Chloride diffusion and pore structure of hybrid fiber-reinforced concrete in marine

Corrosion tests were performed on hybrid fiber-reinforced concrete (HFRC) subjected to seawater wetting–drying cycles to assess its resistance to chloride-induced deterioration. Chloride concentration and pore structure characteristics were evaluated using an automatic titration system and low-field nuclear magnetic resonance technology. The study examined the influence of three types of basalt fibers – twisted basalt fiber (BF), unstructured basalt fiber (bF), and spiral basalt fiber – on chloride concentration, chloride diffusion coefficient (K), surface chloride concentration (C_s), and the pore structure of HFRC. The results demonstrated that incorporating 1.5% BF significantly reduced the chloride concentration compared with 0.25% bF. Following a power–law relationship, the C_s increased with the number of wetting–drying cycles. In contrast, the K exhibited an inverse trend. Furthermore, increasing BF content led to a reduction in the T₂ spectral area and refinement of the pore structure. Conversely, higher bF content expanded the T₂ spectral area, indicating the development of larger internal pores and degradation of the pore structure. The pore system of HFRC displayed clear fractal characteristics, with overall fractal dimensions (D_T) ranging from 2.883 to 2.922. A strong linear correlation was identified between D_T and K.