Comparative study on the properties of basalt and steel fiber reinforcement waste rock concrete

This study aims to convert waste rock into sustainable building materials by using it as coarse and fine aggregates to prepare basalt fiber and steel fiber-reinforced concrete (BFRC and SFRC). The optimal dosages and reinforcement mechanism of fibers were determined through mechanical performance tests, P-wave velocity tests, slump tests, and SEM analysis. Experimental research shows that incorporating an appropriate amount of fiber can improve the performance of concrete, and all BFRC and SFRC specimens meet the strength requirements. The concrete achieves the best strengths with 40 kg/m³ of steel fiber and 2 kg/m³ of basalt fiber. Compared to the control specimens, steel fiber greatly improves tensile strength by 22.2% and flexural strength by 27.4%, and basalt fiber increases them by 20.2% and 17.4%, respectively. Although SFRC specimens exhibit higher strengths, the production cost and CO₂ emissions of SFRC are significantly higher, with 2.46 times and 1.21 times than that of BFRC. SEM analysis revealed that the incorporation of an optimal dosage of fibers resulted in a denser microstructure within the concrete matrix. Basalt fiber and steel fiber with high elastic modulus and tensile strength provide significant bridging effects and crack resistance. The uniform distribution of fibers forms a dense network structure, limiting the generation and propagation of microcracks, thereby improving the mechanical properties. Overall, the addition of basalt fiber in waste rock concrete may be a more favorable choice. Besides, this study provides a theoretical basis for the resource utilization of waste rock and contributes to promoting the application of waste rock concrete in engineering.