A long-term ultraviolet aging procedure on foamed WMA mixtures

Abstract

Long-term thermal and ultraviolet (UV) aging procedures of asphalt mixtures are complicated, but can be simulated in the laboratory. The objective of this study was to investigate the influence of long-term thermal and UV aging on foamed warm-mix asphalt (WMA) mixtures. Rut resistance, indirect tensile strength (ITS), deformation, dissipated elastic energy, and fracture energy were measured for all mixtures. The experimental design included two aggregate sources; three aging states (unaged, thermal and UV aging); one water-bearing WMA additive and water foaming technology; two PG 64-22 binders, and three air void contents (2, 4, and 7 %). A total of 24 mixtures were evaluated and 144 specimens were made and tested in this study. The test results indicated that thermal and UV aging procedures had limited contribution in improving the rut resistance of a mixture as air void content was low. Unaged samples had the highest ITS values amongst three aging states while UV aged samples had the lowest. In addition, UV aged mixtures generally had greater dissipated energy than thermal aged mixtures regardless of foaming technology, aggregate source, and air void. Moreover, the foaming technology might reduce the stored elastic energy of the mixture due to additional water or released water from water-bearing additive. Furthermore, UV aging generally reduces the fracture resistance of an asphalt mixture than standard thermal aging. In addition, when using WMA foaming technology, aggregate source affects the fracture resistance of the asphalt mixture.