Effect of 3D porous graphene on the mechanical properties and microstructure of ultra-high ductility concrete

To enhance the mechanical and microstructural properties of ultra-high ductility concrete (UHDC), this study introduced three-dimensional porous graphene (3DG) as a nano-reinforcement and systematically investigated its effects on the workability, mechanical properties, pore structure, and hydration behavior of UHDC. Results showed that 0.03 wt% 3DG yielded optimal improvements. Compressive strength increased by 18.8 % and tensile strain capacity rose by 71.75 % compared to the control. At this dosage, after measuring the actual elongation of the tensile specimens and counting the number of cracks, it was found that the average crack width decreased from 267 micrometers to 185 micrometers, while the number of cracks within an 80-millimeter gauge length increased from 21 to 39. MIP analysis revealed that 3DG refined the pore structure by reducing harmful pores (>100 μm) and increasing medium-sized pores (60–100 μm), despite a slight rise in overall porosity. XRD and TGA results indicated that 3DG promoted the formation of dense C–S–H gels and enhanced hydration, resulting in higher crystallinity and thermal stability. SEM images confirmed the formation of a dense fiber–matrix interface and complex C–S–H networks surrounding 3DG particles. These improvements stem from 3DG's bridging, nucleation, and internal curing functions, offering a multiscale reinforcement effect that significantly boosts toughness and crack resistance.