Comparative Evaluation of Aggregate Surface Energy Using Sessile Drop and Dynamic Vapor Sorption Methods and Its Effect on Aggregate–Bitumen Compatibility

摘要

Incompatible combination of aggregate and bitumen can lead to premature failure in pavements like stripping, raveling, and fatigue cracking. The compatibility of aggregate-bitumen system can be determined using their surface-free-energies (SFE). It is worthwhile to note that aggregate SFE plays a vital role to determine compatible combination of aggregate-bitumen system. It can be measured using two different methods, namely, sessile-drop (SD) and dynamic vapor sorption (DVS). However, both methods may result in different range of SFE, which can influence compatibility ratio (CR) of aggregate-bitumen system. Therefore, the present study is motivated to compare SFE of two different aggregates measured using SD and DVS methods, and their influence on compatibility. Two aggregates (basalt and quartzite) and two binders (PMB40 and CRMB60) were used in this study. Aggregate SFE was measured using SD and DVS methods, while bitumen SFE was measured using SD method. First, SFE of both the aggregates measured using DVS method was used to find compatibility of aggregate-bitumen system. The results showed that quartzite-CRMB60 had highest CR, followed by quartzite-PMB40, basalt-PMB40, and basalt-CRMB60. However, ranking of aggregate-bitumen systems was found to be different when aggregate SFE was measured using SD method. The results showed that basalt-PMB40 had highest CR, followed by quartzite-CRMB60, quartzite-PMB40, and basalt-CRMB60. Therefore, both SD and DVS methods resulted in different compatibility between aggregate-bitumen systems. In addition, SD method was found to underestimate aggregate SFE compared with DVS method which affects compatibility with bitumen. Hence, care must be taken before using SD method for evaluating the SFE of aggregates.