Rearch On The Preparation Of Binding Materials And Concrete With Phosphogypsum

Phosphogypsum is a solid waste from the industrial production of phosphoric acid or phosphate fertilizer. Our country is the first largest country of the production of phosphoric acid phosphate in the world, with the rapid development of phosphate fertilizer industry, the emissions of phosphogypsum, also presents the trend of increased year by year. So far, the amount of phosphorus gypsum in China is more than300million tons, annual quantity will be more than70million tons. Phosphogypsum contains harmful impurities, if it is a large amount of storage, will not only take up a lot of land, and also pollute the environment, this has brought serious adverse effects to the state and enterprise’s development. The resource utilization of phosphogypsum has become an important task of phosphate fertilizer industry, also has important significance to the protection of ecological environment, natural resources saving, low carbon economy development and the achievement of sustainable development.The paper mainly studied the following four aspects of content:The first one is the microstructure, chemical composition of the phosphorusgypsum and the analysis of the grain size composition of phosphorusgypsum powder. The second one is the preparation of binding materials with phosphorusgypsum as an additive to replace part of the cement, studied the influence of the different dosage of phosphorus gypsum and polycarboxylate to the mechanical properties and hydration process of binding material. The third one is the preparation of C30concrete with phosphorusgypsum as an additive to replace part of the cement, studied the influence of the different dosage of phosphorus gypsum and polycarboxylate to the compressive strength, workability and permeability resistance of C30concrete. The last one is the preparation of binding materials with phosphorusgypsum of different specific surface area, studied the influence of the specific surface area of phosphorusgypsum to the mechanical properties and hydration process of binding material.Dihydrate calcium sulphate is the main mineral composition of phosphogypsum by XRD and SEM analysis. The Crystalline form of phosphorusgypsum is the diamond or cylindrical plate structure, its size is between30-40microns. The main chemical composition of phosphogypsum is CaO and SO3, and there is a small amount of SiO2, MgO, Al2O3, Fe2O3and P2O5in phosphogypsum.There is also15.35%Attached water and11.74%water of crystallization in phosphogypsum. Phosphorusgypsum After grinding, while The average particle size20.71microns, the maximum particle size139.36microns, particle size less than53.46microns particles accounted for99.60,can be as an additive to prepare the binding materials and concrete.Phosphorusgypsum was used as an additive to replace part of cement to prepare the binding materials with the addition of polycarboxylate.The results of the experiment of micellae showed that, the compressive and flexural strength of the binding materials decreased with the increment of the dosage of phosphogypsum. The greater the dosage of polycarboxylate, the strength of the gelled material is higher, when polycarboxylate in the range of0.6%-1.2%, and under the condition of the same dosage of phosphorusgypsum. The compressive and flexural strength of the mortars with the addition of5%phosphogypsum in the binding material met the standard requirements of P.O42.5, while the compressive and flexural strength of the mortars with the addition of10-15%phosphogypsum met the standard requirements of P.032.5. The setting time and stability of mortars were up to standard. Phosphogypsum could generate more hydration products with cement in the hydration process of the binding material, also increase the density of gelled material at the same time.Phosphorusgypsum was used as an additive to replace part of cement to prepare C30concrete with the addition of polycarboxylate. The compressive strength of concrete decreased with the increment of the dosage of phosphogypsum. Under the same dosage of phosphogypsum, the compressive strength of concrete is the highest by adding2.0%polycarboxylate. By adding less than Using less than25%of phosphogypsum and2.0%-2.3%of polycarboxylate, C30concrete, which can reach P12impermeability grade requirements, was prepared. In the hydration process of concrete, phosphogypsum could in good condition with the other components of concrete hydration, and had the sulfate excitation effect to the cement, and kept the density and strength of the hardening body increasing.Increasing the specific surface area of phosphogypsum, the compressive and flexural strength of the binding material showed a trend of decrease after the first increase. When the specific surface area of the phosphorus gypsum was about630m2/kg, compressive and flexural strength of the binding material is the highest. The reason is that the appropriate increase the specific surface area of phosphogypsum, can improve the activity of phosphorus gypsum, which could generate more hydration products with cement, improve the density of the binding material hardening body at the same time.