复合改性硫氧镁水泥的性能研究

The Properties of Compound Modified Magnesium Oxysulfate Cement

目的研究当总掺量不同时,复合改性硫氧镁水泥的物相组成、抗压强度及耐水性能,提出提高和改善硫氧镁水泥力学性能和耐水性能的方法.方法按材料用量的不同进行硫氧镁水泥基本配比试验;制备复合改性硫氧镁水泥;利用扫描电镜和X光谱衍射进行微观分析.结果硫氧镁水泥的抗压强度达到最大时的基本配比:质量分数为30%,固液比为1.2,粉煤灰掺量为30%;复合酸总掺量取2%,草酸质量与柠檬酸质量比为1∶3的配比时,硫氧镁水泥28 d的抗压强度为72.5 MPa左右,是不添加改性剂硫氧镁水泥的2倍多;复合酸使水泥软化系数在0.95以上,微观分析确定新物相为5Mg(OH)_2·MgSO·7H_2O.结论加入复合酸使水泥内部更加密实,孔隙率降低,抗压强度提高,并表现出较好的耐水性能和力学性能;新物相的生成是复合改性硫氧镁水泥耐水性能和力学性能显著提高的主要原因之一.

The phase composition,compressive strength and water resistance property of modified magnesium oxysulfide cement with varied total dosages were investigated,and a method was proposed to improve the mechanical property and water resistance of the magnesium oxysulfide cement.Experiments with regards to basic mixing proportion for the magnesium oxysulfide cement were carried out based on different dosages of the raw materials.Modified magnesium oxysulfide cement was prepared and analyzed by XRD(X-ray diffraction)and SEM(Scanning electric microscopy)method.When a basic mixing proportion was the mass percentage of 30%,solid to liquid ratio of 1.2 and fly ash of 30%by mass the compressive strength of magnesium oxysulfide cement reached an optimal value.The compressive strength of the magnesium oxysulfide cement at 28 d was 72.5 MPa when total compound acid dosage was 2%and oxalic acid to citric acid ratio was 1∶3 by mass,which was more than 2 times that of the unmodified magnesium oxysulfide cement.A softening coefficient more than 0.95 could be achieved,and a new phase,namely,5 Mg(OH)2·MgSO·7 H2O was identified by SEM method.The incorporation of the compound acid could contribute to denser microstructure,lower porosity and higher compressive strength of the cement,in other words,the mechanical properties and water resistance was greatly improved.The hydrated new phase(5 Mg(OH)2·MgSO·7 H2O)was one of the prime reasons which resulted a significant improvement on the water resistance and mechanical properties of the compound acid modified magnesium oxysulfide cement.