Experimental Study on the Suitability of Waste Plastics and Glass as Partial Replacement of Fine Aggregate in Concrete Production

Abstract

Solid waste management is a major environmental challenge, especially in developing countries, with increasing amounts of waste glass (WG) and waste plastic (WP) not being recycled. In Ethiopia, managing WG and WP requires innovative recycling techniques. This study examines concrete properties with WG and WP as partial replacements for fine aggregate. Tests were conducted on cement setting time, workability, compressive strength, splitting tensile strength, and flexural strength. Concrete of grade C-25, with a target compressive strength of 25 MPa, was prepared by partially replacing fine aggregate with WP and WG. The mechanical properties were evaluated after 7 and 28 days of curing. At a 20% replacement level, workability decreased at water–cement ratios of 0.5 and 0.6 but remained stable at 0.4, leading to the selection of the 0.4 ratio for further testing. A 10% replacement of fine aggregate, using a ratio of 3% WP and 7% WG, was found to be optimal, resulting in an increase in compressive strength by 12.55% and 6.44% at 7 and 28 days, respectively. In contrast, a 20% replacement led to a decrease in compressive strength by 14.35% and 0.73% at 7 and 28 days, respectively. On the 28th day, the splitting tensile strength at the optimal replacement level was 4.3 MPa, reflecting an 8.5% reduction compared to the control mix. However, flexural strength improved significantly by 19.7%, from 12.46 MPa to 15.52 MPa. Overall, the incorporation of WG and WP in concrete enhances flexural strength but slightly reduces splitting tensile strength.