Investigation of Mineral Carbonation with Direct Bubbling into Concrete Sludge

Mineral carbonation, which is CO₂ fixation through a carbonation reaction using alkaline earth metals, is being investigated as a carbon capture and utilization method to reduce CO₂ atmospheric emissions. Concrete sludge is an alkali waste material from the concrete industry and contains abundant calcium components. We investigated the applicability of concrete sludge for mineral carbonation. In this study, gas containing CO₂ was bubbled through the model concrete sludge solution and the effects of the solid-liquid ratio, bubbling time, gas flow rate, and the partial pressure of CO₂ on the CO₂ fixation ratio and fixation rate were investigated. The CO₂ fixation ratio decreased with increasing CO₂ bubbling time, CO₂ flow rate, and CO₂ partial pressure. The CO₂ fixation rate increased with increasing CO₂ flow rate and CO₂ partial pressure. The formation of calcite, a form of calcium carbonate, was confirmed.