严寒地区重大供水工程用水工混凝土抗冻耐久性研究

发布时间：2018-05-13 00:01

本文选题：严寒环境 + 抗冻性　；参考：《沈阳工业大学》2014年硕士论文

【摘要】：我国地域辽阔，北方地区大部分处于严寒地带，许多重大供水工程都在我国三北地区兴建，在建设完成并使用的期间内，均有不同程度的局部混凝土冻融破坏或大面积的混凝土冻融破坏或冻胀开裂，从而致使混凝土抗压强度、抗拉强度、弹性模量等相关力学性能大幅度下降，最终甚至有些水坝工程项目在运行十几年后，由于水工混凝土发生的冻融破坏现象，而不得不报废。本文对水工混凝土抗冻耐久性的冻融机理和研究成果进行调查研究，明确水工混凝土的冻融破坏机理，并确定影响水工混凝土抗冻性的影响因素，为试验研究提供理论依据，首先对强度等级为C25的水工混凝土在冻融温度变化范围为8±2oC～-17±2oC的冻融循环实验；其次对严寒地区重大供水工程用水工混凝土试件进行冻融循环试验；最后通过对强度等级为C35的水工混凝土施加大小为0.1ft拉应力，在持载的状态下进行冻融试验。本文的主要工作和得到的结果如下。（1）通过强度等级为C25的水工混凝土在冻融温度变化范围为8±2oC～-17±2oC的冻融循环实验，测量并分析冻融循环条件下水工混凝土的质量损失、相对动弹性模量、抗压强度和抗折强度的变化规律及原因，对水工混凝土的相关力学性能进行研究分析，试验结果表明当参照《水工混凝土配合比设计规程》（DL/T5330-2005）计算出的水工混凝土的配合比具有较好的抗冻性。（2）针对于严寒地区水工混凝土的抗冻耐久性，将试验的冻融温度变化范围设定为8±2oC～-22±2oC，将试验得出的结果与标准快冻法下的试验结果进行对比，，结果表明最低冻结温度对混凝土冻融破坏的影响极为重要，标准快冻法下试件的相关力学性能不能准确地反应出严寒环境下的水工混凝土的抗冻性能。（3）通过对强度等级为C35的水工混凝土施加大小为0.1ft拉应力，在持载的状态下进行冻融试验，施加预拉力明显削弱了混凝土试件的抗冻性能，未达到设计的抗冻标号F300。
[Abstract]:Our country has a vast territory, and most of the northern regions are in the cold zone. Many major water supply projects have been built in the three northern regions of our country. During the period of completion and use of the construction, There are different degrees of freezing and thawing failure of local concrete or freeze-thaw failure or frost heaving cracking of large area of concrete, which results in the decrease of mechanical properties of concrete, such as compressive strength, tensile strength, elastic modulus and so on. Finally, some dam projects have to be scrapped because of freeze-thaw failure of hydraulic concrete after more than ten years of operation. In this paper, the freezing and thawing mechanism and research results of hydraulic concrete are investigated, and the mechanism of freezing and thawing failure of hydraulic concrete is clarified, and the influencing factors of frost resistance of hydraulic concrete are determined, which provides a theoretical basis for experimental study. Firstly, the freeze-thaw cycle test of hydraulic concrete with strength grade C25 in the freeze-thaw temperature range of 8 卤2oC~-17 卤2oC is carried out, and the freeze-thaw cycle test of hydraulic concrete specimens used in severe water supply projects in severe cold regions is carried out. Finally, freezing and thawing tests were carried out on hydraulic concrete with strength grade C35 under the condition of holding capacity by applying tensile stress of 0.1ft. The main work and results obtained in this paper are as follows. 1) the mass loss and relative dynamic elastic modulus of hydraulic concrete under freeze-thaw cycle condition are measured and analyzed through the freeze-thaw cycle experiment in which the freezing and thawing temperature ranges from 8 卤2oC~-17 卤2oC to C25. The change law and reason of compressive strength and flexural strength, the related mechanical properties of hydraulic concrete are studied and analyzed. The experimental results show that the mixture ratio of hydraulic concrete calculated by DL / T5330-2005 has good frost resistance. (2) aiming at the durability of hydraulic concrete in severe cold region, the range of freezing and thawing temperature is set to 8 卤2oC~-22 卤2oC, and the test results are compared with the test results under the standard fast freezing method. The results show that the effect of the minimum freezing temperature on the freeze-thaw failure of concrete is very important, and the relevant mechanical properties of the specimen under the standard rapid freezing method can not accurately reflect the frost resistance of hydraulic concrete under the cold environment. 3) by applying 0.1ft tensile stress to hydraulic concrete with strength grade C35, freezing and thawing tests are carried out under the condition of holding capacity. The application of pretensile force obviously weakens the frost resistance of concrete specimens, and does not reach the designed freezing resistance mark F300.
【学位授予单位】：沈阳工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TV431

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