盐冻与石粉耦合作用对C50机制砂混凝土耐久性影响及作用机理  

Coupling effect and mechanism of salt freezing cycle and stone powder content of manufactured sand on durability of C50 concrete

作　　者：李鹏举 黎鹏平[2] 熊建波[2] 张志杰[3] Li Pengju;Li Pengping;Xiong Jianbo;Zhang Zhijie(CCCC Fourth Harbor Engineering Co.,Ltd.,Guangzhou 510290,China;Key Laboratory of Harbor&Marine Structure Durability Technology,Ministry of Communications,Guangzhou 510230,China;School of Materials Science and Engineering,South China University of Technology,Guangzhou 510640,China)

机构地区：[1]中交第四航务工程局有限公司,广州510290 [2]水工构造物耐久性技术交通运输部重点实验室,广州510230 [3]华南理工大学材料科学与工程学院,广州510640

出　　处：《建筑结构》2022年第S01期1529-1533,共5页Building Structure

基　　金：中交四航局基础研发项目(2020031B);广东省重点领域研发计划项目(2019B111106002)

摘　　要：采用浸泡试验法,结合混凝土孔隙结构测定、扫描电镜和纳米压痕测试手段研究了盐冻与石粉耦合作用对混凝土氯离子扩散系数的影响及作用机理,结果表明混凝土氯离子扩散系数不仅随石粉含量的提高先减少后增大,还随盐冻循环次数增加而显著增大,混凝土氯离子扩散系数最低试件的石粉含量随盐冻循环次数增加而降低,石粉含量为8%时混凝土氯离子扩散系数最低,盐冻循环210次和300次时氯离子扩散系数最低试件的石粉含量分别为5%和3%。石粉含量低于8%时石粉含量变化对混凝土平均孔径影响较小,但高于8%之后混凝土平均孔径随石粉含量提高而显著增大。在石粉含量低于8%范围内,盐冻循环对混凝土孔隙结构的影响是在总孔体积变化不明显的情况下增大了混凝土平均孔径,然后再引起总孔体积明显增加导致混凝土劣化。在盐冻循环环境下C50机制砂混凝土的石粉含量不宜超过8%。The influence and mechanism of the coupling effect of salt freezing and stone powder content on the chloride diffusion coefficient of concrete were studied by using the immersion test,concrete pore structure measurement,scanning electron microscope and Nano-indentation techniques.The results show that the chloride diffusion coefficient of concrete not only decreases first and then increases with the increase of stone powder content,but also increases significantly with the increase of salt freezing cycles.The stone powder content of the specimen with the lowest chloride diffusion coefficient decreases with the increase of salt freezing cycles.When the stone powder content is 8%,the chloride diffusion coefficient of concrete is the lowest,while the salt freezing cycles are 210 and 300,the stone powder content of the specimen with the lowest chloride diffusion coefficient is 5%and 3%respectively.The change of stone powder content has little effect on the average pore diameter of concrete when the stone powder content is lower than 8%,but the average pore diameter increases significantly with the increase of stone powder content when it is higher than 8%.When the content of stone powder is less than 8%,the effect of salt freezing cycle on the pore structure of concrete is to increase the average pore size of concrete when the change of total pore volume is not obvious,and then cause the obvious increase of total pore volume,which finally resulting in the deterioration of concrete.Under the salt freezing cycle environment,the stone powder content of C50 manufactured sand concrete should not exceed 8%.

关 键 词：盐冻循环 氯离子扩散系数 机制砂 高性能混凝土 孔隙结构 

分 类 号：TU528[建筑科学—建筑技术科学]