This paper investigates the interface debonding behavior of graphene (G) on a calcium silicate hydrate (C-S-H) substrate using molecular dynamics (MD) simulations. The effect of interfacial water content on the debonding behavior of graphene on cement-based composites was studied. Simulation results reveal that there is only a van der Waals force between G and C-S-H; the interface bonding strength is weak; and the debonding properties (maximum peeling force (F_max) and work (W)) are low. The debonding energy of graphene decreases with an increase in interfacial water content, indicating that water intrusion will weaken the binding effect of G and C-S-H, and reduce the difficulty of graphene’s debonding on a C-S-H substrate. Exploring the adhesion behavior of graphene on C-S-H under the influence of humidity at the nanoscale is of great significance for understanding the basic adhesion mechanism, optimizing composite material properties, and promoting the development of related disciplines.

Graphene and graphene oxide (GO) are promising nanofillers for improving thermal transport in cementitious materials, but their performance is strongly affected by interactions with calcium silicate hydrate (C-S-H). Understanding how these fillers retain or lose their heat-transport capability after incorporation into the cement hydrate matrix is therefore important for rational nanocomposite design. Reverse non-equilibrium molecular dynamics simulations were conducted to compare isolated graphene/GO sheets with the corresponding sheets embedded in C-S-H. The extrapolated thermal conductivity of pristine graphene decreased from 1854.6 to 1264.2 W/(m·K) after embedding, giving a retention ratio of 0.68. Increasing the oxidation degree reduced the intrinsic conductivity of GO through defect-induced phonon scattering, while the additional reduction caused by C-S-H progressively weakened. At an oxidation degree of 20%, GO retained more than 90% of its isolated-sheet conductivity. Atomic heat-flux analysis showed that C-S-H markedly broadened the transport-direction distribution of graphene but produced only limited additional disturbance in GO. Interfacial binding energy increased with oxidation degree, and radial distribution function analysis identified short-range Ca-O coordination and hydrogen bonding at the GO/C-S-H interface. Phonon density of states analysis further revealed pronounced substrate-induced phonon softening in graphene, whereas the vibrational spectrum of GO remained comparatively stable. These results clarify the trade-off between intrinsic conductivity and matrix-induced thermal stability in graphene-based cementitious nanocomposites.

The thermal properties of calcium silicate hydrate (C-S-H) and its interaction with graphene oxide (GO) are explored using the molecular dynamics method. As the main hydration product of cement, understanding the intrinsic thermal transport of C-S-H is crucial for solving the heat dissipation problem of mass concrete. The three principal thermal conductivities of C-S-H along x-, y-, z- axis are estimated respectively. The results show that C-S-H exhibits anisotropic thermal characteristics, and the volumetric thermal conductivity is calculated to be 1.28 W/(mK). Furthermore, the interfacial binding energy between C-S-H and graphene/GO is investigated to evaluate the stability of the composite system. It is found that the binding energy increases with the oxidation degree of GO, and the xy-plane of C-S-H exhibits the strongest affinity. The results provide fundamental data for the thermal design of cement-based composites.