Study Of The Glass-Phosphogypsum Cementing Material And Its Products

Phosphogypsum is the by-product of the production of phosphoric acid by wet process with apatite and sulphuric acid. Phosphogypsum has many excellent properties, the most distinguished two merits are the high content of dihydrate(commonly 90%) and the good fineness, it can save the cost of crushing and grinding. However, there are many impurities in phosphogypsum which includes the phosphoric acid, various kinds of phosphates, fluorides, organic ingredients, aluminous compounds and soluble salts. All these foreign matters bring influence to the strength and setting property of the phosphogypsum product, and also bring difficulty to the application of it.Based on the principles of material chemistry, this paper uses the lime hydrate as the alkali activator. It can not only neutralize acids in phosphogypsum but also work as the powerful activator to the slag. And the chosen accelerator enable it to react with the components in above material system to generate accelerated hydration product--ettringite.In this paper, the components system and optimum mix proportion of phosphogypsum cementing material are designed by experiments. The main technological factors influencing the properties of the cementing material are explored. With advanced testing methods of XRD, SEM, thermoelectric conduction calorimeter,etc, the hydration kinetics and hydration products, the hardening mechanism and the microstructure of hardened pastes are analyzed. The application of cementitious materials is carried out in laboratory.The study in this paper doesn't require such pretreatments as water scrubing and burning of phosphogypsum. And under the action of compound activators, it can react directly with slag and sand to produce environment-protecting cementing material with 28d compressive strength above 30Mpa and various kinds of construction products. It is energy saving and it won't bring the secondary pollution. The result has great value of application and social benefits.According to the LCA evaluation of the glass-phosphogypsum cementing material, it can be determined that this material has excellent property in environment conditioning.