Mechanical characteristics of shear strength ratio used for moisture susceptibility evaluation of asphalt mixtures

Abstract

ABSTRACT One of the widely used parameters in evaluating moisture susceptibility of asphalt mixtures is tensile strength ratio (TSR). From a mechanical point of view, TSR is only appropriate at the bottom of asphalt concrete (AC) layer where tensile stress is predominant since near the surface or in the middle of AC layer shear stress is the major driving force to create moisture damage. Therefore, a better parameter that can describe moisture susceptibility for the entire AC layer is needed. In this study, the potential of shear strength ratio (SSR) in evaluating moisture susceptibility at different AC depths is attempted. The mechanical relationship among the SSR, TSR, cohesion and indirect tensile (IDT) strength has been studied wherein it was found that the SSR can be mechanically represented by the TSR and cohesion. In addition, the SSR values are determined from mechanistic analyses using the shear properties obtained from laboratory tests conducted for three types of asphalt mixtures. The results show that the SSR values are significantly varying along the depth of AC layer, while the TSR values are constant. Therefore, SSR could be a good alternative parameter in evaluating the moisture susceptibility of asphalt mixtures at different AC depths.