Effects of Polymeric Coating the Aggregate Surface on Reducing Moisture Sensitivity of Asphalt Mixtures

This paper presents the theoretical and experimental concepts of predicting moisture damage in asphalt concrete mixes using the surface free energy (SFE) concept and laboratory dynamic test, respectively. The SFE characteristics of aggregates and asphalt binders have been evaluated using a Universal Sorption Device (USD) and Wilhelmy Plate (WP) methods, respectively. To validate the results of SFE tests, a dynamic modulus test was conducted on the asphalt mixtures in a controlled stress mode under dry and wet conditions. The results of this study show that the polyvinyl chloride (PVC) coating decreases significantly the total SFE and polar SFE, and leads to an increase in the non-polar SFE of the aggregates, which make aggregates be hydrophobic. This occurrence increases the coating ability of aggregates by the asphalt binder. Comparison between the results of dynamic modulus test in dry and wet conditions confirms the results obtained from the SFE method. P index, which is the percentage of the aggregate surface that experiences stripping in different cycles of loading in wet condition, is obtained by the relation between the concepts of two investigated methods in this study.