Characteristics and Performance of Ceramic Tiles Incorporated with Recycled Wastes

<p dir="ltr">The management of municipal solid waste (MSW) is a growing global environmental challenge. According to the World Bank, annual global MSW production reached 2.01 billion tonnes in 2016 and is projected to rise to 3.40 billion tonnes by 2050. Among various waste items, cigarette butts (CBs) are one of the most littered, posing severe environmental threats due to poor biodegradability and the release of toxic chemicals. With an annual consumption of 5.7 trillion cigarettes and a 75% littering rate, effective recycling methods for CBs are crucial.</p><p dir="ltr">In addition to CBs, this study also focuses on recycling fly ash from waste incineration, another significant waste by-product. Incineration reduces waste volume and allows for energy recovery but produces fly ash containing heavy metals and soluble salts. This research examines recycled paper production boiler fly ash, similar to municipal solid waste incineration (MSWI) fly ash but containing large amounts of waste paper fibres. Due to variances in waste composition, incineration equipment, and methodologies, the chemical makeup of these wastes also varies. Therefore, fly ash is analysed as two distinct waste types: MSWI FA from facilities processing more municipal solid waste in Victoria, and IWA from facilities processing more construction and demolition waste in Queensland.</p><p dir="ltr">This innovative study investigates the potential of using CBs, MSWI FA, and IWA as substitutes in ceramic tile production, aiming to promote sustainable practices in the ceramics industry by converting waste materials into valuable resources. Experimental trials integrated these waste materials into ceramic tiles in varying proportions, evaluating the balance between environmental benefits and the functional quality of the tiles. Comprehensive assessments included physical, chemical, and mechanical properties, as well as detailed analyses like microanalysis, heavy metal leaching, energy consumption, thermal behaviour, and life cycle assessment (LCA). The aim was not merely to alter tile composition but to offer a novel perspective on resource use and sustainability in the ceramics industry.</p><p dir="ltr">Key findings include:</p><p dir="ltr">• Incorporating CBs in ceramic tiles increased water absorption at higher CB content but complied with Group III (Ev >10%) wall tile criteria. Tiles with 0.5% CB content showed improved bending strength (from 15.56 MPa to 16.33 MPa) and potential energy savings compared with control sample tiles.</p><p dir="ltr">• MSWI FA was successfully used in enhanced tile formulations and manufacturing processes, meeting the Group BIIa floor tile requirements (3% < Ev ≤ 6% and MOR≥ 22 MPa) and ensuring compliance with heavy metal leaching standards. Even tiles with 15% MSWI FA met wall tile requirements.</p><p dir="ltr">• IWA was examined as a substitute for potassium feldspar, with up to 30% IWA incorporation producing high-performance tiles (Ev= 5.9% and MOR= 30 MPa) and substantial estimated energy savings (33.86%) when fired at 1300 °C. IWA also enhanced thermal conductivity, making tiles suitable for underfloor heating systems. The LCA highlighted significant reductions in environmental impacts, including decreases in terrestrial ecotoxicity (22.47%), terrestrial acidification (10.09%), and climate change impacts (8.49%) for 30% IWA tiles.</p><p dir="ltr">These findings demonstrate the feasibility and environmental benefits of incorporating waste materials in ceramic tile production, offering sustainable, performance-enhancing, and cost-effective alternatives. Waste materials can replace traditional ceramic raw materials, contributing to waste reduction and resource efficiency. Further optimisation of material proportions and processing conditions is necessary to maximise the potential of these recycled materials in the ceramic industry. This research contributes to sustainable materials and waste management in ceramic tile production, aligning with global efforts towards environmental protection and sustainable development.</p>