Abstract
The author this time offers the measuring scale for grading sands in 1 week mortar strength. According to this scale the result well aggrees with that of by the 4 week test, which is already shown. In order to detect that scale he prepared a pair of test groups. Each group is composed of two-way-layout experiment (sand)×(water-cement ratio); 2 test pieces are formed from every mortar mix, one for 1 week test, the other for 4 week. The strength of the above two samples corresponds each other in conformity to the respective age. Analysing the two sets of data apart, comparing the variances of the experimental errors, testing the significancy of the factors and the significant levels, he arrives the conclusion that the 4 week scale should be modified for 1 week by the ratio of the respective standard deviation of the two experimental errors, because the original scale is derived from the population standard deviation of the error in 4 week test. At last he applys the acquired scale to the 1 week data and shows the result well aggrees with the 4 week test. Thus we can grade sands through 1 week mortar test.
