Plastic waste-based construction composites: a review of composition, processing, performance, and environmental impacts

Abstract

Plastic waste represents a critical global environmental challenge due to its persistence, high production rates, and limited recycling. Construction materials, particularly bricks and blocks, offer a promising avenue for plastic valorization owing to their large material demand and tolerance for heterogeneous feedstocks. This review synthesizes recent developments in the production and characterization of recycled plastic-based construction composites (RPBCs), with a focus on composition, fabrication optimization, performance evaluation, and sustainability implications. The discussion covers dominant plastic feedstocks, including HDPE, LDPE, PET, and PP, and their interactions with fillers such as sand, fly ash, cement, and natural fibers. Processing techniques, including melting-mixing, extrusion-compression, and thermoforming, are analyzed in relation to thermal behavior, mechanical performance, and process optimization frameworks. Material characterization studies indicate that optimized plastic-to-filler ratios ( ca . 70 to 75 wt% plastic, 15 to 25 wt% filler) can achieve compressive strengths suitable for non-load-bearing and selected semi-structural applications, while maintaining dimensional stability and water resistance. Thermal, morphological, and durability assessments highlight performance trends and the influence of matrix–filler adhesion, supported by SEM, FT-IR, and DSC analyses. Environmental performance is critically evaluated, showing that potential reduction in plastic waste generation and life-cycle impacts depend on feedstock composition, processing energy, system boundaries, and end-use scenarios. Limitations, including fire safety, creep, long-term polymer degradation, micro(nano)plastic release, and end-of-life management, are discussed alongside opportunities for hybrid fillers, process standardization, durability, validation, and circular design. Essentially, RPBCs represent a promising route for plastic waste valorization in non-structural construction applications, although broader implementation will require standardized testing, long-term performance validation, and supportive regulatory frameworks.