ABSTRACT
ABSTRACT A potential solution for both sustainability in demolition and increased service life is repurposing concrete that is taken out of service as recycled concrete aggregate (RCA). This material allows for a more economical aggregate source for towns that are located far from any virgin aggregate sources. Recycling existing concrete for use as aggregate in new construction has gained consideration in recent years because of high costs of disposal of waste concrete and shortage of natural aggregate. In Japan, insufficient of natural aggregate has become more concerned for construction companies. Furthermore, the deterioration of concrete structures that lead to a large amount of concrete waste from demolition is also of great concern. Recycle concrete aggregate is one of the efficacious ways to solve the problems. However, the application of recycled concrete aggregate in the construction field is still finite due to quality and cost-related problems. In Japan recycled aggregate are classified into three categories namely; high, medium and low recycled aggregate symbolized by H, M and L. The classification is based on absolute dry density and water absorption rate. High cost of H class of RCA and the low quality of M and L classes of RCA has limited the utilization of RCA in concrete structure. In this research, studies were carried out to investigate the effect of using carbonation technology in improving the low classes of RCA produced from concrete of different water cement ratio. Concrete of different water-cement (30%, 50%, 70% and 35% 45%, 55%, 65%) were cast and RCA were produced and carbonated. 18 types of RCA were used in this study. The Recycled aggregate concrete is evaluated according to compressive strength, tensile strength and drying shrinkage. Additionally, the double mix method of RCA for improving strength is evaluated. It was found that carbonation of RCA can increase the density and decrease the water absorption of RCA. the results showed that the strengths of the recycled aggregate concrete(RAC) has a direct relation to the water-cement ratio of the original concrete and carbonation of RCA can increase the strengths of RAC. It was also found that by exposing recycled aggregates to carbon dioxides decreases drying shrinkage of RAC.
