Mechanical and Economic Evaluation of Recycled Concrete Aggregate as Granular Road Base and Subbase Material

AbstractIn this study, the usability of recycled concrete aggregates (RCAs) together with crushed aggregate (CA) in granular road base (GRB) and granular road subbase (GRSB) layers was investigated. Three different RCAs as RCA1, RCA2, and RCA3 were used according to their parent concrete compressive strength. The performance of the designs created by mixing three different RCAs with CA at 25%–50%–75% by mass was examined by laboratory tests [modified Proctor, California bearing ratio (CBR), permeability, resilient modulus, and plastic deformation]. CBR values for pure RCAs were higher than 100% and the CBR values were decreased for the mixture designs. Permeability coefficient (k) values of the CA and RCAs were close to each other. Resilient modulus (Mr) values were evaluated for three different models. In general, the lowest Mr values were obtained for pure RCAs, while the highest Mr value was obtained for pure CA. There was no statistically significant correlation between Mr values and CBR values. The plastic deformation (εp) value of the pure CA was significantly smaller than the εp values obtained for the pure RCAs and mixture designs. The RCAs generally increased the εp values. Flexible pavement thickness and cost analyses were performed for the 50CA 50RCA2 design, which was determined to be the most suitable for GRB material, 100RCA2, and 100CA designs for comparison. The 50CA 50RCA2 design reduced the GRB cost by 13% compared to using pure CA. As a result, it was determined that 50% RCA in GRB reduced the cost and had no adverse effect considering the material properties. Recycling of concrete wastes in this way can make significant contributions to reducing environmental pollution and prevent the depletion of natural resources.