Production of Sustainable Concrete Materials through Innovative Uses of CO_2

摘要

This presentation discusses the innovative uses of CO_2 for the curing of concrete products, surface treatment of concrete and performance enhancement of recycled concrete aggregates (RCA). Using carbon dioxide for concrete curing is based on the chemical reactions between CO_2 and the main silicate phases in the presence of water. This technology allows several advantages over traditional moisture curing in terms of decreasing the duration time of early curing and improving the mechanical properties and dimensional stability of concrete. Concrete surface treatment is one of the effective protection methods to improve the durability of concrete. CO_2 treatment produced a carbonated layer, but increased the compressive strength, and effectively reduced the water permeability, water-vapor transmission and chloride migration. The cement paste attached on natural aggregates has a significant effect on the quality of RCA because it usually has higher porosity and lower strength than natural aggregates. This work attempted to improve the quality of RCAs through carbonation treatment. Carbonation increased the density and decreased the water absorption and crushing values of the RCA. Compared with the mortars made of uncarbonated RCAs, the mortars made with carbonated RCAs increased autogenous shrinkage, reduced drying shrinkage, water absorption, and chloride migration.