Comparative study on the properties of WMA mixture using foamed admixture and free water system

Warm mix asphalt (WMA) technologies that use a foaming effect are one of the most commonly used WMA technologies due to their cost-effectiveness. The concept behind the foamed WMA is that the water turns to steam and is dispersed throughout the asphalt, which provides corresponding temporary reductions in viscosity while requiring no extra additives. The purpose of this paper is to evaluate both WMA techniques using foamed admixture and free water systems. For foamed admixture, ADVERA® WMA was selected; whereas for free water systems, WMA was foamed by injecting a small amount of water that was produced under a laboratory setup. Subsequently, for the asphalt mixture preparation, the mixture design used was based on specifications for a local asphalt mixture used in Michigan, USA. The nominal maximum aggregate size is 9.5 mm and the designed traffic level is less than 3 million ESALs based on the current Superpave™ asphalt mixture design procedure. The control mixture and WMA mixture were evaluated through the asphalt pavement analyzer rutting test, flow number test, indirect tensile strength ratio, and the four point beam fatigue test. From the results, it was found the fatigue life of most of the samples prepared with ADVERA® WMA were higher than the control hot mix asphalt (HMA). However, foamed WMA has a significantly lower aging factor compared to control HMA which results in higher rutting potential.