Optimizing Aqueous Amine Blends for Enhanced Carbon Capture and Mineralization in Cement-Based Materials

Aqueous amine-based carbon mineralization in cementitious materials is a novel and sustainable approach to carbon capture, conceptualizing cementitious structures as 'synthetic trees'. This study evaluates the effectiveness of five individual aqueous amine systems—2-(methylamino)ethanol (MAE), N-methyl diethanolamine (MDEA), 2-amino-2-methyl-1-propanol (AMP), ethylenediamine (EDA), and 2-(2-aminoethylamino)ethanol (AEEA)—as well as MAE blended with piperazine (PZ) at different PZ/MAE ratios, for carbon mineralization in calcium hydroxide (Ca(OH)2(s)) and hydrated cement paste granules (HCPG). A wet carbonation method with 5 vol.% CO2(g) bubbling was employed to assess carbonation performance. For Ca(OH)2, the MAE system exhibited the highest carbonation efficiency, while the EDA and AEEA systems showed lower carbonation than the control. In contrast, for HCPG, the AEEA and EDA systems demonstrated the highest carbonation enhancement. However, when evaluating wt.% CaCO3(s) per mole of nitrogen in the system, MAE was identified as the most efficient individual amine for carbonation. Among PZ/MAE blends, the 1:1 PZ/MAE ratio yielded the highest CaCO3 formation in both Ca(OH)₂ and HCPG carbonation. XRD quantitative phase analysis of HCPG revealed significant decalcification of C-S-H in the AEEA system, predicting poor durability upon AEEA-assisted carbonation. Overall, the findings demonstrate the potential of aqueous amines and amine blends in cementitious materials for effective carbon capture and mineralization.