Evaluation of Moisture Susceptibility Minimization Strategies for Warm-Mix Asphalt: Case Study

Abstract

Warm-mix asphalt (WMA) technologies aid in reducing mixing and compaction temperatures for asphalt concrete mixtures, allowing for savings in fuel consumption and extending haul distances and construction season. The reduced temperatures also provide a greener technology as emissions are lowered at the plant and the construction site. Engineering and environmental benefits promoted the rapid implementation of WMA technologies, but concerns remain regarding the difference in mixture performance of WMA versus hot-mix asphalt (HMA) because of the changes in the production process, specifically in terms of moisture susceptibility. This case study evaluates moisture susceptibility through the use of laboratory tests including the wet indirect tensile (IDT) strength test, the tensile strength ratio (TSR), and the Hamburg wheel tracking test (HWTT) analyzed with a novel methodology. The performance of two WMA technologies (Evotherm DAT and foaming) versus a control HMA is analyzed with and without antistripping additives and/or recycled materials after field and laboratory aging. Findings suggest that the WMA mixtures are more prone to moisture susceptibility in their early life as compared with HMA. The incorporation of recycled materials did not show a clear benefit for the WMA, whereas the inclusion of antistripping additives and aging significantly improved WMA in terms of moisture resistance, rendering mixtures with equivalent performance to HMA.