Evaluating Physical, Rheological and Chemical Properties of Modified Bitumen

In India, the methods for rheological characterization of bituminous binders are inadequate to characterize the bitumen. Hence a complete rheological study and characterization of bitumen using dynamic shear rheometer would be helpful. Also there is limited insight about the chemistry of modified bitumen. Modification of asphalt binders can serve several purposes. It can increase the overall performance of a binder by widening the range between the binder?s high and low-temperature grades. In this paper VG30 bitumen and two polymers: Styrene Butadiene Styrene (SBS) block copolymer and Ethylene Vinyl Acetate (EVA) polymers were used as modifiers. SBS copolymers derive their strength and elasticity from physical and cross linking of molecules into three dimensional networks. Increasing the SBS content results in increased polymer swelling, which in turn produces increase in asphaltenes and reduction in maltene content resulting in harder and viscous matrix whereas EVA modifies bitumen by forming tough, three dimensional, rigid network to resist deformation. The change in physical properties such as penetration, softening point, penetration index and mass loss were studied and compared before and after modification. Rheological parameters such as complex modulus and phase angle before and after modification were studied by using Dynamic Shear Rheometer. The results indicate that polymer modification leads to decrease in penetration value, and increase in softening point and rutting parameter (G*/Sinδ). Modifiers used for bitumen modification are normally polymeric materials which have different structures such as atactic, isotactic and syndiotactic. These structures give characteristic features in spectroscopy analysis. Thus, Infra Red Spectroscopy techniques was employed in identifying the structure and functional groups present in polymeric materials.