Warm Mix Asphalt for Cold Weather Paving

Increased environmental awareness and stricter emissions regulations have led to a development of warm mix asphalt (WMA) to reduce the high mixing temperatures of regular hot mix asphalt (HMA). Its benefits are reduction in energy consumption during production and reduced emissions during production and placement. The three most tested methods are; WAM Foam, Aspha-min zeolite and Sasobit wax. All three methods reduce the viscosity of the binder at a certain temperature range, allowing the aggregate to be fully coated at lower temperatures than in HMA production.

Previous research has not focused much on how WMA functions in cold weather paving. This paper investigates WMA’s potential in cold weather conditions and specifically how Iceland, with such conditions, can benefit from it. The conclusions in this paper are drawn from a literature review and a survey that was conducted among Iceland’s paving industry professionals.

Reduced emissions are especially beneficial in densely populated areas and in non-open air paving. The decreased viscosity allows effective ompaction at lower temperatures where cool down rates are slower. WMA’s disadvantages are mainly related to rutting and moisture susceptibility issues. Using WMA processes at HMA production temperatures: 1) Increases the temperature gap between production and cessation, allowing e.g. increased haul distances 2) Facilitates compaction, which is beneficial for; stiff mixes and RAP, paving during extreme weather conditions and reduction in compaction effort.

Icelandic professionals are generally positive towards WMA, interested in testing it further for Icelandic conditions, and hopeful about its potential for helping with some key problems in Icelandic paving. The final conclusion is that WMA is a viable option for cold weather conditions and for the paving industry in Iceland, Sasobit is most suitable of the three methods, and usage incentives are twofold: 1) As a compaction aid for mixes produced at, or close to, regular HMA production temperatures, used to increase haul distances and/or pave during cold and difficult weather conditions, and sometimes slightly reduce fuel consumption as well. 2) As an environmentally friendly method when emissions approach limits, although not an issue today it may become one with stricter emissions regulations or increased production.
Publication Date: 
Friday, December 1, 2006
Publication Number: 
WA-RD 650.1
Last modified: 
10/12/2016 - 15:42
Olof Kristjansdottir.
University of Washington. Dept. of Civil and Environmental Engineering.
Number of Pages: 
Warm mix paving mixtures, Hot mix paving mixtures, Cold weather construction, Environmental impacts, Pollutants, Energy consumption