ABSTRACT
This paper describes some of the parameters leading to the unique bond behavior of newly developed steel fibers, called Torex fibers, which are polygonal in cross section and twisted along their length. Pull-out tests, whereby a single fiber is pulled out from a cementitious matrix, are used to study the bond behavior of these fibers. The results of several series of pull-out tests are described and analyzed based on the following parameters: 1) the cross-sectional shape of the fiber, that is, a triangular or a square cross section, 2) the number of ribs (induced by twisting) per unit length of fiber, 3) the compressive strength of the matrix (from 10 to 50 MPa) and the tensile strength of the fiber, and 4) the embedded length of the fiber. Some comparison with smooth and hooked steel fibers is also provided. The high efficiency of the new fibers implies that a lesser volume of them is needed to achieve a certain level of composite performance. It is concluded that the new fibers are also a key to advancing the development of both strong and ductile high performance fiber reinforced cement composites
