Abstract:

Different activators were used to activate fly ash?calcium carbide slag?titanium gypsum system，and the effect of activator on the strength and setting time of the system was studied.By analyzing the phase composition and microscopic morphology of the system，the hydration mechanism of different activators was proved.The results showed that the addition of activator could effectively shorten the setting time of the system and improve the strength of the sample.Among them，NaOH as activator had the best compressive strength at each age，which could reach 10.4 MPa at 28 d.X-ray diffraction（XRD），scanning electron microscope energy dispersive spectrum（SEM-EDS） analysis showed that the hydration products were mainly C-（A）-S-H gel and ettringite，and the type of activator had great influence on the formation of hydration products.The amount of ettringite in Ca（OH）₂ system was the largest.NaOH system was mainly gel with low ettringite content.Due to the formation of syngenite in KOH system，the amount of ettringite was small in early stage and increased in late stage.When NaOH was used as the activator，the high basicity and the fast consumption of free SO₄^2- promoted the participation of Fe in the reaction to form Ca₄Fe₂SO₁₀·16H₂O（Fe-AFM），which was conducive to the direct utilization of the original titanium gypsum.

Key words: titanium gypsum, activator, hydration mechanism, cementitious materials