征西遥,刘秀秀,吴俊,等.2020.超细水泥对固化软土早期抗压强度影响的试验研究[J].工程地质学报,28(4):685-696.doi:10.13544/j. cnki.jeg.2019-240.
    引用本文: 征西遥,刘秀秀,吴俊,等.2020.超细水泥对固化软土早期抗压强度影响的试验研究[J].工程地质学报,28(4):685-696.doi:10.13544/j. cnki.jeg.2019-240.
    Zheng Xiyao,Liu Xiuxiu,Wu Jun,et al.2020.Impact of ultra-fine cement on early compressive strength of cement stabilized soft soil[J].Journal of Engineering Geology,28(4):685-696.doi: 10.13544/j.cnki.jeg.2019-240.
    Citation: Zheng Xiyao,Liu Xiuxiu,Wu Jun,et al.2020.Impact of ultra-fine cement on early compressive strength of cement stabilized soft soil[J].Journal of Engineering Geology,28(4):685-696.doi: 10.13544/j.cnki.jeg.2019-240.

    超细水泥对固化软土早期抗压强度影响的试验研究

    IMPACT OF ULTRA-FINE CEMENT ON EARLY COMPRESSIVE STRENGTH OF CEMENT STABILIZED SOFT SOIL

    • 摘要: 为研究超细水泥含量对水泥固化软土的早期力学性能的影响,本文通过在普通水泥中加入不同掺量的超细水泥组成复合水泥固化剂用以固化软土。具体研究不同超细水泥掺量、不同初始含水率、及不同养护围压条件下,复合水泥固化剂对固化软土早期抗压强度及刚度的影响。采用自制K0围压养护装置(施加不同轴向压力的方式)、无侧限抗压强度仪(UCS)、X射线衍射仪(XRD)、电镜扫描仪(SEM)和低场核磁共振孔隙测试仪(NMR)等试验手段获取复合水泥固化软土不同龄期的抗压强度、刚度及微观结构的变化规律,并揭示其固化机理。研究结果表明:(1)相同轴向压力作用下,随着超细水泥掺量的增加,固化软土的抗压强度和弹性模量均有提高,其中复合固化剂中的活性颗粒发生水化反应生成大量胶凝产物用以黏聚土颗粒和填充孔隙,惰性颗粒用于填充土颗粒间的孔隙;(2)随着含水率的提高,固化软土中孔相对发育,从而使固化软土结构致密性减弱,抗压强度降低;(3)在K0围压养护7d时,固化软土的抗压强度和弹性模量随着轴向压力的提高而增加,表明养护围压对软土颗粒的压缩作用能提高固化软土的密实性,同时围压对固化软土产生有效应力,与水化产物共同促进固化软土形成密实的土骨架,进而使其在7d内具有较高的抗压强度。基于试验结果,建立轴向压力、含水率和超细水泥掺量等多因素的固化软土强度预测公式,并提出复合水泥固化软土结构模型,为工程实践提供理论基础。

       

      Abstract: In order to investigate the effect of ultra-fine cement on the early compressive strength development of cement stabilized soil, the composite cement binder is proposed by adding different contents of ultrafine cement into ordinary cement binder. Factors influencing the early strength of the composite cement stabilized soft soil were investigated. They include the content of the ultra-fine cement, the water content of soft soil and the curing stress. The curing equipment was designed and fabricated to apply the curing stress on the composite cement stabilized soil sample. The mechanical and micro-structural properties of the composite cement stabilized soft soil were obtained and analyzed via the unconfined compressive strength(UCS)test, the X-ray diffractometer(XRD)test, electron microscopy scanner(SEM)test, and proton nuclear magnetic resonance(NMR)test. The experimental results showed that at the same curing stress, the early compressive strength and the stiffness of the composite cement stabilized soft soil increased with the higher replacement contents of ultra-fine cement, regardless of the initial water content in the soft soil. The active particles with the smaller size in the composite cement binder could hydrate with free water in the stabilized soil, and then form the gelled products which would bind the soil particles and fill the pores of the soft soil. While, the inert particles with the coarser size in the composite cement binder were only served to fill the pores of the soil. With the higher initial water content of soft soil, the more amount of meso-scale pores were observed in the stabilized soil, which might induce the lower early compressive strength of the stabilized soil. With the increase of curing stress, the compressive strength and the stiffness of the composite cement stabilized soft soil enhanced in the 7-days curing period. The compactness of the stabilized soil became denser due to the higher curing stress. The function of the curing stress was found to develop the pre-stress state in the gel skeleton of the stabilized soil, and hence increase the compressive strength of the stabilized soil. Based on the test results, the formula was established to predict the early strength of the composite cement stabilized soil. At the same time, the hydration model of the soft soil stabilized by the composite cement binder was proposed.

       

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