Reinforcing cementitious composites with nitrogen-doped graphene: insights into molecular interactions and interfacial behavior

Abstract

Graphene materials are useful functional fillers in cementitious materials. They are essential in creating intelligent cementitious materials, enabling the construction of internal conductive networks and the addition of thermoelectric properties. The success of this process hinges on the functional filler's compatibility with the cement matrix, which must be excellent to ensure optimal results. In this study, we delved into the interactions between nitrogen-doped graphene and calcium silicate hydrate (C-S-H), which is the principal binding phase in cementitious materials, employing Density Functional Theory (DFT) calculations. In this study, we explored diverse nitrogen doping configurations and levels, while concurrently analyzing the influence of calcium cations at the C-S-H matrix interface. The findings indicate that nitrogen atoms in doped graphene interact considerably with nucleophilic oxygen atoms on silicate chains, forming covalent N-O bonds with high bonding energies (length 1.4 A, −107.81 kcal/mol) during graphitic nitrogen doping. The presence of calcium ions further strengthens the interaction energy between C-S-H and graphene, suggesting a synergistic effect between different types of nitrogen doping. The binding and total bond energies under the synergistic effect were −479.52 kcal/mol and −183.23 kcal/mol, respectively. These values were 1.5 times higher than those of single nitrogen doping. These findings offer significant insights into the molecular-level interaction between CSH and carbon nanoparticles.