Molecular dynamic simulation on the anisotropic tensile properties of the calcium silicate hydrate enhanced by graphene oxide

Abstract

Benefiting from its superior mechanical properties, abundant oxygen-containing functional groups and ultrahigh specific surface area, graphene oxide (GO) can effectively strengthen cement-based materials. However, the calcium silicate hydrate (C–S–H), as the most significant binding phase in cement, has apparent anisotropy characteristics. The enhancement of GO on the tensile performance of C–S–H in different directions requires to be revealed. Hence, in this work, the molecular dynamic simulation was applied to study the influence of GO in different directions on the tensile properties of C–S–H composites and the corresponding reinforcing mechanisms. The results demonstrate that the GO nanosheets incorporated in parallel water layers can reinforce the ductility of C–S–H, with the tensile strain energy density increasing up to about 43.9%. The structural characteristics demonstrate that the GO nanosheets incorporated in parallel water layers significantly change the C–S–H failure mode, whose initial failure diffuses from the GO surface. By contrast, the failure mode of plain C–S–H composites is diffused from the high-stress zone. Nevertheless, when GO nanosheets are incorporated in the vertical water layer direction, the destruction form of the C–S–H composite changes little, with the tensile strain energy density only increasing by 11.9%. The energy evolution characteristics verify that the external work of GO nanosheets added in the parallel water layer is increased by about 53.4%, about 2.4 times higher than that of GO nanosheets added in the vertical water layer. The findings of the study not only promote boarder understanding of GO-reinforced cementitious composite but also assist nanomodification cement design in the future.