The Formation Rule Of Ettringite In Low PH Value Sulfoaluminate Cement Pastes

Glass fibre reinforced cement products produced by low pH value sulfoaluminate cement combining with alkali-resistant glass fibre are more perfect building materials. They have a wide applied in structural engineering. The main hydrate of low pH value sulfoaluminate cement is ettringite. The ration of C₂S/C₄A₃S|- has an important effect on the formation of ettringite. The theory study in formation of ettringite is deepened by the study about formation rule of ettringite in course of hydration of low pH value sulfoaluminate cement. And the theory foundation for producing cement with special capability becomes richer than before.The amount of the ettringite formed in different age was determined in three low pH sulfoaluminate value cement pastes whose ratios of C₂S/C₄A₃S|- are different. And the formation curves of ettringite were drawn. Then the crystallization kinetics of ettringite was analyzed. The results indicate that the formation of ettringite is the nucleus firstly, and then is the crystal. Besides, when the ratio of C₂S/C₄A₃S|- is large, the formation ratio of ettringite is great, and the time of turning into"the automation catalyze age"is early at forepart of hydration. However, at later stage of hydration, the increase of the formation ratio of ettringite becomes slow. At the same time, the influence of different formation rules of ettringite on the performance of low pH value sulfoaluminate cement was analyzed. the result of the experiment show that there are different effects on set time, expansion and strength when the ratio of C₂S/C₄A₃S|- is different.Also, the influences of alkali and slag on the formation of ettringite in low pH value sulfoaluminate cement pastes were studied. The alkali affects the formation of ettringite and the performance of low pH sulfoaluminate cement only at forepart of hydration. But at later stage of hydration, the influence isn't obvious. After added slag, the formation rule of ettringite didn't change, and the performance of cement became improved yet.