CO2-Absorbed Diethanolamine in Cement: Strength Development Regulated by in-situ Carbonation

Carbon capture with chemical absorption method represents a critical pathway toward carbon neutrality in industry. However, its application faces challenges including high capture energy requirement for CO 2 desorption and limited CO 2 utilization routes. This study employed diethanolamine (DEA) as a CO 2 absorbent to prepare CO 2 –absorbed DEA (termed DEA–CO 2 ) with different CO 2 absorption amount. DEA–CO 2 was employed to modulate cement strength development, bypassing the energy-intensive CO 2 desorption step. Effects of DEA–CO 2 on cement hydration and the microstructure of the hardened cement pastes were investigated to reveal the regulation mechanism by in-situ carbonation. Results demonstrate that DEA-CO 2 additions show the potential to enhance 3d and 28d strength. Optimal performance occurs with 0.15% DEA and 0.22% CO 2 (D0.15%C0.22%), elevating 3d and 28d compressive strength by 15.3% and 29.3%, respectively. The enhancement is attributed to the accelerated hydration of aluminates and silicates by DEA–CO 2 to achieve a more condensed structure. Moreover, carbonation in cement pastes by DEA–CO 2 effectively mitigates the retardation effect of 0.15% DEA on early cement hydration. However, in the presence of DEA–CO 2 , the accelerated reaction of C 3 A with gypsum delays C 3 S hydration, especially for D0.15%C1.32%. It is hypothesized that the precipitated CaCO 3 or CaCO 3 –AFm on the surface of cement particles also inhibits further silicates hydration. Therefore, D0.15%C1.32% reduces the compressive strength before 28d. These results confirm the potential of utilizing DEA–CO 2 without desorption to optimize the strength development of cementitious materials, provided that the CO 2 dosage is carefully controlled.