(409h) Studying the Interface of Warm Mix Asphalts

Asphalt is a complicated mixture by millions of compounds. It is originally from crude oil distillation and is widely applied in road pavement and roof patching. One of the new developments in the asphalt technology is Warm Mix Asphalt, an environmental benign and energy efficient technology compared with the state of practice of Hot Mix Asphalt (HMA). In the warm mix asphalt technology, water or other water release chemicals were injected to asphalt mix to act as the lubricant to help asphalt mix with aggregate efficiently at relatively low temperature. The interface formed between asphalt and water can affect the mixing process and the long-term properties of asphalt pavement. Thus, studying the interface properties of water-asphalt system, and relationship with the chemical composition of asphalt, and its microstructure at different temperature and pressure conditions is important. As a first step, molecular dynamics simulations have been performed to work on the interfaces between the major components in asphalt and water. The surface tension, interaction energy between different components, radial distribution function of different kinds of molecules, and density distribution have been calculated. The surface energy of WMA films was characterized with surface contact angle measurements. The results show that the introduction of air voids reduces the surface energy of asphalt film, which might help to improve the WMA against the moisture damages. The result may suggest the best remedy to improve the warm mix asphalt technology.