Methodology to Evaluate the Effect of Warm-Mix Additives on the Wettability of Asphalt Binder on Aggregates

Abstract

The wettability of asphalt binders on aggregates primarily depends on the interfacial interactions between the binder and the aggregates, as well as the surface tension of the binder. It can be enhanced by warm-mix additives. This study investigates the effect of warm-mix additives on the wettability of binder on aggregates by using the sessile drop technique in the high-temperature range. Asphalt binders with different dosages of a surfactant-based additive and a wax-based additive were prepared. Drops of asphalt binders were placed on aggregate and Teflon-coated substrates at temperatures ranging from 60°C to 160°C. The surface tension is determined from the shape of the drop, whereas the contact angle is determined from the binder drop on aggregate substrates. The results indicate that the improvement in wettability achieved with both the wax-based and surfactant-based additives exceeds what can be achieved by simply increasing the temperature of the base binder. These additives not only decrease the surface tension but also decrease the contact angle between the binder and aggregates.