Repair of undersea concrete using biopolymer-assisted plant urease

Concrete repair in marine environments is influenced by various factors, particularly underwater pressure and dynamic water flow. Traditional materials used for underwater concrete repair suffer from issues such as dilution, dispersion, susceptibility to erosion by moving water , and poor grout retention. In this study, a novel biopolymer-based undersea crack repair material composed of quaternized chitosan (Hydroxypropyl trimethyl ammonium chloride chitosan, HACC), sodium alginate (SA), urease, and aggregates was developed. It investigated the impact of biopolymers on urease's physiological and biochemical properties, as well as its mineralization capacity. Additionally, It conducted a comprehensive evaluation of the fluidity, rheological behavior , grout retention, mechanical properties, and anti-permeability rate of the bio-grouting material. The results showed that the optimized bio-grouting material exhibited suitable viscosity and fluidity. After injection, it rapidly formed a cohesive seal, with a grout retention rate exceeding 90 % at 48 days. The water resistance of the repaired concrete reached 93 %. Microstructural analysis using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) revealed strong electrostatic interactions between HACC and SA molecular chains . These interactions encapsulated mineralization products and sand particles, resulting in a denser microstructure.