Abstract
The passing ability of fresh concrete is an important characteristic, which ensures fresh concrete to have enough pumpability and pass through steel bars smoothly. Particle size effect and condensation of aggregate particles due to segregation are generally considered as main blocking causes of fresh concrete at openings. However, the effect of boundary restraint of opening on the flow of fresh concrete is yet unclear. In this paper, to clarify why deformation resistance of fresh concrete increases at openings, the resulted normal stress on shear plane when the shear deformation is restrained in normal direction, was investigated experimentally with a shear box apparatus, in which a stress-controlled method was adopted. And the effects of fluidity, maximum size of coarse aggregate, and loading rate on the normal stress were examined in detail. Based on the experimental results, a normal stress model was proposed to quantify the boundary restraint on the flow of fresh concrete. A method was further proposed to predict the decline of flow ability of fresh concrete at openings. Finally, a prediction example of restrained shear strain was given.
