Hydraulic, Volumetric, and Mechanical Approach in Asphalt Mixture Design for Impervious Barriers

Asphalt concrete has been used as an appropriate impervious barrier for water retention. The performance of asphalt concrete in dam cores, reservoir coatings, and canals is comparable with other existing alternatives. However, the methodology used to determine the amount of asphalt binder in the mixture is based on some experiences and recommendations; knowledge about the effect of the aggregate gradation on the permeability of asphalt concrete used in these barriers is limited. In this investigation, permeability and cracking susceptibility of asphalt concrete specimens made from different gradations and asphalt binder content are studied to propose a design method of asphalt mixtures for impervious barriers. Permeability tests under different conditions of hydraulic head and indirect tensile strength (ITS) tests were performed. As an outcome, for the materials used in this study, gradation limits were determined for pervious and impervious asphalt concrete. Considering that the mineral aggregate can have asphalt binder absorptions in a very wide range, it is proposed to use effective asphalt film thickness to determine the minimum asphalt binder content. It was found that the best performance of the mixture was achieved with an effective film thickness between 10 and 13m.