| Magnesium oxysulfide cement(MOS)is a rigid gel material formed from light burned magnesia powder and a certain concentration of seven water Magnesium Sulfate solution according to the design molar ratio.Magnesium oxysulfide material has the advantages of light weight,high strength,wear resistance,stability,sound insulation and so on.It has a broad application space in building decoration materials.However,the poor water resistance of magnesium oxysulfide cement limits its application in highway bridges and building facades.Therefore,it is of great significance to further optimize the properties of magnesium oxysulfide cement.The annual output of steel slag in China is huge.Due to the single utilization mode and low utilization rate of steel slag,a large number of steel slag can not be reasonably developed and utilized,resulting in resource dislocation and environmental pollution.The application of steel slag micro powder to magnesium oxysulfide cement can not only broaden the resource utilization of steel slag,but also enhance the properties of magnesium oxysulfide cementAccording to the advantages of various physical and chemical properties of magnesium oxysulfide cement,this paper studies the ratio of modified magnesium oxysulfide cement composite modifier that meets the current industry standard,and explores the influence of steel slag micro powder on various properties of modified magnesium oxysulfide cement,so as to realize the resource utilization of steel slag micro powder.Based on the optimal combination of steel slag micro powder and composite modifier,the changes of phase composition and micro morphology of magnesium oxysulfide cement before and after immersion in water were explored by XRD and SEM.Combined with the micro level,the strength,water resistance and frost resistance of steel slag micro powder modified magnesium oxysulfide cement prepared in this paper were improved.The main research contents and conclusions are as follows:(1)Through the single factor test,the modified magnesium oxysulfide cement(m-mos)was prepared with the molar ratio of Mg O / Mg SO4 / H2 O of 8:1:20.Through reading a large number of literature,the content range of modifier was selected: the content of tartaric acid(TA),citric acid(CA)and ferric sulfate(FS)was0.6% ～ 1.8%,and the volume content of basalt fiber(BF)was 0.15% ～ 0.45%.Based on this,L9(34)orthogonal test is designed,and the optimal ratio of composite modifier is obtained,that is,Ta: CA: BF: FS = 1.2%: 1.20%: 0.15%: 1.8%.The compressive and flexural strength after 28 days of curing are 69.47 MPa and 7.67 MPa respectively,and the water resistance coefficient after 28 days of immersion is0.56.(2)The effects of different amounts of steel slag powder on the physical and chemical properties of m-mos were studied.When the content of m-mos is 20%,the mechanical properties of m-mos are the best.The compressive strength at 7d,14 d and28d are 68.9mpa,69.9mpa and 79.8mpa respectively,and the water resistance coefficient after 28 d immersion is 0.96.Combined with the quantitative analysis of XRD and SEM scanning imaging results,the addition of steel slag powder is conducive to the stable existence of 517 phase in MOS..(3)Steel slag micro powder modified magnesium oxysulfide cement has good frost resistance and can meet the needs of application in areas with severe cold or large temperature difference.After 300 freeze-thaw cycles,the mass loss rate of mmos with 20% steel slag powder is 2.694%,and the dry shrinkage rate of the specimen is-0.072%.At the same time,the physical and chemical properties of the steel slag micro powder modified magnesium oxysulfide cement decorative board prepared in this paper meet the current national standards,and have been applied in practical engineering design. |
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