Green construction with sustainable foam mortar utilizing recycled polyethylene terephthalate waste for enhanced thermal insulation and durability properties

This study explores the development of a sustainable foam mortar incorporating recycled polyethylene terephthalate (PET) waste as a partial sand replacement to enhance thermal insulation and promote circular economy practices. Foamed mortars incorporating recycled polyethylene terephthalate (PET) waste were developed in this study, with the overall goal of addressing the dual challenge of waste management and resource depletion. PET waste, commonly discarded as environmental pollutants, was processed into fine aggregate sizes and used as a partial replacement for sand. There were six mix proportions with PET replacement ratios (0, 5, 10, 15, 20, and 25%). PET improved thermal insulation by lowering thermal conductivity from 0.31 W/mK to 0.26 W/mK and reducing density by up to 15%. At 28 days, the compressive strength varied between 12.5 MPa (0% PET) and 9.8 MPa (25% PET), suggesting that it is viable for non-structural applications. Similar declines of 25-30% and 20-25%, respectively, in flexural and tensile strengths were ascribed to weakened interfacial bonding between PET and the cement matrix. At higher PET levels, durability increased, with a 20% decrease in water absorption and a substantial decrease in chloride ion penetration. The use of PET significantly improved thermal properties, and microstructural analysis confirmed more refined pore structures and homogeneous dispersion of PET particles. These results show that PET can be a sustainable alternative to foam mortar, promoting environmentally friendly construction methods and the concepts of the circular economy.