Failure evolution and fiber toughing mechanism of ultra-high performance concrete under uniaxial compression

The addition of steel fibers and coarse aggregates can greatly improve the toughness and compressive performance of ultra-high performance concrete (UHPC), however it will also introduce more interface transition zones (ITZ) with lower strength. This study reveals the evolution of compressive mechanical properties and the fiber toughening mechanism of UHPC. Combined with the concrete damaged plastic (CDP) model and the meso-random method, the 2D mesoscopic compression damage process of UHPC is simulated. The accuracy of the mesoscale numerical model and the feasibility of the research method are verified. The damage of ITZ occurs earlier than that of mortar and coarse aggregates under the compression load, and the development of damage ratio in ITZ is obviously different from those of coarse aggregates and mortar. The fiber stress changes significantly from compression state to tensile state, and the development of stress in a toughened functional fiber is related to its distribution angle.