A new type of CO2 fixation process with concrete sludge was proposed and its feasibility was examined with laboratory experimental woks. Concrete sludge is a waste generated as excess concrete, returned concrete, or washing water at concrete-using plants. Concrete sludge is a waste composed of hydrated cement, aggregates, and water, and generated as slurry of which the water content depends on the sources. Because of cement component including calcium hydroxide, the concrete sludge is alkaline, and should be treated by neutralization with acids before disposal. In this study, the waste concrete sludge is utilized as a fixation material for CO2. The generation rate of waste concrete sludge is several % to 10% of the concrete used. Thus, the concrete sludge can be a potential and low-cost candidate for CO2 fixation. In this study, we examined the CO2 fixation performances of concrete sludge in laboratory experiments using cement powder. A known amount of cement powder was mixed with a fixed volume of water, and allow the mixture to be hydrated for a given hydration time to prepare model concrete sludge. Then gaseous CO2 flow with different concentrations balanced with nitrogen was introduced to the mixture for a certain time with a fixed flow rate. The pressure of the feed gas was the atmospheric pressure, and the temperature was the room temperature. After the reaction time, the mixture was filtered and the solid content was dried. The composition of the solid was analyzed with thermo gravimetric method (TG), and the fixation rate of CO2 was determined. The experimental results showed that CO2 can be fixed with the model waste concrete sludge, and the effects of the operation conditions such as the hydration time, flow rate, solid/liquid ratio were examined. The results demonstrated the process is feasible as a CO2 fixation.

Fixation of CO<sub>2</sub> with concrete sludge

248th National Meeting (2014)

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Fixation of CO2 with concrete sludge

Fixation of CO₂ with concrete sludge