A Review on Crumb Rubber Content in Modifying Asphalt to Save the Environment from the Solid Waste Crisis

Crumb rubber is one of the major wastes which causes environmental pollution. Crumb rubber is the waste, generated from tires of trucks, buses, cars, etc., if it is burned air pollution occurs as it releases toxic gases, or if landfilled, the fertility of the soil decreases as it is a non-biodegradable waste material. The waste tires can’t be reused or recycled safely without any threat to the environment. The best raw materials are used to manufacture a truck or passenger car tire. However, at its end of life, a tire poses a great environmental challenge owing to its highly engineered nature, which makes it non-biodegradable. A tire consists of natural rubber, synthetic rubber, plasticizers, carbon black, silica, and other metallic components from its original formulation. These constituents can find use in other fields, the rubber component can be used to modify bitumen to construct roads. Therefore, this review paper attempts to discuss how bitumen’s physical properties (viscosity, penetration value, softening point) and rheological properties (viscoelastic behavior) change after adding crumb rubber in different proportions. The review paper discusses how the addition of crumb rubber into bitumen, lowers bitumen's temperature susceptibility. Temperature sweep tests can be used to determine the sensitivity of CRMB to temperature. The storage modulus (G’), loss modulus (G”), and phase angle (δ) also increased. Overall, the review study demonstrates that incorporating crumb rubber into bitumen not only extends the lifespan of the flexible pavement but also, reduces the quantity of discarded tires that contribute to pollution.