Meso-scale modeling of hybrid industrial/recycled steel fiber-reinforced concrete

This paper investigates the mechanical behavior of fiber-reinforced concrete (FRC) and focusses on the quantifying the effect of replacing Industrial Steel Fibers (ISFs), commonly adopted as spread reinforcement in FRC, with Recycled Steel Fibers (RSFs) recovered from waste tires. More specifically, it analyses the bending behavior of FRC beams reinforced with a constant volume fraction of steel fibers and variable proportions of ISFs and RSFs. First, a numerical model is formulated by assuming that FRC behaves as a multi-phase medium, where the nonlinear material behavior of the concrete matrix is simulated by following a discrete-crack approach for meso-scale analysis. Then, steel fibers are modeled as short cables, randomly distributed and embedded within the concrete matrix. The internal forces in the steel fibers are obtained by considering both bond-slip behavior and dowel effect. Comparisons between experimental results, obtained by the authors in a previous study, and numerical simulations, performed by means of the proposed numerical model, are discussed: the significant predictive capability of the latter confirms the soundness of the mechanical assumptions on which the model is based. Moreover, the possibility of predicting the behavior of FRC with Hybrid Recycled/Industrial Fibers paves the way toward the actual application of this sustainable material in real applications.