Comparative evaluation of moisture susceptibility of modified/foamed asphalt binders combined with different types of aggregates using surface free energy approach

Abstract

Moisture damage in asphalt pavement is a major concern for the state and federal highway agencies for many years. The surface free energy (SFE) is demonstrated to be a reliable mechanistic approach for evaluating the moisture-induced damage potential of asphalt mixes. The objective of this study was to use SFE approach to evaluate the effects of foamed/modified asphalt binders and aggregate type on the moisture susceptibility of asphalt mixes. The SFE components (polar and dispersion) of PG 64-22 asphalt binders, modified with 2–4% SBS, 2–4% nanoclay, 2–4% fly ash, 3.5% devulcanized rubber (DVR), or foamed by injecting water, were estimated from contact angle measurement. Also, the SFE components of five types of aggregates, namely limestone, gravel, basalt, granite, and sandstone were obtained from the literature. The energy ratio parameters calculated from the work of cohesion and adhesion were used to estimate the moisture-induced damage potential of various asphalt mixtures. The results showed that the total SFE and work of cohesion of PG 64-22 increased with the addition of SBS, nanoclay, and fly ash while decreased with the use of DVR and foaming process in asphalt binder. Based on the energy ratio parameters, the combination of asphalt binder with different types of aggregates has been recommended with the resistance to moisture-induced damage potential. The results presented herein are expected to assist in selecting appropriate asphalt binder and aggregates with desirable moisture resistance.