Proof-of-concept design, characterization, and life cycle assessment of recycled PET–sand composite bricks via solvent-based dissolution

Plastic waste, especially polyethylene terephthalate (PET), presents severe environmental challenges due to its persistence in landfills and oceans. Traditional recycling methods, such as melting PET for composite bricks, are energy intensive. This study introduces an innovative chemical approach, dissolving PET with phenol crystals and chloroform, to integrate PET waste with local sand from Qatar, creating sustainable brick materials. Various PET-to-sand ratios (1:4, 1:8, 1:16, and 1:24) were tested for their mechanical, thermal, and hydrophobic properties. Results indicate that the 1:16 ratio achieved optimal load-bearing capabilities, with a compressive strength of 13.56 MPa and flexural strength of 2.88 MPa after 28 days. The 1:4 ratio demonstrated superior water resistance, showing 0 % water absorption, while the 1:24 ratio absorbed 2.89 %, highlighting the hydrophobic benefits of higher PET content. Thermogravimetric analysis (TGA) confirmed thermal stability up to 300°C, with degradation occurring between 300°C and 500°C. An environmental assessment revealed that phenol and chloroform contributed significantly to environmental impacts; however, recycling these solvents greatly reduced impacts across categories, lowering the global warming potential (GWP) from 1107.73 kg CO₂ eq to 37.48 kg CO₂ eq in the optimized scenario.