荷载与冻融共同作用下氯离子在海工混凝土中扩散行为研究
发布时间：2019-03-24 18:08
【摘要】：本论文针对耐久性问题最为突出的海港工程混凝土结构,通过对我国具有代表性的实际海港工程混凝土结构服役期应力水平测试与分析,获得典型构件在实际服役环境中的荷载类型和具有代表性的荷载水平范围；采用自主开发的恒定加压载荷和弯曲载荷装置,以工程实际的荷载类型和荷载水平为基础,从压／弯曲等静荷载类型、施加载荷范围、混凝土掺合料种类及掺量、混凝土配比参数等方面,通过室内海水模拟试验箱的人工加速模拟试验方法以及混凝土结构微观测试手段,开展处于“荷载+氯盐”条件下和“荷载+氯盐+冻融”作用下的海港工程混凝土结构氯离子扩散行为的研究。得出以下主要结论：(1)数值模拟、理论计算和现场实际测试与分析表明：所研究的海港工程混凝土构件服役期的实际应力水平有限元分析基本在7%-50%范围；“永久荷载+可变荷载”应力水平约在30%-40%之间。(2)混凝土氯离子扩散系数与弯曲应力水平间呈指数函数关系,可用公式Y=A·eBx进行表述。对于掺入活性矿物掺合料的海工高性能混凝土,其氯离子扩散系数的恒定弯曲荷载作用影响因子表达式为：Dη=0.9769·D0·e1.363η;弯曲荷载和冻融共同作用影响因子表达式为：Ddη=1.0224·D0·e1.6383η。(式中,η为自变量应力水平,Do为无荷载混凝土的氯离子扩散系数,Ddη、Dη为应力水平为η时混凝土的氯离子扩散系数。)(3)混凝土氯离子扩散系数随着压应力的增加呈现先降低后增高的趋势,所研究的混凝土约施加应力水平为30%时最低；压应力单独作用下,应力水平为η混凝土的氯离子扩散系数D。与无荷载时混凝土氯离子扩散系数D0关系式为：(4)基于室内的研究成果,对以可靠度理论为基础而建立的海工混凝土结构耐久性寿命预测模型中的关键参数进行了考虑恒定弯曲荷载作用的修正,建立了恒定弯曲荷载作用下海工混凝土结构耐久性寿命预测模型：(5)盐冻条件下,混凝土的相对动弹模量随冻融循环次数的增加而降低；混凝土的质量损失率随冻融循环次数的增加而增加,混凝土的质量损失率还随承受弯曲荷载应力水平的提高而增大。(6)弯曲荷载与冻融共同作用和弯曲荷载单独作用都会引起混凝土孔隙结构的变化,提高应力水平不仅会提高混凝土的平均孔径和总孔体积,还改变了混凝土的孔径分布。荷载与冻融共同作用对混凝土孔隙结构的影响要大于荷载单独作用对混凝土孔隙结构的影响,孔隙结构变化是引起氯离子扩散系数变化的主要因素。
[Abstract]:In this paper, the concrete structure of seaport engineering, which is the most prominent durability problem, is tested and analyzed by testing and analyzing the stress level of concrete structure of practical seaport engineering, which is representative of our country. The load type and the representative load level range of the typical members in the actual service environment are obtained. Based on the actual load type and load level of the project, the static load types such as compression / bending, the range of load applied, the type and the amount of concrete admixture are adopted by the self-developed constant load and bending load device, which is based on the actual load type and load level of the project. In the aspects of concrete proportioning parameters, the artificial accelerated simulation test method of indoor seawater simulation test box and the micro-testing method of concrete structure are adopted. The diffusion behavior of chloride ions in concrete structures of harbour engineering under the condition of "load chloride salt" and "freeze-thaw of load chloride salt" was studied. The main conclusions are as follows: (1) numerical simulation, theoretical calculation and field test and analysis show that the actual stress level finite element analysis of concrete members in seaport engineering is basically in the range of 7% to 50%; The stress level of "permanent load variable load" is about 30% ~ 40%. (2) there is an exponential function relationship between chloride diffusion coefficient and bending stress level, which can be expressed by formula Y = A 路eBx. For marine high performance concrete mixed with active mineral admixture, the influence factor of chloride diffusion coefficient under constant bending load is expressed as follows: d 畏 = 0.9769 路D 0 路e 1.363 畏; The expression of Dd 畏 = 1.0224 路D _ 0 路e _ 1. 6383 畏 for the interaction of bending load and freezing-thawing. (here, 畏 is the stress level of independent variables, and Do is the chloride diffusion coefficient of unloaded concrete, Dd 畏, When the stress level is 畏, the chloride diffusion coefficient of concrete.) (3) the chloride diffusion coefficient of concrete decreases at first and then increases with the increase of compressive stress, and the applied stress level of the concrete studied is the lowest when the applied stress level is about 30%. Under the action of compressive stress alone, the stress level is the chloride diffusion coefficient of 畏 concrete. The formula of chloride diffusion coefficient D _ 0 between concrete and concrete without load is as follows: (4) based on the research results in laboratory, The key parameters in the durability life prediction model of marine concrete structures based on reliability theory are modified considering the action of constant bending load. The durability life prediction model of marine concrete structure under constant bending load is established: (5) under salt freezing condition, the relative dynamic elastic modulus of concrete decreases with the increase of freezing and thawing cycles; The mass loss rate of concrete increases with the increase of freezing and thawing cycles. The mass loss rate of concrete also increases with the increase of bending load stress level. (6) the interaction of bending load with freeze-thaw and bending load alone will cause the change of concrete pore structure. Increasing the stress level will not only increase the average pore size and total pore volume of concrete, but also change the pore size distribution of concrete. The influence of the interaction of load and freeze-thaw on concrete pore structure is greater than that of concrete pore structure by load alone. The change of pore structure is the main factor that causes the change of chloride ion diffusion coefficient.
