环境作用下混凝土内部相对湿度与宏微观性能演变研究

发布时间：2018-03-02 03:02

本文关键词： 混凝土内部相对湿度自干燥水分扩散抗压强度化学结合水氢氧化钙孔结构　出处：《青岛理工大学》2013年硕士论文　论文类型：学位论文

【摘要】：混凝土材料以其卓越的性能成为目前应用最广、使用最成功的结构材料，而混凝土的宏微观性能受其内部相对湿度（Iternal Relative Humidity, IRH）变化的影响，研究早龄期混凝土由水分扩散和自干燥引起的IRH变化规律，混凝土IRH随环境演变规律，以及自干燥环境下早龄期混凝土内部湿度场与力学性能、化学结合水含量、氢氧化钙（CH）含量以及孔结构发展特征之间的关系，既具有理论意义又具有实践意义。本文通过试验研究与分析，取得了以下研究结论。一、研究了恒温恒湿环境中，早龄期混凝土由水分扩散和自干燥引起的IRH变化规律。研究表明：（1）恒温恒湿环境中混凝土IRH的衰减由自干燥和水分扩散共同影响决定，衰减速度先快后慢，龄期28d内IRH衰减值可达到112d总衰减值的80%以上。（2）W/C越大，仅由自干燥引起的混凝土IRH的衰减程度越小，仅由水分扩散引起的衰减程度越大；超细矿粉（GGBS）能使两种原因引起的混凝土IRH的衰减程度有所增大，而粉煤灰（FA）可大大降低IRH的衰减程度；测试深度越大，由水分扩散引起的混凝土IRH衰减程度越小。（3）随着W/C的增大，自干燥对混凝土IRH下降的影响比例逐渐减小，，而水分扩散的影响比例逐渐增大；掺50%FA的混凝土受水分扩散影响较大，其他主要受自干燥影响；测试深度越大，水分扩散的影响比例越小。二、研究了海洋环境和模拟海洋环境下混凝土IRH的变化情况。研究表明：（1）海洋大气区和浪溅区环境湿度对混凝土IRH有重要影响，混凝土IRH会随着环境湿度变化而变化，但混凝土内部湿度响应较慢。（2）在烘干过程中，测试深度越小，混凝土IRH开始下降的越早，下降的速度和幅度越大，且4.0cm处的湿度在测定的时间内没有达到平衡，说明混凝土IRH变化存在时间上的滞后效应。（3）在吸水过程中，距离吸水面越近，混凝土IRH增加的越早，增长速度越快，达到饱水状态所需的时间越短；混凝土IRH的增长是先由慢变快，而后又逐渐减慢并最终达到100%的过程。（4）在干湿循环过程中，低潮位附近的混凝土IRH将达到饱和状态（IRH=100%），但表面层IRH则随环境湿度变化而变化；而高潮位附近的混凝土IRH将处于非饱和状态（IRH100%），易导致海水中腐蚀离子快速渗入。三、研究了自干燥环境下混凝土力学性能、化学结合水含量、CH含量以及孔结构的发展与混凝土IRH的关系。研究表明：（1）自干燥环境下混凝土IRH的逐渐下降阶段与化学结合水含量、抗压强度的变化及CH含量下降阶段都具有显著的线性相关性。自干燥环境下混凝土IRH与化学结合水含量、抗压强度及CH含量的定量关系可依次用式y=ahs+b描述。（2）自干燥环境下混凝土IRH变化与最可几孔径及总孔隙率的定量关系均可用式y=A*exp(-x/t)+y0表示，IRH与最可几孔径具有显著的非线性关系，但与总孔隙率之间的非线性相关性较弱；IRH变化与平均孔径的定量关系可用R=ahs+b表示，具有较好的线性关系。
[Abstract]:The concrete materials become the most widely used for its excellent performance, the use of structural materials for the most successful, and the macro and micro properties of concrete by the internal relative humidity (Iternal Relative, Humidity, IRH) the impact of changes in early age concrete research by moisture diffusion and self dry IRH variation of dryness caused by the evolution of concrete IRH with the environment, and since the dry environment of early age concrete internal humidity field and mechanical properties, chemical combined water content, calcium hydroxide (CH) the relationship between content and pore structure characteristics, has both theoretical significance and practical significance. This paper through experimental research and analysis, obtained the following conclusions.
First, the change law of IRH in early age concrete caused by water diffusion and self drying in constant temperature and constant humidity environment is studied.
(1) the attenuation of concrete IRH in constant temperature and humidity environment is determined by the co effect of self drying and moisture diffusion. The attenuation speed is fast and slow. The attenuation value of IRH in 28d reaches 80% of the total 112d attenuation.
(2) W/C is larger, only by the degree of attenuation of IRH concrete self desiccation caused by the smaller, only by the diffusion of water caused by the greater degree of attenuation; ultrafine slag (GGBS) concrete degree of attenuation of IRH can make the two causes of the increase, and fly ash (FA) can greatly reduce the degree of attenuation of IRH the test; depth increases, the concrete moisture diffusion caused by IRH decay degree is smaller.
(3) with the increase of W/C, since the effects of drying on the concrete of the decrease of IRH ratio decreased, and the effect of ratio of moisture diffusion increases; influence of moisture diffusion of concrete mixed with 50%FA, the other is mainly affected by self desiccation effect; test depth increases, the influence of water diffusion ratio is smaller.
Two, the changes of the concrete IRH in the marine environment and the simulated marine environment are studied.
(1) the environmental humidity in the marine atmospheric area and splash zone has an important influence on the concrete IRH. The concrete IRH will change with the change of the environmental humidity, but the humidity response inside the concrete is slower.
(2) during the drying process, the smaller the test depth, the earlier the concrete IRH began to fall. The greater the speed and the magnitude of the decrease, the 4.0cm humidity did not reach equilibrium in the time of testing. This indicates that there is time lag effect on the change of concrete IRH.
(3) in the process of absorbing water, the closer the distance to the suction surface is, the earlier the concrete IRH increases, the faster the growth rate is, the shorter the time to reach the satiety state. The growth of concrete IRH is slow and fast, and then gradually slows down and finally reaches 100%.
(4) in the dry wet cycle process, concrete IRH near the low tide will reach saturation (IRH=100%), but the surface layer of IRH with humidity change; and the tide near the concrete IRH in the unsaturated state (IRH100%), easily lead to seawater corrosion from rapid infiltration.
Three, the relationship between the mechanical properties of concrete, the content of chemical combined water, the content of CH and the development of the pore structure and the relationship between the pore structure and the concrete IRH are studied.
(1) since the dry environment of concrete IRH gradually decreased and the chemical combined water content changes, and the content of CH compressive strength decline stage has a significant linear correlation between the dry environment. Since the concrete IRH and the chemical combined water content, the compressive strength and the content of CH quantitative relationship can be followed by the y=ahs+b description.
(2) since the quantitative relationship between the changes of IRH concrete under dry environment with most pore size and porosity can be y=A*exp (-x/t) +y0, IRH and the pore has a significant nonlinear relationship, but weak correlation between nonlinear and total porosity; quantitative relationship between the change of IRH and the average pore size of the available R=ahs+b that has a good linear relationship.

【学位授予单位】：青岛理工大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU528

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