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Abstract
The main objective of this research work was to characterise the performance
related properties of asphalt mixtures (rutting, and cracking) through dynamic
testing. Appropriate analytical and experimental procedures were developed to
determine the elastic moduli and resistance of asphalt concrete to permanent
deformation and fatigue cracking through a routine test program. A repeated loading
apparatus called MATTA (Material Testing Apparatus) along with a direct tension
test device developed in the School of Civil Engineering were used in this research
study.
A dense graded asphalt with one type of aggregate having a maximum size of 20
mm along with four binder types (C-170, C-320, Multigrade, and Cariphalte) were
used. Two types of equipment were used for compaction of the specimens. Gyropac
was used for manufacturing cylindrical specimens for the resilient test, creep test,
indirect tensile fatigue, and direct tension tests. A new Shear Box apparatus was
employed to manufacture rectangular beams for the four point beam testing.
This experimental study investigated the effect of mix variables, temperature, and
a polymer additive (SBS) on the mechanical properties of different asphalt mixes.
Indirect repeated tensile resilient modulus test and uniaxial repeated creep tests were
carried out to characterise the resilient and plastic behaviour of asphalt concrete. A
Phenomenological approach was used to characterise the fatigue behaviour of
asphalt concrete. Furthermore, two mechanistic methods, fracture mechanics and
dissipated energy approach were employed to characterise fatigue behaviour of
asphalt concrete using the four point beam test.
Models were developed to estimate the resilient modulus of several asphalt mixes
at different temperatures and rise times. It was found that a polymer modified binder
( Cariphalte) significantly enhanced the resistance of asphalt concrete to permanent
deformation (rutting). It was also found that the indirect tensile fatigue test could be
used to characterise the fatigue behaviour of asphalt concrete providing, a quick and
affordable test method. A new approach for the definition of the failure point and the
number of repetitions to crack initiation and crack propagation were developed. It
was found that dissipated energy could be used to obtain fatigue properties of
asphalt concrete without performing a time consuming fatigue test. A surrogate
model chosen from limited mixes was developed to estimate the fatigue life of
asphalt mixes based on initial mix stiffness and initial phase angle. A new simple
and affordable approach was used to apply fracture mechanics principles in order to
determine crack initiation and crack propagation of asphalt concrete as well as the
parameters needed by Paris' law.