【学位授予单位】：华南理工大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TV33
本文编号：2446559
[Abstract]:In this paper, the concrete structure of seaport engineering, which is the most prominent durability problem, is tested and analyzed by testing and analyzing the stress level of concrete structure of practical seaport engineering, which is representative of our country. The load type and the representative load level range of the typical members in the actual service environment are obtained. Based on the actual load type and load level of the project, the static load types such as compression / bending, the range of load applied, the type and the amount of concrete admixture are adopted by the self-developed constant load and bending load device, which is based on the actual load type and load level of the project. In the aspects of concrete proportioning parameters, the artificial accelerated simulation test method of indoor seawater simulation test box and the micro-testing method of concrete structure are adopted. The diffusion behavior of chloride ions in concrete structures of harbour engineering under the condition of "load chloride salt" and "freeze-thaw of load chloride salt" was studied. The main conclusions are as follows: (1) numerical simulation, theoretical calculation and field test and analysis show that the actual stress level finite element analysis of concrete members in seaport engineering is basically in the range of 7% to 50%; The stress level of "permanent load variable load" is about 30% ~ 40%. (2) there is an exponential function relationship between chloride diffusion coefficient and bending stress level, which can be expressed by formula Y = A 路eBx. For marine high performance concrete mixed with active mineral admixture, the influence factor of chloride diffusion coefficient under constant bending load is expressed as follows: d 畏 = 0.9769 路D 0 路e 1.363 畏; The expression of Dd 畏 = 1.0224 路D _ 0 路e _ 1. 6383 畏 for the interaction of bending load and freezing-thawing. (here, 畏 is the stress level of independent variables, and Do is the chloride diffusion coefficient of unloaded concrete, Dd 畏, When the stress level is 畏, the chloride diffusion coefficient of concrete.) (3) the chloride diffusion coefficient of concrete decreases at first and then increases with the increase of compressive stress, and the applied stress level of the concrete studied is the lowest when the applied stress level is about 30%. Under the action of compressive stress alone, the stress level is the chloride diffusion coefficient of 畏 concrete. The formula of chloride diffusion coefficient D _ 0 between concrete and concrete without load is as follows: (4) based on the research results in laboratory, The key parameters in the durability life prediction model of marine concrete structures based on reliability theory are modified considering the action of constant bending load. The durability life prediction model of marine concrete structure under constant bending load is established: (5) under salt freezing condition, the relative dynamic elastic modulus of concrete decreases with the increase of freezing and thawing cycles; The mass loss rate of concrete increases with the increase of freezing and thawing cycles. The mass loss rate of concrete also increases with the increase of bending load stress level. (6) the interaction of bending load with freeze-thaw and bending load alone will cause the change of concrete pore structure. Increasing the stress level will not only increase the average pore size and total pore volume of concrete, but also change the pore size distribution of concrete. The influence of the interaction of load and freeze-thaw on concrete pore structure is greater than that of concrete pore structure by load alone. The change of pore structure is the main factor that causes the change of chloride ion diffusion coefficient.
【学位授予单位】：华南理工大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TV33
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