Effect of warm mix additives on asphalt cement, asphalt rubber and asphalt mixture quality and durability

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The proposed research is to investigate the effect of warm mix asphalt technologies on asphalt quality and durability. Over the past decade, the Ontario Ministry of Transportation (MTO) has embarked on several programs that improve sustainability. The recent introduction of warm mix asphalt facilitates compaction at much reduced temperatures (30C-50C). Last year MTO placed 220,000 tonnes of warm mix and this amount is expected to increase significantly in years to come. The use of asphalt rubber allows for the recycling of large quantities of rubber tires and has the potential to significantly improve lifecycle costs. In support, MTO has constructed numerous trials using crumb rubber modifier. The Ontario Tire Stewardship (OTS) and MTO are now committed to the construction of three warm mix asphalt rubber trials in 2013. The lower temperatures facilitated by warm mixes provide several advantages that are particularly desirable for asphalt rubber: reduced emissions, reduced energy costs, facilitation of longer haul distances, and late season paving. However, there is a dearth of studies that specifically assess the effect such additives have on quality and durability. We define quality as the ability of an asphalt cement to resist rutting, fatigue, thermal cracking, and moisture damage. Durability is defined as the ability to maintain desired properties over a long service life. We hypothesize that there will be pronounced quality and durability differences for the various additives (warm mix and rubber) that have yet to be recognized by users and producers alike. Cold temperatures in much of Canada could produce unwanted early distress resulting in future costs, making the continued use of potentially beneficial concepts in cold climate paving unsustainable. The research results will help the asphalt industry with the selection of warm mix and asphalt rubber technologies that provide the greatest benefit in terms of long term cost and risk control. The project will train a number of graduate and undergraduate students in the latest aspects of asphalt science and engineering. The findings related to the interaction of warm mix additives with the asphalt cement could also have potential applications in other areas such as petroleum processing.