Now That's Cool

Low-energy asphalt mixes such as warm-mix asphalt (WMA) are becoming increasingly popular due to their easy workability and environmental benefits. This article, Part 5 of a seven-part series on the chemistry of road building materials, discusses the chemistry behind WMA. WMA is formed by mixing one of several solid or liquid chemical compound additives with asphalt mix in the plant, or by foaming the mix with water at the plant. The WMA processes reduce the viscosity of the liquid asphalt through a variety of means, and can enable the complete coating of aggregates at temperatures that are 35-100° F lower than conventional hot mix asphalt. The warm mix asphalt process can reduce emissions and fuel consumption at the plant, while improving the work environment in the field.