Research on the fracture mechanical performance of basalt fiber nano-CaCO3 concrete based on DIC technology

•The addition of basalt fiber can make the meso-structure of concrete more compact.•The bridge effect of basalt fiber is mainly reflected before 90% of peak load.•Basalt fibers have significant influence on the second and third stages. Nano-CaCO3 concrete (NCC) has good mechanical properties due to its dense structure, and the addition of basalt fiber can effectively improve its fracture properties. The study of the full-stage failure of basalt fiber nano-CaCO3 concrete (BFNCC) during the fracture process is helpful to explain its toughening mechanism. In order to explore the fracture properties and fiber strengthening mechanism of basalt fiber nano-CaCO3 concrete (BFNCC). In this study, concrete specimens with 6 different nano-CaCO3 contents (0%, 1.5%, 2%, 2.5%, 3%, and 3.5%), cured for 3 days, 7 days, 14 days and 28 days, were prepared to explore the optimum nano-CaCO3 content by conducting tensile and compressive mechanical tests. Based on the optimum content, the basic mechanical performance test and three-point bending beam fracture test were carried out to explore the fracture properties of BFNCC with 4 fiber contents (0%, 0.1%, 0.2%, and 0.3%). In this study, the basic mechanical performance test and three-point bending beam fracture test were carried out to examine the fracture mechanical performance and fiber reinforcing mechanism of basalt fiber nano-CaCO3 concrete (BFNCC) with different fiber contents (0%, 0.1%, 0.2%, and 0.3%). The research results show that the addition of an appropriate amount of basalt fiber can improve the basic mechanical properties and fracture performance of nano-CaCO3 concrete, with the best effect achieved by the BFNCC-0.2% working condition. According to the fracture test analysis, the bridging effect of basalt fibers is mainly exhibited during the period before reaching 90% of the peak load. The inhibiting effect of basalt fibers on crack propagation begins to increase when the load reaches 70% of the peak load, and will gradually decline when the load is reduced to 90% of the peak load. Moreover, by applying the Scanning Electron Microscopy (SEM) technology to conduct a meso-analysis of the stress mechanism of BFNCC, combined with the results of the Digital Image Correlation (DIC) technology, the fracture mechanical properties and the stress mechanism of BFNCC were revealed. This study systematically analyzed the reinforcing effect of basalt fibers on nano-CaCO3 concrete, and provided a theoretical basis for the app