Abstract
With the increase in demand of flexible pavements, due to their various advantages over rigid pavements, there is a need to improve the aging properties of the bitumen in order to enhance its resistance against different types of distresses such as rutting, fatigue cracking. This research focus 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 are evaluated for their effect on the aging mechanism in comparison with the unmodified bitumen. Aging of the original and modified bitumen is realized by the Rolling Thin Film Oven (RTFO) and Pressure Aging Vessel (PAV). Physical properties of the aged and unaged asphalt binders are evaluated through empirical testing like penetration, ductility and softening point 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 asphalt are evaluated with the help of a Dynamic Shear Rheometer (DSR). Results indicate improvement in 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 indicates better oxidation resistance of the modified samples. Morphological analysis proves good compatibility of the modifiers with asphalt binders. DSR results indicate improved viscoelastic properties of the modified binders. Hence it can be concluded that Polyethylene and Sulphur are good options to improve the aging resistance of asphalt in terms of their cost effectiveness and environment friendly nature.
Highlights
Pakistan is a developing country where roads and highways are major source of transportation
Aging index used in this research are Penetration Aging Ratio (PAR), Softening Point Increment (SPI), Ductility Retained Ratio (DRR), Phase Angle Aging Index (PAAI) and Complex Modulus Aging Index (CMAI) which can be calculated by the given formulas: Aged Penetration Value
The penetration results after the short term aging and long term aging of the modified bitumen are presented in the form of PAR in Figures 8(a) and 8(b)
Summary
Pakistan is a developing country where roads and highways are major source of transportation. Failure of the highway occurs due to the non-structural rutting or different types of cracking. Non-structural rutting occurs due to the poor asphalt mixture properties, heavy traffic loads, or due to high temperatures. Aging is defined as the oxidation of light components which causes the stiffening of bitumen during construction and service phase [5, 7]. It affects the chemical and rheological properties of bitumen, causing it to fail before the estimated service life. Asphalt aging affects the pavement flexibility negatively after many years of service life in field [8]. The process of aging is greatly dependent on the chemical composition of bituminous mixture [4]
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