Dissolution, nucleation, and crystal growth mechanism of calcium aluminate cement

This study presents a theoretical prediction of calcium and aluminate ion concentrations of calcium aluminate cement (CAC) system on dissolution and nucleation behavior, induction time (tind), interfacial free energy (γ), and crystal growth mechanism. Such data can influence the early-age hydration of CAC. Better understanding of the data is applied to predict and manipulate its early-age hydration. It is well-understood that at 20 °C the CAC compositions of CaAl2O4•10H2O (CAH10) and Ca2Al2O5•8H2O (C2AH8) were the main hydrated products. Results in the study indicated that the nucleation of calcium phase was the controlling nucleation mechanism, not the aluminate. The calculated γ-value of CAH10 was lower than the C2AH8; meaningly, CAH10 was more stable than C2AH8. SEM images also revealed two-dimensional (2D) mediated growth of CAH10. Based on the theoretical predictions and SEM study, the crystal growth mechanism for CAC system at 20 °C was the 2D-mediated growth mechanism.