固化超氯盐渍土中不同方式生成的水化硅酸钙生成过程与产物研究

Chloride saline soil erode cement and steel seriously. Therefore, the foundation treatment methods in which cement and steel are uesed are excluded in ultra-chloride saline soil district. The ultra-chloride saline soil was stabilized with the stabilizer Y which different with cement developed by the applicant, and the results were great satisfaction. It was discovered in the pre-research that in the ultra-chloride saline soil the amount of calcium silicate hydrate (CSH) produced by cement reduced obviously but that produced by the stabilizer Y was not influnced. This phenomenon implys that the influence of high-concentration saline environment on the generation process and products of C-S-H generating from the materials with different C-S-H generation modes is diverse. In this sdudy, the cementitious materials which generate C-S-H in different modes will be prepared by the cement mineral, the vitreous cemetitious material containing SiO2, the pozzolanic material containing SiO2, and the C-S-H dehydrated hydrate phase. Then specimens will be made by mixing the ultra-chloride saline soil or brine with them. The strength of the specimens will be measured, and the generation process and the characters of the products such as CSH in the specimens will be observed and measured by X-ray diffraction, scanning electron microscopy, and thermal analysis, etc. Founded on the abouve results, the influence of different kinds of salt, different salt concentration, different salt combination, as well as high-concentration saline environment on the generation process and products of C-S-H generating from the materials with different C-S-H generation modes and in turn on the microstructure and the strength of the stabilized soil will be investigated. Based on the above results, the design method of the stabilizer for the ultra-chloride saline soil will be proposed, by which the components of the stabilizer could be selected according to the salt species and concentration in the ultra-chloride saline soil.

氯盐渍土对水泥和钢材有严重腐蚀，故许多超氯盐渍土地区排除了使用水泥和钢材的地基处理方案。申请者用不同于水泥的自制固化剂Y固化超氯盐渍土取得满意结果。预研发现水泥固化超氯盐渍土所产生的水化硅酸钙(CSH)明显减少，而固化剂Y产生的CSH量无明显变化。这表明高浓度盐环境对不同方式生成的CSH的生成过程与产物有不同的影响。本研究拟用水泥矿物、含活性氧化硅的玻璃体、含氧化硅的火山灰材料和水化硅酸钙脱水相等构成CSH生成方式不同的胶凝材料，将其与超氯盐渍土和卤水制备固化土和净浆试样，通过测定试样强度，用X-衍射、扫描电镜、热分析等手段观测CSH等水化物的生成过程和产物特征，研究高浓度盐环境以及不同盐类、不同浓度及其不同的组合变化对不同方式生成的CSH的生成过程及产物的影响、进而对固化土的结构与强度的影响。在此基础上，提出超氯盐渍土固化剂的设计方法，该法可根据盐渍土中盐的浓度、种类选择胶凝材料组成。

超氯盐渍土对水泥和钢材有严重腐蚀，故许多超氯盐渍土地区排除了使用水泥和钢材的地基处理方案，因此迫切需要开发新的地基处理技术。预研发现超氯盐环境对不同方式生成的水化硅酸钙（C-S-H）的生成过程与产物有不同影响。以此为基础，本研究采用水泥矿物、含SiO2的玻璃体、含SiO2的火山灰材料和C-S-H脱水相等构成C-S-H生成方式不同的胶凝材料，首先系统研究它们水化生成C-S-H的过程和产物特性；进而选取水泥矿物（水泥，PC）和含SiO2的玻璃体（矿渣，KC）进一步研究，将其与含氯盐卤水和超氯盐渍土混合制备净浆和固化土试样，通过测定试样强度，用X-衍射、扫描电镜、热分析等方法观测C-S-H等水化物的生成过程和产物特征，研究氯盐环境对不同方式生成的C-S-H的生成过程及产物的影响、进而对固化土结构与强度的影响。在此基础上，提出适用于超氯盐渍土的固化剂设计方法。结果表明：PC净浆和PC固化氯盐渍土强度均随NaCl掺量的增加而降低，原因是净浆和盐渍土中大量存在的NaCl未参与水化反应，反而抑制了PC水化生成C-S-H。KC净浆和固化盐渍土强度均随NaCl掺量增加而增强，KC可与NaCl、Ca(OH)2发生反应生成AFm类水化物水化氯铝酸钙（Fs）和NaOH。对KC净浆而言，Fs对强度的提高无明显作用，而NaOH使净浆孔隙液pH值升高，促进KC水化，C-S-H生成量增加，从而增强净浆强度。对KC固化盐渍土而言，Fs生成过程中固相体积膨胀，可填充固化土孔隙；NaOH提高了固化土孔隙液pH值，促进KC水化，提高C-S-H生成量，并使得Fs与C-S-H的生成过程相协调；Fs和NaOH两者共同作用，最终使得固化土强度的提高。由此提出“基于AFm类水化物与C-S-H协调生成理论”的氯盐渍土固化剂设计思路和设计方法，并制得了高强固化氯盐渍土。本项目研究成果在新疆公路盐渍软基处治过程中得到初步应用，证明了提出的机理和方法在超氯盐渍土中的有效性。因此，本研究成果具有广阔的应用前景。