In recent years, the issue of water demand for cement has attracted more and more attention.Especially in the cement industry in the Guangdong and Guangxi regions,the concrete industry always hopes that the water demand should be as small as possible,so that less water reducing agent can be added and the cost of commercial mixing can be reduced. In fact,there are many factors affecting the water demand of cement.The impact of water demand on concrete is also multifaceted.
The effect of gypsum on water demand
The form of gypsum usually has gypsum(CaSO4·2H2O),natural anhydrite
(CaSO4),hemihydrate gypsum (CaSO4·0.5H2O),soluble anhydrite (CaSO4),natural anhydrite and gypsum have similar solubility,soluble anhydrite and The solubility of hemihydrate gypsum is similar.However, their dissolution rates are quite different.The dissolution rate of hemihydrate gypsum is fast.The rate of dissolution of natural anhydrite is much slower than that of gypsum.The soluble anhydrite is made by controlled dehydration of gypsum or hemihydrate gypsum,and its rate is slow.Therefore,the matching between them also affects the rheological properties of cement.Highly active C3A dissolves quickly,the level of early Ca2+ in the cement is high,and the gypsum used should have a proper amount of dissolution rate; the low active C3A dissolves slowly,and the Ca2+ in the cement should not be consumed at an early stage.There should be a certain level in the later stage,so the gypsum used should have a proper amount of components with a slow dissolution rate.
Compared with natural anhydrite,different amounts of desulfurized gypsum have little effect on the physical properties of cement.The strength of the cement l day is better than natural gypsum mixed with desulfurized gypsum,but the strength of cement in later stage is better than that of desulfurized gypsum.As the amount of desulfurized gypsum increases,the water consumption of the standard consistency of cement decreases accordingly.