Evaluation of waste plastic-coated C&D waste aggregate in cement concrete mix and its durability at elevated temperatures

The main objective of this research work is to create high-density polyethylene plastic (HDPE) coated construction and demolished (C&D) waste aggregate as a substitute for natural coarse aggregate (NCA) for the M20 grade of concrete mix. Hence, this research aims to utilize plastic coated construction and demolished waste aggregate (PCDA) over construction and demolished waste aggregate (CDA) in concrete composite by evaluating their physical and mechanical properties under different circumstances. Physical properties show that the shape and texture of both CDA and PCDA are almost the same and quite similar to NCA. The specific gravity of PCDA is around 25% lower than that of NCA, and CDA absorbs around 39% more moisture than PCDA due to its permeable pores. Due to lower specific gravity, PCDA can be used to make low-density concrete. As 28 days compressive strength of concrete specimens reduces by 24.5% and 14% respectively (at 40°C) with the use of CDA and PCDA, and concrete cubes with the use of PCDA achieved higher strength than concrete samples with CDA, an attempt was made to replace 50% of PCDA with the same quantity of NCA. It was observed that the 28-day compressive strength of concrete cubes was enhanced by 8.56% by this partial replacement of PCDA. As the aggregate (PCDA) was formed by coating molten plastics on CDA, and HDPE plastic has a lower melting point, concrete made with such a type of aggregate (50%) was subjected to elevated temperatures. The thermal exposure results show up to 200°C temperature, PCDA retained its own shape and size, and at 250°C, the coating of plastic melted, which indicated higher reduction in percentage of weight loss, compressive strength, ultrasonic pulse velocity (UPV) readings, and dynamic modulus of elasticity results.