Research On Properties And Application Of Titanium-based Gypsum Mortar

Titanium gypsum is produced in the process of producing titanium dioxide with calcium sulfate dihydrate as the main component of waste residue.In recent years,China’s titanium dioxide production continues to increase,titanium dioxide production has become the first in the world,which leads to the annual production of titanium gypsum more than 2300 Wt,but the comprehensive utilization rate is only 10%,resulting in excessive accumulation,occupy a large amount of land resources and cause environmental pollution.Therefore,the resource utilization of titanium gypsum has become the key to the sustainable development of titanium dioxide industry.In this paper,the titanium gypsum produced by a titanium white factory in Wuzhou,Guangxi is taken as the research object.Based on the existing research,the performance of titanium gypsum based mortar and its application in ready-mixed mortar are systematically studied.Using "Titanium Gesso + Slag + Cement" as cementitious material,the mortar is prepared to study its related properties.The research contents and results are as follows:1.Study on mechanical properties and rheological properties of titanium-based mortara)Through the tests of different water-cement ratios and strength,and the regression analysis of the data,it is concluded that the cement to water ratio of titanium gypsum based mortar with each mix ratio has a linear relationship with the compressive strength,which conforms to the water-cement ratio rule.It shows that porosity is still the main factor affecting the strength of titanium-gypsum mortar.b)In the test age of 120 days,the strength development law of titanium gypsum based mortar is as follows: under the standard curing condition,the flexural strength of titanium gypsum based mortar shows a linear growth trend in the period of 7d to 56 d,and the strength develops slowly in the period of 56 d to 120 d.The compressive strength showed a linear growth trend from 7d to 90 d,and the strength developed slowly from 90 d to 120 d.Natural curing is closer to the development trend of cement mortar,showing a linear growth trend in the period of 7d to 28 d,and the strength develops slowly in the period of 28 d to 120 d.c)The effect of steam curing,standard curing and natural curing on mortar strength was studied.The results showed that the steam curing system with temperature of 70℃ and curing time of 6h was more appropriate;The effect of three curing systems on the early and late strength of titanium gypsum mortar is as follows: steam curing can obviously improve the early(7d)strength,and natural curing has the highest strength at 28 d.d)Titanium gypsum mortar slurry shows the rheological properties of Bingham fluid.The shear stress increases linearly with the increase of shear rate.Under the same water-cement ratio,the yield stress,plastic viscosity and thixotropy of the slurry increased with the increase of titanium gypsum content.After time treatment,the slurry still conforms to the characteristics of Bingham model.The yield stress and plastic viscosity of each mix ratio increase linearly,and the growth rate increases first and then decreases with the increase of titanium gypsum content,indicating that the hydration reaction rate increases first and then decreases.2.Durability of titanium gypsum based mortara)The results of the dry shrinkage test show that the dry shrinkage value of the mortar in the first 7d is negative,indicating that the system is slightly expanded,while the dry shrinkage value increases rapidly from 7d to 28 d,indicating that the water loss and shrinkage.With the age increasing,the dry shrinkage value increases slowly.The 180 d dry-shrinkage values of the four mortar ratios were all lower than those of cement mortar.By comparing the dry shrinkage value at 180 d,the higher the ratio of titanogypsum to slag,the greater the dry shrinkage value.b)The sulfate corrosion resistance test results show that the mass loss rate of the mortar soaked in sodium sulfate solution is negative in the first 3 days,and then it stabilizes for a period of time.With the increase of the drying and wetting cycles of sodium sulfate solution,the mass loss rate increases.The relative elastic modulus increased rapidly in the first three cycles,and then dropped to a certain extent.With the increase of cycles,the volatility of the relative elastic modulus decreased.After 30 sodium sulfate solution cycles,the corrosion resistance coefficient decreases with the increase of titanium gypsum content.c)Water resistance test results show that with the extension of soaking time,the water absorption rate increases,the softening coefficient decreases,the water resistance decreases,and the increase of cement content will also reduce the water resistance.d)The antifreeze test results show that: in the freeze-thaw cycle,the mass loss rate of the first five cycles is negative,and then the mass loss rate increases rapidly.In the first five cycles,the relative elastic modulus increased rapidly,and then the volatility of relative elastic modulus decreased.After 30 freeze-thaw cycles,the compressive strength and flexural strength decrease,and the specimen is seriously damaged.With the increase of titanium gypsum content,that is,titanium gypsum content increases,the antifreeze performance will significantly decrease.3.Study on high temperature performance of titanium-based mortarIn the test temperature range of 65℃-450℃,the properties of mortar change as follows:with the increase of temperature,the mass loss rate increases;The relative dynamic modulus also continues to decrease.Water absorption per unit area increased gradually;The strength deteriorates seriously,and the loss rate of compressive strength reaches 66.76%-86.67%.The loss rate of flexural strength reached 70.00%-86.11%.The results of mercury injection test show that with the increase of temperature,the pore structure parameters of titanium gypsum mortar are increasing,the distribution range of pore size is also gradually increased,and the pore size distribution with the increase of the mixture ratio of titanium gypsum and mineral powder,showing a trend of increasing the proportion of harmful holes and more harmful holes,harmless holes and less harmful holes decrease.Through XRD and SEM analysis,it is concluded that the increase of temperature leads to the increase of porosity and the degradation of mechanical properties and physical properties.4.Study on application of titanium gypsum based mortar in ready-mixed mortar To the ready-mixed mortar masonry mortar M5,M10 and plaster mortar M15,M20,as the object,through the orthogonal experiment it is concluded that the factors of titanium gypsum based ready-mixed mortar consistency and the influence degree of the compressive strength from big to small in the order: contrast material than water,the dosage of cellulose ether in meeting the ready-mixed mortar(GB/T25181-2019)on the basis of base mixture ratio:masonry mortar M5 contrast 1:4,water ratio,0.17,0.1 ‰ dosage of cellulose ether;M10cement to sand ratio 1:3,water to material ratio 0.165,cellulose ether content 0.1‰;Plastering mortar M15 cement sand ratio 1:2,water material ratio 0.185,cellulose ether content 0.1‰,latex powder content 0.1%;M20 cement sand ratio 1:2,water to material ratio0.185,cellulose ether content 0.1‰,latex powder content 0.1%,water reducer content 0.09%.