钢筋混凝土早龄期约束收缩试验研究

Restrained Shrinkage Experiments of Reinforced Concrete at Early Age

针对现浇混凝土结构早期变形开裂问题,设计了适用于轴向配筋试件的刚性框架端部约束收缩试验装置,进行不同配筋率和不同钢筋布置方式下C30混凝土干燥约束收缩试验,并以素混凝土试件和配筋试件端部自由收缩试验作为对比。测试配筋试件和素混凝土试件收缩变形、约束荷载、内部相对湿度随龄期的发展变化。结果表明：端部自由情况下,配筋试件干燥收缩小于素混凝土试件,约束率随配筋率增加而增大;端部约束情况下,配筋试件约束荷载远小于素混凝土试件,仅为素混凝土试件的1/8~1/17;干燥收缩过程中混凝土内部相对湿度呈“3阶段”规律变化。研究结果为混凝土早期变形开裂及防裂措施的研究提供参考。

A special rigid frame device was developed that can be used for testing uniaxial restrained drying shrinkage of reinforced concrete. Restrained shrinkage test series of C30 concrete was performed at different reinforcement ratio and configurations, in parallel with the free shrinkage test for comparison. The measured values are the free shrinkage, the restraint loads, and the relative humidity inside of concrete. The results show that for the end-free condition, the shrinkage of reinforced concrete is smaller than plain concrete, the restraint rate increasing along with the reinforcement ratio; and that for the endrestrained condition, the restrained load in reinforced concrete is much smaller than in plain concrete due to the effect of reinforcement, and is only 1/8-1/17 of plain concrete, and that the internal relative humidity presents ＂ 3-stage＂ curve. These results are good references for analyzing the deformationcaused cracking and for anti-cracking measures in concrete structures.