PSI - Issue 66

ScienceDirect Structural Integrity Procedia 00 (2025) 000–000 Structural Integrity Procedia 00 (2025) 000–000 Available online at www.sciencedirect.com Available online at www.sciencedirect.com ScienceDirect Available online at www.sciencedirect.com ScienceDirect

www.elsevier.com/locate/procedia

www.elsevier.com/locate/procedia

Procedia Structural Integrity 66 (2024) 337–343

8th International Conference on Crack Paths Characterization of the fracture behavior of UHPFRC by considering the influence of specimen size and fiber content Bineet Kumar a * , Awadhesh Sharma b , Sonalisa Ray c 8th International Conference on Crack Paths Characterization of the fracture behavior of UHPFRC by considering the influence of specimen size and fiber content Bineet Kumar a * , Awadhesh Sharma b , Sonalisa Ray c a ,b,c Indian Institute of Technology Roorkee, India, 247667

a ,b,c Indian Institute of Technology Roorkee, India, 247667

Abstract

Abstract

The remarkable compressive and flexural strength, along with the dense microstructure of ultra-high-performance fiber-reinforced concrete (UHPFRC), offers a significant advantage in constructing durable and efficient structural elements. However, accurately predicting the hardening/softening profile of UHPFRC , and crack propagation in relation to post-cracking tensile behaviour poses challenges, particularly when considering the influence of specimen size. Additionally, the influence of fiber content on the post-peak behavior of UHPFRC is also important to understand. Therefore, in this study, an attempt has been made to characterize the post-cracking tensile behavior and crack propagation of UHPFRC by considering the effect of specimen size and fiber content. In this work, three different beam-size specimens have been considered, prepared with hooked-end long steel fiber having dosages of 1.5% and 2.5%, and load-CMOD behavior has been examined under flexural loading conditions. Simultaneously, the digital image correlation technique (DIC) has been utilized to monitor the crack propagation. It has been observed that the load-CMOD behavior of beam samples with a fiber percentage of 1.5% shows a sudden decrease in load-carrying capacity after the peak load. Subsequently, it shows hardening behavior and reach the local peak. However, beam samples with 2.5% fiber report higher peak load and show gradual softening after the peak load. It indicates that the fiber content strongly influences the post-peak bridging mechanism. It may be possible that matrix cracking affects the bridging mechanism in case of lesser fiber content, and significant cracking occurs in the absence of fibers. Additionally, fiber-bridging and pull-outs also influence the fracture process in the post-cracking region. Moreover, it also reveals that fiber-bridging zone increases with an increase in specimen size. Therefore, an analytical framework has also been proposed to characterize the post-cracking tensile behavior along with crack propagation by considering the influence of specimen size and fiber content. The remarkable compressive and flexural strength, along with the dense microstructure of ultra-high-performance fiber-reinforced concrete (UHPFRC), offers a significant advantage in constructing durable and efficient structural elements. However, accurately predicting the hardening/softening profile of UHPFRC , and crack propagation in relation to post-cracking tensile behaviour poses challenges, particularly when considering the influence of specimen size. Additionally, the influence of fiber content on the post-peak behavior of UHPFRC is also important to understand. Therefore, in this study, an attempt has been made to characterize the post-cracking tensile behavior and crack propagation of UHPFRC by considering the effect of specimen size and fiber content. In this work, three different beam-size specimens have been considered, prepared with hooked-end long steel fiber having dosages of 1.5% and 2.5%, and load-CMOD behavior has been examined under flexural loading conditions. Simultaneously, the digital image correlation technique (DIC) has been utilized to monitor the crack propagation. It has been observed that the load-CMOD behavior of beam samples with a fiber percentage of 1.5% shows a sudden decrease in load-carrying capacity after the peak load. Subsequently, it shows hardening behavior and reach the local peak. However, beam samples with 2.5% fiber report higher peak load and show gradual softening after the peak load. It indicates that the fiber content strongly influences the post-peak bridging mechanism. It may be possible that matrix cracking affects the bridging mechanism in case of lesser fiber content, and significant cracking occurs in the absence of fibers. Additionally, fiber-bridging and pull-outs also influence the fracture process in the post-cracking region. Moreover, it also reveals that fiber-bridging zone increases with an increase in specimen size. Therefore, an analytical framework has also been proposed to characterize the post-cracking tensile behavior along with crack propagation by considering the influence of specimen size and fiber content. © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of CP 2024 Organizers 1. Introduction Ultra-high-performance fibre-reinforced cementitious composites (UHPFRC) distinguish themselves from conventional normal-strength concrete (NSC) by their significantly higher compressive strength, which generally surpasses 120 MPa, alongside their enhanced ductility and durability. These composites are defined by their high 1. Introduction Ultra-high-performance fibre-reinforced cementitious composites (UHPFRC) distinguish themselves from conventional normal-strength concrete (NSC) by their significantly higher compressive strength, which generally surpasses 120 MPa, alongside their enhanced ductility and durability. These composites are defined by their high Keywords: UHPFRC, fracture, size effect, tensile properties, fibre orientation, wall effect Keywords: UHPFRC, fracture, size effect, tensile properties, fibre orientation, wall effect

* Corresponding author. E-mail address: bkbineet@gmail.com * Corresponding author. E-mail address: bkbineet@gmail.com

2452-3216 © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of CP 2024 Organizers 10.1016/j.prostr.2024.11.084 2452-3216 © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of CP 2024 Organizers 2452-3216 © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of CP 2024 Organizers