Evaluating Burner Fuel Savings and Pavement Performance from Lowering Asphalt Production Temperatures with Warm Mix Asphalt Additives

Abstract

This study evaluated the effects of producing warm mix asphalt (WMA) at lower temperatures, compared to conventional hot mix asphalt (HMA), on energy consumption and asphalt mixture performance at both material and pavement levels. Two field projects were conducted in Alabama. The first evaluated two chemical WMA additives, while the second assessed further temperature reductions using one of the WMA additives with a different mix design. Burner fuel usage was monitored during production to quantify energy savings. Laboratory testing using the Asphalt Mixture Performance Tester (AMPT) included dynamic modulus (|E*|), cyclic fatigue, and stress sweep rutting (SSR) tests. The FlexMAT™ v2.2 program was used to analyze mechanistic test results, and pavement performance—specifically, fatigue cracking and rutting—was evaluated using FlexPAVE™ v2.2 under representative traffic and climate conditions. In Experiment 1, limited temperature reductions resulted in no significant difference in burner fuel consumption among mixtures. In Experiment 2, production temperature reductions of 22°C (40°F) and 36°C (65°F) yielded burner fuel savings of approximately 8% and 19%, respectively. Across both experiments, WMA mixtures demonstrated lower mixture Glover–Rowe (G-Rm) values, indicating improved non-load-related cracking resistance, while cyclic fatigue indices (D^R and S_app) were similar to those of HMA control mixtures. However, WMA mixtures exhibited increased rutting susceptibility and higher Rutting Strain Index (RSI) values, especially at the lowest production temperature. FlexPAVE™ v2.2 modeling predicted slightly higher fatigue damage and rutting in WMA mixtures compared with HMA. Overall, the findings suggest that WMA technologies can substantially reduce burner fuel use while maintaining acceptable pavement performance, provided mix design adjustments are made to control rutting at lower production temperatures.