Performance enhancement of recycled concrete aggregate - A review

Recycled concrete aggregate differ from natural aggregate as the former contains hardened cement mortar. The adhered cement mortar on recycled concrete aggregate has higher porosity and water absorption and lower strength than natural aggregate do. It has negative effects on the mechanical properties and durability of fresh and hardened concrete made with recycled concrete aggregate. Therefore, it will facilitate the applications of recycled concrete aggregate if the adhered cement mortar can be enhanced. Removing and strengthening the adhered mortar are the two main methods for enhancing the properties of recycled concrete aggregate. This paper reviews the published enhancement methods for recycled concrete aggregate, and points out their advantages and disadvantages so as to facilitate the selection and further development of suitable enhancement methods for recycled concrete aggregate. It suggests that carbonation treatment is an efficient and feasible method for improving the mechanical properties and durability of recycled concrete aggregate. Carbonation treatment of recycled concrete aggregate is not only an efficient way for enhancing the properties of recycled concrete aggregate, but also an environmental friendly approach.