Abstract
The results of the present study are summarized as follows : 1) Concrete subjected to similar conditions in setting slabs shows a more rapid drying speed immediately after placing so that the compressive strength and the Young's modulus are greatly reduced. 2) Concrete subjected to similar conditions in setting walls shows a large increase of the compressive strength for a period of 6 months, but thereafter the compressive strength and the Young's modulus are decreased. 3) Concrete subjected to similar conditions in setting columns shows no decrease in the compressive strength and Young's modulus due to its large volume. After 2 years columns have a greater compressive strength than concrete cured in water for 4 weeks. However, the Young's modulus is somewhat smaller afters 2 years, and should continue in time to decrease in size. 4) The ratio of the compressive strength or the Young's modulus of high-strength concrete (F_<28>=354kg/cm^2) in walls and slabs after 2 years to F_<28> or E_<28> is about the same as the ratio of the compressive strength or the Young's modulus of low-strength concrete (F_<28>=181kg/cm^2) in walls and slabs to F_<28> or E_<28>. The above does not apply in the case of concrete set in columns. 5) The compressive strength and the Young's modulus of concrete shows great variation according to the degree of dryness that concrete exhibits. It seems necessary to define a new equation for the estimation of the Young's modulus, as the Young's modulus of concrete when dried is less than that for structural calculation.
