地下工程混凝土的梯度功能设计与性能研究

Study of Performance and Functionally Gradient Design of Concrete Used in Underground Engineering

为了解决地下工程混凝土的耐久性技术难题，在地下工程混凝土的结构设计中引入梯度功能设计思路．采用Cl-离子扩散法检测功能梯度混凝土的抗渗性能，采用收缩试验评价其收缩变形一致性，采用显微硬度计、SEM测试其微观性能．结果表明，与单一的高性能混凝土相比，功能梯度混凝土的抗渗性能明显提高，特别是其抗离子渗透性，Cl-扩散系数DNEL下降了1～2个数量级，表观Cl^-扩散系数Da下降了50％左右；功能梯度混凝土的收缩变形匹配良好；适用于地下工程结构混凝土保护层的无细观界面过渡区水泥基材料的集料与水泥石界面过渡区由传统混凝土的60～100pm细化为30pm以下，从而有效地阻断了侵蚀性介质的渗入通道．

The design thought of gradient function is introduced to the structure design of concrete used in underground engineering to resolve its durability. The impermeability of functionally gradient concrete was studied by chloride ion diffusion method, the shrinkage deformation consistency of that was obtained by shrinkage test, and the microstructure of that was investi- gated by Microhardness and SEM. The results show that compared to the high performance concrete the impermeability of functionally gradient concrete is obviously improved, especially the ability to resist chloride ion penetration. The chloride ion diffusion coefficient is decreased by one to two orders of magnitude and the apparent chloride diffusion coefficient decreased by 50%. The shrinkage deformation of functionally gradient concretes is good. A meso-interfacial transition-zone-free cement-based material （MIF） for concrete covering of underground engineering structures was developed. In comparison to ordinary concrete, where the thickness of the interfacial transition zone is 60 to 100 μm, the thickness of interfacial transition zone of MIF is less than 30 vm, which effectively inhibits the penetration of corrosive media in MIF.