Investigating the effect of warm mix additive on the performance of asphalt mixtures

Warm mix asphalt (WMA) is a technology that has seen widespread growth in Canada since its introduction to North America in 2002. Since this technology is relatively new, there are still concerns about how these asphalt mixtures will perform over long-term, especially regarding resistance to moisture damage. Moisture damage is the primary driver for the deterioration of asphalt in the field, and can also exacerbate existing life-cycle stresses and cause premature failure. The wide range of different techniques being used for this technology makes it difficult to make broad generalizations, as some seem to perform much better than others in a laboratory setting. With this in mind, a study comparing the results from plant produced WMA against a known hot Mix Asphalt (HMA) will provide useful information on what can be expected from the mixes currently in use. This study compared a WMA mix using a 0.3% Evotherm M1 additive and an HMA mix produced by a local provider in New Brunswick. These asphalt mixtures were prepared using the same locally sourced binder and aggregate. The WMA mix performed well compared to the control HMA mix in a Modified Lottman Test; both had tensile strength ratio (TSR) values above the minimum of 75%, and it was found that there is no difference between the WMA and HMA Tensile Strengths. Additional testing on the performance of the mixtures using the Hamburg Wheel rutting test was performed, and the mechanical response of the mixtures was characterized using the Dynamic Modulus Test. Additionally, the impact on the life cycle and a comparison using the Mechanistic-Empirical Design Method were analyzed and no difference was found in long-term performance of WMA and HMA.