冻融环境下的混凝土经时抗压强度

Time-dependent compressive strength of concrete in freeze-thaw environment

随着服役龄期的增加,在役RC结构混凝土强度表现出多龄期退化特性。为研究冻融环境下混凝土抗压强度经时变化规律,采用超声-回弹综合法与钻芯抽样修正试验相结合的方式,对哈尔滨、吉林及其周边地区在役RC结构混凝土抗压强度进行现场实测。通过对获取的924组混凝土抗压强度数据进行归一化及归并处理,采用非参数检验确定混凝土经时强度概率分布函数,并对相关参数与服役龄期的相关关系进行回归分析。结果显示:冻融环境下,超声-回弹综合法的钻芯法修正时变模型满足线性变化规律;不同服役龄期下混凝土相对抗压强度均服从正态分布;混凝土相对抗压强度均值、标准差随服役龄期的变化规律可分别利用二次多项式模型与线性模型表征。

With the increase of service life,the concrete strength of existing RC building structure degradates.To study the change law of the time-dependent compressive strength of concrete under freeze-thaw environment,the compressive strength of concrete of existing RC buildings in Harbin,Jilin and its surrounding areas was tested on the spot by combining ultrasonic-rebound stress test with core-drilling method.By normalizing and merging 924 groups of concrete compressive strength data,nonparametric test method was adopted to determine the probability distribution function of the normalized concrete strength,and the relationship between relevant parameters and service age was analyzed by regression analysis.The test results show that under freeze-thaw environment,the modified time-varying model of ultrasonic-rebound stress test satisfies the linear variation law,the time-dependent concrete compressive strength obeys normal distribution,the variation of mean value and standard deviation of concrete relative compressive strength with service age can be fitted by quadratic polynomial model and linear model respectively.