Influence of tricalcium aluminate on the microstructure evolution of CaO specimen during hydration

C 3 A-containing CaO specimen was prepared and the evolution of its microstructure during hydration process was investigated to clarify the protective mechanism of tricalcium aluminate (C 3 A) on hydration resistance of CaO specimen. The slit-shaped micropores were formed on the grain boundary of CaO due to the stacking of lamellar C 4 AH 13 formed by the hydration of C 3 A. The contact area of residual C 3 A with the moisture was reduced by the porous C 4 AH 13 layer at the original site, which resulted in a slower dissolution rate of C 3 A grain through the porous layer. In addition, the crack propagation and the formation of macropores were inhibited by the pinning effect of C 4 AH 13 , which was beneficial to the improvement of hydration resistance.