Sustainable ceramic tiles incorporated with waste fly ash from recycled paper production

Waste incineration is an effective solid waste disposal method; however, its by-product pollutants hinder its widespread adoption. This research aims to develop novel unglazed ceramic tiles by recycling industrial solid waste incineration fly ash (IWA) from recycled paper mills. Experimental investigations were conducted on ceramic tiles with IWA additions (0–30 wt%) and firing temperatures (1100 ◦C, 1200 ◦C, and 1300 ◦C). Various scientific tests, including XRF, XRD, strength, water absorption, thermal properties, heavy metal leaching, SEM analysis, and micro-CT analysis, were performed. The results suggest that the addition of IWA may deteriorate the technical performance of ceramic tiles; however, satisfactory performance can still be achieved by tailoring the firing temperature due to the existence of iron and calcium in the IWA, which narrows and displaces the densification temperature range. Remarkably, tiles with 30 wt% IWA, which completely replaced the flux materials and fired at 1300 ◦C, achieved the highest flexural strength (exceeding 30 MPa). These tiles exhibited promising attributes such as water absorption of 5.9%, an estimated energy saving of 33.86%, and compliance with heavy metal leaching limits. This study proposes a sustainable solution for IWA disposal by utilising recycled paper mill fly ash as a substitute for flux material in ceramic tile manufacturing. The findings contribute to minimising environmental impact and conserving non-renewable natural resources, supporting sustainable development.