Improved Ring Test For Early Age Shrinkage Of Concrete

Nowadays, concrete has become the largest amount of building materials in construction projects, with its experience of ordinary concrete, high strength concrete, is now developing in the direction toward high performance concrete. In order to reach the purpose of high performance, it had to be reduced the water cement ratio and increased the amount of the cementitious materials, which lead to increasing the probability of early age cracking. Especially for high-performance concrete, to research the early age shrinkage may be more important than in the late because that the shrinkage mainly occurred in the early age and it was larger. In recent years, a lot of research had been done on the concrete early age shrinkage cracking, but there was no a standard test method for the concrete restrained shrinkage in early age, so far, the researchers had to apply different research methods or experimental program due to the different research object and content.The early age shrinkage of concrete was affected mainly by the cement hydration rate and the water loss rate of evaporation, and because of uneven shrinkage in concrete, which lead to the existence of shrinkage stress gradient and the constraints between layers. In order to reduce the effect of stress gradients and constraints, the traditional restrained shrinkage ring test device was improved as the layered constraints steel ring.In this dissertation, the layered ring restrained shrinkage test device was used to research the early age shrinkage of concrete on the effect of water-cement ratio, slurry-aggregate ratio, the amount of fly-ash, steel fiber and basalt fiber. And the early age shrinkage of self compacting concrete was be researched.The results indicated that the layered ring test method could predict the cracking of concrete more sensitively and accuracy in early age shrinkage testing than the traditional test method.