Study On The Influence Of Wollastonite Powder On The Properties Of Magnesium Oxysulfade Cement

As an environment-friendly and green cementitious material,the new magnesium oxysulfade cement is more in line with the development requirements of "low carbon" in the current society.Compared with traditional cement,it has many advantages such as light weight and high strength,but its application is limited due to its late stability and other problems.At the same time,because wollastonite has the function of fiber toughening and has certain hydration activity after calcination,there are few ways to use wollastonite at present.Therefore,the development of more ways to utilize wollastonite has been put on the agenda.First of all,in this thesis,wollastonite powder before and after calcination is used as an additive to study its influence on the mechanical properties of magnesium oxysulfade cement,and the wollastonite powder and magnesium oxysulfade cement system before and after calcination(1000℃)are analyzed through synchronous comprehensive thermal analyzer,p H meter,X-ray diffractometer,scanning electron microscope,mercury porosimeter,particle size analyzer and corresponding analysis software,The influence of wollastonite powder before and after calcination on the phase composition,micro morphology and pore structure of magnesium oxysulfide cement was also studied.The experimental results show that the calcined wollastonite powder has certain reactivity,and the alkaline environment provided by Mg O is more conducive to stimulating the reactivity of calcined wollastonite.When the content of calcined wollastonite is 20%,the 28 d flexural strength and compressive strength of magnesium oxysulfade cement reach the maximum value,which are 11.4MPa and63.4MPa respectively,and the increment compared with the blank control group can reach 71.4% and 21.2%;At the same time,wollastonite powder optimizes the pore structure of magnesium oxysulfade cement,and reduces the proportion of more than100 nm pores in the magnesium oxysulfade cement system.The calcined wollastonite has good interface compatibility with magnesium oxysulfade cement,which is more conducive to improving the mechanical properties of magnesium oxysulfade cement.Next,the influence of wollastonite powder on the water resistance of magnesium oxysulfade cement was studied.The effects on water resistance mainly include:(1)Adding wollastonite powder with different particle sizes into magnesium oxysulfade cement,it is concluded that the natural wollastonite powder enhances the performance of magnesium oxysulfade cement mainly because of its fiber toughening effect.At the same time,the toughening effect of wollastonite powder with different particle sizes on magnesium oxysulfade cement is different,and the fiber toughening effect will be affected by the particle size of wollastonite powder,so controlling its appropriate particle size has a better effect on magnesium oxysulfade cement.(2)After 28 days of standard curing,the test blocks were immersed in water for 7 days and 28 days,respectively,to test their residual strength and calculate their water resistance softening coefficient.The test results showed that wollastonite powder could improve the water resistance of magnesium oxysulfade cement.When the content of wollastonite was 40%,the strength retention coefficients at 7 days and 28 days were increased by 10.39% and 22.01% respectively compared with the blank control group.Finally,the influence of wollastonite powder on the high-temperature resistance of magnesium oxysulfade cement was studied and its thermal decomposition mechanism was analyzed.By adding wollastonite into magnesium oxysulfade,and then taking out its test block after standard curing for 28 d,calcine it for 2h at different calcination temperatures,and test its residual strength and strength retention coefficient.The test results show that wollastonite powder improves the high-temperature resistance of magnesium oxysulfade cement,and the residual strength value and strength retention coefficient are higher than those of the blank control group.The performance of 40% wollastonite powder is the best,and the strength retention coefficient at 200 ℃,400 ℃,600 ℃ and 800 ℃ can be as high as0.95,0.92,0.38 and 0.13.