Mineralization and utilization of CO2 in construction and demolition wastes recycling for building materials: A systematic review of recycled concrete aggregate and recycled hardened cement powder

When CO 2 reacts with Portland clinker (3CaO·SiO 2 , C 3 S; 2CaO·SiO 2 , β-C 2 S; 3CaO·Al 2 O 3 , C 3 A; 4CaO·Al 2 O 3 ·Fe 2 O 3 , C 4 AF) in cementitious materials, mainly forming the dense microstructure of C-S-H with CaCO 3 and Si-gel (SiO 2 ·nH 2 O). Firstly, CO 3 2– , HCO 3 − and CO 3 2– are formed by CO 2 transportation and dissolution which are the rate-determining-step of early mineral carbonation; with the increasing of the carbonation product, Ca 2+ and CO 3 2– precipitates calcium carbonate to be a new controlling step. • Mineralization can improve utilization of construction and demolition wastes and sequester CO 2 permanently. • The properties of concrete incorporating carbonated RCA or RHCP were comparable with Portland cement concrete. • Mechanism associated to mineral carbonation of RCA and RHCP were summarized. • Mineralization and utilization of CO 2 is critical for cement industry towards net-zero-CO 2 emissions. Climate change, which cause a series of extreme weather events like tropical storms, floods and droughts, is the result of increased anthropogenic greenhouse gas emissions, particularly CO 2 . The decomposition of limestone and combustion of fossil fuels processes involved in the production of cement are a large source of CO 2 emissions. Carbon capture, utilization and storage (CCUS) is a critical emissions reduction technology for cement manufacture. Mineral carbonation of cementitious materials can be applied as a low-carbon cement and concrete production technology, which could provide a route for CO 2 permanent sequestration. Recycled concrete as a low-carbon cement and concrete could be produced by replacing the natural aggregate and Portland clinker with recycled hardened cement powder and recycled concrete aggregate produced from construction and demolition wastes. However, the performance of recycled concrete was inferior to those of Portland cement concrete with the same production process due to the existence of adhered old mortar of recycled hardened cement powder and recycled concrete aggregate. Mineral carbonation in recycled concrete aggregate and recycled hardened cement powder is that CO 2 chemically reacted with calcium hydroxide, calcium silica hydrate, etc., forming thermodynamically stable carbonate minerals to absorb CO 2 , and improve the fine value, high porosity and water absorption of recycled hardened cement powder and recycled concrete aggregate. This paper reviewed currently primary methodologies for the mineralization of CO 2 in construction and demolition wastes recycling for building materials: one is property improvement of recycled concrete aggregate by mineral carbonation, while the other is the injection of CO 2 into recycled hardened cement powder. Moreover, the reaction mechanism of mineral carbonation, factors influencing reaction kinetics, performance of resultant products, and application of mineralization to decarbonation concrete production were discussed. Finally, based on current research state and existing problems, future prospect of construction and demolition wastes recycling for building materials by CO 2 mineralization were proposed.