硫酸钠对水泥土的强度及微观孔隙影响研究

通过不同含量的硫酸钠水泥土抗压强度测试，分析硫酸钠对水泥土X射线衍射（XRD）物相成分改变的化学反应过程，对比分析经Image-ProPlus6.0（IPP）软件处理前、后的微观扫描电镜试验（SEM）图像，计算放大200倍下SEM图像的孔隙平均直径分布规律，探讨硫酸钠对水泥土宏观强度与微观孔隙的影响规律。结果表明，硫酸钠充分参与了水泥土的固化过程，促进了Ca(OH)2、CaSO4、CaCO3与C-A-S-H等水化产物的生成；水泥土强度随硫酸钠含量增加而增大，在含量等于9g/kg时达到最大值；硫酸钠使水泥土的孔径分布发生改变，放大200倍下水泥土微观图像孔隙率随着硫酸钠含量的增大呈减小趋势；当硫酸钠含量小于9g/kg时，生成的水化产物使水泥土的结构呈现较强的粒状-镶嵌-胶结结构，对强度有利，当硫酸钠含量较大时，水化产物产生的膨胀力大于胶结力，使其强度下降。

Effect of sodium sulfate on strength and micropores of cemented soil

In order to simulate and study the effect process and mechanism of cemented soil by different sodium sulfate contents, a series of tests are conducted on the cemented soil samples, such as compression strength test, X-ray diffraction (XRD) phase test and scanning electron microscope (SEM) test, SEM pictures processed by Image-ProPlus6.0（IPP）software; the distribution of pore average diameter of SEM pictures at 200 magnified times is calculated. The test results show that the compressive strength of cemented soil increases with the increase of sodium sulfate content; and the value reaches its peak when the content is 9 g/kg. The distribution of cemented soil pore changes owe to sodium sulfate, and the porosity of SEM photo at 200 times decreases. From the SEM photos analyses show that the microscopic structure of cemented soil by sodium sulfate exhibits the granularity-inlay-cement. Chemical products are analyzed by means of XRD test. The testing results show that the chemical products become more such as Ca(OH)2, CaSO4, CaCO3 and C-A-S-H, after the sodium sulfate participated in chemical reactions. Those chemical products mainly play the role of crystallization action in the chemical reaction process, which is good for cemented soil strength when the chemical products in the sample with sodium sulfate content lower than 9 g/kg. With the sodium sulfate content increasing, the gel around soil particles is broken down, which make the strength of cement soil decrease.