Effectiveness of different conditioning procedures for moisture susceptibility evaluation of foamed bitumen stabilised mixes

Abstract

ABSTRACT The primary objective of the present study is to evaluate the effectiveness of the widely used moisture conditioning methods for moisture susceptibility evaluation while designing the Foamed Bitumen Stabilised Mixes (FBMs). The effectiveness of three different moisture conditioning methods, such as the conventional 24 h of water soaking, vacuum saturation (AASHTO T283), and ASTM D7870 conditioning (hydrostatic pore pressure) were compared based on their ability to distinguish between moisture susceptible and moisture damage resistant FBMs. It was observed that the ASTM D7870 moisture conditioning method could distinguish between moisture-resistant and moisture-susceptible mixes more effectively compared to the existing 24 h of water-soaking method, and can potentially be a more suitable conditioning method for moisture susceptibility evaluation of FBMs. The study also recommended threshold moisture susceptibility criteria in terms of retained tensile strength (TSR) for the ASTM D7870 conditioning method based on the existing moisture susceptibility criteria for 24 h of water soaking by performing Receiver Operation Characteristics (ROC) analysis on the TSR results. For different TSR criteria of 80%, 70%, and 60% for 24 h of water soaking, the equivalent TSR threshold for ASTM D7870 conditioning is recommended as 60%, 55%, and 50% respectively.