Application of Surface Energy Measurements to Evaluate Moisture Susceptibility of Asphalt and Aggregates

This project summary report summarizes the research performed in Texas Department of Transportation (TxDOT) Project 0-4524. Moisture damage in asphalt mixtures can occur within the asphalt mastic (cohesive fracture) or at the aggregate mastic interface (adhesive fracture or failure). This three-year project was conducted to attain fundamental understanding of the moisture damage process by carefully considering the mechanisms that influence durability of the adhesive interface between aggregate and asphalt and the cohesive strength and durability of the mastic. The first phase of the project focused on validation of the surface energy measurements and the dynamic mechanical analysis (DMA) through the evaluation of moisture susceptibility of materials and mixtures with known field performance. The second phase of the project evaluated the surface energy and moisture susceptibility of aggregate and asphalt combinations. The framework and tentative protocols developed in this project can be used to select materials and design mixtures that have good resistance to moisture damage. In contrast to traditional methods that rely solely on testing of whole mixtures, this framework is based on a bottom-up approach to quantify moisture sensitivity of asphalt mixtures. In other words, in this framework materials are screened first, followed by tests on fine aggregate matrix and whole mixtures. Using this approach, the results of this project will contribute to the reduction of asphalt pavements failures due to moisture damage.