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

本项目的目的是获得基本数据，以了解高强混凝土在400~1000kgf/cm~2范围内的应力-应变曲线行为，特别是受压后的掉枝行为。第一年，由于加载火焰的刚度和加载控制技术对加载试验结果的影响很大，提出了一种由高刚度加载火焰和计算机控制的执行器组成的实验系统。第二年，针对加载火焰的刚度和加载控制技术对加载试验结果的影响，提出了由高刚度加载火焰和由计算机控制的执行器组成的实验系统。第二年，针对加载火焰的刚度和加载控制技术对加载试验结果的影响，提出了一种由高刚度加载火焰和计算机控制的执行器组成的加载实验系统。第二年，由于加载火焰的刚度和加载控制技术对加载试验结果的严重影响，提出了由高刚度加载火焰和由计算机控制的执行器组成的实验系统利用加载系统和直径为100 mm、高度为200 mm的混凝土衬砌试件进行了多种影响因素的试验研究。主要研究结果如下：(1)在水中养护、密封养护和空气养护三种养护条件下，水养护混凝土的初始刚度最大，极限强度后强度下降最严重。(2)当养护条件由密封状态变为空气状态时，密封状态下的养护天数越长，上述(1)中的养护行为越显著。(3)普通和高早强波特兰水泥的应力应变关系差异不大。(4)混凝土的初始刚度和极限强度应变变大，极限强度后的强度折减与混凝土的抗压强度成正比。(5)在描述应力-应变曲线的四个方程中，Shirai方程最适合于混凝土在水中养护的试验结果，但对其他养护条件的拟合效果不佳。

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.