Performance appraisal of controlled low-strength material using sewage sludge and refuse incineration bottom ash

This research evaluated the use of sewage sludge and refuse incineration bottom ash to replace calcium sulfoaluminate cement (C A) in making controlled low-strength material (CLSM). Various properties of CLSM mixtures were characterized in terms of unconfined compressive strength, microstructure and leachability. It was found that the strength of tested CLSM mixtures ranged from 3.6 to 9.0 MPa, over the upper excavatable limit of 2.1 MPa. The micro-structural analysis revealed that sewage sludge and bottom ash were crystallochemically incorporated within CLSM systems by forming the needle-like ettringite (C ₃A·3C·H ₃₂) with exiguous tubers via the typical Pozzolanic Reaction, leading to a dense and low-porosity microstructure. Furthermore, the toxicity characteristic leaching procedure evidenced that the cumulative leachable metals in the leachate were much below the regulatory thresholds. The potential for using sewage sludge and bottom ash in CLSM making was thus confirmed.