混凝土表面渗透型超疏水涂层的仿生设计、构建与性能研究

The durability of concrete structures is one of the most important subjects in the field of civil engineering at present. Most of the deterioration mechanisms of concretes can be linked in one way or another with the presence and movement of water. Therefore, it is of importance to find appropriate waterproof treatments for concrete to improve its durability. In this project, organic silane /SiO2 super-hydrophobic coating is prepared by the sol - gel method combined with phase separation, self-assembly technique. This super-hydrophobic coating is structured on concrete surface based on bionics theory, through the design of the surface chemical composition and microstructure. The formation process of super-hydrophobic coating on the surface of concrete will be studied. The interaction mechanism between the super-hydrophobic coating and concrete surface will be studied, so as to realize the controllable regulate on chemical composition and microstructure of concrete surface. We will explore the formation mechanism of micro/nano structure on the surface and how it influences the concrete permeability. In addition, thermodynamics and hydrodynamics action of water on concrete surface treated by super-hydrophobic coating will be calculated, and thereby determine the movement regularity and mechanism of water in the concrete. In order to investigate the application of organic silane /SiO2 super-hydrophobic coating , the internal relationship between the coating composition, microstructure and concrete durability must be figured out. Therefore, laboratory simulation test and the long-term beach exposure test will be carried out to determine the effects of super-hydrophobic coating on some kinds of erosion process. According to the above studies, this project will provide theoretical basis and technical support for the concrete surface protection.

混凝土耐久性问题是当今土木工程界面临的重大课题。在诸多耐久性劣化过程中，水分的存在和迁移是不可或缺的必要条件和关键因素，进行防水处理则是提高混凝土耐久性的有效方法之一。本项目基于仿生学理论，从表面化学组成与微观结构设计出发，利用溶胶-凝胶法，结合自组装、相分离技术，根据混凝土材料的组成、结构特点，直接在其表面构建有机硅烷/SiO2渗透型超疏水涂层。研究超疏水涂层在混凝土表面形成过程的规律性，实现对混凝土表面化学组成与微观结构的可控调节，探索表面微纳米二级结构的形成机理及对混凝土渗透性的影响。通过理论计算探讨经超疏水涂层处理后水分在混凝土表面的热力学与流体动力学行为，明确水在混凝土中的运动规律与机理。通过实验室模拟试验与海边现场长期暴露试验，综合研究超疏水涂层的组分、结构与混凝土耐久性的内在关系，确定超疏水涂层对各类侵蚀过程发展演变规律的影响机理，为混凝土表面防护处理提供理论依据与技术支撑。

混凝土耐久性问题是当今土木工程界面临的重大课题。在诸多耐久性劣化过程中，水分的存在和迁移是不可或缺的必要条件和关键因素，进行防水处理则是提高混凝土耐久性的有效方法之一。本项目首先从诸多硅烷材料中进行优选，同时利用溶胶-凝胶法结合相分离技术，合成出硅烷/TEOS复合材料和硅烷/SiO2溶胶复合材料；然后从混凝土表面化学组成与微观结构设计出发，在其表面构建硅烷/TEOS疏水涂层和硅烷/SiO2溶胶超疏水涂层；最后重点研究了两种疏水涂层对混凝土吸水性能、抗氯离子侵蚀、抗硫酸盐侵蚀、抗碳化和抗冻融能力的影响，并探索了疏水涂层对混凝土耐久性能提升机理。研究结果表明，（1）异丁基三乙氧基硅烷可以与TEOS（正硅酸乙酯）在Span 80和PPG O复合乳化剂作用下，合成出性质稳定的硅烷/TEOS复合材料，并在混凝土表面形成防水效果良好的疏水涂层，透水指数下降50%左右；（2）在硅烷/TEOS疏水涂层的防护下，即使混凝土表面出现0.2mm的裂缝或者受到深达5mm的磨损，仍然具有非常良好的憎水性能，毛细吸水系数比未处理时降低40%~50%；（3）硅烷/TEOS疏水涂层可以有效地阻止氯离子在混凝土中的渗透和扩散，氯离子扩散系数仅为1.3×10-12m2·s-1；（4）采用硅烷和SiO2溶胶可以在混凝土表面构建超疏水涂层，水在混凝土表面的接触角达到149.7°，利用SiO2溶胶与Ca(OH)2的二次水化反应，可使混凝土表面微观结构更加致密，进一步提高了混凝土的防水性能；（5）硅烷/SiO2溶胶超疏水涂层有效降低了Cl-、SO42-等离子在混凝土中的浓度和扩散系数；通过防止水分的扩散，该涂层使混凝土的碳化深度降低了60%；经该涂层处理的混凝土，经过150次冻融循环后，质量损失仅为0.48%，相对动弹性模量达到90.6%，提高了其抗冻融能力。本项目所研发的硅烷/TEOS疏水涂层和硅烷/SiO2溶胶超疏水涂层已经应用于青荣高速铁路双岛湾跨海大桥项目，经过1年多的运行，目前防护效果良好。因此，本项目为提升我国海洋环境下混凝土的耐久性，保障混凝土结构的长寿命运行、低成本维护提供了一定的理论基础与技术参考。