Plastic waste has increased significantly in recent years as a result of fast population growth and urbanization. Studies on the incorporation of plastic aggregates as a substitution for natural aggregates in concrete are needed to successfully reduce both adverse environmental impact and the depletion of natural resources. The objective of this research was to investigate the use of plastic as a partial substitution for natural coarse aggregates in concrete. For this purpose, seven concrete mixes were produced using 0, 10, 15, and 20% plastic coarse aggregates to replace natural aggregates with and without silica fume of similar replacement levels with cement. Fresh density, workability, compressive strength, splitting tensile strength, stress–strain response, and Poisson’s ratio were observed to study the fresh as well as hardened properties of concrete mixtures. Indoor and outdoor thermal performance and thermo-gravimetric analysis were also investigated. The results revealed that the plastic aggregates’ incorporation improved the workability of concrete; however, it negatively influenced the fresh density and mechanical properties of concrete. The compressive and tensile strengths of plastic aggregate concrete without silica fume were reduced by 32 and 33%, respectively. The reduction in strength could be associated with the smooth texture of plastic aggregates. The addition of silica fume with plastic aggregates resulted in denser concrete and improved mechanical properties. In general, the performance of plastic aggregates as a partial replacement for natural aggregates was satisfactory, which suggests their possible use to produce eco-friendlier concrete.

Plastic wastes are a major hazard for the environment and their use in the construction industry is increasing day by day. The major drawback of the use of plastic in concrete is an exceptional reduction in strength and workability. This research work explores the effect of sand coating on two types of recycled plastic aggregates, high-density polyethylene (HDPE) and electronic-wastes (E-wastes), as partial replacement of natural aggregates. The replacement ranged from 0% to 30% along with the use of super plasticizer SP-675 and wet lock sealant. Both recycled plastic aggregates are crushed, melted, and ground to convert them into aggregates of 20 mm size. The workability of concrete containing uncoated recycled plastic aggregates (HDPE and electronic wastes), SP-675, and wet lock sealant has been found to be higher than controlled concrete samples with 0% recycled aggregates. Compressive strength, split tensile strength, and flexural strength of such type of concrete is lower than the controlled concrete samples due to the weak bond between the plastic aggregates and Ordinary Portland Cement. After applying the sand coating to improve bonding, the workability is reduced compared to uncoated samples whereas the compressive strength, split tensile strength and flexural strength of the sand coated plastic aggregate concrete is higher than uncoated plastic aggregate concrete. There is a significant increase in workability of concrete after the addition of SP-675 when added as 2% by weight of cement. The wet lock sealant positively affects the strength properties of concrete. It is recommended that the durability of concrete containing uncoated and sand coated recycled plastic aggregates be further explored in future studies.