Mineral Carbonation Curing of Wollastonite-Blends Paste: Feasibility of Low Lime Calcium Silicate

The mineral carbonation (MC) curing of cement-based materials is a promising CO₂ utilization route, which could fix CO₂ as stable products, and meantime develop building materials. This work aims to investigate the feasibility of applying non-hydraulic materials (low lime calcium silicates for instance) as substitute binder in blended paste to reduce traditional cement usage. Herein the wollastonite-Portland cement blends were employed for MC curing. The impact of mineral blending proportions (5-25%) and mineral particle sizes (10-150μm) on the carbonation reaction rate and final CO₂ uptake were systematically discussed, accompanied with the optimization of curing conditions. Results indicated that the blended minerals show “diluted effect” under low curing pressure and intensify the MC reaction. Decreasing the particle size of wollastonite mineral could also promote the CO₂ fixation. Tests of mercury intrusion porosimetry, scanning electron microscope and X-ray diffraction were conducted to further reveal the compositional and structural changes. Finally, the carbon footprint assessments were carried out to provide a more comprehensive insight on CO₂ emission reduction of MC curing technology, especially in terms of the composition and consumption of cement-based material. The total carbon footprint includes the CO₂ emission during cement production and minerals processing, as well as the CO₂ uptake from MC curing. It is shown that both the optimized CO₂ uptake and reduced consumption of Portland cement contribute to the reduction of carbon footprint, proving the emission reduction benefits of MC curing technology.