Effect of Steric Hardening on the Damage Recovery of Bitumen

Abstract

Bituminous mixtures recover from fracture damage during rest periods and at high service temperatures due to their self-healing ability. Steric hardening of binders is a time-dependent phenomenon whose effect on the mechanical properties is similar to that of healing. Most of the healing evaluation methods used by different researchers do not consider the effect of steric hardening while explaining the effect of healing in the mixes. Hence, an attempt was made in the present study to quantify the contribution of steric hardening to the healing of bitumen. A multistage procedure was employed to separate the effect of steric hardening from the healing effect. In the steric hardening test, the bitumen sample was given a prolonged rest to evaluate the increase in the modulus value due to steric hardening. A storage recuperation test was carried out to quantify the combined effect of self-healing and steric hardening. The true healing potential of the binders was estimated by eliminating the effect of steric hardening from total recovery occurring during the rest period. Steric hardening was observed to be more in stiffer binders and at lower test temperature. Softer binders had more self-healing potential than stiffer binders. It was observed that the effect of steric hardening dictated the trends of total recovery, indicating that its contribution is significant. Thus, neglecting the effect of steric hardening while estimating the true healing potential of bitumen leads to inaccurate estimation and interpretation of healing results.