Direct Tensile Test to Assess Healing in Asphalt

Abstract

Asphalt concrete has the advantageous ability to heal. During rest
periods, damage present In the material is restored to a certain extent.
Healing of the material can be observed in iis regaining of strength
and stiffness after rest periods. In this paper, a new test method is presented.
It was developed to increase the understanding of the healing
phenomenon. The test method focused on asphalt as it v/ss assumed to
be the driver of the healing performance. The test method assessed
the heaUng performance of asphalt In stiffness and strength by testing
the bond strength In tensile mode of two pieces of asphalt that were
assembled under controlled temperature and stress conditions. With
the test method, healing tests ^yere performed on one type of binder;
the load level during healing and the healing tune were varied. The tesi
results showed that after a short healing time of only 6 min, a significant
amount of healing could be detected. That finding indicates the importance
of adhesion between two crack surfaces v/hen the healing capacity
is assessed. It v/as also found that the maximum tensile stress reached a
plateau value after 24 h of healing; the finding indicates thatfull healing
can be realized in short time periods for pure, unaged, soft binders. It
v/as also shov/n that the load level perpendicular to the damage during
heaUng had a significant effect on the observed healing.