水泥基材料气体渗透性研究进展

Recent Research Development on Gas Permeability of Cement-based Materials

综述了水泥基材料气体渗透机理、渗透性测试原理与方法以及气体渗透性的预测模型。气体在水泥基孔隙材料中的渗流过程包括粘性流动、边界滑流以及Knudsen扩散。水泥基材料的透气性测试分为常压流量法、变压流量法以及变压压力法。水泥基材料通过物理孔隙结构和孔隙含水率影响气体渗透性。现有文献表明:气体渗流规律缺少关于对纳米尺度上Knudsen扩散对整体渗流总体贡献的定量研究,使气体渗透性与材料微观结构的模型的适用性受到影响;常压流量法物理原理明确,是实验室测量气体渗透性的标准方法,其他方法需要与之比对来确定其有效性;水泥基材料孔隙结构影响气体渗透性的关键参数是孔隙率和渗流特征尺寸,相关模型对水泥净浆适用性较好,但对砂浆和混凝土较差;水泥基材料孔隙含水率与气体渗透性的关系可通过Van-Genuchten-Mualem模型来表达,但模型参数离散性较大。

The involved flow mechanisms, the experimental methods and the prediction models for the gas permeability of cement-based materials were reviewed. The gas flow mechanisms in pores include the viscous flow, boundary slip and Knudsen diffusion. The experimental methods include the constant pressure flow method, variable pressure flow method and variable pressure method. The microstructure of materials has impact on the gas permeability through the pore structure and pore saturation. On the basis of available literature research, it is found that the contribution of Knudsen diffusion to the global gas flow is not clear in pores on nano-scale so that the prediction models of permeability has not enough basis. The constant pressure flow method is proved to be the most reliable experimental method and the validity of other methods should be tested against this method. The key parameters of pore structure for gas permeability are porosity and characteristic size of gas flow, and the relevant prediction models apply better to cement pastes than to mortars and concretes. The impact of pore saturation on gas permeability can be described by Van-Genuchten-Mualem model but the regressed parameters from literature are scattered.