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

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. A flexible calcium silicate hydrate (C-S-H) composite with a highly ordered structure is fabricated by controlling the assembly of C-S-H in the presence of montmorillonite and polyvinyl alcohol. This composite offers exceptional fire-retardant properties and enhanced durability, while its hierarchical toughening techniques impart an extraordinary energy absorption of 16.2 +/- 2.6 MJ m-3.image