A study of Ni–Ti shape memory alloy-steel fiber hybrid reinforcement in GGBS mortar for corrosion resistance

Fiber-reinforced concrete (FRC) has become popular due to its ability to enhance mechanical properties. However, FRC has limitations regarding aging, durability, and corrosion. A superelastic shape memory alloy (SMA) is an alternate reinforcement material that can enhance a structure’s lifespan. This study evaluates the mechanical, durability, and corrosion resistance characteristics of hybrid combinations of nickel–titanium (Ni–Ti) SMA fibers and steel fibers in mortar. Three hybrid fiber combinations (GH1-75% steel fiber+ 25% SMA fiber, GH2-50% steel fiber+50% SMA fiber, and GH3-25% steel fiber+75% SMA fiber) were investigated in this study, with a total of 0.50% fiber volume ratio. To enhance the durability properties of the mortar, ground granulated blast furnace slag (GGBS) was used as a partial replacement for cement. The engineering properties of these hybrid fiber combinations in GGBS mortar were evaluated through compressive strength, flexural strength, and split tensile strength. Durability features were assessed based on acid, sulfate, chloride, and marine water resistance. The results showed that the hybrid mix with a greater quantity of steel fiber (GH1) had superior mechanical properties due to the steel fiber’s greater modulus of elasticity. However, when exposed to an aggressive environment, the hybrid combination with a greater quantity of Ni–Ti SMA fibers (GH3) in mortar showed higher durability and corrosion resistance. The samples from durability studies were further tested for Scanning Electron Microscopy, Energy Dispersive X-ray Spectroscopy, X-Ray Diffraction Analysis, and Fourier Transform Infrared Spectroscopy. The microstructural studies revealed the factors contributing to the enhanced durability and corrosion resistance of Ni–Ti SMA fibers in the composite.