Multi‐Layered Calcium Silicate Hydrate‐Based Composites: A Nacre‐Mimetic Design for Ultra‐High Toughness

Abstract Cement‐based materials are the most extensively utilized artificial material in the world. The low toughness of cementitious materials has long been a significant constraint in the development of modern concrete, limiting its performance in critical infrastructure applications. As the primary hydration product, calcium silicate hydrate (C‐S‐H) determines the mechanical properties of cementitious materials, in which optimizing C‐S‐H presents a promising avenue for toughness enhancement. In this work, a nacre‐mimetic design strategy is employed to develop a high toughness C‐S‐H composite, achieved by the arrangement of inorganic C‐S‐H “brick” alternated with polyvinyl alcohol (PVA) “mortar”. The unique hierarchically soft/hard structure significantly improved the mechanical properties of C‐S‐H composite, showcasing a substantial improvement on tensile strength, ductility and toughness by 1–2 orders of magnitude compared with fiber/polymer reinforced cementitious composites, especially reaching ultra‐high toughness (20.01±3.64 MJ m −3 ), which outperforms nacre by a factor of over ten and exhibits the highest performance among reported C‐S‐H‐based materials. The nacre‐mimetic C‐S‐H composite displayed exquisite interface and toughening mechanism revealed by density functional theory (DFT), molecular dynamics (MD), and finite element method (FEM) simulations. These findings provide a prospect for toughening cement‐based materials, and broaden the potential applications in advanced functional composite systems.