Environmental and mechanical impacts of waste incinerated acidic sludge ash as filler in hot mix asphalt

In this paper, the feasibility of employing waste incinerated acidic sludge ash (IASA) as a viable alternative to the mineral fillers in hot mix asphalt (HMA) with a siliceous aggregate source from environmental and mechanical aspects was investigated. Environmental impacts were analyzed considering four factors: ignitability, reactivity, corrosivity using pH test, and toxicity using toxicity characteristic leaching procedure test. Mechanical properties of mixtures were obtained using indirect tensile strength (ITS), resilient modulus, moisture sensitivity, and permanent deformation tests. Results revealed that all metal concentrations leached from IASA modified HMA and pH of IASA modified samples comply with the United States Environmental Protection Agency (EPA). It was also demonstrated that incorporation of IASA in HMA leads to enhancement of HMA mechanical properties. ITS and resilient modulus of mixtures containing IASA were higher than those of the control mixtures. Replacing 50 wt.% of siliceous stone dust filler with IASA causes an increment about twofold in the flow number and reduction of the rut depth by about 26 % compared to those of the control sample. Moreover, the hydrophobicity and impermeability properties of IASA modified HMA and the stronger interfacial reaction between asphalt and IASA, resulted in improving the moisture susceptibility of the mixture containing IASA. This paper provides more insights on IASA waste management through its application in an environmentally friendly HMA.