Comparative Performance of Unmodified and ABS-Modified Asphalt Mixtures Containing Calcium Carbonate and Blowdown as Filler

Abstract

Recently, blowdown (B), a carbon-sulfur byproduct material of sulfur purification has been utilized as potential calcium carbonate (CaCO3) mineral filler replacement. This paper evaluated the effects of acrylonitrile-butadiene-styrene (ABS) polymer on dense-graded (DG) mixtures containing two types of filler (CaCO3 and B-waste as alternative filler). Different ratios of ABS (0.5%, 1.0%, 1.5%, and 2.0% by weight of asphalt) were blended with 40/50 paving grade asphalt. Unmodified and ABS-modified asphalt binders were subjected to physical and homogeneity tests. Blowdown-DG combinations with unmodified and ABS-modified asphalt binders were constructed for the study, and they were tested against the CaCO3-DG reference mixtures. The B and CaCO3 concentration in the DG mixture was set at 5% (by weight of aggregate). The performance tests, including Marshall stability (MS), Marshall quotient (MQ), tensile strength (TS), tensile strength ratio (TSR), cracking tolerance index (CTindex), and deformation strength (DS) in a Kim test were carried out on unmodified and ABS-modified DG mixtures containing both fillers (B and CaCO3). Also, CTindex was calculated from load-displacement curve data of indirect tensile strength. According to the testing results analyzed by Minitab software using analysis of variance least significant difference (ANOVA LSD), a B-mixture showed higher MS and DS, with lower TSR and CTindex than the CaCO3 mixture, while 1.5% ABS-modified CaCO3 mixtures showed higher resistance to rutting and moisture damage with lower cracking and fatigue resistance when compared with BA mixture containing 1% ABS. Further, these results indicated that the BA mixture needs a lower dosage (1%) of ABS than CaCO3 mixture, which needs 1.5%, meaning that B-mixture is a cost-effective solution and eco-friendly than CaCO3 mixture for pavement application.