非饱和冻融损伤混凝土的气体渗透率和毛细吸水率研究
首发时间:2015-02-05
摘要:论文利用快速冻融循环的方法来制备含有不同程度均匀微裂纹损伤的混凝土试件,采用冻融循环次数、相对动弹性模量和超声损伤指标来表征冻融损伤程度,研究了冻融损伤程度和初始含水饱和度对相对气体渗透率和表面毛细吸水率这两个物质传输性能指标的影响。结果表明,冻融循环次数能很好地表征初始干燥状态下气体渗透率和毛细吸水率随冻融作用累积而发展的过程。此外,含水饱和度对相对气体渗透率和表面毛细吸水率影响显著。建议的含曲折度因子的近似公式能很好地表征含水饱和度对本征气体渗透率的影响,且拟合得到的曲折度因子起初随冻融循环次数的增大而减小,在达到100次冻融循环时又开始增大。对初始非饱和损伤混凝土材料的表面毛细吸水率来说,表面毛细吸水率随着初始含水率的增大而快速减小,成显著的非线性关系。微裂纹损伤及初始含水饱和度对气体、水分进而水溶性离子往混凝土材料内部迁移的速度影响非常显著,量化分析实际混凝土材料的耐久性时,必须合理考虑微裂纹损伤及含水饱和度的影响。
关键词: 结构工程 饱和度 冻融循环 气体渗透率 表面毛细吸水率
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The gas permeability and sorptivity of unsaturated concrete material after freezing-thawing cycles
Abstract: In this paper the rapid freezing-thawing cycles is employed to prepare concrete specimens with different degrees of uniform micro-crack damage, which is characterized by the number of freezing-thawing cycles, the relative dynamic elastic modulus and the ultrasonic damage. The effects of freezing-thawing damage and initial water saturation on two substantial mass transport propertries, the relative gas permeability and capillary water absorption (sorptivity), are experimentally investigated. The results showed that the development of gas permeability and sorptivity of initial drying status along with the accumulation of freezing-thawing damage can be well characterized by the number of freezing-thawing cycles. In addition, the relative gas permeability and sorptivity for partially saturated concrete specimen are significantly affected by the initial water saturation degree. The effect of initial saturation degree on intrinsic gas permeability can be well approximately quantified by the proposed expirical formula with tortuosity factor. Moreover, the fitted tortuosity factor initially decreases with the increasing number of freezing and thawing cycles. However, it began to increase with freeze-thaw cycles after 100 times. When concerning the sorptivity of the initially unsaturated damaged concrete material, it decreased rapidly with the increasing initial water content in a significant nonlinear manner. The ingression rate of gas, liquid water as well as dissolved ions will be greatly influenced by micro-cracking damage and initial water saturation, which should be taken into consideration when assessing the actual durability performance of concrete mateiral under real services.
Keywords: structural engineering saturation degree freezing-thawing action gas permeability sorptivity
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No.4631259103360914****
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