Experimental Research On β Mould Gypsum Enhancement

Gypsum mould has many advantages, such as conveniently manufacture,rich in raw material originate, low cost, good water absorbing performance,light quality, recycle and having no pollution to environment. So it waswidely used as shaping tool of porcelain industry in our country. Butbecause of gypsum material also has many shortcomings, such as: lowintension, bad water resistrnce, bad wear-ability resistence. So the use timesof gypsum mould is not as long as to meet the need of moulding techniques.With the improvement of the craft, the pressure of making pattern increasehigh, the quantity of product improve, the request of brightness and durableof the pattern of gypsum to be more and more high, the common patter ofgypsum has can't satisfy with the production demands.In this study, the modified function of admixture and paste material ongypsum material is systemically analyzed. The setting time, strength, waterabsorption rate and corrosion rate of modified gypsum were determined bygeneral methods and the mechanisms were also discussed based on theexperimental results such as SEM and XRD. We chose three kind of retarders: citric acid, sodium tripophophate andthe borax, and we determined their influence of setting time and strength onthe gypsum; The results indicate that the addition percentage of sodiumtripophophate is 0.03% which can obviously improve the operatingperformance of gypsum, but lose of strength is low. The addition percentageof SM reducing agent is 0.6% which can reduce W/G and increase thestrength of gypsum.It was chosen as intensifier inorganic binding material that they arecement and anhydrite burned at high temperature. After mixingsulphoaluminate cement, white Portland cement and ordinary Portlandcement, the setting time and strength of mould gypsum were improved, andits corrosion rate reduced. Synthesized various aspects performance, withcement as the gypsum intensifier can obviously improve its performance.However, the cement's content is not large, otherwise reduce its strength.Take the anhydrite as intensifier, and take calcined alunite and the potassiumsulfate two kinds of sulfate as anhydrite excitant, their content is 4% and 2% distinctly. The results indicate that the anhydrite with 4% calcinedalunite has positive affection, but the anhydrite with 2% potassium sulfatehas negative affection.