Aqueous CO2 Sequestration for Low-Carbon Ready-Mix Concrete

Abstract

The cement industry accounts for 8% of global energy- and process-related greenhouse gas emissions. To achieve global net-zero emission targets by 2050, the need for commercially ready low-carbon construction materials is becoming increasingly urgent. The fixation of captured carbon dioxide in concrete through CO₂ sequestration is a crucial area of study to reduce concrete embodied carbon. This paper discusses the development of a low-carbon ready-mix concrete (RMC) with aqueous CO2 sequestration, and the synergy between carbon dioxide and other constituent materials. The effectiveness of this approach was evaluated through mineralogical composition analysis using TGA, and the mechanical and rheological properties of various concrete mixes were studied. Aqueous CO2 sequestration using carbonated mixing water can stably fix up to 0.84% of CO2 by weight of cement within the cement matrix as CaCO3. The poor workability and incompatibility with GGBS that results from this approach were addressed by the inclusion of RCA as an external source of alkalinity and lubrication. This mix of low-carbon RMC has similar strength and rheological properties to conventional RMC and achieved an embodied carbon reduction of approximately 47%.