The Influence of Mayenite Employed as a Functional Component on Hydration Properties of Ordinary Portland Cement

Influence of C₁₂A₇ (12CaO·7Al₂O₃) as a functional component on hydration properties of Ordinary Portland Cement is studied using isothermal microcalorimetric technique, X-ray diffraction analysis, and thermodynamic calculation. Meanwhile, hydrate assemblages are simulated by hydrothermal software. C₂AH₈ (2CaO·Al₂O₃·8H₂O) is generated as a transition phase during the hydration of pure C₁₂A₇, while formation of CAH₁₀ (CaO·Al₂O₃·10H₂O) is uncertain. Heat-releasing behavior of Ordinary Portland Cement (OPC) could be noticeably affected by C₁₂A₇, especially for the duration of interaction at boundary stage reduces with C₁₂A₇ replacement. Correspondingly, all hydration kinetic parameters first increase and then diminish with C₁₂A₇ replacement. Simulation results manifest in the main hydration products of OPC being ettringite, C-S-H (Calcium-Silicate-Hydrate) gel, portlandite and brucite. Increasing C₁₂A₇ replacement accelerates the consumption rates of gypsum and calcite that are typically included in OPC, and thus the ettringite content is changed and carbonate phases will be produced. Therefore, the microstructure properties of hydrated products of OPC are affected and the compressive strength is influenced. These predications are in good agreement with experimental findings. C₁₂A₇ can be used as a functional component to adjust the consumption rate of suphates in OPC, and also components of carbonate phases can be modified in hydrate assemblage.