【作者】 侯子义；

【导师】 徐东强；

【作者基本信息】 河北工业大学 ， 结构工程， 2012， 博士

【摘要】 耐久性问题是水泥混凝土研究的重要课题之一。冻融对铺面混凝土使用寿命的影响非常大。冻融循环对混凝土强度的影响较为明显，随着冻融次数的增加，混凝土强度特性呈下降趋势。抗折强度反映最敏感，变化最快，下降幅度也最大。对铺面混凝土冻融破坏的评定指标进行了研究，提出仅以相对动弹性模量和质量变化率来衡量是不够的，应增加抗弯拉强度损失率这个指标。对于铺面混凝土采用普通冻融试验，相对动弹性模量和质量变化率两个指标过于宽松，应根据混凝土含气量情况分类重新界定。对于抗冻混凝土，相对动弹性模量判定指标定为80%，质量变化率指标定为1%。对于非抗冻混凝土，相对动弹性模量判定指标为60%，质量变化率指标为5%。综合现场气温资料和室内冻融温度循环特征，将现场混凝土经历的冻融循环次数在损伤等效意义下转化为等效的试验室冻融环境下的标准冻融循环次数,定义为等效室内冻融循环次数。利用等效冻融循环次数和标准冻融试验数据可近似地估计一个地区水泥混凝土冻融耐久性使用年限。建立了不同降温速率、不同降温区间动弹模量损失率0.4的冻融循环次数。冻结温度对混凝土的冻融破坏有明显的影响，冻结温度由-5℃降低到-10℃时，混凝土的冻融破坏效果将出现一个突变，也即当混凝土中最低冻结温度达-10℃时，冻融破坏的力量将明显加大，因此,对于混凝土冻结温度有可能到达-10℃或更低温度的建筑物，必须设计较高的混凝土抗冻标号。冻结速率对混凝土的冻融破坏有一定的影响，冻结速率提高，冻融破坏力加大，混凝土容易破坏。应用混凝土冻融损伤模型，理论计算得到铺面混凝土抗冻标号与自然冻融循环次数之间定量对应关系为1:14的数量级，参考室内外对比试验结果及考虑一定安全系数，取铺面混凝土抗冻标号与自然冻融循环次数之间的定量对应关系为1:14。更多还原

【Abstract】 It is one of the important problems to study of cement concrete durability. Freezing andthawing of concrete affects pavement life in much large degrees. There is evidently influencethat freezing and thawing cycling to concrete strength. Concrete strength decreases withfreezing and thawing cycling times. Flexural strength is a mostly sensitive parameter varyingrapidly and largely. Being not efficient only with relative dynamic elastic modulus and masschanging rate, a parameter was discussed in which to appraise the damage degrees of concreteas freezing and thawing. The losing rate of flexural strength parameter should be used inappraising concrete freezing and thawing property. For pavement concrete freezing andthawing test，the parameters of relative dynamic elastic modulus and mass changing rate aretoo loose, so it should be determined again based on concrete air volume. For freezingresistant concrete, the limit of relative dynamic elastic modulus should be80%and masschanging rate1%. For common concrete, the limit of relative dynamic elastic modulus shouldbe60%and mass changing rate5%. Based on site and laboratory condition, freezing andthawing cycling times of concrete in site was changed to equivalent cycling times inlaboratory environment which was named as equivalent freezing and thawing cycle times.Servicing life of concrete in freezing and thawing may be estimated based on the equivalentfreezing and thawing cycle times and laboratory test data. It was been set up that the freezingand thawing times when dynamic elastic modulus losing by40%. There is evident influencethat freezing temperature to concrete damage. There is an abruptly change for concretefreezing and thawing damage effect when freezing temperature falls from-5℃to-10℃.Freezing and thawing damage force would be much great when temperature falling to-10℃.For construction concrete would endure freezing temperature lower than-10℃, the highfreezing-resistant grade concrete should be used in design. There is an influence betweentemperature decreasing rates to concrete freezing damage. Concrete would be badly damagedwhen temperature decreasing rapidly. Based on concrete freezing and thawing damagingmodel, relation between resistance grade to freezing-thawing of pavement concrete andnatural freezing and thawing cycle times was calculated out which is about1:14. Based onlaboratory and site test result and a certain safety factor,1:14was chosen as the quantityrelation.更多还原