Akbulut, Z.F.2025-05-102025-05-1020251964-818910.1080/19648189.2025.24720542-s2.0-86000261051https://doi.org/10.1080/19648189.2025.2472054https://hdl.handle.net/20.500.14720/3526This study investigates the durability of cement mortars against hydrochloric (HCl) acid attacks by incorporating silica fume (SF), melt-extracted straight stainless steel (SST), and double-hooked steel (DHST) fibers. The addition of SF increased the mortar viscosity, reducing workability but significantly improving mechanical strength and resistance to HCl degradation. Combining SF with hybrid SST/DHST fibers showed promising results, demonstrating synergistic effects. SF’s pozzolanic activity promoted the formation of calcium-silicate-hydrate (C-S-H) bonds, filling pores, reducing permeability, and enhancing the mortar’s resistance to HCl exposure. Furthermore, hybrid SST/DHST fibers outperformed DHST fibers alone in mitigating micro and macro crack formation. Their combined ability to bridge and restrict crack propagation reinforced the mortar’s structural integrity. In conclusion, incorporating SF and hybrid fibers effectively improves mortar durability against HCl attacks. The findings highlight that the pozzolanic reaction of SF improves the durability of cement-based materials by enhancing the formation of C-S-H, which increases strength and reduces permeability. Additionally, the synergistic effect of hybrid fibers boosts crack resistance by distributing stress evenly and preventing crack propagation, offering valuable insights for optimizing cement mortar formulations in aggressive environments. © 2025 Informa UK Limited, trading as Taylor & Francis Group.eninfo:eu-repo/semantics/closedAccessCement MortarDouble Hooked Steel FiberHydrochloric AcidSilica FumeStraight Steel FiberArticleQ3Q2