Flexural Toughness of Basalt Fibre-Reinforced Shotcrete and Industrial-Scale Testing

Abstract

This study focuses on toughness enhancement of basalt fibre-reinforced shotcrete (BFRS). Four-point bending experiments of underground shooting and curing beams combined with a roadway-supporting deformation monitoring test were conducted. The flexural performance was analysed based on the toughness standards, namely, DBV-1998, JSCE SF-4, and nuclear magnetic resonance (NMR) pore testing. The results demonstrate that, given a basalt fibre (BF) dosage of 0-7.5 kg/m3, 18 mm BF can significantly increase the residual stress under the same deformation, rather than the peak values of the flexural strength. Meanwhile, the trend in the flexural toughness increases to a peak at a dosage of 3-4.5 kg/m3, followed by a declining curve. The pores from an NMR test can be divided into three types based on size: (1) closed pores, R < 0.01 μm, (2) capillary pores, 0.01 μm < R < 5 μm, and (3) connected pores, R > 5 μm. The connected pores are detrimental, playing a crucial role in the shotcrete performance. Furthermore, the deformations of the roadway walls are significantly restrained by the BFRS, and the 80-day convergences are approximately 2 mm, which is only 25% of the control. Finally, the comprehensive results indicate that a dosage range of 3-4.5 kg/m3 can demonstrate reasonable beneficial effects for the BFRS performance.