The application of Recycled Concrete Aggregate (RCA) for Hot Mix Asphalt (HMA) base layer aggregate

Abstract

Recycled Concrete Aggregate (RCA) is different from natural aggregate because of RCA’s cement paste and contaminants that cause low density and high porosity. In many cases, these properties of RCA that lead to poor engineering qualities are the major reasons that RCA is not recommended as aggregate for Hot Mix Asphalt (HMA). In this research, the performance of HMA mixtures with RCA is quantitatively evaluated using various tests to verify the applicability of RCA as aggregate for HMA material. For this verification, the Indirect Tensile (IDT) strength test, Kim test, wheel tracking test, and tensile strength ratio test accompanied by fundamental material property tests were performed on asphalt mixtures with four types of aggregate blends. In addition, asphalt mixtures with RCA, whose binder contents were determined from the Superpave mix design method, were utilized and evaluated against Marshall design criteria in order to effectively reflect both field specifications and field compaction conditions in South Korea. As a result of this study, it is observed that the study asphalt mixtures with RCA (Mixes II and III) show good performance compared to the asphalt mixture with natural aggregate only (Mix I) in terms of indirect tensile strength ratio, deformation strength, rut depth, and IDT strength, whereas Mix IV, which consists of coarse and fine RCA, does not exhibit good performance. By evaluating the Marshall test properties of each mixture, it is also concluded that the dynamic loading in the Marshall test compaction method possibly causes friction in the RCA of the asphalt mixtures and, therefore, leads to an underestimation of the engineering properties of HMA with RCA.