Mechanical and thermal properties of lightweight recycled plastic aggregate concrete

The non-biodegradable character of plastics is of concern to the scientists and environmentalists worldwide. Consequently, there is an exigent need to identify avenues for the utilization of recycled plastics. Its use in concrete is one of potential applications. The utilization of recycled plastic in concrete, as a partial/full replacement of natural aggregates, resolves the concern related to its safe disposal and conserves resources of natural aggregates. The reported study was conducted to assess the possibility of utilizing recycled waste plastic, as a replacement of natural aggregates in concrete. Concrete specimens were prepared utilizing three different types of recycled plastics at varying proportions and they were evaluated to assess their mechanical and thermal properties. Lightweight concrete with a unit weight of 1500 kg/m³ and a compressive strength of 17 MPa was developed utilizing 100% recycled plastic aggregate (RPA). However, the unit weight and compressive strength of concrete with 25% RPA were 2000 kg/m³ and 35 MPa, respectively. The flexural strength, modulus of elasticity and bond strength of the RPA concrete decreased with increasing quantity of RPA. A similar behavior in thermal conductivity was noted. The thermal conductivity of the control concrete was 1.7 W/mK while it was around 1.1–0.5 W/mK for the RPA concrete. Correlations between the mixture parameters and mechanical and thermal properties of RPA concrete were also developed. Recommendations on the quantities of RPA to be used for the production of lightweight concrete of varying strength grades are also provided.