<b> ABSTRACT </b> <br>

Over recent years, Electric Arc Furnace Slag (EAFS), a by-product of the steel-making industry, has been used as a replacement of natural aggregates to produce high-performance concrete. In EAFS concrete, fibers are normally added to improve post-cracking behavior, thereby prolonging the durability and range of applications of the composite. Despite the rise in its production, the mechanical performance of fiber-reinforced EAFS concrete is still poorly understood, posing important barriers to its daily use.

This paper aims to study the effect of fiber materials (steel and synthetic) on EAFS concrete performance. To do so, the paper proposes, firstly, an experimental campaign and, secondly, a numerical simulation to model the effect of fibers both in the pre-cracking and post-cracking stages. Importantly, for the numerical study, an in-house Finite Element (FE) code is developed using interface elements to capture crack propagation. The FE code uses, as input, data obtained in the experimental campaign and is validated against previously unseen experimental results. The overall framework gives important insights on how fibers improve the post-cracking behavior of EAFS concrete and the relevance of fiber material in the overall performance. The validated numerical tool can be used in the future to design EAFS fiber-reinforced concrete structures and therefore increase the applicability of such composite material.

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<b> ACKNOWLEDGEMENTS</b> </br>

The authors wish to express their gratitude to the following entities for having funded this research work: the Spanish Ministries MCI, AEI, EU and ERDF [RTI2018-097079-B-C31; PID2020-113837RB-I00; 10.13039/501100011033]; the Junta de Castilla y León (Regional Government) and ERDF [UIC-231, BU119P17]; the Basque Government research group [IT1619-22 <b>SAREN</b>]; the University of Burgos [Y135.GI]. Likewise, our thanks to CHRYSO and HORMOR for supplying the materials used in this research.