外加剂对硫氧镁水泥力学性能的影响及水化机理分析

对比了柠檬酸、磷酸二氢钠、乙二胺四乙酸3种外加剂掺量分别为0、0.5%、1.0%、1.5%(以氧化镁的质量计)时对硫氧镁水泥强度的影响,并通过XRD、XPS、FTIR、SEM对加入外加剂后硫氧镁水泥的水化机理进行了分析。结果表明:3种外加剂中,柠檬酸对硫氧镁水泥的改性效果最好;掺加1.5%柠檬酸的硫氧镁水泥28 d抗压强度达到73.33 MPa,较未掺加外加剂的试块提高了56.5%;加入外加剂后水化产物中出现了针状的5Mg(OH)2·MgSO4·7H2O相(517相)晶体,可以很好的改善硫氧镁水泥的力学性能;外加剂的加入阻碍了活性MgO表面Mg(OH)2的生成,促进了碱式硫酸镁复盐的形成。

Effect of admixture on mechanical properties of magnesium oxysulfide cement and analysis of hydration mechanism

When the admixture dosage is 0,0.5%,1.0%,1.5%(based on the mass of magnesium oxide),the effects of three admixtures of citric acid,sodium dihydrogen phosphate and ethylenediamine tetraacetic acid on the basic properties of magnesium oxysulfate cement were studied.And the hydration mechanism of magnesium oxysulfate cement after adding admixture was analyzed by XRD,XPS,FTIR and SEM.The results showed that among the three admixtures,citric acid had the best modification effect on magnesium oxysulfate cement.The 28 day compressive strength of the magnesium oxysulfate cement reached 73.33 MPa,which was 56.5% higher than that of the test piece without the added additive.Acicular 5Mg(OH)2·MgSO4·7H2O phase(517 phase)crystal appeared in the hydration product after adding the additive,which can improve the compressive performance of magnesium sulfide cement.The addition of admixture hinders the formation of Mg(OH)2 on the surface of active MgO and promotes the formation of basic magnesium sulfate double salt.