Recycling and Repurposing Plastic Waste in Ajayi Crowther as a Partial Replacement for Quarry Dust in Interlocking Block Production

Plastic waste disposal remains a significant environmental challenge due to its non-degradable nature. Additionally, the rising cost of construction materials necessitates alternative sustainable solutions. This study evaluates the recycling and repurposing of plastic waste in Ajayi Crowther as a partial replacement for quarry dust in interlocking block production to determine its feasibility in sustainable construction. Waste plastic bottles were collected, burnt, and milled into powder form. Specific gravity and sieve analysis tests were conducted on both quarry dust and milled waste plastic bottles (MWPB). The materials were batched by weight using a 1:6 cement-quarry dust mix ratio with a 0.45 water-cement ratio. A slump test was performed to assess workability, and interlocking paving blocks were cast with 0%, 10%, 20%, 30%, and 40% MWPB replacement and cured for 7, 14, 21, and 28 days. The mechanical properties of the paving stones were evaluated through compressive strength, splitting tensile strength, and flexural strength tests. The results indicated that quarry dust exhibited a specific gravity of 2.39 and a well-graded particle distribution, while MWPB had a specific gravity of 1.08 and a gap-graded particle structure. The slump test showed increased workability with higher MWPB content. However, compressive strength values for 7-day curing decreased from 11.5 MPa (0% MWPB) to 4.24 MPa (40% MWPB). Similar declining trends were observed in splitting tensile and flexural strengths, highlighting a reduction in overall structural integrity with increased plastic content. This research demonstrates that while incorporating MWPB enhances workability, it negatively impacts strength, limiting its application in high-load-bearing structures. However, interlocking blocks produced with up to 20% MWPB can be effectively used in low-traffic areas such as pedestrian pathways and recreational spaces. This study advances sustainable construction by providing an innovative approach to reducing plastic waste while maintaining construction quality.