干湿交替作用下受弯开裂钢筋混凝土梁内氯离子侵蚀特性

发布时间：2018-09-15 05:51

【摘要】：为了研究干湿交替条件下受弯开裂混凝土内氯离子侵蚀机理及其分析方法,对两两自锚并保持开裂状态下的混凝土梁进行氯盐溶液干湿循环试验。借助15和30次干湿循环的两次取样结果,分析完好截面、裂缝截面及其周围一定范围内的自由氯离子含量分布规律,并对提出的等效氯离子扩散模型的适用性、弯曲裂缝宽度的影响规律以及扩散系数的时变特性等问题进行探讨。研究结果表明:1氯盐干湿交替作用下,开裂截面处的表层对流区深度在10~20mm之间,弯曲裂缝的存在将加快混凝土内部氯离子的渗透速度;2裂缝周围混凝土内的氯离子传输受到裂缝(0.1mm)及混凝土弯曲拉应力的共同影响,当与裂缝距离增大时,混凝土弯曲拉应力对氯离子传输的影响也会增大;3拟合结合表明,当裂缝宽度w0.30mm时,用等效扩散模型分析开裂截面的氯离子含量分布是可行的,且等效氯离子扩散系数的劣化特性可用w的多项式函数进行回归分析;4对普通混凝土而言,氯离子扩散系数的时间衰减指数m与水灰比有关,且随水灰比的减小而减小。
[Abstract]:In order to study the chloride erosion mechanism and analysis method of flexural cracking concrete under dry and wet alternating conditions, the chloride solution wet and dry cycle tests were carried out on the concrete beams with self-anchoring and keeping cracking state. Based on the two sampling results of 15 and 30 dry and wet cycles, the distribution of free chlorine ion content in the intact section, crack section and its surrounding area is analyzed, and the applicability of the proposed equivalent chloride ion diffusion model is discussed. The influence of bending crack width and the time-varying characteristics of diffusion coefficient are discussed. The results show that the depth of the surface convective zone at the cracking cross section is between 10~20mm and 10~20mm under the dry and wet alternating action of 1: 1 chloride salt. The existence of bending crack will accelerate the permeation rate of chloride ions in concrete. The chloride ion transport around the crack is affected by the crack (0.1mm) and the bending tensile stress of concrete. When the distance to the crack increases, The effect of flexural tensile stress on chloride ion transport is also increased. The fitting results show that it is feasible to use equivalent diffusion model to analyze the chloride content distribution in cracking section when the crack width is w0.30mm. For ordinary concrete, the time decay index m of chloride diffusion coefficient is related to the water-cement ratio, and decreases with the decrease of water-cement ratio.
【作者单位】：江苏大学;
【基金】：国家自然科学基金(50908103,51278230,51378241) 中国博士后科学基金(2012M511215) 教育部博士点基金(20123227110006) 高性能土木工程材料国家重点实验室开放基金(2011CEM010) 江苏大学高级专业人才科研基金(11JDG132)
【分类号】：TU528.571

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