Contributions crumb rubber in hot mix asphalt to the resilient modulus

Pavement on the structure of the surface layer receives direct load from the vehicles. Road surfaces are designed to withstand the wear from vehicle loads. Therefore, we need a way to improve the durability of the pavement. Road damage may reduce the life of roads and increase the maintenance costs. The retention rate of road surface material is affected by the environmental conditions, one of them is temperature. To overcome the issues related to temperature, material additives are added to the asphalt mixture. These additive materials would change the binding properties of bitumen and the characteristics of strain and stress before the damage due to repeated traffic loading. Crumb rubber (CR) is a type of polymer additives and thermoplastic elastomers are obtained from scrap tires and rubber waste that is utilized in order to preserve the environment. This study investigated the contribution of the crumb rubber in terms of the value of resilient modulus and resistance to deformation. Hot mix asphalt used was asphalt Pen 60/70, coarse aggregate, fine aggregate and filler. Crumb rubber was made from scrap tire rubber, in the form of fine powder with sieve no. 30 (0.6 mm). CR additive was added to the base asphalt at several rates of 5%, 10%, 15%, and 20% at a temperature of 177° C. The test data used the indirect tensile test with a tool UMATTA at temperatures of 25°, 35°, and 45° C. The test results showed that the levels of crumb rubber on the asphalt decreased the penetration rate, increased the bitumen softening point, and improved the resistance to permanent deformation. The addition of additive materials was evidenced to improve the penetration index, reduce the temperature sensitivity, and increase the viscosity. Subsequently, it can extend the temperature range of viscoelasticity. The contributions of crumb rubber in hot mix asphalt included the increase of the recoverable deformation and the decrease of the value of resilient modulus. This study indicated that by the addition of crumb rubber, the pavement material becomes more elastic, so it can reduce the level of damage in the form of cracks on roads, but it also declines the ability of the pavement to withstand the loads.