Establishing threshold value of surface free energy and binder bond strength parameters for basaltic asphalt mixes

Abstract

The present work was undertaken to establish the possible threshold values for Surface Free Energy (SFE) and Binder Bond Strength (BBS) methods for screening asphalt-aggregate systems to ensure excellent moisture damage resistance. A total of sixteen combinations of asphalt-aggregate systems consisted of warm mix additives (WMA) and recycled asphalt pavement (RAP) and WMA-RAP combinations. In addition, the study evaluates the effects of RAP, WMA, and WMA-RAP on compatibility ratio (CR), bitumen bond strength ratio (BSR), and indirect tensile strength ratio (TSR) for different combinations of aggregate-asphalt system. The results showed that compatibility and bond strength between asphalt binders and aggregates deteriorated with the addition of RAP and WMA additives. Threshold criteria for CR and BSR values were identified as 4.80 and 0.90, respectively, with reasonably good accuracy of 90% for the SFE method and 75% for the BBS method. The threshold values, along with the practical framework established in the present study, would help the highway agencies select the most compatible asphalt-aggregate combinations.