Experimental Study on Cement Brick Using Low-Density Polyethylene (LDPE) Plastics and Biochar

The construction industry's high demand for conventional materials like cement and sand poses significant environmental challenges, including high CO₂ emissions and natural resource depletion. Concurrently, the management of non-biodegradable plastic waste (LDPE) and agricultural biomass remains a critical issue. This study investigates the feasibility of producing sustainable cement bricks by partially replacing cement with biochar (10%, 20%, 30%) and sand with shredded LDPE plastic waste (5%, 10%, 15%). Three prototype bricks were developed and subjected to comprehensive tests for compressive strength, water absorption, efflorescence, hardness, and flammability. Results indicate that Prototype Brick 1 (10% biochar, 5% LDPE) achieved the highest compressive strength of 7 MPa at 28 days, comparable to first-class clay bricks, while exhibiting balanced properties in water absorption (11%) and low flammability. Although higher replacement levels reduced mechanical strength, all prototypes remained suitable for non-structural applications. This research demonstrates a viable pathway for waste valorization, reducing the carbon footprint of construction materials and promoting a circular economy in the building sector.