Design And Preparation Of Magnesium Oxysulfate Foamed Cement Composite Functional Materials

In the context of national vigorous promotion of building energy conservation policy,foamed cement material has been more and more widely used as a new type of inorganic functional material,currently,the cementitious materials used for making foamed cement is mainly the traditional silicate,this kind of foamed cement has the disadvantages of low compressive strength,high water absorption and poor insulation effect,etc.Therefore,the development of new green foamed cement functional materials has become a hot research focus at home and abroad.Magnesium oxysulfate cement is an air hardening MgO-MgSO4-H2O three-element cementitious material made of active magnesium oxide and magnesium sulfate solution with a certain concentration.It has the characteristics of light weight,high strength and good heat resistance,thus being an ecological green environmental building material.In this paper,the foam was innovatively introduced into magnesium oxysulfate cement and a series of experimental studies on the composite functional material of magnesium oxysulfate foamed cement were made.Firstly,the basic proportion of composite materials for preparation of magnesium oxychloride foamed cement was researched,and experiment showed that when the composite modifier dosage was controlled in 0.3%,there was a large number of 5·1·7 generated in the magnesium oxychloride gel system,with the compressive strength of magnesium oxychloride foamed cement with the dry density of 800?850 kg/m3 being 5.3Mpa,magnesium oxychloride foamed cement has the best mechanical properties when the baume degree of magnesium sulfate solution was about 28°Be.Pure magnesium oxychloride cementitious material is a polycrystalline polymer system.The addition of three admixtures of fly ash,tailings powder and blast furnace slag will have different effects on its microstructure,thereby affecting the mechanical properties,heat insulation and water resistance of the test specimen.Method for preparation of composite materials of light-weight and high-strength magnesium oxychloride foamed cement with fly ash as admixture was studied,and the results show that when the fly ash replacement is 40%,the compressive strength of magnesium oxychloride foamed cement with density degree of A05-A08 can be effectively improved,the mixture of fly ash did not result in new hydrate phase,the micro-aggregate effect of fly ash particles could make the microstructure of magnesium oxychloride foamed cement more dense.Besides,the effects of glass fiber mesh on the material properties was also studied,with the results showing that the glass fiber mesh can significantly improve the rupture strength of porous magnesium oxychloride cement with the dry density of 800?850 kg/m3,and can improve the absorbing properties of materials to a certain extent,when the glass fiber mesh is 3 layers/cm,the improvement effect reached the best.The double-layer sandwich structure can significantly improve the absorbing property of materials,when the total material thickness was 8mm,and when the middle resistor film is 400 Q/?,the absorbing capacity of the specimen in the 2.6-18 GHz frequency band was lower than that of-10dB,and there was good electromagnetic absorption function.Considering the control need of urban space for electromagnetic pollution and stealth military building requirements,electromagnetic absorption property of composite functional material of magnesium oxychloride foamed cement with the admixtures of iron tailings powder in Hainan Changjiang was deeply studied in this paper,and research found that the addition of iron tailings powder made the real part of '?,and ?' of electromagnetic parameters of magnesium oxychloride composite cement gradually decrease,while the imaginary part ?" and ?" gradually increase.When the content of tailings powder is 45%,and when the thickness of magnesium oxychloride foamed cement with dry density of 800?900 kg/m3 is 15mm and 18mm,it can be achieved that the absorption of electromagnetic wave in 2?18GHz frequency band is lower than-10dB.