This research aimed to explore the use of foamed concrete (FC), a lightweight concrete, by replacing sand with crushed plastic from washing machines to improve environmental and thermal properties. The primary components included traditional materials like cement, water, and a foaming agent, along with the innovative use of waste plastic (WP). Utilizing Minitab software, the study applied the Response Surface Method to optimize mix designs, reducing the experimental mixtures to 31, which were then tested for dry density, porosity, water absorption, shrinkage, compressive strength, splitting tensile strength, and thermal conductivity. Results indicated a significant 24% reduction in dry density when using plastic as fine and coarse aggregates, yielding superior thermal insulation. The statistical approach facilitated a regression model correlating mix ingredients with strength and density. Notably, adding fly ash to the plastic aggregate mix maintained strength comparable to that of conventional mixes. The optimal mix, containing 20% fine and 70% coarse WP, achieved the highest density reduction with minimal strength loss. The study concludes that incorporating crushed plastic waste in FC significantly reduces density while retaining strength, offering both environmental benefits and enhanced thermal insulation, thereby presenting a sustainable solution for construction. Additionally, this innovative approach highlights the potential for large-scale WP use, reducing landfill pressure, decreasing carbon footprint, and promoting circular economy practices within the construction industry, paving the way for future green building innovations.
