Effects of Combined Environmental Factors on Stiffness and Rutting Properties of Warm Mix Asphalt

Warm mix asphalt (WMA) is a sustainable clean product that can be fabricated at lower temperatures. This is an environmentally friendly mixture due to its lower emission and energy consumption in asphalt production plants. Moisture conditioning and aging process are two environmental factors that can adversely affect the stiffness properties of this product. In the field, WMAs are subjected to both moisture damage and aging. In this paper, a new laboratory method was used for evaluating the combined effects of aging and moisture conditioning of WMA samples. WMA specimens were fabricated at various compaction temperatures with different amounts of a surfactant-wax warm additive. Stiffness properties of asphalt mixtures were quantified from the resilient modulus and dynamic creep test. The results showed that moisture conditioning and aging are competing to affect the stiffness properties of mixtures. Polymer modified asphalt mixtures were found to be less susceptible to moisture damage when compared to mixtures fabricated with unmodified binder. Compaction temperature was the most significant factor that affected the resilient modulus of WMA. In the dynamic creep test, the combined effects of aging and moisture conditioning reduced the cumulative micro strain of samples regardless of binder type, additive content and compaction temperature.