Abstract
Thermodynamic equilibrium based modelling was carried out to quantify the influence of temperature on the mineralogy of hydrated ordinary Portland cement. In typical Portland cement system hydrated at 25 °C interlayer sites in the AFm phase are occupied by OH, SO4 or CO3 ions. Chloride which can be added as a set accelerating admixture or ingress from the outside environment, has the ability to displace hydroxide, sulfate and carbonate from the AFm structure leading to the formation of ‘Friedel's salt’ (Cl-AFm). However temperature variations may cause important compositional changes or even destabilization of Friedel's salt. A description of phase relations and changing balances between AFm and AFt (ettringite) phases is presented in a range of temperatures between 5 and 85 °C. With an increasing temperature Friedel's salt is predicted to decompose at the expense of monosulfoaluminate (SO4-AFm) formation. Due to the higher stability of hydroxy- AFm (OH-AFm) at lower temperature the OH substitution in the Friedel's salt is expected to be slightly higher as compared to room temperature.
Published Version
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