Improving the Aging Resistance of Asphalt by Addition of Polyethylene and Sulphur

Abstract

The demand for bituminous pavement is increasing with the increase in traffic volume. Pavement distresses are the main cause that affect the service life of bituminous pavement. Failures in asphalt pavement are not only due to the increased traffic load but also due to the extreme climate conditions. One of the main cause of early deterioration of pavement is the aging of asphalt binder. Aging can be defined as the hardening of asphalt binder due to oxidation and volatilization of light components in the asphalt binder materials during construction and service phase. The phenomena of aging significantly affect the chemical and rheological properties of asphalt binder. The structural changes as well as the permanent hardening occurring as a result of aging may cause significant loss in the bituminous binder’s elasticity and therefore induce effects such as rutting, fatigue cracking, thermal cracking and moisture sensitivity. As a result, this reduces the estimated service life and comfort associated with the pavement. Therefore to extend the service life span of an asphalt pavement, it is necessary to improve its anti-aging performance characteristics. There are many modifiers available that have proven to improve the aging characteristics of asphalt binder. This research focuses on the use of one polymeric additive Polyethylene (PE) and one non polymeric additive Sulphur (S) to enhance the aging resistance of asphalt. These modifiers were evaluated for their effect on the aging mechanism in comparison with the unmodified base binder. Aging of the original and modified asphalt binder will be realized by the RTFO and PAV. Physical properties of the aged and unaged asphalt binder are evaluated through empirical testing like Penetration test, Softening point test and Ductility test. Optimum content of the modifiers is obtained by comparing the results of conventional properties before and after aging. Fourier transformed infrared spectroscopy (FTIR) and scanning electron microscope (SEM) are performed to bring out the chemical and morphological changes in the modified binder. Rheological properties of modified asphalts are studied using a Dynamic Shear Rheometer (DSR). Results indicate improvement in the physical properties of the modified asphalt even after the aging. Penetration index increased which shows less temperature susceptibility of the modified binders. Carbonyl and sulfoxide index are used as aging indicators which shows reduction in case of modified samples. Decrease in the sulfoxide and carbonyl index indicate better oxidation resistance of the modified samples. Morphological analysis proves good compatibility of the modifiers with asphalt binder. DSR results indicate improved visco-elastic properties of the modified binders.