Triethanolamine-promoted separation of calcium from recycled concrete fines during aqueous carbonation

The heterogeneous nature of recycled concrete fines (RCFs) complicates their reuse in new concrete mixtures. A possible solution to this challenge involves separating the calcium-rich cement from the quartz aggregates through aqueous carbonation (AC), forming CaCO3. AC typically requires large solvent volumes and multiple steps, hindering the industrial application of the process. To address these problems, a one-step AC procedure with low water-solid ratios and the addition of 0.2-1.0 wt% of triethanolamine (TEA) was tested to enhance calcium separation from RCFs as CaCO3. Pre- and post-carbonation analysis with XRF, Q-XRD, TGA, and sieving revealed that the addition of TEA resulted in an approximately twofold increase in calcium precipitation below 63 mu m and increased the amount of sequestrated CO2 by 16-21 %. These findings showcase the feasibility of AC with low water-solid ratios and the addition of TEA as a means to separate calcium from RCF, aiding RCF reuse.