Effect of MgO on microstructure evolution and exothermic characteristics of tricalcium aluminate during hydration

The phase composition, microstructure, and hydration process of C3A with different MgO content were compared to elucidate the mechanism of hydration resistance of CaO improved by MgO-C3A solid solution. The process of hydration heat release was detected by isothermal calorimetry and the hydration products were analyzed by X-ray diffraction and scanning electron microscope. The results showed that the addition of MgO resulted in lattice distortion of C3A. In the middle and late stages of the hydration process, Mg(OH)2 and amorphous gel-like substances covered the surface of the unreacted C3A and reduced the hydration reaction rate. The addition of MgO effectively reduced the hydration activity of the MgO-C3A solid solution that indicated the addition of MgO can improve the hydration resistance of CaO materials.