摩尔比对MMOS水泥力学性能和变形行为的影响及机理

Effect of Molar Ratio on Mechanical Properties and Deformation Behavior of Modified Magnesium Oxysulfate Cement and Its Mechanism

研究了原材料摩尔比(n(MgO)∶n(MgSO_(4))∶n(H_(2)O))对改性硫氧镁(MMOS)水泥力学性能和变形行为的影响,并采用X射线衍射仪(XRD)、扫描电镜(SEM)、傅里叶变换红外光谱(FTIR)及热重分析(TG)等测试技术对其机理进行分析.结果表明:MMOS水泥的抗压强度和抗折强度随着水硫比和氧硫比的提高均呈提升趋势.其中原材料摩尔比为10∶1∶12时,水泥力学性能最优.不同摩尔比MMOS水泥在56d龄期内均呈膨胀变形,其中总变形随水硫比和氧硫比的提高呈减小趋势;自收缩变形随水硫比的提高而减小,随氧硫比的提高呈先增后减趋势.这主要是由于硬化后不同摩尔比MMOS水泥中的水化产物Mg(OH)_(2)和5·1·7相(5Mg(OH)_(2)·MgSO_(4)·7H_(2)O)含量各有不同.当Mg(OH)_(2)含量减少,而5·1·7相含量增加时,MMOS水泥的膨胀变形量降低,同时其抗折强度和抗压强度有所提升.

The effect of the molar ratio(n(MgO)∶n(MgSO_(4))∶n(H_(2)O))in the raw materials on the mechanical properties and deformation characteristics of modified magnesium oxysulfide(MMOS)cement was studied,and the mechanism was analyzed by testing techniques,such as X-ray diffraction(XRD),scanning electron microscope(SEM),Fourier transform infrared spectroscopy(FTIR)and thermogravimetric analysis(TG).The results show that the compressive strength and flexural strength of MMOS cement matrix shows an increasing trend with the increase of water-sulfur ratio and oxygen-sulfur ratio.The specimen with a molar ratio of 10∶1∶12 has the highest compressive and flexural strength.The deformation of MMOS cement specimens with different molar ratios during the period from completion of pouring to 56 days of curing is mainly expansion deformation.The total deformation of MMOS cement specimens shows a decreasing trend with the increase of water-sulfur ratio and oxygen-sulfur ratio,while the autogenous deformation shows a decreasing trend with the increase of water-sulfur ratio and a first increasing and then decreasing trend with the increase of oxygen-sulfur ratio.The MMOS cement specimens with different molar ratios exhibit differences in expansion deformation,mainly due to the different contents of hydration products Mg(OH)_(2),5·1·7 phase(5Mg(OH)_(2)·MgSO_(4)·7H_(2)O)and unreacted MgO phase in the hardened matrix.When the content of Mg(OH)_(2) decreases and the content of 5·1·7 phase increases,the expansion deformation phenomenon of MMOS cement specimens weakens,while their flexural strength and compressive strength are improved.