Experimental Investigation and Service Life Prediction of Basalt Fiber–Iron Ore Tailing Recycled Concrete Under Carbonation–Freeze–Thaw Cycle Coupling

In this study, iron ore tailings (IOTs) with different mass replacement rates (0%, 20%, 40%, 60%, 80%, 100%) and basalt fibers (BFs) with different volume contents (0, 0.1%, 0.2%, 0.3%) were co-incorporated into recycled concrete. To better simulate real-world conditions, a coupled carbonation–freeze–thaw cycling test was performed on C30 cubic specimens. Each test cycle comprised 7 days of carbonation followed by 25 freeze–thaw cycles, with four total cycles conducted. For specimens subjected to different numbers of test cycles, measurements were taken of the recycled concrete’s variations in mass, dynamic elastic modulus, and compressive strength. Scanning electron microscopy (SEM) was employed to examine the microscopic morphology of concrete under the test conditions and to analyze the mechanism through which the two materials influence the durability of recycled concrete in the experimental environment. Based on the Weibull distribution, a damage prediction model for basalt fiber iron ore tailing recycled concrete (BF-IOT-RAC) under the test environment was developed, and the service life of BF-IOT-RAC in Northwest China was predicted. The results indicate that the two materials can enhance the performance of recycled concrete when their dosages are appropriate; however, excessive dosages exert adverse effects. BF1T40 had a mass loss rate of 1%, an RDEM of 92%, and the cube compressive strength of 33.5 MPa at the conclusion of this test, with all three indicators being higher than those of recycled concrete with a single material incorporated. SEM observations revealed that the surface of BF1T40 was more intact than that of other recycled concretes after the test. According to the prediction, BF1T40 has the longest service life in the northwest region, reaching 42–43 years.