Life-cycle assessment of emerging CO2 mineral carbonation-cured concrete blocks: Comparative analysis of CO2 reduction potential and optimization of environmental impacts

CO2 mineral carbonation (MC) curing technology provides a promising solution for large-scale CO2 utilization and construction sectors towards low-carbon and environmentally friendly production of concrete, but studies on the total environmental impacts of this technology are scarce. Accordingly, this paper evaluated the life cycle environmental impacts of seven promising concrete blocks from CO2 MC curing manufacturing pathways (Ordinary-Portland cement block, MgO-Portland cement block, wollastonite-Portland cement block, limestone-Portland cement block, calcium silicate cement block, slag-Portland cement block and Waste Concrete Aggregate block), offering detailed results of cradle-to-gate life cycle assessment and inventory. Identification of the contributions of subdivided raw materials and manufacturing processes, as well as the energy consumption, transportation, and upstream processes for raw materials was performed. It was shown that 292–454 kg CO2-eq global warming potential (GWP) of 1 m3 CO2-cured non-hollow concrete blocks were obtained. By contrast, results indicated the 419 kg CO2-eq GWP from a base case of conventional (steam-cured, non MC) Ordinary-Portland cement block. Up to 30% of CO2 emission avoidance could be achieved when replacing steam curing by MC curing and adjusting the binder types. From the point of view of materials and manufacturing, the reduced use of Portland cement is a key step for environmental optimization, while reducing the energy consumption for maintaining high-pressure carbonation helps to cut down the cumulative energy demand. Increasing the blending ratio in binary binders and the lightweight redesign also proved to be beneficial solutions for mitigating environmental impacts of CO2-cured concrete blocks. Wollastonite-Portland cement block and slag-Portland cement block using natural wollastonite and blast furnace slag in binary binders obtained the most favorably scores in all impact assessment indicators, and thus, are arguably considered as the most sustainable types of concrete blocks.