Assessment of rheological and toughening behavior of basalt fiber sprayed cementitious composites (BFSCC)

Shotcrete has been widely applied in construction projects such as tunnels, mining tunnels, and slope protection due to its unique construction method. This study investigates the synergistic effect of basalt fiber and supplementary cementitious materials on the properties of basalt fiber sprayed cementitious composites (BFSCC). The toughening effect of basalt fiber was evaluated through basic mechanical property tests and three-point bending toughness tests, with P-CMOD curves obtained. The pumpability of BFSCC was assessed using an ICAR rheometer, and microscopic mechanisms were explored through SEM testing. Experimental results indicate that both fiber length and dosage increase the dynamic yield stress of BFSCC. Specifically, compared to the control group, the addition of 18 mm fibers at a volume fraction of 0.25% increases the dynamic yield stress by 241 Pa. Additionally, the incorporation of 20% fly ash reduces the dynamic yield stress of BFSCC by approximately 45%. The adverse effects of fibers on the workability and easiness of BFSCC can be mitigated by adding supplementary cementitious materials. Basalt fibers significantly contribute to the early compressive and flexural strength of BFSCC. At an age of 1 day, 12 mm fibers at 0.15% volume fraction increase compressive strength by 19%, while 18 mm fibers at 0.25% volume fraction show the highest enhancement in flexural performance, reaching approximately 39%. Research on fracture performance reveals that basalt fibers enhance the initial cracking load and fracture toughness of BFSCC, retarding crack propagation and imparting ductility to the fracture process. The fracture energy of BFSCC with 18 mm basalt fibers reaches 167.1 N/m, representing a 24% improvement compared to the control group. A predictive model for fiber dosage and length fracture parameters was established using response surface methodology, achieving a prediction accuracy of 0.94 with good correlation. SEM images show hydration products adhering to fiber surfaces, forming protruding particles that increase internal friction, thereby inhibiting and altering the development direction of microcracks.