Effect of polypropylene plastic on concrete properties as a partial replacement of stone and brick aggregate

The application of waste materials in concrete is getting more popular in the concrete industries as it can reduce the associated costs and environmental impacts. The present study investigates the performances of concrete while incorporating polypropylene (PP) plastic, derived from waste plastic products, as a partial replacement of natural stone aggregate (SA) and burnt clay brick aggregate (BA). The main variables include the percentage of PP aggregate (PPA) (0%, 10 %, 20 %, and 30 %), water-cement ratio (0.45 and 0.55), and types of aggregate (SA and BA). Results are presented in terms of workability, hardened density, compressive, tensile strengths, modulus of rupture, modulus of elasticity (MoE), ultrasonic pulse velocity (UPV), and cost analysis. Furthermore, empirical equations are proposed for predicting different properties of concrete; especially, predicting compressive strengths from the UPV values. Results indicated that the slump value increased with increasing the percentage of PPA. Concrete with 10 % PPA exhibited higher compressive strength, modulus of rupture, and splitting tensile strengths, even, higher than that of the control stone aggregate concrete (SAC) and control brick aggregate concrete (BAC). The UPV values varied with aggregate types and PPA content. Both the compressive strength and the UPV values decreased with the increasing percentages of PPA from 10 to 30. Furthermore, SAC exhibited higher compressive strength and UPV values compared to BAC. A good correlation was found between the compressive strength and the UPV values for concrete with PPA. From the cost sensitivity analysis, it was observed that concrete containing 10 % PP content had the highest strength over cost ratio compared to the control and other PPA concrete. Therefore, it is recommended to use up to 10 % PPA either with stone aggregate or brick aggregate for structural concrete. Finally, this study will open new opportunities for producing green concrete by using non-biodegradable waste plastic materials.