Incorporation of Glass and Plastic Waste into Alkali-Activated Mill Residue Bricks

Abstract

Recycling of glass and plastic waste has been increasingly attracting the attention of researchers worldwide. Relevant studies have been conducted to prove the feasibility of incorporating glass and plastic wastes into cement-based concrete and fired bricks. However, the high embedded energy and large carbon footprint of these materials have hindered the achievement of sustainable goals. Hence, this study attempts to diversify the recycling pathways for glass and plastic waste via a low carbon route. The brick clay mill residue has been used as a precursor to prepare alkali-activated bricks containing plastic and glass fines with a specific curing regime. The compressive strength, water absorption, linear shrinkage, and microstructure were investigated with varied content of glass and plastic content. The results showed that the maximum acceptable ratio of glass fines was around 55 wt.% for samples with the glass waste solely, achieving the compressive strength of 22 MPa. While foror samples incorporating plastic (PET) waste only, the maximum allowable ratio was only 2 wt.%, because excessive plastic resulted in the spalling of the sample surface. When both the glass and plastic waste were added to the samples, the maximum substitution ratio was 25 wt.% of glass and 2 wt.% of plastics. Scanning Electron Microscope images indicates that the plastic particles had more adverse effects on the microstructure of the alkali-activated samples than the glass particles. There was little or no bonding between plastic waste and alkali-activated mill residues. In contrast, the bonding between glass particles and alkali-activated mill residues was captured. The effect of the addition of glass and plastic samples on the durability of alkali-activated mill residue material needs to be further investigated, such as dimension stability, resistance to salt attack, freeze and thaw, and so on.