Crystal-pit-cracking formation on composite modified slag fiber in long-term water immersion

Composite modified slag fiber (CMSF) has been widely used as insulation material for enclosures in the field of construction; however, its corrosion characteristics and crack formation are unclear. Therefore, the damage behavior of CMSFs with two acidity coefficients (ACs) immersed in water for 365 days was studied; the fiber structure and composition were measured. The crystalline phase on the fiber surface was identified as CaCO3 deposits that dissolved after long-term immersion, resulting in pits. Owing to continuous replacement of H+, Ca2+ continuously migrates from the inside to the outside of the fiber, resulting in a stepwise increase in the AC of the fiber cross-section; the surface pits significantly increased and joined together to form an axial crack. However, the Si-O-Si bond has no significant fracture during long-term immersion. These findings support the theory on the crack behavior of CMSFs during long-term immersion for practical applications. [Display omitted] •Fibers undergo crystal-pit-axial cracking during long-term immersion.•Lateral distribution of acidity coefficient affects the fiber structure stability.•H+ and Ca2+ exchange caused dimensional differences, resulting in porosity and pits.•Si-O-Si bond has no significant fracture during long-term immersion.