Moisture damage evaluation of asphalt-aggregate constituents and warm mix asphalt using imaging techniques and tensile tests

Abstract

Warm Mix Asphalt (WMA) is more susceptible to adhesive failures at the asphalt-aggregate interface than Hot Mix Asphalt (HMA) due to its lower production temperature. This paper presents an innovative approach to quantify the adhesive failures of asphalt-aggregate constituents and mixtures in direct and indirect tensions, respectively. Advanced imaging techniques were utilized to compute the specimens percentage adhesive failure. A PG-64 bitumen was the conventional binder used. Hydrated Lime (HL) and Pavement Modifier (PMD) were used as anti-stripping fillers, while Evotherm (EV) was incorporated as the surfactant-WMA additive. Three moisture conditioning levels were performed namely; unconditioned, 1 freeze-thaw (F-T) and 3 F-T cycles prior to testing. The specimens percentage adhesive failure increased, while tensile strength reduced with F-T cycle. PMD specimens exhibited slightly lower percentage adhesive failure than HL specimens. The percentage failure further reduced with the incorporation of EV. The effects of incorporating EV were more pronounced when combined with PMD as shown by the higher tensile strength and lower percentage failure than HL-EV. Limestone specimens showed superior moisture resistance than granite in moist condition. The high percentage broken aggregate on the fractured surfaces of tested asphalt mixtures was found to be more related to aggregate orientation than shape.