Inflence of curing and loading conditions on stress-strain relationship of super high strength concrete.

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The object of this project is to obtain fundamental data in order to clarify behavior of stress-strain curve of structural concrete with high strength ranged from 400 to 1000 kgf/cm^2, and especially the behaivor of falling branch after compresivve strength.In the first year, since stiffness of a loading flame and a control technique of loading influence severely the results of loading test focused on such behaviors, an experiment system was proposed, which consisted of a loading flame with high stiffness and an actuator controled by a computer system.In the second year, experimental study on many influence factors on the behavior carried out by using the loading system and concrete sylinder specimens with a diameter of 100mm and a hight of 200mm. The results are summarized as the follows :(1)The concrete curing in water has the largest initial stiffness and severest strength reduction after the ultimate strength among three conditions of curing in water, sealing and air. (2)In case of curing condition changed from in sealing to in air, the more curing days in sealing is, the more remarkable the behavior mentioned in (1) is. (3)The difference of stress-strain relationship is little between normal and high-early-strength Portland cements. (4)The initial stiffness and the strain at ultimate strength become larger and the strength reduction after ultimate strength becomes severer proportional to compressive strength of concrete. (5)Among the four previous equations expressing the stress-strain curves, Shirai's equation is the best fit to the experimental resurt of concrete curing in water but not good to the other curing conditions.