From Waste to Walkways: Recycled Plastic Pavement Blocks for a Circular Economy

The indiscriminate disposal of plastic waste poses significant environmental and economic threats, necessitating innovative recycling strategies that align with circular economy principles. The primary objective was to assess the impact of varying plastic-to-sand ratios on the compressive strength of these composite pavement blocks, optimising resource utilisation. These objectives were achieved through research investigating the feasibility of utilising four common post-consumer thermoplastics—HDPE, PP, PET, and PS, as binding agents in pavement block production. This directly addresses the circular economy imperative by transforming waste into a valuable construction resource, minimising landfill burden, and creating a closed-loop system. Compared with conventional concrete pavers, these plastic-sand blocks offer the potential for a reduced carbon footprint by valorising waste materials and potentially decreasing reliance on energy-intensive cement production. The methodology involved melting each plastic type individually and combining it with sand at five different ratios: 3:7, 4:6, 5:5, 6:4, and 7:3 (plastic:sand). The resulting mixtures were moulded into pavement blocks and subjected to compressive strength testing. One-way ANOVA revealed varying optimal plastic-to-sand ratios for HDPE, PP, PET, and PS pavement blocks, as determined by compressive strength analysis. For HDPE, while ratios of 30:70, 50:50, 60:40, and 70:30 showed comparable performance, and the 40:60 combination exhibited the highest compressive strength. In contrast, PP mixtures demonstrated optimal strength at a 60:40 ratio, with the 40:60, 50:50, and 70:30 ratios showing similar behaviour that could be substituted. PET mixtures achieved peak strength at a 30:70 ratio, and only the 40:60 and 70:30 ratio combinations could be substituted without impacting the compressive strength. Similarly, PS mixtures exhibited optimal performance at a 50:50 ratio, with some substitution potential observed at 30:70, 40:60, 60:40, and 70:30 ratios. These findings demonstrate that specific plastic types have unique optimal mixing ratios with sand to achieve maximal compressive strength, thereby transforming plastic waste into durable pavement blocks that support a circular economy.