粉煤灰充填材料早龄期物理力学特性及其水化过程分析

Physic-mechanical properties of fly ash filling material at early age and its hydration process

针对粉煤灰充填材料早期强度低、变形量大、流动性差、泌水严重等缺陷,基于电阻率法和力学特性测试法研究3种配比粉煤灰充填材料早龄期的体积电阻率、孔隙溶液电阻率、单轴抗压强度和弹性模量随时间的变化规律;结合充填材料初始孔隙度和1 d孔隙度的测试结果,对孔隙度随时间的变化规律作进一步分析。结果表明:(1)材料的体积电阻率随时间呈升高、降低、再升高的变化规律,孔隙溶液的电阻率随时间呈先急剧下降后趋于稳定的变化规律,但材料的电阻率变化在时间上和数值上受粉煤灰掺量的影响;(2)材料的单轴抗压强度和弹性模量随水化时间的延长而增大,随粉煤灰掺量的增加而降低;(3)材料的孔隙度随水化时间的延长呈负指数规律降低,随粉煤灰掺量的增加先降低后增加;(4)在水化后期,材料的单轴抗压强度和弹性模量与其体积电阻率呈对数相关;(5)材料早龄期的水化过程可分为吸附期、溶解期、凝结期和硬化期4个阶段。研究结果为进一步了解、改善粉煤灰充填材料早龄期的物理力学特性和实现材料特性的无损检测提供了一定的理论与应用参考。

Fly ash filling materials at early age have low strength,large deformation,poor liquidity and severe water bleeding. Several experiments on the fly ash filling materials with three different mixing ratios at early age were carried out to study the bulk electrical resistivity,the electrical resistivity of pore solution,the uniaxial compressive strength and the elastic modulus varied with time. The porosity variation with time was analyzed with the initial porosity and measured 1 d porosity of the filling material. The bulk resistivity was found to increase-decrease-increase with time. The resistivity of pore solution decreased firstly then tended to a stable value. Both the bulk resistivity and the resistivity of pore solution were influenced by the dosage of fly ash. The uniaxial compressive strength and elastic modulus increased with the extending of the hydration time,but decreased with the increase of the dosage of fly ash. The porosity decreased inversely exponentially with the extending of hydration time and decreased firstly then increased with the dosage of fly ash. In the late age of hydration,both the uniaxial compressive strength and elastic modulus were related to bulk resistivity logarithmically. The hydration process at early age can be divided into four stages,such as adsorption period,a dissolution period,setting period and hardening period.