pull-off tensile strength
test.
This
study was conducted to evaluate the relationship of the cohesion
of asphalt binder, the resistance of asphalt binder to strip
from aggregate surface (adhesion), and the resistance of asphalt
mixtures to moisture damage in the laboratory. The resistance
of mixtures was measured using the Indirect Tensile Test, the
Uniaxial Compression Permanent Deformation Test, and the Hamburg
Wheel-Tracking Test. Different types of asphalt binders including
original, polymer modified, and anti-stripping modified binder
were used. Two types of aggregate mineralogy, limestone and
granite, were selected to produce the asphalt mixtures. All
other mix design variables were controlled to minimize their
effect on the performance of asphalt mixtures.
The
results of this study indicated that the cohesion and adhesion
of asphalt binder could be used as a good indicator to predict
the performance of asphalt mixtures in resisting moisture damage.
It is clear that asphalt modification with polymer can substantially
improve cohesion and adhesion. In addition, the anti-stripping
additive provides significant improvement of adhesion but neutral
effect on cohesion. Finally, the aggregate mineralogy was also
found to be an important factor in such a way that the granite
mixture exhibits more susceptibility to the moisture damage
than the limestone mixture for most of binder combinations.
