The asphalt paving industry is constantly exploring technological improvements that will enhance the material’s performance, increase construction efficiency, conserve resources, and advance environmental stewardship. Current and impending regulations on emissions and energy conservation are making attractive the reductions in asphalt mix production temperature. Warm mix asphalt (WMA) is a means to this end and several systems have been developed including: foaming, emulsions, additives, synthetic binders and others. Warm mix asphalt is produced at temperatures 20 to 40ºC lower than hot mix asphalt (HMA). The immediate benefit of producing and placing asphalt mixes at a lower temperature is the reduction in energy consumption, greenhouse gas emissions, fumes, and odors generated at the plant and the paving site. Furthermore, the technical benefits are substantial including reduction of short term binder hardening, reduction of mixture tenderness, possible increase of percentage of reclaimed asphalt pavement in new asphalt pavement mixes and possible extension of the construction season. This paper presents an overview of the current warm mix asphalt state-of-practice. A review of the various warm mix asphalt systems is provided. Findings of various studies concerning the observed and measured field performance and the environmental benefits in terms of energy conservation and reduced greenhouse gas emissions are also detailed in the paper.
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