Fully waste-derived PET-eggshell-sand composite paver tiles: processing, microstructure, and mechanical performance

Recycling waste materials into useful products is an effective strategy for reducing environmental pollution while providing cost-effective alternatives. This study highlights the novelty of using 100% waste materials to fully replace cement and aggregates, offering a sustainable and eco-friendly approach for paver tile production. Unlike previous studies, where PET was used as aggregate and eggshell powder as partial cement replacement, here PET is melted to serve as the binder/matrix, while eggshell powder and river sand act as fillers, fully substituting conventional materials. The waste materials were collected, sorted, washed, dried, and processed to appropriate particle sizes, then blended in precise proportions to produce four formulations: 50:25:25, 60:15:25, 70:20:10, and 85:10:5 (PET/eggshell/river sand). Three samples were prepared per formulation. PET was melted at 150–260 °C, fillers were added at 160 °C, stirred until uniformly incorporated, poured into molds, and cooled. Flexural strength was 3.34, 2.89, 4.10, and 2.54 MPa, compressive strength was 13.01, 12.10, 18.63, and 6.20 MPa, and water absorption was 1.30%, 0.83%, 0.53%, and 0.41% for the 50:25:25, 60:15:25, 70:20:10, and 85:10:5 formulations, respectively. Statistical and SEM/EDS analyses show the 70:20:10 composition achieves highest strength and lowest water absorption, with a dense, well-bonded microstructure, while other compositions reduce performance. The results confirm that the developed composite tiles are suitable for pedestrian and light-traffic applications. The tiles exhibited 4.10 MPa flexural strength, 18.63 MPa compressive strength, and 0.53% water absorption. Flexural and compressive strengths meet IS 15658:2006, ASTM C902, EN 1338, and Quality C standards, with low water absorption confirming durability.