Design and Evaluation of Asphalt Mixtures Containing Crumb Rubber as Aggregates Replacement

Crumb rubber (CR) as a modifier has been used by many for asphalt binders and asphalt concrete (AC) mixtures production. Nevertheless, the engineering properties of AC mixtures containing CR as aggregate replacement still need to be determined. Nevertheless, it is essential to ascertain the engineering qualities of AC mixtures that incorporate CR as a replacement for aggregates. This study investigates the durability and mechanical attributes of conventional AC mixtures and CR/AC mixtures. The assessment involves analyzing various properties, such as Marshall stability, static creep compliance, indirect tensile strength (ITS), tensile strength ratio (TSR), and deformation strength in the Kim test. One AC control mixture and four CR combinations were created. The CR contents of four CRAC mixes were 0.5%, 1.0%, 1.5%, and 2.0% wt. of aggregates. Optimum asphalt content increased and bulk specific gravity decreased with increasing crumb rubber content. The AC mixture with 0.5% CR content showed approximately similar Marshall stability, moisture resistance, deformation strength, and static creep compliance to those of the AC mixture without CR. Whereas, AC mixture with 1.0% CR content showed higher plastic flow. The stability and TSR values remained higher than the ASTM specification's minimum values, which cap CR up to 1.0%. This study introduces a design methodology for crumb rubber-asphalt mixtures, which determines the appropriate amount of CR by considering the durability and mechanical properties of the asphalt mixture. According to this study, 0.5–1.0% of the CR by weight of aggregates can be replaced as aggregates for paving applications.