CO2 mineralization by recycled concrete aggregate

With increasing urbanization in developing countries, the demand for high-strength, durable, and low-cost concrete is increasing. This is accompanied by an increased demand for coarse and fine aggregates, which account for about 70% of the total concrete volume. This will result in over-exploitation of stone and river sand and an increased burden on the natural environment globally. At the same time, the construction of high-rise buildings will result in the massive demolition of old and low-rise buildings, which will lead to a large number of discarded concrete components and serious environmental problems. The use of C&D waste as a substitute for NA can reduce the exploitation of natural resources and contribute to sustainable social and economic development. In the past 20 years, many researches on recycled concrete aggregates (RCA) have been conducted, and RCA are recognized to play an important role in reducing the use of NA and reducing environmental pollution. However, RCA usually consists of virgin aggregate, adherent mortar, and an interfacial transition zone (TTZ) between the adherent mortar and virgin aggregate ( Figure 7.1 ). The presence of adherent mortar and more interfacial transition zones causes RCA to have higher porosity and water absorption and more microcracks than NA, which in turn leads to more fragile mechanical properties and durability of RCA (Guo et al., 2018 ; Shi et al., 2016 ). Figure 7.1 Composition of RCA (Mao et al., 2021 ). A graph depicting the variation in density of CO2 mineralized recycled concrete aggregates, with data points showing density changes, and lines indicating the 5th to 95th percentile range, median, and mean values. https://www.w3.org/1999/xlink" content-type="colour" xlink:href=" https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781003627531/69fcfb02-8f43-4909-b248-29df408da7d2/content/fig7_1_C.tif "/>