Fiber geometrical parameters of fiber-reinforced high strength concrete and their influence on the residual post-peak flexural tensile strength

Abstract

The mechanical behavior under flexural tensile stress of fiber-reinforced concretes is strongly conditioned by fiber density and orientation; in particular, the residual strength values under tensile stress forces. However, although a lot of research has been conducted to understand how the casting and type of compaction affects the fiber distribution and orientation, up to date neither fiber location nor fiber orientation can be controlled during the concreting process. The uncertainty of fiber distribution within the material implies scatter results, in such a way that apparently identical fiber-reinforced concrete specimens can show very different results, in terms of mechanical behavior. The use of CT-Scan technology means that the exact location and orientation of the fibers within a concrete specimen may be depicted. In addition, as a non-destructive test, it can be done prior to mechanical testing.This paper studies the relation between fiber density and orientation and behavior under flexural tensile stress, through the use of CT-Scan technology. To do so, a high-strength steel-fiber reinforced concrete wall was constructed and 8 100 × 100 × 350 mm prismatic specimens were extracted from different sections of the wall, with the intention of revealing different fiber density and orientation values. First, the specimens were scanned using a CT-Scan, to obtain the real fiber density and orientation values. Subsequently, they were tested in a three-point-bending test, to obtain the curves tension –CMOD, and LOP values and residual strength under tension. Finally, empirical relations are shown between those values and fiber density and orientation.