Warm mix asphalt: an overview

One of the causes of pollution associated with the construction of transportation infrastructures is the emission of greenhouse gases into the atmosphere. Even though the use of Warm Mix Asphalt technology has many advantages that are not related to the reduction of gas emissions, WMA technology is also good for the environment because it produces asphalt at temperatures 20–40° lower in comparison to Hot Mix Asphalt. The temperature reduction achieved by WMA comes from the use of various technologies that have been developed in recent years, and which can be classified in the following three groups: organic additives, chemical additives, and water-based or water-containing foaming processes. Although all of them pursue the same goal, the manufacturing process differs. Thus, their aim is mainly to reduce bitumen viscosity, which in turn improves mix workability, produces fewer emissions, and generally creates better working conditions. This paper is an overview of the different technologies used in the manufacturing of WMA. It analyzes the materials, additives, mix design and performance of the asphalt made by this technology. It also describes its benefits and drawbacks, and underlines the need for further research in this area.