Evaluate the mechanism of the effect of hydrated lime on moisture damage of warm mix asphalt

With increasing interest in the use of warm mix asphalt in the paving industry, more studies in this field for improvement of warm mix asphalt properties seem to be necessary. In spite of many warm mix asphalt advantages, moisture susceptibility is one of the potential disadvantages of warm mix asphalt mixtures. In this study, the effects of using hydrated lime as a common anti-strip additive on moisture susceptibility of asphalt mixtures has been evaluated by determining the mechanism that affects the adhesive bond between the aggregate and asphalt binder using the surface free energy method. Two types of aggregates, limestone and granite, and two types of warm mix asphalt additives, namely sasobit and asphamin, as well as hydrated lime as anti-strip additives were evaluated in this study. The results of the surface free energy method indicate that hydrated lime increases the wettability of asphalt binder on the aggregate and improves the adhesion between the asphalt binder and aggregate. Also, the difference between surface free energies of asphalt-aggregate and water-aggregate is higher in samples made with untreated aggregates, as using hydrated lime caused these values to decrease. This implies that more energy is needed for stripping phenomena to occur, and the rate of moisture damage decreases.