Mechanical properties and meso-microscopic mechanism of basalt fiber-reinforced recycled aggregate concrete

This study aims to evaluate the macro-micro-meso-mechanical properties of basalt fiber (BF)-reinforced recycled aggregate concrete (BFRAC). Firstly, the effects of BF with different contents and lengths on the mechanical properties of recycled aggregate concrete (RAC) at different ages were analyzed. In addition, the distribution of BF, bond between BF and matrix, failure form of BF, and element composition of the fiber interface transition zone were analyzed using scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS). Finally, the numerical simulation of cubic compression and splitting tensile tests of RAC specimens were carried out, and the stress–strain curve and failure morphology of RAC under static loading was studied. The results show that BF content is the main factor affecting the mechanical properties of concrete within the range of test fiber content (0.1%–0.3%), and the optimal content of BF is 0.2%. The length of BF has little effect on the compressive properties of RAC, but the increase of BF length can improve the splitting tensile and flexural properties of RAC. Through SEM-EDS, the toughening and cracking resistance mechanisms of the BF are obtained. In the meso-simulation, the numerical simulation results are in high agreement with the experimental phenomenon, and this method provides an effective technical method for the prediction and establishment of RAC failure model. In summary, the research results can be used as reference for the establishment of the RAC mechanical model, performance research, and practical engineering application in the future.