A study of factors that influence the hydration activity of mono-component CaO and bi-component CaO/Ca2Fe2O5 systems

The compositions and formation process of f-CaO in steel slag were identified and simulated to understand its expansion rules and hydration activity. BSE showed that the compositions of f-CaO, which included the calcium iron phase and calcium iron manganese phase, were diverse. The hydration activity sequence was Ca2Fe2O5 in bi-component CaO/Ca2Fe2O5 systems < CaO in bi-component CaO/Ca2Fe2O5 systems < mono-component CaO; only Ca2Fe2O5 was hard to hydrate, and the volume expansion rates of the bi-component CaO/Ca2Fe2O5 systems varied with different compositions. Inductively, in steel slag, the hydration activity sequence was solid solution CaO-FeOx in bi-component f-CaO < CaO in bi-component f-CaO < mono-component f-CaO; the volume expansion rates of bi-component f-CaO changed with different compositions, and CaO-FeOx was difficult to hydrate. The reason why CaO-FeOx was hard to hydrate was that its hydration reaction driving force, which is the absolute value of standard molar reaction Gibbs functions, decreased.