Aspects of Permeability in Modelling of Concrete Exposed to High Temperatures
Aspects of Permeability in Modelling of Concrete Exposed to High Temperatures
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DOI：
10.1007/s11242-012-0066-1
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发表时间：
2012-12-01
影响因子：
2.7
通讯作者：
Bicanic, N.
中科院分区：
文献类型：
--
作者：
Davie, C. T.;Pearce, C. J.;Bicanic, N.
混凝土中热量和水分传输的发展对孔隙压力的发展至关重要，孔隙压力被认为是暴露于高温下的混凝土中损坏和热剥落的主要驱动因素。根据文献中某些材料特性和本构或参数描述值的不确定性和变化，进行了各种数值实验，以研究固有渗透率、与温度相关的渗透率演变以及作为饱和度函数的流体相的相对渗透率在预测和分析正常条件下混凝土干燥行为中的意义，低温、等温条件和暴露于在火灾期间可能遇到的非常高的温度条件下。混凝土的一个完全耦合的湿热力学有限元模型，渗透率值和参数函数在模型中根据需要改变。质量损失和气体压力随时间的发展的结果被认为是在有关的潜在的发生损坏和热剥落，这被认为是不同的这些过程。分析表明，渗透率，其随温度的变化，是非常重要的控制在低温和高温下的预测行为。其中最重要的是用来定义相对渗透率的关系。这些都被证明是强有力的控制低温和高温问题的分析结果，并可能意味着明显不同的渗透性值相同的混凝土。
The development of heat and moisture transport in concrete is critical to the development of pore pressures, which are thought to be a primary driver of damage and thermal spalling in concrete exposed to elevated temperatures. In the light of uncertainty and variation in the value of certain material properties and constitutive or parametric descriptions found in the literature, various sets of numerical experiments were conducted to investigate the significance of the intrinsic permeability, the evolution of permeability related to temperature and the relative permeability of the fluid phases as functions of saturation in predicting and analysing the behaviour of concrete drying under normal, low temperature, isothermal conditions and under exposure to very high temperature conditions as might be encountered during a fire. A fully coupled hygro-thermo-mechanical finite element model for concrete was employed with the permeability values and parametric functions altered in the model as required. Results of mass loss and the development of gas pressures with time were considered in relation to the potential for the occurrence of damage and thermal spalling, which is thought to be variously related to these processes. The analyses showed that permeability, and its variation with temperature, are very important in controlling the predicted behaviour at both low and high temperatures. Most significant of all were the relationships chosen to define the relative permeabilities. These were shown to strongly control the results of analyses of both low and high temperature problems and to potentially imply apparently different permeability values for the same concrete.