Cool Mix Asphalt: Redefining Warm Mix Asphalt

Dear Colleagues,

The plant mixing temperatures of WMA vary widely because WMA is generally defined as a temperature reduction from hot mix asphalt (HMA), say between 30°F (17°C) and 120°F (67°C). The WMA definition, however, further varies because the temperature of HMA varies between 260 and 335°F (127 and 168°C) depending on the asphalt binder grades. EAPA defines production temperatures of WMA as between 212 and 302°F (100 and 150°C) and those of HMA as 248 and 374°F (120 and 190°C) with overlapping temperatures of up to 54°F (30°C) (EAPA, 2014). Production and compaction temperatures are key control indicators for the construction of asphalt mixtures, but no unified standard method has been established yet (Liu et al. 2023). It is time to define the absolute temperature range for HMA, WMA, and cool mix asphalt (CMA), a new window to the future.

In this Special Issue, it is proposed that HMA should be defined as asphalt mixtures produced at temperatures between 284 and 320°F (140 and 160°C), WMA at temperatures between 248 and 284°F (120 and 140°C), and CMA at temperatures between 212 and 248°F (100 and 120°C). By defining their actual production temperatures rather than reduction temperatures from HMA, WMA and CMA will be clearly defined independent of varying HMA temperatures. Adopting these clear definitions will allow researchers, engineers, and contractors to compare apples versus apples rather than apples versus oranges. This Special Issue specifically calls for papers that involve the testing, design, production, construction, maintenance, and performance of CMAs that were produced at between 212 and 248°F (100 and 120°C). 

References

EAPA. 2014. The Use of Warm Mix Asphalt. EAPA Position Paper. European Asphalt Pavement Association.

Lee, H., Glueckert, T., Ahmed, T., Kim, Y, Baek, C. and Hwang, S. 2013. Laboratory evaluation and field implementation of polyethylene wax-based warm mix asphalt additive in USA. International Journal of Pavement Research and Technology, Vol.6, No.5., pp. 547-553. 

Liu, N., Liu, L., Li, M. & Sun, L. 2023. A comprehensive review of warm-mix asphalt mixtures: mix design, construction temperatures determination, performance and life-cycle assessment, Road Materials and Pavement Design, Taylor & Francis, DOI: 10.1080/14680629.2023.2268194.

Williams, B. A., Willis, J. R., & Shacat, J. 2021. Annual asphalt pavement industry survey on recycled materials and warm-mix asphalt usage: 2020 (No. Information Series 138 (11th edition)). National Asphalt Pavement Association.

Prof. Dr. Hosin Lee
Guest Editor

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• cool mix asphalt (CMA) with production temperatures between 100 and 120°C
• warm mix asphalt (WMA) with production temperatures between 120 and 140°C
• hot mix asphalt (HMA) with production temperatures between 140 and 160°C
• low-embodied carbon (LEC) materials
• innovative mitigation partnerships for asphalt and concrete technologies (IMPACT)
• low-carbon transportation materials (LCTM)