Enhancing tensile strength and microstructural properties of solidified high-moisture dredged sediment through solid waste-based binder stabilization and basalt fiber reinforcement

The study of materials with good mechanical properties for backfilling Urban Underground Spaces (UUS), such as abandoned underground spaces and ground subsidence, has important practical significance for achieving urban safety. A binder developed with solid waste materials was employed to solidify dredged sediment, transforming it into a Liquefied Stabilized Backfill Material (LSBM) for UUS. This study investigates the reinforcing effect of Basalt Fibers (BF) on the Splitting Tensile Strength (STS) behavior of solidified dredged sediment treated with a waste-based binder. A comprehensive experimental program was conducted to assess the influence of BF content, BF length, curing time, initial moisture content, and binder dosage on both STS and stress-strain responses. The results indicate that the optimal BF contents for maximizing STS at 3, 7, and 28 days were 0.1%, 0.1%, and 0.2%, respectively. Meanwhile, the corresponding STS values were 182.20 kPa, 191.98 kPa, and 242.74 kPa, representing STS increases of 120.9%, 65.2%, and 31.3% compared to the solidified sediment without BF. A fiber length of 3 mm yielded the best reinforcing effect on the tensile strength behavior of LSBM, with the STS reaching peak values of 104.47 kPa, 183.12 kPa, and 260.89 kPa at the curing times of 3, 7, and 28 days, respectively. Moreover, BF incorporation significantly improved the ductility of the solidified matrix. A regression model with a high coefficient of determination was developed, which reads S T S = 85.37 C + 3.58 L + 4.08 T − 2.26 M + 9.78 B (R 2 =0.947), enabling effective analysis and estimation of STS from the given parameters under comparable conditions. Additionally, a strong linear relationship between the STS and Unconfined Compression Stress (UCS) for the LSBM samples was established. Microstructural analysis revealed that the BF enhances tensile performance by increasing interfacial friction and filling pores via associated hydration products, thereby facilitating a broader stress distribution within the dense matrix. Additionally, a simplified economic and environmental benefit analysis demonstrated that per 100 kPa of STS, the 28d solidified sediment with 0.2% BF exhibited a 7.3% reduction in cost and a 15.7% reduction in CO 2 emissions per ton compared with the solidified sediment backfill material without BF. Overall, the findings of this study demonstrate that BF-reinforced, waste binder-treated dredged sediment presents a technically viable and environmentally sustainable solution for UUS backfilling.