Volume 40, Issue 2 (March 2012)
Effects of Additives for Warm Mix Asphalt on Performance Grades of Asphalt Binders
Laboratory tests were carried out on a neat asphalt binder and a styrene-butadiene-styrene (SBS) asphalt binder containing Sasobit and Aspha-min as warm mix asphalt (WMA) additives to quantitatively evaluate the effects of the additives on the continuous grading temperatures and grades of asphalt binders in the framework of the performance grading system. Test results and data analyses indicate that the significances of the effects of WMA additives depend on the asphalt binder type, additive type, additive content, and rolling thin film oven (RTFO) aging temperature. The wax-type additive Sasobit has a stiffening effect on the grading temperatures. At typical 3 % content, the upper temperatures can be increased by up to 13.5 °C, the lower temperatures can be increased by up to 6.9 °C, and the intermediate temperatures can be increased by up to 5.0 °C. In the commonly used content range, the zeolite-type additive Aspha-min has little effects on the upper, lower, and intermediate grading temperatures. Although there is a special case, in which the upper grading temperature increase is canceled out by 3.8 °C, the reduction in RTFO aging temperature from 163 °C to 133 °C does not generally result in notable changes in the grading temperatures.