Microscale fracture and creep analysis of 3D porous graphene-based cementitious material by nanoindentation test and energy-based method

As an exceptional nanomaterial, three-dimensional (3D) porous graphene possesses a promising capacity to enhance the performance of cementitious materials and reduce the usage of cement. However, the microscopic understanding of the fracture and creep behaviors of 3D porous graphene-based cementitious materials remains unclear. Here, we combine nanoindentation experiments and the energy-based method to investigate the microscale fracture and creep behaviors of both mortars and cement pastes. Specifically, we use the energy-based method to assess elastic modulus, hardness, fracture toughness, energy releasing rate, creep modulus, and creep characteristic time of cementitious materials containing 3D porous graphene. Our outcomes indicate that the additions of 3D porous graphene to both the mortar and cement paste improve their elastic behaviors. The fracture toughness and energy releasing rate reach the optimal values at 3D porous graphene content of 0.05 wt%. In addition, the presence of 3D porous graphene promotes the formation of high-density calcium silicate hydrate (C-S-H) and reduces the creeps in cementitious materials. Our findings provide insights into the performance of graphene-cementitious composites and represent a step forward toward the practical application of 3D porous graphene in concrete.