【作者】 杨进波；

【导师】 阎培渝；

【作者基本信息】 清华大学 ， 土木工程， 2009， 博士

【摘要】 混凝土保护层指最外层钢筋到混凝土外表面之间的一层混凝土,是钢筋混凝土结构的一部分。与混凝土材料相比较,混凝土保护层的结构与渗透性具有特殊性。混凝土保护层是钢筋混凝土结构抵抗外界侵蚀的重要防线,对钢筋混凝土结构的耐久性具有重要意义。本文研究了混凝土保护层的结构与渗透性,以及混凝土保护层渗透性的现场检测方法。研究内容与取得的成果如下:(1)采用数字图像分析技术,以毫米为单位,在垂直混凝土保护层表面的一维方向上逐层分析粗骨料的体积含量等分布特征。由于边界效应,混凝土在垂直成型面方向上由外到内粗骨料体积含量逐渐增加,超过边界效应层后,骨料分布趋于均匀。边界效应层的厚度实际上在5mm左右。粗骨料最大粒径对边界效应层厚度的影响并不明显。对于级配良好的粗骨料,控制边界效应层厚度的是粗骨料最小粒径。采用自行设计的试验方法对钢筋的卡阻效应进行了初步研究。在满足规范要求的条件下,钢筋对粗骨料的通过有一定的阻挡作用。这主要表现为保护层混凝土中的粗骨料含量略少,浆体量略多;但是卡阻效应对保护层内的骨料粒径分布影响不大。(2)通过对PERMIT离子迁移试验与NEL试验进行对比试验,证明两种方法的实验结果有良好的相关性。PERMIT离子迁移试验方法设备简单,操作方便,试验时间短,可以正确反映保护层混凝土或结构表层混凝土的抗氯离子渗透性。(3)通过室内试验并结合青岛海湾大桥工程现场实测,改进了PERMIT试验结果的分析和数据处理方法,提出了用回路最大电流值来计算氯离子扩散系数,简化了PERMIT离子迁移试验方法。PERMIT离子迁移试验方法可以用于评价透水模板布对混凝土保护层抗渗性的改善效果。PERMIT离子迁移试验给出的氯离子扩散系数可以定性地评价混凝土的抗氯离子渗透性,用于混凝土工程的现场质量控制。更多还原

【Abstract】 The cover concrete is defined as a layer of concrete between the most outside steel bar and the concrete surface. It is a part of the real reinforcement concrete structure. The structure and permeability of cover concrete aredifferent from the bulk concrete. Cover concrete is the most important defensive layer of reinforcement concrete structure to resist environmental deteriorations. The structure and permeability of cover concrete, as well as the in-situ test method for testing the permeability of cover concrete are researched. The main content and results are listed as follows:(1) Using digital image processing techonology, along the vertical direction of the concrete surface, the distribution characterics of coarse aggregate are studied millimeter by millimeter. The coarse aggregate volume amount increases from the surface to the inside caused by wall effect. Exceeding the wall effect layer, the distribution characteristics of coarse aggregate become uniform. In fact, the thickness of wall effect layer is about 5mm and the maximum diameter of coarse aggregate does not influence the thickness of wall effect layer obviously. When the grading design of coarse aggregate is reasonable, the thickness of wall effect layer is ones equaling almost to the minimum diameter of coarse aggregate. Using self designed method, the obstruction effect is studied elementarily. Although the neat distance of steel bars meets the request of code, the steel bars still obstruct some coarse aggregates. It behaves that there is more mortar and less aggregate in cover concrete. But the grading is not influenced by the obstruction effect.(2) Parallel experiments are carried out for PERMIT ion migration test and NEL test. The experimental results prove that there is a good correlation between them. The PERMIT ion migration test can be carried out quickly and effectively on site with minimum prior planning. It can reflect the permeability of cover concrete or surface concrete correctly.(3)Through the laboratory tests and in-situ test in the construction of Qingdao Bay, the analysis and calculation procedure of experimental data is modified and a new equation for calculating the chloride diffusivity using the peak current is given. It can simplified the test and reduce experimental error. The PERMIT ion migration test can be used to evaluate the improving effect of the resistance to the chloride ion penetration caused by CPF. The chloride diffusivity of the PERMIT ion migration test is capable to be used for evaluating the resistance to the chloride ion penetration of cover concrete and controlling the construction quality in-situ.更多还原