Study on the Properties of Basalt Fiber-Calcined Gangue-Silty Clay Foam Concrete for Filling Undermined Goaf Areas of Highways

The collapse of surface goaf beneath highways can result in instability and damage to roadbeds. However, filling the goaf areas with foam concrete can significantly enhance the stability of the roadbeds while considerably reducing the costs of filling materials. This study analyzes the effects on destructive characteristics, mechanical properties, stress-strain curve features, and relevant metrics, while also observing the microstructure of basalt fiber-calcined gangue-silty clay foam concrete (BF-CCG-SCFC). The results indicate that the water-binder ratio significantly influences the cubic compressive strength, split tensile strength, and fluidity of BF-CCG-SCFC. Silty clay reduces the cubic compressive strength, split tensile strength, and fluidity of BF-CCG-SCFC. Conversely, an appropriate amount of calcined gangue and basalt fiber significantly increases the cubic compressive strength and split tensile strength, while decreasing fluidity. To satisfy the strength and fluidity requirements of the filler material in hollow areas, the optimal water-binder ratio for BF-CCG-SCFC is 0.55, the ideal mixing ratio of calcined gangue to silty clay is 2:2, and the basalt fiber content should be 1%. The study examines the influence of varying water-binder ratios, the combined proportions of calcined gangue and silty clay, and different basalt fiber contents on the elastic modulus, peak stress, and peak strain of BF-CCG-SCFC. Additionally, the water-binder ratio influences the matrix strength through the non-hydration reactions of doped particles, while gangue and clay induce a "gradient hydration effect" during the hydration process. The incorporation of basalt fibers enhances the mechanical interlocking between the fibers and the matrix.