高寒地区桥墩混凝土开裂原因及修补技术应用研究

发布时间：2019-03-02 15:31

【摘要】：裂缝是混凝土工程中普遍存在而又难以解决的问题，也是混凝土结构病害和缺陷的集中表现。高寒地区，年平均气温较低，日温差较大，紫外线照射强烈，气候干燥。这些因素极大的加剧了混凝土的塑性收缩、自收缩、干燥收缩、冷收缩等。因此，研究高寒地区混凝土裂缝修补材料、技术与工艺，采取有效修补技术以防止裂缝进一步发展、维护混凝土结构的使用性能，对提高混凝土结构的耐久性与使用寿命具有重要的现实意义。论文的主要工作和成果包括以下几个方面：（1）通过对高寒地区桥梁墩台和隧道裂缝进行现场调查和分类，桥梁墩台裂缝主要为非结构性裂缝，其中以收缩裂缝为主，隧道裂缝既有结构性裂缝又有非结构性裂缝，但结构性裂缝偏多。提出了桥梁混凝土裂缝的危害及控制途径，其中非结构性裂缝的危害主要有引起钢筋的锈蚀、加速混凝土碳化和缩减了混凝土的耐久性及使用寿命。结构性裂缝的危害有降低的结构承载能力及影响结构的使用安全。（2）对高寒地区典型的桥梁和隧道裂缝宽度及深度进行了检测，并且对裂缝宽度、深度和走向进行了统计分析和特征分析。通过PH值测定实验方法，，建立了裂缝宽度与碳化耐久性之间的对应关系，以PH=12.0时钢筋钝化膜失效为依据，提出了裂缝宽度为0.21mm是高寒地区铁路桥墩裂缝允许宽度限值。分别从环境因素、保湿养护、冻融和氯盐环境及混凝土材料对裂缝的影响进行了分析。（3）用于裂缝表面封闭的改性FEVE氟碳涂料与普通市售柔性氟碳相比，老化性能良好，且具有附着力强、拉伸强度高和弹性好的特点；聚合物水泥复合涂层具有弹性好、粘结力强、耐久性好等优点。用于裂缝注浆的柔性环氧树脂和聚氨酯的各项性能指标均满足高寒地区特殊环境下注浆材料技术要求，特别是断裂伸长率提高明显，并且与基体粘结强度高。提出了高寒地区桥梁墩台混凝土裂缝总体修补方案。并对混凝土裂缝进行长期动态跟踪监测；对裂缝修补材料的高原适应性进行了选点实验。（4）对胶体抗压强度和抗拉强度进行了实验研究，由实验结果对比分析可得：混凝土灌注胶体改性后的抗压强度有所降低，但是其降低程度对胶体的抗压强度影响不是很大。改性后的灌注胶体抗拉强度及伸长率得到了改善，且都有所提高。根据高寒地区桥墩和隧道混凝土开裂原因、修补技术的研究结果，对高寒地区桥梁墩台和隧道混凝土裂缝进行了现场修补试验研究。
[Abstract]:Crack is a common and difficult problem in concrete engineering. It is also a concentrated manifestation of defects and defects of concrete structure. In the alpine region, the annual average temperature is lower, the daily temperature difference is larger, the ultraviolet radiation is strong, and the climate is dry. These factors greatly aggravate the plastic shrinkage, self-shrinkage, drying shrinkage, cold shrinkage and so on. Therefore, the material, technology and technology of concrete crack repair in alpine area are studied, and the effective repair technology is adopted to prevent the further development of cracks and maintain the service performance of concrete structure. It is of great practical significance to improve the durability and service life of concrete structures. The main work and achievements of this paper include the following aspects: (1) through on-the-spot investigation and classification of bridge pier-abutment and tunnel cracks in alpine region, the cracks of bridge pier and abutment are mainly non-structural cracks, among which shrinkage cracks are the main ones. Tunnel cracks have both structural and non-structural cracks, but structural cracks are more. The harm and control measures of bridge concrete cracks are put forward, among which the non-structural cracks mainly cause corrosion of steel bars, accelerate the carbonization of concrete and reduce the durability and service life of concrete. The damage of structural cracks has reduced structural bearing capacity and affects the safety of structural use. (2) the crack width and depth of typical bridge and tunnel in alpine and cold area are tested, and the crack width, depth and trend are analyzed statistically and characteristic. The corresponding relationship between crack width and carbonation durability is established by measuring PH value. Based on the failure of rebar passivation film in PH=12.0, it is proposed that the crack width of 0.21mm is the limit value of crack width of railway piers in alpine and cold regions. The effects of environmental factors, moisture retention, freezing and thawing, chloride environment and concrete materials on cracks were analyzed. (3) the modified FEVE fluorocarbon coating, which is used to seal the crack surface, has good aging property, strong adhesion, high tensile strength and good elasticity compared with the general market flexible fluorocarbon coating; Polymer cement composite coating has the advantages of good elasticity, strong adhesion and good durability. The properties of flexible epoxy resin and polyurethane used in crack grouting meet the technical requirements of grouting materials in the cold area, especially the elongation at break is improved obviously, and the bond strength between epoxy resin and matrix is high. The overall repair scheme for concrete cracks of bridge pier and abutment in alpine region is put forward. Long-term dynamic follow-up and monitoring of concrete cracks are carried out, and point selection experiments are carried out on the plateau adaptability of crack repairing materials. (4) the compressive strength and tensile strength of colloid were studied experimentally. The experimental results showed that the compressive strength of concrete modified colloid was decreased, but the degree of decrease had little effect on the compressive strength of colloid. The tensile strength and elongation of the modified colloid were improved, and both of them were improved. According to the cracking reason of bridge pier and tunnel concrete in alpine and cold area and the research result of repair technology, the site repair test of bridge pier and tunnel concrete crack in high cold area is carried out.
【学位授予单位】：兰州交通大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U445.7

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