硬化水泥浆体气体渗透特征研究

渗透性直接决定了有害物质在混凝土等水泥基材料中的传输速度,是影响混凝土耐久性的关键指标。基于水泥浆体三维孔隙结构和压汞试验数据,分别采用Katz-Thompson方程和格子Boltzmann方法模拟计算水泥浆体试样的渗透率,并与气体渗透测试结果进行对比,其结果表明:硬化水泥净浆气体渗透率测试结果为3.82×10^-18~7.29×10^-18 m²;Katz-Thompson方程的预测结果仅具有数量级的准确度,不能真实准确地预测水泥浆体孔隙结构的渗透率;格子Boltzmann方法能够准确地预测水泥浆体的本质渗透率,为4.88×10^-19~15.48×10^-19 m²;气体渗透测试结果比模拟结果高约2~10倍,表明水泥浆体中毛细孔依然是渗透的主要路径,而气孔和微裂缝仅在局部起到了提高气体渗透率的作用。

Characterization of Gas Permeability of Hardened Cement Paste

Permeability directly determines the transport speed of harmful substances in porous volume of cement-based materials (such as concrete). Thus, it is the key to influence the durability of cement-based materials. Based on 3D pore structure and MIP (Mercury intrusion porosimetry) result of cement paste, the permeability of cement paste was calculated by Katz-Thompson equation and lattice Boltzmann method (LBM), respectively. Then, the calculated values were compared with those by gas permeability test. Results show that the tested gas permeability of cement paste is of 3.82×10^-18 m² to 7.29×10^-18 m². The Katz-Thompson equation only has the accuracy of order of magnitude and cannot accurately predict the permeability of cement paste. In contrast, the lattice Boltzmann method accurately predicts the intrinsic permeability of cement paste, 4.88×10^-19 m² to 15.48×10^-19 m², which is about 2 to 10 times smaller than the tested ones. This implies that the capillary pores in cement paste are still the main path of gas flow, whereas the air holes and micro cracks only locally improve the gas permeability.