This
thesis presents a comprehensive study of the effects of shear stress reversal
on the behavior of asphalt concrete, specifically with respect to the resulting
deformation and damage. The study consisted of a series of simple shear tests
in a cyclic loading. The tests were performed without stress reversal
(consistent with conventional methods of testing) and with stress reversal, as
obtained from traveling vehicle's wheels. The purpose of the tests was to
measure the damage and healing characteristics of the material. The difference
in the damage caused to the material in the two tests was examined. The simple
shear tests included two types of tests, frequency sweep tests and trapezoid
loading tests. The frequency sweep tests were carried out before the trapezoid loading
tests, after 20,000 cycles of trapezoid load testing and after a few days of
rest. The load in the frequency sweep tests did not cause any damage to the
material. The damage to the material after 20000 load cycles was measured in
two ways: [1] by the frequency sweep tests, according to the ratio between the
shear modulus that was obtained from the tests before and after the trapezoid
loading and [2] by the trapezoid loading, according to the ratio between a visco-elastic shear strain that was calculated from a visco-elastic model
without damage and the visco-elastic component of the shear strain that was
obtained from the tests. The damage measurement that was obtained from the
tests with stress reversal was approximately two times greater than the damage
that was obtained from the tests without stress reversal.
