水泥-镁渣固化盐渍土力学性能实验

Mechanical properties test of solidified saline soil with cement-magnesium slag

为改善宁夏盐渍土地基混凝土渠道衬砌易冻胀、易腐蚀等缺陷,提高当地镁渣利用率,采用水泥-镁渣对盐渍土进行固化研究,设计13种不同配比的水泥-镁渣固化盐渍土试样,通过三轴试验、 XRD和SEM表征手段分析试样的抗剪强度指标及水化机理。结果表明:对7、 28 d龄期试样,水泥-镁渣固化盐渍土的黏聚力、内摩擦角均随压实系数的增大而增大;单掺水泥时,固化盐渍土的黏聚力和内摩擦角随水泥含量的增加而变大;镁渣的加入对试样的黏聚力影响较大,对摩擦角影响较小;建立水泥及镁渣掺量与固化盐渍土抗剪强度指标的关系模型;固化盐渍土的水化产物及抗剪强度增强来源均以水化硅酸钙为主;28 d龄期试样的固化盐渍土颗粒能更好地填充孔隙,微观结构更致密,从而强度更高;水泥-镁渣固化盐渍土的抗剪强度显著提高,其中水泥质量分数为3%、镁渣质量分数为10%的固化盐渍土力学效果较佳。

In order to improve the lining defects of concrete channel in saline soil foundation in Ningxia,such as frost heave and corrosion,and to improve the utilization rate of local magnesium slag,the study on solidification of saline soil was carried out with cement-magnesium slag.Thirteen kinds of cement-magnesium slag with diferent mass fractions were designed to cure saline soil samples,and the shear strength and hydration mechanism of the samples were analyzed by XRD and SEM characterization methods.The results show that the cohesion and internal friction angle of cement-magnesium slag solidify saline soil increase with the increasing of compacting coefficient for samples at 7 and 28 d of age.The cohesion and internal friction angle of solidified saline soil increase with the increasing of cement content.The addition of magnesium slag has a great effect on the cohesion of the sample,but a small effect on the friction angle.The relationship model between cement and magnesium slag content and shear strength index of cured saline soil is established.Hydrated calcium silicate is the main source of hydration products and shear strength enhancement of cured saline soil.The solidified saline soil particles at the age of 28 d can fll the pores and the microstructure is more dense,thus the strength is higher.The shear strength of cement and magnesium slag solidified saline soil is improved significantly,and the mechanical effect of cement and magnesium slag solidified soil is better when the cement fraction is 3%and the magnesium slag fraction is 10%.