Fatigue behaviors of graphene reinforcing concrete composites under compression

•Fatigue behaviors of graphene reinforced concrete composites are investigated.•Graphene significantly improves fatigue life and deformation of composites.•Graphene modifies pore structure and interfacial transition zone of composites.•Thermal stress reduction caused by graphene is beneficial for the improvement.•Fatigue life equation of composites is established based on secondary strain rate. This paper first studies the fatigue behaviors of multi-layer graphene (MLG) reinforcing reactive powder concrete (RPC) under compressive loads. It provides experimental results including fatigue life, fatigue deformation development, damage index and energy absorption, investigates temperature difference inside concrete composites by monitoring hydration temperature at different locations, and studies micro-structures of internal weakness of RPC via Scanning Electron Microscope (SEM), Energy-Dispersive Spectroscopy (EDS) and Digital Image Processing (DIP) method. The results show that, incorporation of MLG significantly reduces internal weakness of RPC. Specifically, MLG decreases temperature difference and thermal stress inside concrete composites, refines harmful pores in fatigue cracking zone (diameter above 100 nm), and stabilizes chemical composition of interfacial transition zone. By bridging micro-cracks and bonding with hardened cement matrix, the sheet-formed MLG slows down the generation of microcracks at creep-fatigue coupling stage, delays the start of fatigue stage, and increases fatigue failure strain. Consequently, even at 0.075 wt% MLG content, the fatigue life, energy absorption, and damage index of RPC are increased up to 49.3% (in terms of logarithm), 333.1%, and 22.23%, respectively. In addition, based on strain increase per circle at the creep-fatigue coupling stage, a fatigue life prediction equation is derived, which provides an approach to estimating the fatigue reliability of the structures using this composite.