Laboratory Evaluating of Physical and rheological properties of modified bitumen Containing Crumb rubber and EVA

The use of waste materials, including plastics, to improve the properties of asphalt mixtures, in addition to economic benefits, has environmental benefits. Crumb rubber (CR) is one of these wastes that can improve many of the properties of asphalt mixtures, especially at low temperatures. But this additive also has weaknesses that can be compensated by making a double additive based on CR. In this study the influence of CR and EVA polymer on rheological and physical properties of unmodified bitumen has been studied and evaluated. To this aim, penetration, softening point, rotational viscosity and dynamic shear rheometer tests by using DSR machine were done on control bitumen and modified bitumen with a combination of 10 and 15% CR and EVA polymer based on the weight percentage of base bitumen (control) has been done with different ratios. The results of the dual combination of these additives with control bitumen show that the softening point and rotational viscosity increase and the degree of penetration decreases, which confirms the decrease in thermal sensitivity of the modified bitumen compared to the control bitumen. In addition, the results of the DSR Test also show that all modified bitumen have a larger complex shear modulus (G*) and a smaller phase angle(δ), and as a result have a larger sinusoidal coefficient (sin δ / G*) compared to the control bitumen. Besides, the fatigue coefficient caused by loading in the middle temperatures of all bitumen modified with dual compounds of these additives is smaller recommended. According to the findings of this study, the most appropriate dual combination of EVA additives and CR for improving the physical and rheological properties of base bitumen with a penetration rate of 60/70 is the use of dual combination of 25% EVA and 75% CR by proportion of 15 percent of bitumen.