荷载与环境共同作用下固废掺合混凝土结构耐久性研究

发布时间：2018-01-05 16:18

本文关键词：荷载与环境共同作用下固废掺合混凝土结构耐久性研究　出处：《南昌航空大学》2016年硕士论文　论文类型：学位论文

【摘要】：随着我国城市化进程加快,港口码头等水工建筑物的混凝土耐久性问题也越来越得到人们的重视。本文研究了荷载与氯离子以及荷载与盐冻共同作用下混凝土结构耐久性退化规律以及机理分析。对于荷载、冻融循环、氯盐溶液多因素共同作用下的混凝土试件,施加不同的荷载等级、不同掺合料的弯曲荷载、压荷载试件进行冻融循环试验,在标准实验室环境下用AgNO3滴定的方法测出距离混凝土表面不同深度的氯离子的百分含量。根据FICK第二定律,分析恒定荷载与氯离子共同作用下的混凝土以及恒定荷载和盐冻综合作用下的耐久性退化规律。(1)弯曲荷载会使氯离子等加速在混凝土中无规律迁移,随着弯曲应力水平的增加,混凝土样品的氯离子扩散系数跟着增大,氯离子扩散系数与应力水平间近似呈指数函数关系,且不同荷载应力水平下的氯离子扩散系数可表示为D0/Dη=A·e-Bη,56天龄期时A=1.02,B=1.363,混凝土结构在耐久性设计中应考虑弯曲荷载对氯离子扩散系数的影响。(2)弯曲荷载和压荷载不仅会在混凝土骨料和浆体的界面过渡区产生裂缝,还会引起浆体孔隙结构的变化,这是荷载引起混凝土氯离子扩散系数变化的根本原因。(3)在冻融循环的作用下,随着弯曲应力水平的增加,混凝土样品的氯离子浓度跟着增大,且随着应力水平的增加,混凝土内的氯离子渗透深度同时增大。冻融和荷载耦合作用会影响混凝土中的氯离子浓度分布。(4)在弯曲荷载和冻融耦合作用下不同弯曲应力水平与混凝土氯离子扩散系数间呈近似指数函数关系Dd0/Ddη=A·e-Bη,其中A、B是与胶凝材料组成有关的参数,对于轴压荷载和冻融耦合作用的混凝土试件,压应力水平与试件内氯离子扩散系数的关系为,且Dd0=k·D0,冻融因子k是一个与胶凝材料组成有关的参数：无掺合料时k=1.72；掺30%的粉煤灰时k=5.95；掺60%的矿粉时k=1.29；复掺粉煤灰和矿粉时k=1.0。
[Abstract]:With the acceleration of urbanization in China. More and more attention has been paid to the durability of concrete in hydraulic structures such as port and wharf. In this paper, the degradation law and mechanism of durability of concrete structures under the combined action of load and chlorine ion and the action of load and salt freezing are studied. Analysis. For loads. Freeze-thaw cycle, chloride solution under the action of multiple factors of concrete specimens, under different load levels, different admixtures of bending load, compression load specimens for freeze-thaw cycle test. The content of chloride ions at different depths from the surface of concrete was determined by AgNO3 titration under the standard laboratory environment. According to the second law of FICK. It is analyzed that the concrete under constant load and chloride ion, and the durability degradation law under constant load and salt freezing. 1) bending load will accelerate the irregular migration of chloride ions in concrete. With the increase of bending stress level, the chloride diffusion coefficient of concrete samples increases, and the relationship between chloride ion diffusion coefficient and stress level is approximately exponential function. The chloride diffusion coefficient under different load stress levels can be expressed as D _ 0 / D 畏 A 路e-B 畏 _ (56) days. In the durability design of concrete structure, the influence of bending load on chloride diffusion coefficient should be considered. (2) bending load and compressive load will not only produce cracks in the interface transition zone of concrete aggregate and slurry. It will also cause the change of pore structure of slurry, which is the fundamental reason for the change of chloride ion diffusion coefficient of concrete caused by load. 3) under the action of freeze-thaw cycle, with the increase of bending stress level. The chloride concentration of concrete samples increases with the increase of stress level. The depth of chloride ion permeation in concrete increases simultaneously. The coupling of freeze-thaw and load will affect the chloride concentration distribution in concrete. Under the coupling of bending load and freezing and thawing, the relationship between the different bending stress levels and the chloride diffusion coefficient of concrete is approximately exponential Dd0/Dd 畏 A 路e-B 畏. For concrete specimens subjected to axial compression and freeze-thaw coupling, the relationship between compressive stress level and chloride diffusion coefficient is Dd0=k 路D0. The freeze-thaw factor k is a parameter related to the composition of cementitious materials. When 30% fly ash is added, KG 5.95; The addition of 60% ore powder is 1.29; When mixed with fly ash and mineral powder, KG 1.0.
【学位授予单位】：南昌航空大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TV33

【相似文献】