Effects of graphene oxide on shearing performance of C–S–H composites: a molecular dynamics study.

By virtue of its ultra-high strength, toughness and specific surface area, graphene oxide (GO) has been a research hotspot in nano-cement because of its excellent electrical, thermal and mechanical properties. The GO-cement composite owns greatly improved microstructure, and mechanical and permeability-related performances compared with plain cement. Clarifying the reinforcing mechanisms of GO on cementitious composites is a prerequisite for the large-scale application of GO in the cement industry. Hence, in this work, the effect of the GO nanosheets on the shear properties of the calcium silicate hydrate (C–S–H) composites and the corresponding reinforcing mechanisms were investigated using molecular dynamics (MD) simulations. The simulated results reveal that the orientation angle between GO nanosheets and C–S–H layers is a significant factor influencing the enhancing effects of GO on the shear behaviour of C–S–H/GO composites. As the orientation angle ranges from 30° to 60°, the shear strain would cause bending deformation of GO nanosheets in composites. The bent GO nanosheets then absorb the deformation energy in the system, effectively isolating the transfer of shear-induced force chains. The ultimate shear strength reaches about 861.2 MPa for the orientation angle equalling 30°, increasing 23.5% compared with that of plain C–S–H. The microstructural damage characteristics analysis further indicates that it is crucial to trade off the effective anchorage of GO nanosheets in C–S–H gel and the structural integrity of C–S–H matrix when using GO nanosheets to enhance the shear performance of C–S–H composites. We expect the findings from this work can enhance the understanding of GO-reinforced cementitious composites and assist GO-based cement design in future work. [ABSTRACT FROM AUTHOR]