Molecular dynamics modeling of the interface between surface functionalized graphitic structures and calcium-silicate-hydrate: Interaction energies, structure, and dynamics

Molecular dynamics simulations were performed to study the molecular-scale energetic, structural, and dynamic properties of the interface between surface functionalized graphitic structures and calcium-silicate-hydrate (C-S-H). The 9 angstrom tobermorite structure was used as a model for C-S-H, the main building block ("the glue") that hold a cementitious matrix together. Six types of carbon surface structures were investigated: a pristine graphite plane and five graphite planes functionalized with hydroxyl (-OH), carboxyl (-COOH), carboxylate (-COO-, deprotonated carboxyl), carbonyl (C = O), and amine (-NH2) groups. Results demonstrated the dominant role of electrostatic forces in the interfacial interactions and indicated that the polarity of the functional group can be used as an indicator of affinity to C-S-H. MID simulations revealed that an optimal number of polar oxygen containing groups may exist for efficient graphitic structure/cement interaction and emphasized the mediating role of Ca2+ counterions in the interfacial interactions. (c) 2008 Elsevier Inc. All rights reserved.