Basalt fiber-reinforced controlled low strength material

Controlled low-strength material (CLSM) has been developed to enhance the stability of underground structures and overcome the drawbacks of traditional backfill materials, such as compacted sandy soils. The objective of this study is to develop CLSM reinforced with basalt fibers (BF) and to evaluate the flowability, setting time, and strength characteristics of BFreinforced CLSM. Basalt fibers are incorporated into CLSM with four fiber lengths and three fiber contents to form BFreinforced CLSM specimens. Flow and Vicat needle tests are performed to evaluate the fluidity and setting times of BFreinforced CLSM. Uniaxial compression tests and splitting tensile tests are conducted on 3 and 28 days after curing. The results reveal that the incorporation of BF into CLSM reduces the fluidity as well as the initial and final setting times. After 3 days of curing, BF-reinforced specimens with fiber lengths of 18 and 24 mm exhibit higher uniaxial compressive strength than unreinforced specimens; however, at 28 days, the reinforcement effect is marginal. The splitting tensile strength of all reinforced specimens, at both 3 and 28 days, exceeds that of the unreinforced specimens. In particular, at 28 days, the splitting tensile strength of all reinforced specimens generally increases with fiber length. Therefore, the use of BF in CLSM can enhance early compressive strength and improve both early-age and long-term tensile strength in underground structures backfilled with CLSM.