Influence of amino acids on the properties of carbonated pseudowollastonite composites: Development of a high-reactivity CO2 sequestration binder

This study investigated the influence of amino acids (L-glutamic and L-aspartic acid) on the compressive strength, mineral carbonation, and microstructure of carbonation-cured pseudowollastonite pastes. Pseudowollastonite was synthesized without a compaction step, and its potential as a CO₂ sequestration binder was evaluated. The results indicated that the effects of amino acids with a concentration of 0.5 % and 1 % varied significantly. The addition of 0.5 % amino acids enhanced compressive strength up to 24.0 %, compared to the control. Calcite, vaterite, and amorphous CaCO₃ (ACC) were identified as the CaCO₃ phases in the pastes. The introduction of 0.5 % amino acids promoted ACC formation in the early stage, followed by almost complete recrystallization of ACC into calcite. In addition, the use of amino acids enhanced internal carbonation and inhibited the macro crack formation, contributing to the improved compressive strength of the pastes. It was confirmed that volume fraction of cracks governs the carbonation degree of the pastes with amino acids as well as compressive strength. Considering that pseudowollastonite exhibits the highest carbonation reactivity among wollastonite polymorphs, incorporating amino acids into pseudowollastonite rather than natural wollastonite may offer a promising approach for producing an ultra-low calcium, highly reactive CO₂ sequestration binder.