Abstract
This poper describes the various factors which cause variation in concrete strength in making concrete, and presents statistical methods which are useful in interpreting these variations. The effects of the various factors influencing concrete strength are analysed in detail. The paper presents the calculated values of the standard deviations and variances in concrete strength with four degrees of control, in using the mix proportions of concrete and the procedure for designing mixes, which has been recommended by Japanese Architectural Standard Specification, number five, at present. It is apparent from these values that the coefficient of variation is independent of the average strength of the concrete under "good control," and does not remain constant under "fair control" and "poor control." On the other hand, the standard deviation does not so apparent trend as the coefficient of variation.
