Water Resistance And Modification Studies Of Magnesium Oxychloride Cement

Magnesium oxychloride cement(MOC)has high compressive strength,low density,and many other excellent properties,but because of its poor water resistance severely restricted its application in engineering.Therefore,the modified of MOC water resistance is significanly for effective use of resources to exPand the scope of its application.In this Paper,orthogonal design was firstly used to study the influences of curing temperature,magnesium chloride concentration and MgO/MgCl2 molar ratio on MOC compressive strength,and choose the maximum value as the basis proportion,based on which the imPacts of curing temperature,chloride concentration and MgO/MgCl2 molar ratio on MOC properties were studied;then studied the influences of mineral admixtures,phosphates,sulfates,organic lotions portland cement and other additives on MOC performance by Parallel experiment,and obtained the results of admixture dosage range;finally,mixture design was used to analysis diverse admixtures imPact on MOC performance,and optimized the ratio to obtain the compressive strength and softening coefficient in the optimal ratio.X-ray analysis(XRD)and scanning electron microscopy(SEM)were employed to study the variation of the phase composition and t phase morphology and structure of MOC,and discussed the influence of the structure on the MOC properties.Summarized the following conclusions:(1)Curing temperature,chloride concentration and MgO/MgCl2 molar ratio greater imPact the performance of the MOC,the best ratio is:23.4%magnesium chloride concentration,molar ratio of 6,curing temperature of 20 ℃,the compressive strength of MOC made as which ratio was 56.91 MPa.(2)Mineral admixtures,phosphate and magnesium sulphate cement had modification effect on MOC properties.Admixture changing the MOC density by its physical activity,and phosphates and sulfates reacting with magnesium ions,thus promoting coagulation caused to achieve the purpose of modification,the law were similar,where different from others was introduced different cations,which imPacted the water resistance;the modification effect of styrene-acrylic emulsion was by physical isolation effect to achieve the purpose of improving the water resistance;Portland cement has an adverse effect on MOC.(3)When the ratio of fly ash to silica fume was 0.51:0.49,the 28 d compressive strength of MOC was 39.99 MPa,softening coefficient was 0.73;when the ratio of potassium dihydrogen phosphate to hexametaphosphate was 0.93:0.07,the 28 d compressive strength of MOC was 50.11 MPa,softening coefficient was 1.00;when the ratio of sulfuric acid to aluminum sulfate was 0.41;0.59,the 28d compressive strength was of MOC was 46.76 MPa,softening coefficient was 0.66.(4)Multi-species admixtures complex doped significant improved the performance of MOC,and mixture design can effectively optimize and analysis multi-component.Added as the proportion in(3),when without mineral admixtures,the ratio of phosphate to sulfate and styrene-acrylic emulsion were 0.92:0.04:0.04,the 28 d compressive strength of MOC was 50.27 MPa,softening coefficient was 1.00;if mineral admixtures added as 30%,phosphate was 3%,the 28 d compressive strength of MOC was 56.90 MPa,softening coefficient was 1.11.This Paper systematically studied the influences of curing temperature,chloride concentration,MgO/MgCl2 molar ratio on MOC properties,and using mixture design to analysis the improvement of activities on MOC,and its products production and serve as a guide for materials research put forward new ideas.