The hydraulic interface towards the anti-fatigue performance of fiber-calcium silicate hydrate composites under cyclic loading

Fibers effectively hinders the structural deteriorations of cementitious composites under repeated loadings. However, fatigue behavior of the interface between fiber and hydraulic cement matrix is still mysterious. In this work, we show by atomic modelling that fiber, pore water, and calcium silicate hydrate (C-S-H) construct a solid-liquid-solid interface, which creates a dynamically balanced system, keeping the stability of cement matrix under cyclic loading. Specifically, simulation results demonstrate that more than 95% of maximum stress is kept in humid fiber-C-S-H system after 2000 loading cycles. Further, the reinforcing mechanisms are fully elucidated. Particularly, the debonding and self-healing of the interface accompanied by the formation and breakage of H-bonds, continuously adsorbing the dissipative energy, and redistributing the stress field, thereby preventing the interfacial expansion and microcrack initiation. This work portrays atomistic understandings of fiber-C-S-H anti-fatigue mechanisms under cyclic loadings and calling for new strategies for atomic scale cement structural design.