Investigation of Critical Factors Determining the Accuracy of Binder Bond Strength Test to Evaluate Adhesion Properties of Asphalt Binders

摘要

The bond strength between asphalt and aggregates is a crucial parameter in evaluating the ability of asphalt mixture resistance to moisture-induced damage. Factors affecting the bond strength were investigated based on the binder bond strength (BBS) test. The effects of asphalt film thickness and loading rate on the results of the BBS test and the relationship between these two factors were further studied. Then, specimens were subjected to four moisture conditions to study the impact of water on the bond strength. Furthermore, the impact of the complex modulus on the bond strength was studied using the dynamic shear rheometer (DSR) test. Finally, the pull-off test results were compared with the findings obtained from the Hamburg wheel-tracking device (HWTD) test regarding the moisture sensitivity of mixtures under dry and wet conditions. Results indicate that the pull-off tensile strength (POTS) increased with an increase of the loading rate, whereas POTS decreased with the increase of the film thickness. It was proved that an equivalent relationship between these two factors existed in the BBS test. It is interesting that the measured POTS values were basically equal when the loading curves of the same asphalt overlap under different combinations of film thickness and loading rate. Water had a significant impact on the bond strength, and the moisture condition in the early state was important in determining the moisture sensitivity of the mixtures. Furthermore, POTS increased with the complex modulus of asphalt binder, whereas the phase angle of asphalt determined the extent to which the film thickness will affect the BBS test results. The comparison of the BBS and HWTD tests confirmed that the BBS test could address the mixture resistance to water damage.