Effects of using brake pad waste powder as a filler material on the rheological and mechanical properties of a sulfur modified asphalt mixture

Abstract

Thiopave sulfur product has been recognized as a kind of asphalt-binder replacement agent providing the asphalt mixture with better anti-rutting performance. However, there is often a concern about its poor resistance to the moisture damage and the low temperature. This study investigated the applicability of brake pad waste (BPW) in the sulfur modified asphalt mixture as a means to enhance its moisture, cracking, and high temperature-rutting resistance properties. The laboratory manufactured BPW powder with a size less than 0.075 mm was used as filler to substitute the limestone powder with different proportions. The effect of the BPW powder on the physical and rheological properties were assessed by the penetration test, the softening point test, the ductility test, and the dynamic shear rheometer test. In addition, the effect of the BPW on the properties of the sulfur modified asphalt mixture was evaluated using the Hamburg wheel tracking test, the freezing-thawing test, the dynamic uniaxial compression test, the semi-circular bending test, and the fatigue test. The results showed that the BPW could improve the high temperature properties of the sulfur modified asphalt mixture. In general, the anti-rutting performance of the sulfur modified asphalt mixture increased as the BPW increased. Optimum anti-moisture and anti-cracking properties of the sulfur modified asphalt mixture were also found to occur at 50% BPW powder content of the whole filler content. At an applied micro-strain of less than 300 με, the sulfur modified asphalt mixture with 50% BPW powder exhibited the longest fatigue life, with an increasing trend as the micro-strain decreased. In general, 50% BPW powder content was found to be the optimal and best substitution dosage for the limestone filler at all the laboratory performance indices that were evaluated.