Research On Simulation And Modification Of Titanium Gypsum And Natural Gypsum

As an alternative of natural gypsum resources, titanium gypsum is a precious wealth although in the cement retarder and light wall materials by some applications, but because of its poorhydration activity, the strength of the titanium gypsum is hard to stimulate and treated as waste disposal, so it is the industrial waste gypsum which has the most narrow scope of application. The reason of high water requirement of normal consistency and low mechanical strength of titanium gypsum is explored which is based on the simulation method of morphology and composition. On this basis, the physical and chemical modification methods are used to stimulate the activity of titanium gypsum and improve its physical properties. The modified titanium gypsum is used in building materials field, in order to further contribute to new ways of resource application development of titanium gypsum.The difference between the physical form and chemical composition of titanium gypsum and natural gypsum was studied by the instrument such as particle size analyzer, X-ray fluorescence spectrometer. The results showed that the diameter distribution of titanium gypsum was relatively narrower than that of natural gypsum. The average particle size of titanium gypsum was smaller than that of natural gypsum. The impurities element content(such as Fe, Al and Si) of titanium gypsum were higher than that of natural gypsum, especially the content of Fe element. The physical properties of titanium gypsum were clearly different from that of natural gypsum, including the water requirement of normal consistency of titanium gypsum was 2.57 times than that of natural gypsum, the setting time was noticeably longer 2h than that of natural gypsum, the mechanical strength could not achieve the GB/T 9776-2008 standard for the building gypsum.The grinding gypsum series were got by controlling the grinding time. The particle size analysis found that the sample which was grinded for 40 min had the same specific surface area, average grain size and grain size distribution with that of titanium gypsum, which was named the morphology simulation of titanium gypsum(hereafter referred to as MTG). Compared with natural gypsum, the water requirement of normal consistency of MTG increased slightly, but it was only 3/5 of that of titanium gypsum. Compared with natural gypsum, the initial and final setting time of MTG extended 6min and 8min, respectively, but the initial and final setting time were short of 14 min and 24 min than that of titanium gypsum, respectively. Compared with natural gypsum, the 2h flexural and compressive strength of MTG was reduced by 31.27% and 31.27% respectively, but it was higher than that of titanium gypsum by 198.15% and 134.78% respectively. It showed that the physical morphology of gypsum hydration hardening body had a certain impact on the physical properties, but it was not the determinant factors which led to the worse performance of titanium gypsum.The chemical composition simulation titanium gypsum(hereinafter referred to as the CTG) was got through adding alumina of 2.69%, silica of 1.23%, iron oxide of 13.01% and iron hydroxide of 17.39% into the MTG in turn. Alumina, silica and iron oxide in turn could not cause the physical properties change obviously, while iron hydroxide added to the MTG, the physical properties of the specimens changed significantly. Only mixed iron hydroxide, the physical properties of the MTG also changed dramatically. When the dosage of iron hydroxide was 17.5%, the water requirement of normal consistency of sample was 149.8%, the initial and final setting time was 27 min and 55 min, respectively, the 2 h flexural and compressive strength was 0.295 MPa and 0.759 MPa, respectively, the physical properties of sample were same with that of titanium gypsum. So the physical factor which led to the poor physical properties of titanium gypsum was iron hydroxide.The titanium gypsum was stimulated by Physical and chemical methods. The experimental results showed that the optimal calcination temperature of titanium gypsum was 180℃, compared with the sample of 100℃ calcination, the water requirement of normal consistency of sample decreased by 15.8%, the initial and final setting time shortened by 27 min and 39 min respectively, the2 h flexural and compressive strength were 0.46 MPa and 0.91 MPa. The water requirement of normal consistency, initial and final setting time, 2h flexural and compressive strength of titanium gypsum sample had been obviously improved by acid modification, the water requirement of normal consistency reduced by 10.73%, the initial and final setting time shortened by 30.43% and 19.61% respectively, the 2h flexural and compressive strength increased by 21.96% and 70.20%, respectively. The naphthalene water reducer had the best effect on titanium gypsum and its dosage was 3.0%. The optimal formula of compound with exciting agent was determined by the orthogonal experiment: sodium sulfate of 0.5%, CaO of 2.5%, exciting agent K of 1.5%. The physical performance index of the titanium gypsum sample was as follows: the water requirement of normal consistency was 80.2%, the initial and final setting time were 4min, 10 min respectively, the 2h flexural and compressive strength were 1.63 MPa, 3.17 MPa, respectively. It achieved the GB/T 9776-28 standard for the building gypsum.Finally, the preparation of titanium gypsum foaming materials was studied, the best ratio of raw materials were as follows: hydrogen peroxide of 5%, stable foam agent H of 4%, the compound repelling agent of 2%. The physical indicators of titanium gypsum foaming materials were as follows: the density of 234kg/m3, the thermal conductivity of 0.065 W/(m· K), the flexural and compressive strength of 0.23 MPa and 0.43 MPa, the water absorption of 9.5%. It could satisfy the technical requirements of building exterior wall with inorganic insulation board performance requirements of shandong province.