钻芯法检测混凝土强度及其标准差研究

Study on Strength and Standard Deviation of Concrete Assessed by Core Drilling Method

为探求钻芯法检测混凝土强度及其标准差的影响因素,对比分析了中国、美国、欧洲相关规程在取芯方式、龄期、规格、样本数量、是否含有钢筋、是否进行无损检测、试验环境、强度推算公式等方面的异同。通过收集整理22篇文献中钻芯法的试验数据,经过综合分析发现:芯样直径相近时,抗压强度随高径比的增加而减小。芯样高径比相近的情况下,高径比小于1时,芯样直径相对于最大骨料粒径越大,芯样强度越高;高径比大于1小于1.5时则相反。在板与宽梁中,平行于浇筑方向钻取的芯样抗压强度大于垂直于浇筑方向钻取的芯样抗压强度;在窄梁中则相反。芯样高径比与直径相近时,加载速率越快,芯样抗压强度越高。高径比对芯样抗压强度标准差没有影响。大部分情况下,对相同芯样计算出的推定强度,从大到小依次为中国规程、美国规程、欧洲规程。

In order to explore the influence factors of the concrete strength and its standard deviation measured by the core drilling method,the standards of the core drilling methods in China,America and Europe are firstly analyzed.The three standards are different in terms of drilling method,age,core size,core number,reinforced or not,non-destructive testing or not,test environment,and calculation formula.Through analyzing the test data of the core drilling method in 22 references,it is found that when the core diameter value is close,the strength of cores decreases as the height-to-diameter ratio increases.When the height-todiameter ratios are close and less than 1,the strength of cores increases as the height-to-diameter ratio increases.The results are reversed when the height-to-diameter ratio is between 1 and 1.5.The compressive strength of cores which are drilled parallelly to the pouring direction is larger than that when it is drilled perpendicularly to the pouring direction in slab and wide beam,whereas in narrow beam the results are reversed.When the diameter and the height-to-diameter ratio of the cores are close,the compressive strength of the cores increases as the loading rate increases.In majority of cases,for the same core sample,the magnitude order of estimated strength from large to small is like such as evaluated by Chinese code,American code and European code.Height-to-diameter ratio of cores does not affect the standard deviation of compressive strength of core samples.