Effect Of Aluminate Cement On The Properties Of Magnesium Sulfide Cement

Magnesium oxysulfide cement has the characteristics of light weight,high strength and fire resistance,which has great value in the field of construction and building materials.In recent years,many researches have been carried out on the mechanism and properties of magnesium oxysulfide cement,but the mixed use and application of magnesium oxysulfide cement and calcium cement are still in the primary stage.In this paper,magnesium oxysulfide cement is modified by different kinds of calcium cement,mainly including the influence of different special cement on the macro performance of magnesium oxysulfide cement,such as compressive strength,water resistance,etc.;the micro analysis of modified magnesium oxysulfide cement is carried out by means of XRD,DSC-TG,SEM.（1）After adding sulphoaluminate cement,the early compressive strength of sac-mos decreases and the stability of hydration products is improved.The addition of sac can reduce the content of 5·1·7 phase in MOS hydration products.When the content of sac is less than 10%,the water resistance of MOS cement can be improved,and the strength retention coefficient of 7%sac-mos group is 13.02%higher than that of MOS group.At the same time,the gypsum phase in sulphoaluminate cement will affect the formation of 5·1·7 phase,reduce the compressive strength and stability of the sample group,and lead to the later expansion cracking of the sample group.After immersion,the micromorphology of different sulphoaluminate clinker is characterized by gel phase and MOS water resistance.（2）The addition of CAC improves the compressive strength of MOS cement.The addition of CAC promotes the crystallization of hydration product 5·1·7 phase in MOS cement.When the content of CAC is 5%,10%,15%and 20%,the compressive strength of CAC-MOS cement after 28 days of air curing increases by 18.23%,25.11%,28.91%and 34.90%respectively;when the content of CAC is more than20%,the compressive strength does not increase.The addition of CAC improves the water resistance of MOS cement.After incorporation of CAC cement,the3Ca O·（Al₂O₃）·3Mg（OH）₂·（30～32）H₂O phase consumed the remaining Mg O in the MOS cement system,while the hydration product also introduced the aluminum gel phase to increase the water resistance of the system.When the content is 10%,the water resistance of the sample is the best,and the strength retention coefficient is 0.99after air curing for 28 days and then soaking for 28 days.The addition of CAC can reduce the final formation of hydration product Mg（OH）₂and effectively improve the strength shrinkage of MOS cement.When the content of CAC is more than 15%,the compressive strength of C₃AH₆phase will be reduced.Therefore,considering the compressive strength and water resistance,the optimal content of CAC is 10%.（3）CAC-MOS new rapid repair cement can ensure the strength,impermeability,stability and other properties of the cement,while reducing the cost and environmental protection.It has positive significance for the development of magnesia resources and the preparation of fast repair cement in the future.The feasibility of preparing a new type of rapid repair cement with aluminate cement modified magnesium oxysulfide cement-based cementitious material is explained.Magnesium oxysulfide cement has been difficult to be applied in actual production due to its poor water resistance.However,the test results show that the modification of magnesium oxysulfide cement with aluminate cement can effectively apply the products in the actual construction industry,and can be applied in the road repair cement industry with low price advantage and environmental protection and green performance.