冻融循环作用下的混凝土应力波传播特性
发布时间：2018-11-13 07:24
【摘要】：目前,国内外关于混凝土耐久性的研究成果显著,但在混凝土结构的安全检测与评价方面仍有待改进。无损检测技术作为一种经济、合理、简捷、高效的检测手段,经常应用于混凝土检测中。通过对冻融循环作用下的混凝土应力波传播特性进行研究,可为混凝土的耐久性研究提供参考,同时对水利工程的安全与运行具有十分重要的现实意义。本文通过室内冻融试验,对冻融循环作用下的混凝土弹性波波速、动弹性模量等进行测试,研究不同水灰比、引气剂掺量、冻融次数对弹性波波速、动弹性模量的影响规律,分析弹性波波速与动弹性模量之间的关系,建立混凝土冻融损伤模型。本文的主要研究内容及结论如下:1)采用冲击弹性波无损检测技术对冻融循环作用下混凝土试件的弹性波传播特性进行研究,分析不同水灰比、引气剂掺量及冻融循环次数时的混凝土试件的弹性波传播规律。试验结果表明:在未添加引气剂的试件中,随着冻融次数的增加,试件的弹性波波速都会减小;试件的水灰比越小,弹性波波速越大;水灰比越大,弹性波波速的下降速度越快。添加引气剂对混凝土试件的弹性波波速产生一定的影响,会使其弹性波波速减少,不过引气剂的添加也会让弹性波波速的衰减过程更为平缓,衰减幅度变小。2)通过对冻融循环作用后的混凝土试件的动弹性模量进行测试,研究水灰比、引气剂掺量以及冻融循环次数等因素对混凝土动弹模的影响规律。试验结果表明:随着冻融次数的增加,试件的动弹性模量均在减少;添加引气剂在一定程度上会引起混凝土试件动弹性模量的减少,但添加引气剂的混凝土试件的动弹性模量的衰减幅度较小,比未添加引气剂的混凝土试件的表现更为稳定。3)通过分析冻融循环作用下混凝土动弹性模量与弹性波传播特性参数之间的联系,建立冻融循环作用下的混凝土耐久性检测模型,为混凝土的冻融研究提供新的检测方法。对试验中的8组试件的弹性波波速与动弹性模量进行函数拟合,发现幂函数拟合效果较好。分别以动弹性模量、弹性波波速为损伤因子确定混凝土冻融损伤度,分析混凝土冻融破坏程度。4)利用相对动弹性模量以及质量损失率作为混凝土是否发生破坏的判断依据,结合试验成果分析混凝土的冻融破坏情况。
[Abstract]:At present, the research results of concrete durability at home and abroad are remarkable, but the safety detection and evaluation of concrete structures still need to be improved. As an economical, reasonable, simple and efficient testing method, nondestructive testing technology is often used in concrete testing. By studying the propagation characteristics of concrete stress wave under the action of freeze-thaw cycle, this paper can provide a reference for the study of concrete durability, and also has a very important practical significance for the safety and operation of water conservancy projects. In this paper, the elastic wave velocity and dynamic elastic modulus of concrete subjected to freeze-thaw cycle are tested through indoor freezing and thawing tests. The effects of different water / cement ratio, air entraining agent content and freeze-thaw times on the elastic wave velocity and dynamic elastic modulus are studied. The relationship between elastic wave velocity and dynamic elastic modulus is analyzed, and the damage model of concrete freeze-thaw is established. The main contents and conclusions of this paper are as follows: 1) the elastic wave propagation characteristics of concrete specimens subjected to freeze-thaw cycles are studied by using impact elastic wave nondestructive testing technique, and different water-cement ratios are analyzed. The elastic wave propagation law of concrete specimen with air entraining agent and freeze-thaw cycle times. The results show that the elastic wave velocity decreases with the increase of freeze-thaw times, and the smaller the water-cement ratio, the greater the elastic wave velocity. The larger the water-cement ratio, the faster the velocity of elastic wave decreases. The addition of air entraining agent has a certain effect on the elastic wave velocity of concrete specimen, which will reduce the elastic wave velocity, but the air entraining agent will also make the attenuation process of elastic wave velocity more smooth. The attenuation amplitude becomes smaller. 2) by measuring the dynamic elastic modulus of concrete specimens after freeze-thaw cycle, the effects of water / cement ratio, air entraining agent content and freeze-thaw cycle times on the dynamic elastic modulus of concrete are studied. The results show that with the increase of freeze-thaw times, the dynamic elastic modulus of the specimens decreases. The addition of air entraining agent can reduce the dynamic elastic modulus of concrete specimen to some extent, but the attenuation range of dynamic elastic modulus of concrete specimen with air entraining agent is smaller. The performance of concrete specimens without air entraining agent is more stable. 3) the relationship between the dynamic elastic modulus of concrete under freeze-thaw cycle and the parameters of elastic wave propagation characteristics is analyzed. The durability detection model of concrete under freeze-thaw cycle is established, which provides a new testing method for freeze-thaw research of concrete. The elastic wave velocity and dynamic elastic modulus of 8 groups of specimens were fitted by function, and it was found that the power function fitted well. The damage degree of concrete is determined by dynamic elastic modulus and elastic wave velocity. 4) the relative dynamic elastic modulus and mass loss rate are used as the basis for judging whether the concrete is damaged or not. The freeze-thaw failure of concrete is analyzed based on the test results.
