Utilization of Recycled Concrete as Aggregate for Hot Mix Asphalt Concrete

Abstract

Natural aggregates (NA), obtained from rock quarry, are widely utilized in all construction projects, including road construction. Aggregates are employed for over 80% of the materials used for road construction. Consequently, road construction projects require substantial quantities of natural aggregates, leading to a growing demand that contrasts with the limited supply of these materials. This disparity leads to extensive research and the development of innovative technologies to explore and assess alternative materials that can replace natural aggregates. In this study, the construction and demolition waste (C&DW) was selected to produce Recycled Concrete Aggregate (RCA) as a substitute for natural aggregates. The RCA was utilized in asphalt concrete mix design using the Marshall method, in accordance with the standards of the Department of Highways. The study compared the engineering properties and performance of three asphalt concrete mixtures: (1) conventional asphalt concrete, (2) asphalt concrete containing 40% RCA, and (3) asphalt concrete containing 90% RCA. Asphalt cement type AC 60/70 was employed as the binder. The results indicated that asphalt concrete containing 40% RCA, and 90% RCA required a higher amount of asphalt cement compared to conventional asphalt concrete. The results from stability and flow tests demonstrated that both 40% RCA and 90% RCA asphalt concretes conformed to the Department of Highways standard. However, indirect tensile strength (IDT) tests revealed that the tensile resistance of asphalt concrete containing 40% RCA, and 90% RCA was 1% and 16% lower, respectively, than that of conventional asphalt concrete. The cost analysis revealed that asphalt concrete containing 40% RCA, and 90% RCA incurred higher costs—11% and 47% more, respectively—than conventional asphalt concrete. This cost increase is attributed to the higher asphalt cement content required for mixtures incorporating RCA.