PSI - Issue 70

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ScienceDirect

Procedia Structural Integrity 70 (2025) 509–516

Structural Integrity and Interactions of Materials in Civil Engineering Structures (SIIMCES-2025) Enhanced Mechanical and Flexural Performance of M40 Concrete with Hybrid Fibers and Fly Ash Replacement Vudata Harsha sai a, *, Lingeshwaran N a , Pratheba S b , B. V. Lakshmi c a Department of Civil Engineering, Koneru Lakshmaiah Education Foundation (Deemed to be University), Guntur, Vaddeswaram, India b Akshaya college of Engineering and Technology, Bhagavathipalayam, Kinathukadavu, Coimbatore, Tamil Nadu 642109 c Department of Architecture, Koneru Lakshmaiah Education Foundation (Deemed to be University), Guntur, Vaddeswaram, India Abstract This study investigates the mechanical and flexural performance of concrete incorporating steel, polypropylene, and coir yarn fibers with varying levels of fly ash as partial cement replacement. Thirteen M40 grade concrete mixes were developed using 10%, 20%, and 30% fly ash replacement levels and reinforced individually with 1% volume of each fiber type. Compressive strength, split tensile strength, flexural strength, and load-deflection behaviour were evaluated after 28 days of curing. Results showed that 20% fly ash replacement optimized performance, increasing compressive strength by 12% and improving matrix densification. Steel fibers achieved the highest strength gains, increasing flexural strength by 30% and split tensile strength by 25% compared to control specimens. Polypropylene and coir yarn fibers enhanced ductility, energy absorption, and crack resistance, with improvements of up to 18% and 22% in flexural and tensile strength, respectively. Load-deflection analysis confirmed significant gains in ductility and post-cracking behaviour in fiber-reinforced mixes. The use of coir yarn, a biodegradable natural fiber, and fly ash, an industrial by-product, demonstrated substantial environmental benefits. The findings highlight a sustainable and high-performance alternative to conventional concrete for structural applications requiring improved durability and crack resistance. © 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 the responsibility of International Conference on Structural Integrity Organizers

Keywords: Fiber-reinforced concrete; fly ash; steel fibers; polypropylene fibers; coir yarn fibers; flexural behavior.

1. Introduction Concrete is the most widely used construction material due to its high compressive strength and durability. However, its brittle nature makes it prone to cracking and failure under tensile and flexural stresses. To address these

* Corresponding author. Tel.: +91-8341252659. E-mail address: 2301020001@kluniversity.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 the responsibility of International Conference on Structural Integrity Organizers 10.1016/j.prostr.2025.07.084