Enhancement of cement mortar’s resistance to hydrochloric acid using hybrid SST/DHST fibers and silica fume

This 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.