Comparison and relationship between indices for the characterization of the moisture resistance of asphalt-aggregate systems

The complex and diversified asphalt modification makes it harder for the assessment of testing methods capable of characterizing the performance of different modified asphalt in the presence of water. In this study, three representative test methods addressing the moisture performance of asphalt were evaluated and compared: surface free energy (SFE) test, binder bond strength (BBS) test and Hamburg wheel tracking device (HWTD) test. Results indicate that the HWTD test can be a benchmark test while the BBS test is a screening test in characterizing the moisture performance of various modified asphalt. In addition, the surface energy component obtained from the receding procedure in the Wilhelmy Plate Method correlated better with the adhesion property of asphalt than those based on the advancing procedure did. The various indices obtained from the three tests were classified as suitable or unsuitable indices on the basis of the analysis of specific additives. Furthermore, based on the degree of their improvement in the moisture performance, additives were classified into three grades: (1) the first grade including linear styrene-butadiene-styrene (SBS), branched SBS and gilsonite; (2) the second grade including high-density polyethylene, and polyphosphoric acid; (3) the third grade including asphalt rubber and terminal blend asphalt. Finally, it was found that base binders with shorter-chain structures and lower aromatics contents showed better moisture resistance in the HWTD test. High mobility of base asphalt binder negatively influenced the corresponding mixture's moisture sensitivity.