混凝土冻融作用下冻结应力演化规律及对抗冻性能的影响  

The Evolution of Freezing Stress in Concrete Under Freeze-thaw Condition and Its Influence on Frost Resistance

作　　者：戈雪良[1,2,3] 柯敏勇 刘伟宝[1] 陆采荣[1,3] 王珩[1] 梅国兴[1] 杨虎[1] GE Xueliang;KE Minyong;LIU Weibao;LU Cairong;WANG Heng;MEI Guoxing;YANG Hu(Nanjing Hydraulic Research Institute,Nanjing 210029,China;State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering,Nanjing 210029,China;Research Center for Climate Change,MWR,Nanjing 210029,China)

机构地区：[1]南京水利科学研究院,南京210029 [2]水文水资源与水利工程科学国家重点实验室,南京210029 [3]水利部应对气候变化研究中心,南京210029

出　　处：《材料导报》2024年第12期107-111,共5页Materials Reports

基　　金：国家重点研发计划项目(2022YFC3202500);国家自然科学基金重点项目(11932006);国家自然科学基金面上项目(51579155)。

摘　　要：为了探究严寒地区混凝土冻害机理及冻结应力对混凝土抗冻性的影响,基于大型极端气候模拟器模拟-40℃低温冻害的条件,采用研制的冻结应力测试装置对F300高抗冻等级混凝土在冻融单次降温阶段及降温-升温冻融循环两种模式下的冻结应力及抗冻性能进行研究,同时利用了环境扫描电子显微镜对冻融循环作用下的混凝土微观裂缝进行了测试研究。研究表明:-40℃单次降温过程中降温速率越快,冻结应力出现的时间越早、混凝土内部产生的冻结应力增幅也越大;冻融循环降温阶段产生的冻结应力会随降温-升温冻融作用的不断循环而累积增大,且冻结应力的发展存在转变拐点,在相同降温终了试件中心低温条件下,降温阶段的降温速率越大,冻结应力由增加转入减小的拐点出现越早;冻融过程中的冻结应力与混凝土质量损失、相对动弹性模量两个抗冻性常用评价指标有较好的对应关系;冻结应力逐步使水泥浆体产生损伤,表现为微观裂缝的生成与发展,损伤积聚产生冻害。In order to explore the freezing damage mechanism of concrete in severe cold area and the action mechanism of freezing stress affecting the frost resistance of concrete,based on the simulation of-40℃low-temperature freezing damage condition by large-scale extreme climate simulator,the freezing stress and frost resistance of F300 high frost resistance design concrete under single cooling stage and cooling heating freezing and thawing cycle were studied by using the developed freezing stress test system.At the same time,the microstructure of concrete under freeze-thaw cycle was studied by environmental scanning electron microscope.The experimental results demonstrate that in the single cooling process under-40℃low-temperature,the faster the cooling rate is,the earlier the freezing stress appears,and the greater the increase of freezing stress in the concrete.The freezing stress generated in the cooling stage will accumulate and increase with the continuous cycle of freezing and thawing,and there is a transition inflection point in the development of freezing stress.Under the same low temperature condition in the center of the specimen at the end of cooling,the greater the cooling rate in the cooling stage,the earlier the inflection point from growth to reduction of freezing stress appears.There is a good correlation between the freezing stress in the process of freezing and thawing and the two commonly used evaluation indexes of concrete quality loss and relative dynamic elastic modulus.The freezing stress gradually causes damage to the cement paste,which is manifested in the formation and development of micro cracks,and the damage accumulation produces freezing damage.

关 键 词：混凝土 冻融循环 冻结应力 演化规律 抗冻性能 作用机制 

分 类 号：TU5[建筑科学—建筑技术科学]