粉煤灰混凝土碳化与冻融耦合作用研究

发布时间：2018-05-05 10:46

本文选题：粉煤灰混凝土 + 碳化　；参考：《河北农业大学》2015年硕士论文

【摘要】：混凝土结构是目前应用最广泛的建筑结构形式,其耐久性能一直备受关注。针对不同的工作状态和工作环境,混凝土会发生各类耐久性损伤。单一因素造成的耐久性损伤已经得到了各国学者广泛的探讨,而在实际工程中,混凝土损伤并非仅为某一种因素造成的,而是受到两种或者多种因素的共同作用,且这些因素的耦合作用,不是简单的叠加,而是更为复杂的相互促进或相互制约关系。在我国北方,尤其青藏、东北等严寒地区的水工混凝土,不仅受到二氧化碳的侵蚀,还遭受着极其严重冻融破坏,严重影响建筑物的使用寿命。基于此,本文设计了具有高抗冻性能的混凝土,并进行了碳化和冻融耦合作用下的耐久性实验,进一步探讨严寒地区混凝土在碳化和冻融共同作用下的劣化过程和劣化机理。本文将我国严寒地区分为青藏和东北两大类型进行耐久性研究,针对水胶比为0.4的混凝土,按照不同的粉煤灰掺量分成五组,每组再分为四个实验进行研究,包括先碳化再冻融模式(简称CF)和先冻融再碳化模式(简称FC)的两个耦合试验以及单一碳化试验和单一冻融两个对照试验。试验的测量指标有碳化指标(碳化深度和碳化面积)和冻融指标(质量损失率和相对动弹性模量)。主要研究内容为:首先,采用快速碳化试验,探究碳化龄期,粉煤灰掺量与混凝土碳化深度、碳化面积的关系。其次,采用快速冻融试验,探究冻融循环次数,粉煤灰掺量与混凝土的质量损失率、相对动弹性模量的关系。最后,进行碳化和冻融的耦合循环实验,探讨CF和FC模式下冻融和碳化的相互影响关系。分析结果表明:(1)在耦合实验和单一试验条下,混凝土的碳化深度、碳化面积率均随着粉煤灰掺量的增加而增加;混凝土的质量损失率在总体上,随粉煤灰掺量的增加先增加后降低再增加;混凝土的相对动弹性模量,随粉煤灰掺量的增加先降低后增加再降低。(2)CF模式、FC模式相比单一碳化实验的碳化深度、碳化面积率变大,说明CF和FC模式中的冻融破坏为碳化提供有利条件,即冻融加剧碳化。(3)CF模式、FC模式相比单一冻融实验的质量损失率更大、相对动弹性模量下降更快,说明CF和FC模式中的碳化损伤为冻融破坏提供有利条件,即碳化加剧冻融。(4)引气粉煤灰混凝土的抗冻能力很强,抗碳化能力相对较弱。(5)用IPP软件测量混凝土劈裂面碳化面积的方法,可以更准确的分析冻融后混凝土的碳化规律。
[Abstract]:Concrete structure is the most widely used building structure at present, its durability has been paid much attention. According to different working state and working environment, concrete will have various durability damage. The durability damage caused by a single factor has been widely discussed by scholars all over the world. However, in practical engineering, concrete damage is caused not only by one factor, but also by two or more factors. The coupling of these factors is not a simple superposition, but a more complex mutual promotion or constraints. In northern China, especially in the cold areas of Qinghai-Tibet and Northeast China, hydraulic concrete is not only eroded by carbon dioxide, but also severely damaged by freezing and thawing, which seriously affects the service life of buildings. Based on this, the concrete with high frost resistance is designed, and the durability experiment under the coupling of carbonation and freeze-thaw is carried out, and the deterioration process and mechanism of concrete under the joint action of carbonization and freeze-thaw are discussed. In this paper, the cold regions of China are divided into two types, Qinghai-Tibet and Northeast, and the concrete with water-binder ratio 0.4 is divided into five groups according to different fly ash content, and each group is divided into four experiments. It includes two coupling tests of the first carbonization and thawing model (CFC) and the first freeze-thawing and thawing model (FCCfor short), as well as the single carbonization test and the single freeze-thaw control test. The measurement indexes include carbonation index (carbonation depth and carbonation area) and freeze-thaw index (mass loss rate and relative dynamic elastic modulus). The main contents are as follows: firstly, the relationship between carbonation age, fly ash content and carbonation depth and carbonation area of concrete was studied by rapid carbonization test. Secondly, the relationship between the number of freeze-thaw cycles, the content of fly ash and the mass loss rate of concrete and the relative dynamic modulus of elasticity is studied by using rapid freeze-thaw test. Finally, the coupling cycle experiments of carbonation and freeze-thaw were carried out to investigate the interaction between freeze-thaw and carbonization under CF and FC modes. The results show that under the coupling experiment and single test strip, the carbonation depth and carbonization area rate of concrete increase with the increase of fly ash content, and the mass loss rate of concrete is overall. With the increase of fly ash content, the relative dynamic elastic modulus of concrete firstly increases and then decreases, and then increases with the increase of fly ash content, and then decreases with the increase of fly ash content. Compared with the carbonation depth of single carbonization experiment, the carbonation area ratio of concrete increases. The results show that the freeze-thaw failure in CF and FC mode provides favorable conditions for carbonization, that is, freeze-thaw exacerbates carbonization, and the mass loss rate of CF / FC model is larger than that of single freeze-thaw experiment, and the relative dynamic modulus of elasticity decreases more rapidly than that of single freeze-thaw experiment. It shows that carbonation damage in CF and FC modes provides favorable conditions for freeze-thaw failure, that is, carbonization intensifies freezing thaw. 4) the freezing resistance of air-entrained fly ash concrete is very strong. The carbonation law of concrete after freeze-thaw can be analyzed more accurately by using IPP software to measure the carbonation area of split surface of concrete.
【学位授予单位】：河北农业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU528

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