A Study And Application On Gypsum-free Portland Cement

A new type of building material ----- gypsum-free portland cement was invented and developed through the experimentation. Portland cement is a kind of cementitious material made from Portland cement clinker, 0-5% of quicklime or granulated blast furnace slag, etc. appropriate amount of gypsum, by grinding. Among them, gypsum plays the main role in delaying coagulating, reducing the hydration rate of cement clinker and extending the initial setting time, to ensure construction time.Various surface active agents (including some inorganic salts) were repeatedly tested on hydration of cement base material (clinker). First, every kind of surface active agents was tested one by one. Second, choose the better results in terms of the index of setting time and strengths. Through the optimum composition of different agents with different contents, gypsum-free cement was invented by using the method of orthogonal test. The optimum composition of different agents has replaced the use of gypsum. Based on the research of the basic performance of the gypsum-free cement, we can know that the gypsum-free cement has lots of good properties, such as better long-term strength, better stability and better resistance against sulphate erosion, its strength can keep growing during the coming 360 days. It shows that the gel of C-S-H keeps generating during the whole process of the hydration of the gypsum-free cement from beginning to end and the gel of C-S-H constantly fills the voids. Through the test of XRD (X-ray diffraction), we can know that there is no ettringite generated during the hydration of the gypsum-free cement. So it plays an important part in reducing or avoiding the stress generated by the conversion of ettringite. From the above, we can conclude that the gypsum-free cement has higher physical and mechanical properties compared with the ordinary Portland cement. Through the research of the role of grinding AIDS, we can get that the choosen optimum composition of admixtures can play a role in helping to grinding AIDS to some extent. Energy consumption per unit of cement production and equipment abrasion can be reduced. Construction period can be shortened. Concrete strength can be enhanced. The probability of accident also can be cut down.