Cement retarder and method for direct preparation of same by using semi-hydrated phosphogypsum

Abstract

The invention relates to a method for direct preparation of a cement retarder by using the industrial by-product, semi-hydrated phosphogypsum, which belongs to the technical field of cement additives. According to the invention, phosphogypsum is aged at first; when 40% to 80% of semi-hydrated gypsum in phosphogypsum is converted into dihydrate gypsum, phosphogypsum is broken, and an alkaline activating agent and water are added for mixing; granulation is carried out on an obtained mixture, and obtained granules are naturally maintained and dried in air so as to obtain the cement retarder; wherein, the weight percentage of phosphogypsum, the alkaline activating agent and water is as follows: phosphogypsum 80 to 90 parts, the alkaline activating agent 0.5 part to 4 parts, and water 10 to 20 parts. A semi-finished product produced in the process of granulation for the cement retarder provided in the invention coagulates and hardens in a short time; a finished product coming out from a granulator has a certain degree of hardness and has a compressive strength of between 3 to 5 MPa in 5 minutes; when the finished product freely falls from a testing platform of a height of 1 meter, breaking probability of the finished product is less than 10%; the finished product can be directly transported with a loader, thereby greatly saving a storage area for the finished product. Meanwhile, the method has the advantages of simple production process flow, economy and environmental protection.

Description

technical field [0001] The invention relates to a method for directly preparing cement retarder by using industrial by-product hemihydrate phosphogypsum, and belongs to the technical field of cement additive preparation. Background technique [0002] Cement is one of the main raw materials in engineering construction, and has been widely used in a large number. Gypsum is an indispensable retarder in the cement production process, the addition amount is about 4-5%, and the market demand is very large. Most of the retarders used in cement production are natural gypsum. With the development of industry, the use of cement is increasing, and the demand for natural gypsum will also increase accordingly. This will not only cause a shortage of natural gypsum resources, At the same time, the industrial by-product gypsum cannot be effectively utilized. For example, a large amount of phosphogypsum produced by phosphorus chemical enterprises in the production process of wet-process pho...

AI Technical Summary

Problems solved by technology

Although this process saves natural gypsum and solves the problems of large dust, difficult measurement and inconvenient production operation when phosphogypsum is directly used as cement retarder, there are still deficiencies: ① This method uses industrial by-product dihydrate phosphogypsum As the main raw material, the added hemihydrate gypsum is generally obtained by drying, high-temperature calcination and other technological measures, which makes the production process of cement retarder complex, increases energy consumption, and increases costs. The drying process also brings secondary damage to the environment. secondary pollution

②Calcium phosphate dihydrate, an industrial by-product, is directly processed into a cement retarder. Due to the soluble acidic substances (such as H 3 PO 4 , HF, P 2 o 5 etc.), its loose structure is not convenient for application, storage and transportation

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