Effect of acidic amino acids on wet pre-carbonation of β-C2S in steel slag

Wet pre-carbonation of steel slag is an important solution to the steel slag soundness problem. This method, however, can consume a significant amount of silicate phase in steel slag. To address this issue, it is proposed that the consumption of calcium silicate can be reduced while the hydration performance of steel slag can be improved by adding acidic amino acids into the wet carbonation of steel slag. β-C 2 S is the main cementitious component in steel slag. Synthetized β-C 2 S was used to simulate the reaction mechanism of steel slag during carbonation and to study the role of acidic amino acids in carbonation. The carbonation products were characterized by XRD , FT-IR, TG-DTG, and SEM. The results demonstrated that without the addition of acidic amino acids, the carbonation degree of β-C 2 S reaching the maximum at 1 h under the experimental conditions. Calcite and amorphous silica was formed as a result of the carbonation of β-C 2 S. The final carbonation degree was lower after adding higher concentrations (0.1 mol/L) of acidic amino acids than before. Higher concentrations of acidic amino acids increased the content of metastable CaCO 3 , primarily vaterite. Acidic amino acids were added in the pre-carbonation of steel slag, then the steel slag was mixed with cement to prepare cementitious materials . The cementitious materials’ 28-day compressive strength was higher than without amino acids, and the maximum of strength increased by 9.45 % compared to that without amino acids. Whether amino acids were added or not, the boiling expansion value decreased to 0 after 1 h of carbonation, indicating that the carbonation reaction improved the soundness of cementitious materials.