Estudo da resistência à tração de tirantes produzidos com concreto autoadensável fibroso moldados na horizontal e vertical

Abstract

This research aimed to evaluate the influence of horizontal and vertical casting direction on the stress transfer mechanism in self-compacting fiber concrete specimens through uniaxial tension tests and the matrix cracking process. Thus, rheological characterization tests by Abrams cone spreading, Ring "J", Funnel "V" and box "L" were performed. In hardened state, cylindrical samples were evaluated for compression. The self-compacting Fiber Concrete Rods of dimensions 150x150x750mm with 20 and 25mm steel bars, centered on their cross section, were cast in two directions: horizontal and vertical, and evaluated by uniaxial tension tests. The cracking process was evaluated through the use of digital correlation of images and the dispersion and orientation of fibers by Computed tomography. The rheological results indicated satisfactory values in the quality of the mixture to characterize it as an self-compacting, presenting Abrams cone spreading values greater than 550mm, VS2 plastic viscosity and IEV0 visual stability index. The mechanical compression tests indicate that, when in the presence of fibers, the matrix had gains of 14.84% in the resistance and reduction of its longitudinal elasticity module. The mechanical results of the rods pointed influence of the casting direction in the fracture mode of the samples. When cast horizontally, the rods showed stiffening stress due to the orientation of the fibers by wall effect during the flow of the mixture in the fresh state into the form. In the vertical group, the rods showed transverse cracks simultaneously on the front and back faces, which is a result of the randomness of the fibers and the lower presence of fibers in a favorable position to the direction of loading.