Utilisation of waste-to-energy fly ash in ceramic tiles

Abstract

• Sustainable and effective utilisation of high calcium MSWI fly ash (FA) in unglazed ceramic tiles has been investigated. • The tiles containing 3–15 wt% high calcium FA achieved comparable or superior performances to the control sample fired at 1150 °C. • Flexural strength of 3% FA tiles enhanced from 15.88 to 24.41 MPa. • The 3% and 6% FA tiles have a lower water absorption (<6%) than the control tiles. • Heavy metal leaching levels are within the thresholds at pH 2.9 and 5.0. Municipal solid waste incineration fly ash (MSWI FA) derived from the waste to energy plants has growing attention due to its risk of land contamination upon mass disposals. Authorities seek ways and means of its safe disposal by spending high costs to manage these wastes. This paper investigates an efficient and novel use of high calcium MSWI FA to manufacture ceramic tiles which are in high demand to facilitate increased building construction. A number of experiments were conducted by adding 3 wt% − 15 wt% MSWI FA to tiles fired at 1150 °C to investigate the key properties, including firing shrinkage, water absorption, breaking strength, modulus of rupture, and heavy metal leachates. Detailed morphological analysis such as X-ray diffraction, scanning electron microscope imaging, and X-ray micro-computed tomography was also performed with the new fly ash matrix to understand the performance of MSWI FA incorporated ceramic tiles. Results indicate MSWI FA reduces density, but the addition of 3 wt% − 15 wt% MSWI FA can achieve comparable or superior technical performance to the control sample in addition to satisfying heavy metal leachate limits specified by national standards. Outcomes reveal that the novel use of MSWI FA to manufacture ceramic tiles has great potential for a sustainable tile manufacturing process and possible energy savings in the firing process while enabling an efficient way to manage MSWI wastes.