Synergic effect of defects on carbon nanoparticles under interaction with calcium silicate hydrate composites

Abstract

One- and two- dimensional carbon nanoparticles, i.e. graphene and CNT, are amongst the most potent additives in cementitious matrices. Their potential lies within the higher hydration degree, nano-filler effect and cracking-bridging effect that are only realized with a strong connection between the cementitious matrix and graphene. Here, Density functional theory (DFT) and molecular dynamics (MD) used to determine the nature of the interactions between the Tubermorite 14 Å and graphene. We observed that the carbon atoms on the periphery of various types of defects on the surface of a graphene nanosheet and carbon nanotube can form electrophile regions that adsorb silicate chains within the cementitious matrix, forming SiOC covalent bonds between the two species. Single vacancies are highly likely to bond with the silicate chains, with a bond energy of −90 kcal/mol at 1.5 Å length, which is also the case for the silicate – carbon nanotube (CNT) interactions. This is accompanied by the adsorption of Ca ions in Calcium Silicate Hydrates (CSH) on O atoms of functional groups in graphene interactions at the intralayer space, increasing the bond energy between the two nanostructures to 120 kcal/mol. Molecular dynamics (MD) simulations confirm the consolidation of the CSH – graphene around the two interactions, which causes a significant reduction in the mobility of the nanoparticle within the cementitious matrix. These findings provide essential information from the interactions within the interlayer and intralayer regions of CSH with carbon nanoparticles at the molecular level.