Influence of aging on properties of polymer-modified asphalt

Abstract

Although the use of polymeric additives has been widely accepted as a promising strategy to improve broad spectrum of pavement deficiencies, aging-induced mechanisms of polymer-modified asphalt binders and mixtures still have critical aspects that should be studied to a comprehensive extent. The primary objective of this paper is to advance the understanding of aging effect on the properties of polymer-modified asphalt binders and mixtures. In this study, six different polymeric products were of specific interest: styrene-butadiene-styrene (SBS), polypropylene (PP), styrene-acrylonitrile (SAN), high-density polyethylene (HDPE), polycarbonate (PC), and acrylonitrile-butadiene-styrene (ABS), each was applied at rates of 2% and 5% (by the wt. of asphalt binder) to prepare polymer-modified binders and mixtures. The prepared binders passed thin film oven test (TFOT), while the mixtures were subjected to normal and 16 h production aging. The compositional analysis of asphalt binders was discussed based on the elemental analysis tests while the penetration, ring and ball, and rotational viscosity tests were further studied to evaluate the physical properties. The asphalt mixtures were evaluated based on a series of engineering performance-based properties using indirect tensile strength (ITS), moisture susceptibility, uniaxial static creep-recovery, resilient modulus, and diametral fatigue tests. The fatigue tests were conducted without and with rest period so as to provide insight into the healing potential of different modified mixtures. The results showed that the aging increased the carbon component in all blends; however mixed results were attained regarding hydrogen, sulphur, and nitrogen. No obvious trends were ascertained for carbon, hydrogen, nitrogen, and sulphur due to polymer modification. Aging induced effects on polymer-modified binders and mixtures are highly dependent on the polymer type and modification level. Polymer modification had positive influence on ITS, creep strain and recovery ratio, resilient modulus, resistance to moisture damage, and fatigue life. Fatigue tests with rest period proved that the polymer-modified mixtures have higher tendency to heal compared to the unmodified mixtures, which resulted in an improvement in the fatigue performance of the mixtures. Except for the fatigue life, the aging of polymer-modified asphalt mixtures had no detrimental effect on the studied mechanistic properties.