Abstract
The author offers the method of determining water cement ratio for concrete of Portland blast-furnace cement, of pozzolanic cement and of heigh-early-strength Portland cement. He prepared 4 sets of multifactorial experiments in orthogonal arrays; L_<18>(2^1×3^7), L_<54>(2^1×3^<25>), L_<31>(3^<40>) and L_<32>(2^<31>). Factors and levels are about alike in each case though some difference exists in details. Always 3 or 4 kinds of cement was picked up as the levels of cement-factor. They are Portland blast-furnace A, B, pozzolanic B, Portland and high-early-strength Portland cement. (1) He analyses the data in each case and gives partial conclusions in reference to every set of experiment. The results of the 4 sets do not always coincide with one another; in certain cases the estrangth clearly differs in compliance with the kinds of cement and yet we can find no significant difference in other cases. The interaction effect in strength between water-cement ratio and sand is sometimes significant and sometimes is not. (2) In spite of such partial disagreement those experiments are almost equivalent in accurracy and in average strength of concrete. So the author separated concrete strength formulae for each kind of cement from every set of the experiment and after that he put them together respectively in one formula for each kind of cement. (3) Comparing the above 3 formulae, he drew the following conclusion. a) The linear gradients of the 3 formulae do not differ significantly. b) The average strength, denoting in F/K, differs one another, where F is 4 week strength of concrete and K is that of cement. c) Approximately speaking, F/K of h.-l.-s. Portland cement is 110%, F/K of Portland b.-f. cement is 90% as compared with that of Portland cement.
