短期持压荷载与混凝土内水分传输的耦合过程

Water Transport in Concrete Coupled with Short-term Sustained Compressive Loading

荷载与环境因素的耦合作用影响着混凝土内物质传输过程和混凝土结构的服役寿命。为实现短期持续加载和混凝土内水分传输的耦合作用，基于改进的混凝土吸水实时测量装置，对中空圆柱体混凝土试件持续受压加载32h的同时，按规定时间间隔记录水平观测管内水柱长度的变化，测得混凝土累积吸水量曲线，开展了短期持压荷载作用下低应力水平（0～50％）对混凝土毛细吸水性能影响分析，并根据试验结果建立了相对吸水率与体应变关系。基于扩展Darcy定律的非饱和流体理论（UFTmodel），采用指数和幂函数两种形式的水力扩散系数，开展了不同应力水平下混凝土中水分分布的预测分析。结果表明：短期持压荷载对混凝土的毛细吸水性能影响显著；在0-50％应力水平范围内，随着应力水平的提高，混凝土的累积吸水量和初始吸水速度先减小后增大，而后期吸水率和水分侵入深度单调增加；根据UFT模型计算的水分渗透深度预测值与实际观测值吻合较好。

Mass transport process and service life of concrete structures are affected by the coupling of loading and environmental conditions. In order to realize the coupled effect of short-term sustained loading and water absorption process within concrete, the capillary absorption of the hollow cylinder specimens at different compressive stress levels for 32 h was investigated by an improved device for real-time measurement of cumulative absorbed water. According to the cumulative water absorption curve measured by the water length variation through the horizontal observation tube, the effect of low stress levels on the capillary absorption in concrete subjected to short-term sustained compressive loadings was analyzed. The linear quantitative relationship between the relative sorptivity and volumetric strain was discussed based on the experimental results. The water content distribution of concrete at various stress levels, i.e. 0-50%, was predicted by two hydraulic diffusivity fimctions the exponential-law and power function, based on the unsaturated flow theory （UFT） model of the extended Darcy＇s law. The results indicate that short-term sustained compressive loadings have a great influence on the capillary absorption of concrete. In the range of stress levels studied currently, the cumulative water content and initial water absorption rate initially decrease and then increase, and the secondary sorptivity and water penetration depth monotonously increase with the increase of stress level. Moreover, the predicted data of water penetration depth obtained by UFT model are similar to the experimental results.