Reliability of the evaluation of concrete strength in structure with the number of specimen

This paper describes the influence of the core specimen's number on the sample mean and the standard deviation of concrete strength in structure. In this study, about 10 ∼ 40 core specimens collected from the three reinforced concrete structures at each floor, built at about 1955 ∼ 1965, are used. As a result, it is revealed that the mode of sample mean at three core specimens almost equals to the population mean, and that the mode of sample standard deviation at six core specimens almost equals to the population standard deviation.