PSI - Issue 66

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Procedia Structural Integrity 66 (2024) 419–425

8th International Conference on Crack Paths Fracture process zone evaluation of ultra-high performance hybrid fibre reinforced concrete with varying fibre percentage. Sneha a *, Sonalisa Ray b 8th International Conference on Crack Paths Fracture process zone evaluation of ultra-high performance hybrid fibre reinforced concrete with varying fibre percentage. Sneha a *, Sonalisa Ray b

a Research Scholar (Civil Engineering Department, Indian Institute of Technology Roorkee, India) b Professor (Civil Engineering Department, Indian Institute of Technology Roorkee, India) a Research Scholar (Civil Engineering Department, Indian Institute of Technology Roorkee, India) b Professor (Civil Engineering Department, Indian Institute of Technology Roorkee, India)

Abstract Abstract

Ultra-high performance fibre reinforced concrete (UHPFRC) has attracted considerable attention in the construction industry because of its outstanding mechanical properties and advanced performance characteristics. Steel fibres play a crucial role in enhancing the tensile strength and ductility of UHPFRC, leading to improved post-crack behaviour. Therefore, this research aims to examine the post-cracking behaviour of UHPFRC by analyzing its response to various percentages as well as a combination of different types of fibres. To achieve high strength and improved packing density in the UHPFRC composite, fine-grained reactive admixture has been blended with cement. A compressive strength of 126 MPa has been achieved with 2 % of 20 mm straight steel fibres. The beam of dimensions 700 mm ×150 mm ×80 mm with an initial notch of 30 mm and 3 mm width has been used for fracture testing under centre point loading. The experiments have been performed under the crack mouth opening displacement (CMOD) control manner. Additionally, the digital image correlation (DIC) technique has been used to study the fracture process zone (FPZ) development for different fibre lengths and fibre volumes and their combination. Based on the results, it is concluded that the 2% fibre volume shows the highest peak load according to the load-CMOD curve. However, DIC analysis reveals that hybrid fibres demonstrate superior crack-bridging action, resulting in shorter crack lengths and slower crack-widening. Ultra-high performance fibre reinforced concrete (UHPFRC) has attracted considerable attention in the construction industry because of its outstanding mechanical properties and advanced performance characteristics. Steel fibres play a crucial role in enhancing the tensile strength and ductility of UHPFRC, leading to improved post-crack behaviour. Therefore, this research aims to examine the post-cracking behaviour of UHPFRC by analyzing its response to various percentages as well as a combination of different types of fibres. To achieve high strength and improved packing density in the UHPFRC composite, fine-grained reactive admixture has been blended with cement. A compressive strength of 126 MPa has been achieved with 2 % of 20 mm straight steel fibres. The beam of dimensions 700 mm ×150 mm ×80 mm with an initial notch of 30 mm and 3 mm width has been used for fracture testing under centre point loading. The experiments have been performed under the crack mouth opening displacement (CMOD) control manner. Additionally, the digital image correlation (DIC) technique has been used to study the fracture process zone (FPZ) development for different fibre lengths and fibre volumes and their combination. Based on the results, it is concluded that the 2% fibre volume shows the highest peak load according to the load-CMOD curve. However, DIC analysis reveals that hybrid fibres demonstrate superior crack-bridging action, resulting in shorter crack lengths and slower crack-widening. © 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 © 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 Keywords: Digital image correlation, Fracture energy, Fibre percentage, Hybrid fibres, Ultra-high performance concrete. © 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 Keywords: Digital image correlation, Fracture energy, Fibre percentage, Hybrid fibres, Ultra-high performance concrete.

* Corresponding author. E-mail address: sneha@ce.iitr.ac.in * Corresponding author. E-mail address: sneha@ce.iitr.ac.in

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

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.2024.11.094