Moisture susceptibility and environmental impact of warm mix asphalt containing bottom ash

Abstract

Warm Mix Asphalt (WMA) is recognised as a sustainable pavement construction technology due to its economic and environmental benefits. However, there are still some major concerns related to its performance properties, like moisture susceptibility. Certain researchers have reported desired performances using waste and by-products as constituent material in the WMA mixture. Therefore, this study was proposed to assess the Bottom Ash (BA) impact on WMA mixtures moisture susceptibility and environmental properties because its potential has widely been reported in HMA. It was limited to 20 % of fine aggregate substitution with BA and granite stone dust as a filler. Evotherm 3G was used as a WMA additive, and the Hot Mix Asphalt (HMA) mixtures were treated with 2 % hydrated lime by replacing stone dust. The Marshall mix design was followed to fabricate asphalt mixtures, where HMA and WMA specimens were mixed at 165 °C and 140 °C, respectively. The indirect tensile strength, tensile strength ratio, toxicity characteristic leaching procedure (TCLP) and pollutant emission of mixtures were investigated through laboratory tests. The mixtures containing BA improved the indirect tensile strength of mixtures, while Evotherm 3G potentially improved the tensile strength ratio of WMA mixtures containing BA. The results showed that BA as a constituent of asphalt mixture coupled with Evotherm 3G produced a compatible blend for WMA. The findings of the TCLP test showed that the compound of heavy elements found in BA does not leach out if introduced in the asphalt mixtures. Heavy elements concentrations were either undetectable or below the minimal level. However, the presence of BA in the asphalt mixture slightly increased the level of Carbon dioxide (CO2). However, the carbon monoxide (CO) of the WMA mixture containing BA was reduced to approximately 75 %.