Multifunctional sodium-based solid-state structural battery for strengthening and energy storage in near-surface mounted reinforced concrete structures

Abstract The retrofitting of ageing reinforced concrete (RC) structures typically relies on Near-Surface Mounted (NSM) strengthening with carbon fiber reinforced polymers (CFRPs), which provide mechanical enhancement but no additional functionality. To address the growing demand for sustainable, multifunctional solutions, this work introduces a sodium ion based solid-state structural battery that simultaneously serves as a strengthening and energy storage element in NSM applications. The system combines a CFRP shell, providing strength and stiffness, with an embedded sodium-based glass electrolyte exhibiting piezoelectric, pyroelectric and ferroelectric properties. Comprehensive mechanical and electrical characterisation confirmed the multifunctionality of the electrolyte, while pull-out tests on concrete blocks demonstrated effective load transfer, bond behaviour, and failure modes under service conditions. The results validate the dual role of the proposed device, providing both structural reinforcement and energy storage capability, with added potential for structural health monitoring through piezoelectric response. This approach offers a novel pathway towards multifunctional retrofitting strategies for RC structures, integrating mechanical strengthening with energy harvesting and storage.