采用固体硅酸钠激发的一步法地质聚合物在软土固化中的适用性研究

Feasibility study on the one-part geopolymer activated by solid sodium silicate for soft soil solidification

为解决水泥固化软土早期强度不足及制备水泥时高污染、高能耗及高成本等问题,采用固体硅酸钠(Na_(2)O·SiO_(2),简称NS)激发双先驱剂(粉煤灰(fly ash),简称FA)和磨细高炉矿渣(ground granulated blast furnace slag,简称GGBFS)制备一步法地质聚合物浆料(one-partgeopolymer,简称OPG)。研究FA掺量、NS摩尔数、碱激发剂浓度、水灰比等因素对地质聚合物浆料物理及力学性能的影响规律。在此基础上,开展优化配比试验,确定可作为土壤固化剂的地质聚合物最优配比。然后,将综合指标最优的地质聚合物配比用以固化软土。进一步研究双先驱剂中FA/GGBFS质量比和养护龄期对固化软土无侧限抗压强度(unconfined compressive strength,简称UCS)、孔隙率和孔径分布的影响。通过压汞法(mercury intrusion porosimetry,简称MIP)和扫描电子显微镜-能谱仪(scanning electron microscope-energy dispersive spectrometer,简称SEM-EDS)对试验进行微观分析,揭示其固化机制。研究结果表明:固体NS激发下的一步法地质聚合物能有效加固软土,其生成的水化凝胶物(N-A-S-H、C-A-H、C-S-H和C-A-S-H)能有效黏结土颗粒,从而促进形成致密固化土骨架。FA/GGBFS为0.1、水灰比为0.8、NS摩尔数为1.0、碱激发剂浓度为3 mol/L是固体硅酸钠激发的一步法地质聚合物固化软土的最佳配比,其固化软土的28 d无侧限抗压强度可达4.4 MPa,且具有良好的工作性。本研究扩展固体硅酸钠激发的一步法地质聚合物在深层搅拌技术中的应用,为软土地基的加固处理提供理论基础指导。

To address the issues of low early strength in cement-stabilized soft soil,as well as the high pollution,energy consumption,and costs associated with cement binder application,one-part geopolymer(OPG)is prepared by using solid sodium silicate(Na_(2)O·SiO_(2),NS)to activate a mixture of binary precursors,namely fly ash(FA)and ground granulated blast furnace slag(GGBFS),along with water.The factors,including FA dosage,solid NS molarity,alkali molar concentration,and water-cement ratio,are considered for assessing the physical and mechanical properties of OPG.Based on this,optimized proportioning tests were conducted to determine the best mixing ratio of OPG for soft soil stabilization.The effects of the FA/GGBFS ratio in the precursor and curing ages on the unconfined compressive strength(UCS),porosity,and pore size distribution of OPG-stabilized soft soil were further investigated.Micro-analysis was performed using mercury intrusion porosimetry(MIP),scanning electron microscope-energy dispersive spectrometer(SEM-EDS)to reveal the stabilization mechanism.The results indicated that the OPG prepared with solid NS could effectively stabilize soft soil,with hydrated gels(N-A-S-H,C-A-H,C-S-H,and C-A-S-H)effectively bonding soil particles and contributing to the formation of a denser soil skeleton.The mixing proportion of FA/GGBFS of 0.1,water-cement ratio of 0.8,NS molarity of 1.0,and molar concentration of 3 mol/L was found to be optimal for soft soil stabilization.The corresponding OPG had good workability and achieved a UCS of 4.4 MPa.This study extends the application of solid sodium silicate-inspired one-step geopolymers in deep mixing techniques,providing guidance on the theoretical basis for the reinforcement treatment of soft ground foundations.