Effect of particle size of the coated and un-coated crumb rubber on the mechanical properties and water absorption of rubberized concrete

To diminish the environmental impact of enormous waste tires and reduce the concrete cost, crumb rubber (CR) was utilized to replace concrete aggregates. The CR and sand sizes were sieved and separated. Moreover, the CR was pre-coated with silica fume slurry, having a water-to-cement ratio of 0.55. The coated and uncoated CR was used as a partial replacement of sand by five percentages (0, 5, 10, 20, and 25% by volume). Cubes and cylinders were cast and then cured in water tanks until the date of testing. The compressive strength of the control and rubberized concrete (RuC) samples was measured at 7, 28, and 56 days, the tensile strength was obtained at 28 days, and the water absorption was measured at 56 days. Replacing sand with a 2.36 mm particle size with the same CR size showed lower effects on the concrete compressive strength than replacing sand with 1.18 mm CR. Moreover, replacing sand with 5% pre-coated CR (particle size 1.18 mm) enhanced the compressive strength (fcu) by 104.88, 100.44 and 101.9% at 7, 28, and 56 days, respectively, compared to the subsequent mixes with uncoated CR while at 10% pre-coated CR content, the fcu enhancement was 118.3, 108.53, and 104.80%, respectively.