Biomimetic silica coating for steel fibers: A low-cost strategy to enhance interfacial bonding in cementitious composites

This study presents a scalable and cost-effective biomimetic approach for applying a silica coating to steel fibers (SFs), offering a practical alternative to conventional sol-gel methods. Inspired by silica-regulating biological systems, the proposed method involves a simple two-step process: (1) pre-treating SFs with a water-soluble polymer to form a thin, uniform layer and (2) immersing them in a sodium silicate solution to induce controlled silica precipitation. Unlike sol-gel techniques, this process operates under ambient conditions, requires no specialized equipment, complex reaction controls, or costly precursors, and can be readily implemented for large-scale industrial applications. To evaluate the effectiveness of the silica coating, extensive characterization techniques were employed, including scanning electron microscopy (SEM), atomic force microscopy (AFM), energy-dispersive spectroscopy (EDS), Fourier-transform infrared spectroscopy (FTIR), and water contact angle measurements. The interfacial bonding performance was assessed through pull-out tests, nanoindentation analysis, and molecular dynamics (MD) simulations. The impact of silica-coated SFs on steel fiber reinforced concrete (SFRC) mechanical performance was further validated through compressive strength, flexural strength, and three-point bending tests. Results demonstrate that the silica coating significantly enhances fiber-matrix interaction, improving bonding strength by 116 %, pull-out energy by 99 %, compressive strength by 21 %, flexural strength by 31 %, and flexural toughness by 46 %. By eliminating the cost and complexity of sol-gel processing, this biomimetic method provides a rapid, scalable, and sustainable solution for enhancing SF reinforcement in cementitious composites, with direct applicability to on-site and industrial-scale production. • The silica layer is deposited on steel fibers through biomimetic approach with a two-step process conducted at room temperature and near-neutral pH value. • The interface transition zone (ITZ) between SF and concrete matrix is significantly enhanced by this approach. • Up to 116 % improvement on bonding strength between SFs and concrete matrix can be achieved by the treatment. • Over 30 % improvement in flexural strength and 45 % improvement in flexural toughness of steel fibers reinforced concrete (SFRC) can be attained by the proposed approach.