摘要
为了探索混凝土结构在除冰盐作用下的表面冻融损伤规律,采用快冻法进行了普通混凝土(OPC)、引气混凝土(APC)和高性能混凝土(HPC)试验梁在3.5%(质量分数,后同)NaCl溶液中的盐冻试验,用超声平测方法测定了混凝土结构的表面损伤层厚度,并提出了盐冻损伤度这一新的评价指标。讨论了中国《公路钢筋混凝土及预应力混凝土桥涵设计规范》(JTG D62—2004)中除冰盐环境下混凝土结构的最小保护层厚度问题,认为部分规定可能偏于不安全。结果表明:OPC的盐冻损伤度随着冻融循环次数的增加而急剧线性增大,添加引气剂可以有效减小混凝土的盐冻损伤度,提高其抗盐冻能力;矿物掺合料的种类和掺量对于引气HPC的抗盐冻能力具有很大影响;掺加10%硅灰、20%粉煤灰或者50%矿渣时,引气HPC表现出卓越的抗盐冻能力,其典型特征是盐冻损伤度降低、后期增长速度非常缓慢。
In order to explore surface freezing-thawing damage rule of concrete structure exposed to salt freezing condition,the salt freezing experiment with test beams made of ordinary Portland cement concrete （OPC）, air-entrained Portland cement concrete （APC） and high performance concrete （HPC） in 3.5% mass of sodium chloride solution was studied by the accelerated freezing method. Using ultrasonic testing method, the surface damage layer thickness of concrete structure was detected,and a new evaluation index, i. e. the salt freezing damaged degree was put forward. Minimum cover depth of concrete structure exposed to salt freezing condition was discussed, and some regulations required by Code for Design of Highway,a y Reinforced Concrete and Prestressed Concrete Bridges and Culverts （JTG D62 -2004） were considered to be insecure. The results show that the salt freezing damaged degree of OPC increases sharply and linearly with increase of freezing-thawing cycle number. But the addition of air-entrained admixture can efficiently decrease salt freezing damaged degree of the concrete and enhance its salt freezing resistance. Thesalt freezing resistance of air-entrained HPC is prodigiously influenced by the type and the amount of mineral admixtures. Air-entrained HPC with 10% mass of silica fume or 20% mass of fly ash or 50% mass of slag grain has the strongest salt freezing resistance and its typical characteristic is that the salt freezing damaged degree decreases, and in the later period, it increases very slowly.
出处
《中国公路学报》
EI
CAS
CSCD
北大核心
2009年第4期57-63,共7页
China Journal of Highway and Transport
基金
国家重点基础研究发展计划("九七三"计划)项目(2009CB623203)
江苏省自然科学基金前期预研项目(BK2005216)
中国博士后科学基金项目(20060400284)
南京航空航天大学博士生创新基金项目(BCXJ07-04)
关键词
桥梁工程
高性能混凝土
盐冻试验
冻融循环
引气混凝土
损伤层厚度
bridge engineering
high performance concrete
salt freezing experiment
freezing-thawing cycle
air-entrained Portland cement concrete
damage layer thickness
