Dynamic modulus and phase angle of warm-mix versus hot-mix asphalt concrete

Characteristics of dynamic modulus (|E∗|) and phase angle (δ) functions of hot-mix asphalt (HMA) are well known from years of laboratory tests and available models in the literature. On the other hand, the |E∗| and δ functions of warm-mix asphalt (WMA) are not well defined yet for reasons like relatively newer use in United States as well as manufactured by using various WMA technologies (e.g. foaming, Evotherm, Cecabase RT, etc.) which use different WMA agents. This study evaluates the effects of different WMA agents on the |E∗| and δ of asphalt concrete (AC). A control HMA and four WMA mixtures were collected from a plant with identical aggregate type and size distribution. The loose AC mixtures were then compacted, cored and sawed to cylindrical specimens for |E∗| and δ testing in the laboratory. Statistical evidence showed that WMA agents significantly affect the |E∗| and δ of AC mixture. The |E∗|-values of HMA and WMA are comparable at mid-range frequencies only, indicating that fatigue performances at operational temperature of WMA and its HMA counterpart may be similar. However, high temperature rutting and low temperature cracking may not be similar for WMA and its HMA counterpart.