不同水灰比的牛顿型水泥浆液流变性随时间变化规律

水化时间与水灰比对水泥浆液流变性有重要影响，进而决定浆液在岩土体中的运动扩散效果。为研究水化时间与水灰比综合作用对牛顿型水泥浆液流变性的影响作用，以目前实践工程中广泛应用的普通硅酸盐水泥浆液为研究对象，采用NXS-11A 型旋转黏度计对水灰比为1.5、2.0、5.0、10.0的水泥浆液分别在0、5、10、20、30及60 min 6个水化时间的流变性进行了试验研究，并探讨了水化时间、水灰比及其综合作用对牛顿型水泥浆液流变性的定量变化规律。研究结果表明：水化时间、水灰比均对牛顿型水泥浆液动力黏度具有显著性的影响，牛顿型水泥浆液动力黏度随水化时间表现为增长的变化趋势，而随水灰比则呈现为下降的变化规律；指数模型是反映水化时间与水灰比综合作用对牛顿型水泥浆液动力黏度定量变化关系的较优模型，由其得到的理论值与试验值间的误差均在10%以内，而由线性、对数与幂函数3种模型得到的理论值与试验值间有80%的误差都大于10%；并以此构建了考虑水化时间与水灰比综合作用的牛顿型水泥浆液流变方程。研究结果对水泥浆液流变性理论的发展和完善具有一定的理论意义，也可为建筑物基础托换、隧道堵水防渗、基坑加固、地质灾害防控、农业水土保持等实际工程应用提供一定的技术支撑。

Hydration-time-dependent rheological behaviors of Newtonian cement grouts with different water cement ratios

As an inorganic cementitious material with low cost and good property, cement grouts has been widely used in many engineering fields such as highways, tunnel, slopes, foundations, railways, construction, mining and water conservancy. As for cement grouts, the rheological properties of cement grouts are significantly affected by the changes of the hydration time and the water cement ratio, which determine the diffusion state of cement grouts in rocks and soils and have a great influence on the outcome of projects. However, the current research only considered the influence of a single factor on rheological properties of cement grouts, the combined effect of these factors has not been well understood. In this study, Portland cement grouts, a widely used material in practical grouting engineering are used as the research object and the Portland cement grouts with four water cement ratios which are the typical cement ratio of Newtonian fluid (1.5, 2.0, 5.0,10.0) at six moments (0,5,10, 20, 30 and 60 min) were chosen as the experimental group, then combined with the numerical analysis and the theoretical method the effect of hydration time and water cement ratio on rheological properties of Newtonian cement grouts was studied. The results show that: the hydration time and the water cement ratio both have significant influence on dynamic viscosity of Newtonian cement. The former shows a trend of growth, and the longer the hydration time is, the faster the growth trend, the latter shows a trend of decreased, and the smaller the water cement ratio is, the more significant the decreasing trend. Combined with the perspective of statistical theory, practical applicability and accuracy, this study selects four theoretical models to discuss the quantitative relationship of the effect of hydration time and water cement ratio on rheological properties of Newtonian cement grouts, and the four theoretical models are the most basic in mathematics, also the most widely used in practice: the linear model, exponential model, power function model and logarithm model. Then the optimal model will be determined from the fourth according to statistical theory and experimental verification. Comparing the determination coefficients and the regression values of the four fitting models, the exponential model is the optimal model for the quantitative change of dynamic viscosity of Newtonian cement to react the effect of hydration time and water cement ratio on rheological properties of Newtonian cement grouts. The difference between the theoretical value and the experimental value of the exponential model is within 10%, while more than 80% of the difference between the theoretical value and the experimental value of linear, logarithmic and power function models are greater than 10%. Thus, the rheological equation of Newtonian cement considering the hydration time and the water cement ratio are built. The research results can not only improve the rheological theory of Newtonian cement grouts, but also provide certain technical support for practical engineering applications such as the building foundation support, tunnel water plugging and seepage prevention, foundation reinforcement, geological disaster prevention and control, and agricultural soil conservation.