Physical and rheological properties of epoxidized natural rubber modified bitumens

The use of polymers as bitumen modifiers in pavements has been growing rapidly in the last decades because of the distresses on asphalt pavements. However, using polymers as a modifier mostly changes the properties of the asphalt pavement to be more stable and stiffer at high temperatures and more flexible at low temperatures. Therefore, this study was conducted to investigate the empirical and rheological properties of bitumen modified with epoxidized natural rubber (ENR). Four percentages (3%, 6%, 9% and 12%) of epoxidized natural rubber were used as modifiers. The effects of the modifier on the conventional properties, storage stability and rheological properties were investigated. Requirement tests (e.g., penetration, softening point, ductility and viscosity) and rheological analysis (e.g., isochronal plot, master curves, Black diagram and SHRP parameters) using a dynamic shear rheometer (DSR) were conducted to characterize the ENR-modified bitumen. The fundamental parameters were used to describe significant benefits of ENR as a modifier. The results indicated that the storage stability of epoxidized natural rubber modified bitumens (ENRMBs) depended mainly on the ENR content. Based on the results obtained from the DSR test, ENR reduces the temperature susceptibility and facilitated polymeric modification using a highly elastic network within the bitumen. This elastic network increases the viscosity, stiffness and elastic behavior of the ENRMBs. ENR improves rutting resistance and fatigue behavior at high temperatures and low temperatures respectively. The best results were recorded for polymer-modified bitumen containing 6% of ENR.