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

<p class="p1" style="margin-bottom: 0px; font-stretch: normal; font-size: 9px; line-height: normal; font-family: Helvetica; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;">This study investigates the durability of cement mortars against hydrochloric <p class="p1" style="margin-bottom: 0px; font-stretch: normal; font-size: 9px; line-height: normal; font-family: Helvetica; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;">(HCl) acid attacks by incorporating silica fume (SF), melt-extracted <p class="p1" style="margin-bottom: 0px; font-stretch: normal; font-size: 9px; line-height: normal; font-family: Helvetica; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;">straight stainless steel (SST), and double-hooked steel (DHST) fibers. The <p class="p1" style="margin-bottom: 0px; font-stretch: normal; font-size: 9px; line-height: normal; font-family: Helvetica; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;">addition of SF increased the mortar viscosity, reducing workability but significantly <p class="p1" style="margin-bottom: 0px; font-stretch: normal; font-size: 9px; line-height: normal; font-family: Helvetica; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;">improving mechanical strength and resistance to HCl degradation. <p class="p1" style="margin-bottom: 0px; font-stretch: normal; font-size: 9px; line-height: normal; font-family: Helvetica; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;">Combining SF with hybrid SST/DHST fibers showed promising <p class="p1" style="margin-bottom: 0px; font-stretch: normal; font-size: 9px; line-height: normal; font-family: Helvetica; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;">results, demonstrating synergistic effects. SF’s pozzolanic activity promoted <p class="p1" style="margin-bottom: 0px; font-stretch: normal; font-size: 9px; line-height: normal; font-family: Helvetica; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;">the formation of calcium-silicate-hydrate (C-S-H) bonds, filling pores, reducing <p class="p1" style="margin-bottom: 0px; font-stretch: normal; font-size: 9px; line-height: normal; font-family: Helvetica; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;">permeability, and enhancing the mortar’s resistance to HCl exposure. <p class="p1" style="margin-bottom: 0px; font-stretch: normal; font-size: 9px; line-height: normal; font-family: Helvetica; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;">Furthermore, hybrid SST/DHST fibers outperformed DHST fibers alone in <p class="p1" style="margin-bottom: 0px; font-stretch: normal; font-size: 9px; line-height: normal; font-family: Helvetica; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;">mitigating micro and macro crack formation. Their combined ability to <p class="p1" style="margin-bottom: 0px; font-stretch: normal; font-size: 9px; line-height: normal; font-family: Helvetica; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;">bridge and restrict crack propagation reinforced the mortar’s structural <p class="p1" style="margin-bottom: 0px; font-stretch: normal; font-size: 9px; line-height: normal; font-family: Helvetica; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;">integrity. In conclusion, incorporating SF and hybrid fibers effectively <p class="p1" style="margin-bottom: 0px; font-stretch: normal; font-size: 9px; line-height: normal; font-family: Helvetica; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;">improves mortar durability against HCl attacks. The findings highlight that <p class="p1" style="margin-bottom: 0px; font-stretch: normal; font-size: 9px; line-height: normal; font-family: Helvetica; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;">the pozzolanic reaction of SF improves the durability of cement-based <p class="p1" style="margin-bottom: 0px; font-stretch: normal; font-size: 9px; line-height: normal; font-family: Helvetica; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;">materials by enhancing the formation of C-S-H, which increases strength <p class="p1" style="margin-bottom: 0px; font-stretch: normal; font-size: 9px; line-height: normal; font-family: Helvetica; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;">and reduces permeability. Additionally, the synergistic effect of hybrid <p class="p1" style="margin-bottom: 0px; font-stretch: normal; font-size: 9px; line-height: normal; font-family: Helvetica; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;">fibers boosts crack resistance by distributing stress evenly and preventing <p class="p1" style="margin-bottom: 0px; font-stretch: normal; font-size: 9px; line-height: normal; font-family: Helvetica; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;">crack propagation, offering valuable insights for optimizing cement mortar <p class="p1" style="margin-bottom: 0px; font-stretch: normal; font-size: 9px; line-height: normal; font-family: Helvetica; font-size-adjust: none; font-kerning: auto; font-variant-alternates: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-east-asian: normal; font-variant-position: normal; font-feature-settings: normal; font-optical-sizing: auto; font-variation-settings: normal;">formulations in aggressive environments.