Bond-slip response of steel fibers after exposure to elevated temperatures: experimental program and design-oriented constitutive equation

This study aimed to evaluate the effect of elevated temperatures on the bond-slip behavior of hooked-end steel fibers. A total of 180 pullout specimens were tested in post-cooling conditions using a double-sided pullout test with multiple embedded fibers for target temperatures between 25 and 750 °C. Results proved that the bond strength significantly increases for temperatures up to 450 °C, and drastically decreases for temperatures of 600 and 750 °C. The contribution of hooks reduced with temperature and is negligible for temperatures higher than 600 °C, while the fiber-matrix frictional interaction seems to improve for all temperatures evaluated. A temperature-sensitive constitutive equation that allows simulating the bond-slip behavior of hooked-end steel fibers is proposed and its suitability confirmed through a numerical model.The authors would like to thank the Institute for Technological Research (IPT) and its foundation (FIPT) for their financial and institutional support through the New Talents Program (Grants #N.01/2017 and #N.01/2018). This work was also partially supported by the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) [Grant # 305055/2019-4 (Antonio Domingues de Figueiredo) and Grant # 310401/2019-4 (Luís A.G. Bitencourt Jr.)]. The authors would also like to thank the researchers Ph.D. Renata Monte (USP), MSc Priscila Rodrigues Melo Leal (IPT), and Eng. Tiago Haddad Marum (USP) for the technical contributions that improved the quality of this work.Peer ReviewedPostprint (author's final draft