Abstract
This report is on the results of test made for four years (1958〜1961) in connection with middle & smale buildings constructed under the inspection and guidance of the Building & Repair Division of Kinki Regional Construction Bureao: the within day varition, the between day variation, the ratio of eligibility under required strength F_0, etc., in the compressive strength of concrete above referred to have been investigated and in view of the results thus obtained a study has been made of J.A.S.S. 5 regulations on guality control of concrete. The within day variations standard deuiation (σ_ω) of the compressive strength of concrete are smaller in each class than J.A.S.S. 5 values, that is, class A-10kg/cm^2, class B-22 kg/cm^2. The between day variation's standard deviation (σ_♭) of the compressive strength of concrete are: class A-25kg/cm^2, class B-45kg/cm^2, that is, in class A σ_♭ is nearly the same as J.A.S.S. 5 value, in class B that is 1.3 times as big as J.A.S.S. 5 value, and the ratio of eligibility under required strength F_0 is 50%, and in effecting quality control of concrete J.A.S.S. 5 regulations cannot assure the quality required. From this viewpoint there should be regulations in which the between day variation is fully considered. According to this study the standard deviations in each class are: class A-σ_ω≑10kg/cm^2, σ_♭≑25kg/cm^2, σ_<total>≑27kg/cm^2, class B-σ_ω≑22kg/cm^2, σ_♭≑45kg/cm^2,σ_<Total>≑50kg/cm^2.
