抄録
To examine how far the effect of mix proportion in fresh concrete and in hardened concrete, centrifugally placed, upon its properties is dependent on its conditions, six sorts of sand graded according to grain size were selected and several rates of mix proportion s/a were determined for the experiments, which have been performed with these selected materials thus variously mixed. The tests of fresh concrete have been performed to investigate the mutual relation between the different grade of sand and different rate of mix proportion s/a on one hand and on the other the water content required for maintaining constant consistency. Investigation has also been made of the efficacy of water-reducing admixture. The tests of hardened concrete have been made to find the effects of the above mentioned conditions in mixing proportion on the segregation and separation of centrifugally placed concrete, and to ascertain its manifest gain in strength. The main results obtained by them are as follows.
(1) Of the fine aggregates of different grades in grain size of sand, the finer part has effects on the water content, while the coarser part on the mix proportion s/a respectively, and when the mix proportion is properly determined, the centrifugally placed concrete with gap grades of sand will occasionally make better concrete of higher strength with smaller segregation.
(2) The use of water-reducing admixture of good quality will remarkably raise the workability of fresh concrete, and considerably reduce the segregation and separation of centrifugally placed concrete.
