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

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 %

Laboratory investigation of coal bottom ash modified warm mix asphalt

Bottom Ash (BA), a coal combustion by-product, found to be a potential material when used to produce asphalt mixture. However, some of its characteristics make it a questionable material for the surface course. Therefore, this study aims to evaluate the compatibility of BA in Warm Mix Asphalt (WMA) technology through the basic mechanical properties of the asphalt mixtures for binder course layer (AC 28). Two WMA chemical additives, Cecabase RT and Evotherm 3G, were used at the concentrations of 0.3, 0.4 and 0.5% from the binder's weight. The binder properties were assessed through penetration, softening point and viscosity tests. The Marshall mix design was used to determine the optimum binder content (OBC). The additive dosage and production temperature for WMA were determined through Marshall stability, flow, air voids and specific gravity. The results show that the additives did not significantly affect the binder properties, although, at 0.4% Evotherm 3G, a drop of 17.5% in penetration was observed. Cecabase RT produced WMA with promising results but did not enhance the workability of WMA containing bottom ash (BAWMA). By lowering the production temperature of 25 °C, WMA and BAWMA at 0.4 %, Evotherm 3G demonstrated comparable workability to the conventional Hot Mix Asphalt (HMA). The data achieved through this study would be a guiding approach towards the application of BA in WMA technology for sustainable pavements