Performance Evaluation of Sand-Coated Recycled HDPE and E-Plastic Aggregates as Partial Replacements for Coarse Aggregate in Sustainable Concrete

This study investigates the mechanical and microstructural performance of concrete partially incorporating sand-coated recycled HDPE and e-waste plastic aggregates as substitutes for natural coarse aggregates. The novelty of the work lies in its dual approach—utilizing a hybrid plastic waste stream and applying a sand-coating surface treatment to improve the interfacial bond between the plastic aggregates and cement paste. The study compare the workability, compressive strength, and durability-related characteristics, comparing coated versus uncoated plastic aggregates at various replacement levels of previous study. Results demonstrate that sand-coated plastic aggregates yield improved mechanical performance, achieving up to 12% enhancement in compressive strength and better freeze-thaw and chemical resistance compared to uncoated counterparts. The sand-coating treatment significantly mitigates the challenges of weak bonding and poor stress transfer typically associated with plastic-modified concrete. The study contributes to sustainable construction practices by promoting the reuse of non-biodegradable plastic waste and reducing reliance on natural aggregates. This research provides a scalable and eco-efficient solution aligned with circular economy principles and Sustainable Development Goals (SDG 11 and 12). Further work is recommended to explore long-term durability, field-scale applications, and life cycle assessments to validate large-scale implementation. Introduction