Influence of bitumen foam characteristics on moisture susceptibility of foamed bitumen stabilised mixes

Abstract

ABSTRACT The objective of the present study is to investigate the effect of foam characteristics of bitumen such as maximum expansion ratio (ERm) and half-life (HL) on the moisture susceptibility of foamed bitumen stabilised mixes (FBMs). The study investigated the individual as well as the interaction effect of ERm and HL on moisture susceptibility of FBMs. Considering the individual effect of ERm, it was observed that for a given HL, the beneficial effect of ERm on the moisture susceptibility of FBMs exists up to a certain level of ERm, beyond which the performance of the FBMs was found to be compromised. On the other hand, at controlled ERm, the higher HL was found to have beneficial effect on the moisture susceptibility of FBMs, provided the controlled ERm was sufficiently high. When the interaction effect of ERm and HL was considered, the FBMs were found to have higher moisture damage resistance with the increase in ERm as long as the HL was above a certain threshold level. The study also proposed performance-based minimum threshold limits for ERm and HL based on the Receiver Operation Characteristics (ROC) analysis on the retained tensile strength (TSR) results obtained for the FBMs prepared at varying foam characteristics.