High Energy Absorption Nacre‐Like Calcium Silicate Hydrate (C‐S‐H) Composite Toward Elastic Cementitious Materials

Abstract The low toughness under the tension of cement and concrete materials has been a long‐standing issue for decades and it has become increasingly urgent to address in modern society due to the growing demand for the development of high‐performance and sustainable constructions. Manipulating calcium silicate hydrate (C‐S‐H), the main hydration product of Portland cement, which determines the mechanical properties of cementitious materials, is an attractive method for improving their toughness following a bottom‐up approach. Inspired by the microstructure of nacre, a high energy absorption C‐S‐H‐based composite with a highly ordered structure is fabricated by a designed ternary building block, in which exfoliated montmorillonite provides a template for the nucleation and growth of C‐S‐H generating the “brick”, and polyvinyl alcohol acts as a “mortar” binding all the building blocks together. With the hierarchical toughening strategy explored here, the obtained C‐S‐H composite achieves a remarkable energy absorption of 16.2 ± 2.6 MJ m⁻³, which surprisingly outperforms the ultra‐high toughness cementitious materials by a factor of 20–60 and is even higher than that of natural nacre and other nacre‐like composites. These findings not only provide valuable insights into enhancing the toughness of cementitious materials but also open possibilities for broadening potential applications of C‐S‐H.