Warm Mix Asphalt (WMA) has proven to be an innovative green technology that improves the
environmental sustainability of Hot Mix Asphalt (HMA) by reducing emissions and conserving
energy while maintaining or enhancing pavement performance through improved compaction.
Approximately 500,000 tonnes of WMA have been paved on Ministry of Transportation of Ontario
(MTO) roadways since 2008. WMA technologies that have been used include both chemical and
organic additives. While WMA has many benefits, it also has challenges that are being addressed by a joint task group comprised of members from MTO and the asphalt paving industry. In 2010, MTO built several WMA test sections along with HMA control sections to evaluate the performance and environmental benefits of WMA. Emission measurements were conducted at the asphalt plants as well as at the paving sites for both WMA and HMA mixes. Laboratory investigations included
moisture sensitivity testing on production samples, Hamburg wheel track testing, coating,
compactability, and Flow Number. MTO is monitoring the performance of the WMA pavement
sections based on the distress data obtained by MTO’s Automated Road Analyzer (ARAN).
Pavement performance of WMA has been comparable to HMA, with slightly better joint quality.
Given the positive experience with WMA, MTO adopted a permissive specification in 2012 allowing
the contractors to use WMA in lieu of HMA. In conjunction with this specification, the desire to
grow the WMA market has prompted MTO to continue to build WMA projects in 2013 and 2014, by
specifying its use.
This paper presents quality assurance and emissions data collected during construction of our WMA projects. The paper also discusses laboratory test results as well as pavement condition data collected for each of the WMA pavement test sections.
