Rheological properties of styrene-butadiene-rubber modified bitumen

This study investigates the rheological properties of bitumen (asphalt) binder penetration grade 60-70 modified with an additive Styrene Butadiene Rubber (SBR). SBR is an elastomer which is the important sort of synthetic rubber. It is a copolymer which consists of organic compound styrene and butadiene chain which makes up its molecular structure. Bitumen is visco-elastic material where temperature and rate of load application have a great influence on their performance. The properties evaluated include the rheological properties of the modified bitumen binder. These properties were complex shear modulus G* using Dynamic Shear Rheometer (DSR), short term aging by Rolling Thin Film Oven Test (RTFOT), long term aging by Pressure Aging Vessel (PAV), viscosity by Rotational Viscometer (RV), penetration by Penetro meter and softening point by Ring and Ball test. Results obtained from the study indicated the effect of SBR on the binder, and also depends on the quantity (%) of the additive used and test temperature. The binders were mixed with various percentages of the SBR at the 1, 2, 3, 4 and 5% by weight of bitumen binder. Using the SBR showed prominent results in improving the viscoelastic properties of ordinary bitumen. The effects of SBR modifier influenced significantly the rheological behavior of bitumen by increasing its complex shear modulus (G*) and increasing the resistance of mixture against permanent deformation (Rutting). Despite the advantages of SBR on bitumen performance at high temperatures, it does not show a considerable influence on the intermediate temperature performance of bitumen. In addition, results show that increasing the additive content increases the viscosity of modified bitumen. This in return resists the compactive effort and there will be low stability values and there will be more chances for fatigue cracking