Performance of zeolite synthesized from sewage sludge ash as a warm mix asphalt additive

Abstract

The disposal of sewage sludge ash (SSA) is a growing problem with both environmental and economic ramifications. This study aims to synthesize zeolite from SSA as a foaming-based warm mix asphalt (WMA) additive, and comprehensively characterize its performance. The SSA-derived zeolite was first characterized using X-ray Diffractometer (XRD), Scanning Electron Microscope (SEM), and Thermogravimetry-Differential Thermal Analyzer (TG-DTA) tests. Then, WMA mixtures with the SSA-derived zeolite and a commercial zeolite additive, and a conventional hot mix asphalt (HMA) mixture were produced in the laboratory for a wide range of engineering performance tests, including the indirect tensile stiffness modulus test, indirect tensile fatigue test, moisture susceptibility test, and Hamburg wheel-tracking test. The experimental results indicated that the SSA-derived zeolite was pure zeolite A which can release approximately 20% crystal water gradually from 70 oC to 200 oC. The overall performance of the WMA mixture with SSA-derived zeolite was better than that of the WMA mixture with commercial additive, and comparable to that of the HMA mixture except for rutting resistance, which is marginally lower but still satisfactory. Cost-benefit analysis was conducted in the end, which demonstrated that SSA-derived zeolite is eco-efficient. This study concluded that it is feasible to use the SSA-derived zeolite as an effective and sustainable WMA additive.