Orientation-Dependent Modeling of Recycled Steel Fiber-Reinforced Self-Compacting Concrete

Abstract

Recycled tire steel fibers (RSFs) offer a resource-efficient alternative to manufactured industrial steel fibers (ISFs), but their irregular geometry and casting-induced orientation generate pronounced direction-dependent post-cracking behavior. This study develops and evaluates a three-dimensional orientation-conditioned finite element framework for notched splitting tensile tests of self-compacting concrete containing a constant total steel fiber dosage of 90 kg/m3 with ISF:RSF proportions of 90:0, 45:45, 30:60, and 0:90. The experimental mechanical response and independently measured fiber architecture provide the basis for constitutive identification and numerical–experimental assessment. The composite is represented in Abaqus/Standard using the concrete damage plasticity model and eight-node full-integration hexahedral elements. Fiber bridging is introduced through orientation-specific quadrilinear tensile stress-crack-opening laws derived from the measured peak and residual responses, allowing directional fiber effects to be represented without discrete fiber modeling. The simulations reproduce the measured peak, residual, and post-cracking responses for crack planes parallel and perpendicular to the casting flow direction, with deviations below 5% at the evaluated characteristic response points. Progressive RSF replacement reduces peak tensile resistance, whereas hybrid and mono-RSF mixtures retain a smoother post-peak decay. The higher residual capacity observed for the favorable orientation is consistent with the independently measured effective fiber population and orientation factor. The framework provides an efficient continuum strategy for incorporating casting-induced anisotropy into engineering-scale analyses of RSF-reinforced concrete.