Assessment of crumb rubber as a partial substitute with quarry dust for the production interlocking paving stone

The generation of huge amounts of waste rubber from used tires poses serious environmental challenges due to its non-degradable nature. Meanwhile, the rising cost of construction materials has significantly increased overall construction expenses. This research investigates the use of crumb rubber (CR) as a partial replacement for quarry dust in the production of interlocking paving stones. Waste tires were shredded and processed into fine crumb rubber. Sieve analysis were conducted on both materials, revealing that quarry dust was well-graded, while CR was gap-graded, with 66.5% retained at 0.425 mm and 22.6% at 0.300 mm sieve sizes. Cement, quarry dust, and CR were batched by weight with a 1:6 cement-quarry dust ratio and a 0.45 water-cement ratio. Slump tests demonstrated that the addition of crumb rubber improved workability, with slump values increasing from 2 mm (0%) to 11 mm (40%). Paving stones were cast with 0-40% CR replacements and cured for 7-28 days. Compressive strength results showed a decline from 11.5 MPa (0%) to 4.24 MPa (40%) after 7 days, with similar trends observed at 14, 21, and 28 days. Splitting tensile strength also decreased, with 0% replacement yielding 3.27 MPa at 28 days, compared to 1.62 MPa for 40% replacement. Flexural strength followed the same pattern, dropping from 8.5 MPa (0%) to 5.33 MPa (40%) at 28 days. While crumb rubber enhanced workability, its inclusion reduced compressive, tensile, and flexural strengths, compromising structural integrity. This research promotes sustainable civil engineering practices by utilizing waste materials, offering insights into optimizing crumb rubber content to balance workability and strength in construction applications for both economic and environmental benefits.