Preparation, microstructural characterization, and bio-corrosion resistance of novel high-performance marine concrete admixture

Marine biofouling is a critical factor threatening the safety of marine concrete structures, making the development of effective anti-biofouling methods highly significant for engineering applications. This study addressed the inherent limitations of traditional coating protection by focusing on the anti-biofouling performance of internally mixed concrete rather than coatings. Two novel high-performance anti-biofouling composite admixtures were developed: Composite A (Silica-Copper Silicate-Copper Ferrocyanide Composite) and Composite B (Polyaniline-Copper Silicate Composite). The synthesis methods of these composites were described, and their microstructures were characterized to confirm the formation of effective anti-corrosion compounds. The elemental composition and crystal structure of the active components in Composites A and B were determined. Dispersion tests demonstrated that both composites exhibited excellent dispersibility, with Composite A showing slightly better performance than Composite B. Comparative antibacterial tests against common corrosive marine bacteria revealed strong antimicrobial properties for both composites, with their inhibition rates under varying conditions analyzed. Concrete specimens incorporating Composite A were fabricated and subjected to offshore immersion tests, followed by analysis of macro-biofouling colonization and evaluation of their mechanical properties. The results demonstrated that the incorporation of Composite A effectively inhibited macro-biofouling colonization while exhibiting minimal impact on the mechanical properties of concrete, meeting its safety requirements. Furthermore, a Composite A-modified concrete pier was cast at the Donggaoxi Bridge in Fujian, China, for long-term field observation of macro-biofouling colonization. The results comprehensively assessed the anti-macro-biofouling efficacy of Composite A in real marine environments. • Two novel high-performance concrete admixtures were provided; • Microstructure of the active components in the admixtures were investigated. The formation of substances such as copper ferrocyanide, copper silicate, etc., has been demonstrated. • It has been demonstrated that the new composite additives exhibit excellent macroscopic and microscopic dispersibility. • The antibacterial performance of the two composites against common marine corrosive bacteria has been verified, with the antibacterial rates of both composites exceeding 70% in the majority of the tests. • Assessed admixture' effect on concrete strength and anti-biofouling. After the addition of composite A, the compressive strength of the concrete slightly decreased, yet it consistently remained above 50 MPa, ensuring the normal functionality of the target concrete. • Through field trials in the actual marine environment, it has been demonstrated that the addition of composite A significantly reduces the amount of biofouling on the bridge piers.