Trash to Treasure: Eco-Friendly Bricks from Discarded Plastics

Overview

Purpose: Plastic waste accumulation presents challenges, particularly through marine pollution and microplastic contamination. We investigated whether low-density polyethylene, high-density polyethylene, and polypropylene could be repurposed into durable bricks. Procedure: The plastics were shredded, melted, and combined with sand and coconut coir, then molded into bricks and coated. The bricks underwent tests to evaluate mechanical strength, water absorption, freeze–thaw durability, and thermal conductivity, ensuring comparisons to a standard brick. Results: The plastic bricks and the control withstood the maximum applied load of 77 kilograms without cracking or deformation; compressive strength exceeded apparatus limits. After five water absorption cycles (each three days), the control absorbed 14.87% while the plastic bricks retained integrality, though minor peeling occurred with the initial ceramic coating. To address this issue, FPCC Fire Poly coating was implemented to improve performance. After five trials of freeze-thaw testing (each three days) the plastic bricks demonstrated negligible mass change, whereas the control absorbed 2.22%. Since mass absorption for conventional bricks typically ranges from 5–12%, the plastic bricks exhibited superior moisture resistance. Across five trials, PP exhibited the lowest thermal conductivity (0.22 W/m·K), outperforming LDPE (0.34 W/m·K), HDPE (0.46 W/m·K), and a traditional brick (0.76 W/m·K). After all the testing, the PP brick proved to be the most durable brick. Conclusion: Recycled plastic bricks, particularly PP composites, combined with their multifaceted resilience, indicated strong potential for non-load-bearing pavements. Further optimization can expand functional applications and support scalable production for sustainable construction materials.

Competition history

• CSEF 2026 Environmental Engineering (Track 2) (Junior Division) · Entry J-12-05

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