【学位授予单位】：重庆交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU528
本文编号：2328408
[Abstract]:At present, the research results of concrete durability at home and abroad are remarkable, but the safety detection and evaluation of concrete structures still need to be improved. As an economical, reasonable, simple and efficient testing method, nondestructive testing technology is often used in concrete testing. By studying the propagation characteristics of concrete stress wave under the action of freeze-thaw cycle, this paper can provide a reference for the study of concrete durability, and also has a very important practical significance for the safety and operation of water conservancy projects. In this paper, the elastic wave velocity and dynamic elastic modulus of concrete subjected to freeze-thaw cycle are tested through indoor freezing and thawing tests. The effects of different water / cement ratio, air entraining agent content and freeze-thaw times on the elastic wave velocity and dynamic elastic modulus are studied. The relationship between elastic wave velocity and dynamic elastic modulus is analyzed, and the damage model of concrete freeze-thaw is established. The main contents and conclusions of this paper are as follows: 1) the elastic wave propagation characteristics of concrete specimens subjected to freeze-thaw cycles are studied by using impact elastic wave nondestructive testing technique, and different water-cement ratios are analyzed. The elastic wave propagation law of concrete specimen with air entraining agent and freeze-thaw cycle times. The results show that the elastic wave velocity decreases with the increase of freeze-thaw times, and the smaller the water-cement ratio, the greater the elastic wave velocity. The larger the water-cement ratio, the faster the velocity of elastic wave decreases. The addition of air entraining agent has a certain effect on the elastic wave velocity of concrete specimen, which will reduce the elastic wave velocity, but the air entraining agent will also make the attenuation process of elastic wave velocity more smooth. The attenuation amplitude becomes smaller. 2) by measuring the dynamic elastic modulus of concrete specimens after freeze-thaw cycle, the effects of water / cement ratio, air entraining agent content and freeze-thaw cycle times on the dynamic elastic modulus of concrete are studied. The results show that with the increase of freeze-thaw times, the dynamic elastic modulus of the specimens decreases. The addition of air entraining agent can reduce the dynamic elastic modulus of concrete specimen to some extent, but the attenuation range of dynamic elastic modulus of concrete specimen with air entraining agent is smaller. The performance of concrete specimens without air entraining agent is more stable. 3) the relationship between the dynamic elastic modulus of concrete under freeze-thaw cycle and the parameters of elastic wave propagation characteristics is analyzed. The durability detection model of concrete under freeze-thaw cycle is established, which provides a new testing method for freeze-thaw research of concrete. The elastic wave velocity and dynamic elastic modulus of 8 groups of specimens were fitted by function, and it was found that the power function fitted well. The damage degree of concrete is determined by dynamic elastic modulus and elastic wave velocity. 4) the relative dynamic elastic modulus and mass loss rate are used as the basis for judging whether the concrete is damaged or not. The freeze-thaw failure of concrete is analyzed based on the test results.
【学位授予单位】：重庆交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU528
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