Evaluation on moisture sensitivity induced by dynamic pore water pressure for asphalt mixture and its components using the bending beam rheometer method

Abstract

Moisture damage induced by dynamic pore water pressure commonly occurs in asphalt pavement located in regions with rich rainfall. This kind of moisture damage illustrates a special and quite different mechanism compared with that induced by static water immersion and freeze-thaw. Fine aggregate mixture (FAM) plays a vital role on the entire resistance of hot mix asphalt (HMA) to moisture damage. However, there is still a lack of systematic research on the evaluation of moisture sensitivity for both HMA and its components such as asphalt binder and FAM at the same scale. This study adopted the bending beam rheometer (BBR) method to assess moisture sensitivity for HMA and its components induced by dynamic water environment. The results indicated that the creep stiffness for both HMA and its components declined after being conditioned in dynamic water environment. FAM was quite easily eroded and its maximum decrease extent of creep stiffness could even up to 54.8%. In this case, it was clearly shown that the moisture sensitivity of HMA was greatly affected by its FAM component’s performance. The erosion effect of short-term conditioning in a harsh dynamic water environment was comparable to that of long-term conditioning in a mild environment. Softening and emulsifying showed more obvious effects on both asphalt binder and FAM during dynamic water conditioning, which made them exhibit more viscosity. Specially, after the FAM component on the surface of a HMA sample being scoured away, the retained coarse aggregate skeleton made the entire HMA sample still remain a certain mechanical strength and anti-erosion ability. Based on the analysis of the indicator m/S, HMA showed viscous performance in a mild dynamic water environment but tended to exhibit more elasticity with the increase of environment severity.