Atomic-Level Insights into the Mechanisms of Reinforcement and Fracture in a Graphene-Reinforced Bitumen Composite

Graphene can significantly improve the mechanical performance and durability of a bitumen composite. However, the underlying reinforcement mechanism of this enhancement is not yet clear. Here, we use molecular dynamics (MD) simulation to study the mechanisms of tensile fracture and shear fracture in a graphene-reinforced bitumen composite. Two representative volume elements were developed from a single-crystal graphene-reinforced bitumen composite: graphene in the parallel plane and orthogonal plane. The MD results show that graphene in the orthogonal plane is better able to support and transmit shear loads, as evidenced by a 33% higher shear strength than graphene in the parallel plane. Under tensile loading, the failure type of the base bitumen and the graphene in the parallel plane is cohesive; for the graphene in the orthogonal plane, the failure type is adhesive. The shear failure for graphene in the parallel plane is an adhesive failure, which typically occurs at the graphene-bitumen interface. The shear failure for graphene in the orthogonal plane and for base bitumen is likely to be a cohesive failure. The results of the pull-off test validated the results of the simulation, which indicated that the interlayer sliding of graphene and the fracture of the bitumen matrix are the failure modes of a graphene-reinforced bitumen composite under tensile loading. This study provides atomic-level insight into the mechanical reinforcement mechanism of graphene-reinforced bitumen, and can contribute to the future application of advanced carbon nanomaterials in transportation infrastructure.