海水侵蚀下钢渣粉+水泥固化土强度劣化试验研究

为解决水泥固化海相软土工程性差、耐久性低,钢渣堆放、水泥生产污染环境等问题,采用激发钢渣粉替换部分水泥形成新型固化剂,选取海水中对固化土侵蚀影响较大的3种离子,深入探究单一离子引起的固化土强度劣化性能。通过室内物理力学试验,得到固化土在不同离子浓度的海水和蒸馏水养护条件下,各组无侧限抗压强度(UCS)变化规律;通过X-射线衍射(XRD)和电镜扫描(SEM)试验,得到钢渣粉+水泥固化土的微观形貌和物相随侵蚀时间的变化规律。研究发现钢渣粉中C4AF和C2AF可有效降低离子的侵蚀作用,3种离子对固化土的劣化影响为Mg^2+>Cl^-> SO4^2-。Cl^-侵蚀固化土会生成CaCl2和F’s盐,F’s盐的无胶凝性引起固化土劣化;SO4^2-与胶凝材料反应会生成石膏、硅钙石和钙矾石,当这些物质产生的体积膨胀量大于孔隙体积时,会使固化土产生裂纹;Mg^2+侵蚀会生成Mg(OH)2沉淀、Mg-S-H和Mg-A-H,同时也会降低孔隙溶液pH值,引起水化物凝胶的分解,造成固化土强度劣化。从微观结构与物相变化分析宏观物理力学特性变化和侵蚀机理,为钢渣粉+水泥固化软土在工程上的使用提供一定的理论依据。

Experimental study on strength degradation of steel slag + cement-solidified soil under seawater erosion

In order to solve the problems of poor cement projects, such as low durability, low steel slag stacking, and cement production pollution environment, the steel slag is used to replace part of the cement to form a new curing agent, and three kinds of ions which have great influences on the solidified soil erosion in seawater are selected. The strength degradation properties of solidified soil caused by a single ion are thoroughly studied. Through the indoor physical and mechanical tests, the change laws of unconfined compressive strength (UCS) of each group under different seawater and distilled water curing conditions are obtained. The X-ray diffraction (XRD) and electron microscopy (SEM) tests are carried out to obtain the microscopic morphology of the steel slag + cement-solidified soil and the change of its phase with the erosion time. It is found that C₄AF and C₂AF in steel slag can effectively reduce the erosive effects of ions. The effects of three ions on the deterioration of solidified soil are Mg²⁺> Cl^-> SO₄^2-. The Cl^--eroded solidified soil will form CaCl₂ and F's salt, and the non-gelling properties of F's salt will cause deterioration of solidified soil. SO₄^2- reacts with the gelling materials to form gypsum, wollastonite and ettringite. When these materials produce a volume expansion larger than the pore volume, the solidified soil will be cracked. Mg²⁺ erosion will form Mg(OH)₂ precipitate, Mg—S—H and Mg—A—H, and reduce the pH values of the pore solution, causing decomposition of the hydrate gel, and resulting in the deterioration of the strength of the solidified soil. The change of the macroscopic physical and mechanical properties and erosion mechanism are analyzed from the changes of microstructures and phases. This research may provide a theoretical basis for the use of steel slag powder + cement-solidified soft soil in engineering.