Effect of asphalt film thickness on the moisture sensitivity characteristics of hot-mix asphalt

Temperature, air and water are the common factors that profoundly affect the durability of asphalt concrete mixtures. In mild weather conditions, distresses such as permanent deformation, fatigue cracking can be encountered on the pavements due to traffic loading. But when a severe climate is in question, these stresses increase in poor materials; under inadequate control; with traffic as well as with water which are key elements in the degradation of asphalt concrete pavements. Many variables affect the amount of water damage in asphalt concrete layer. Among them, mixture design properties such as air void level, permeability, asphalt content and asphalt film thickness are the ones that must be investigated carefully.This study is aimed to determine the relationship between the various asphalt film thicknesses and the susceptibility characteristics to water of hot mix asphalt (HMA) so that an optimum asphalt film thickness that minimizes the moisture damage of HMA can be obtained. For this purpose, the modified Lottman Test (AASHTO T283) is performed on the Superpave Gyratory compacted specimens that contain 5 different asphalt film thicknesses. A good correlation between the asphalt film thickness and the modified Lottman test results as well as an optimum asphalt film thickness of 9.5–10.5 μm is obtained.