Experimental Study on Impermeability of Concrete Panels Repaired by Enzyme-Induced Calcium Carbonate Precipitation (EICP)

Concrete face rockfill dams (CFRDs) are widely used due to the advantages of high safety, strong seismic resistance, and excellent adaptability. However, under the combined effects of dam weight and reservoir pressure, differential deformation may occur between the concrete face panel and the cushion layer, often leading to cracks in the face panel and subsequent seepage. Traditional crack repair methods mainly rely on physical filling or surface sealing, and often suffer from limited adaptability to micro-cracks, owning high carbon emissions, and environmental pollution. Enzyme-induced calcium carbonate precipitation (EICP) has advantages of high efficiency, environmental sustainability, and durability. This study focuses on repairing cracks in concrete face panels using a combined approach of EICP with either chitosan (CS) or sodium alginate (SA). A series of impermeability model tests were conducted to investigate the effects of crack width, number of repair cycles, water pressure, and pressurization time on the seepage volume and calcium carbonate (CaCO 3 ) adhesion rate. A cubic function model was developed to describe the relationship between seepage volume and CaCO 3 adhesion. The results showed that seepage volume increased with crack width, while increased repair cycles significantly reduced seepage volume. Specifically, when the number of repair cycles reached 20, the average seepage volume decreased by a factor of 35.8 compared to unrepaired concrete panels. Pressurization time had a relatively small effect on seepage volume, whereas increasing water pressure significantly increased seepage volume and decreased CaCO 3 adhesion rate. At a 50% confidence level, the interval narrowed to 0.279, 0.701 with an interval length of 0.008–0.045, indicating the highest estimation accuracy. This study provides valuable practical reference for the application of EICP in the repair of hydraulic concrete structures.