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.
Highlights
Among the various types fibres, including steel [1], glass [2], polymeric [3], and carbon [4] fibres, basalt fibre (BF) is a new type of inorganic material extruded from melted basalt rock.e manufacturing of BF is similar to that of glass fibre, with less energy consumption and no additives, which makes it cheaper than glass or carbon fibres
For BF in a concrete composite, a study on the chemical durability of BF was conducted by Ramachandran et al as early as 1981, which demonstrated the potential of BF in reinforced concrete [8]
Studies have been conducted on a continuous basalt fibre-reinforced polymer (BFRP) as a strengthening material for concrete structures [9,10,11,12]
Summary
Among the various types fibres, including steel [1], glass [2], polymeric [3], and carbon [4] fibres, basalt fibre (BF) is a new type of inorganic material extruded from melted basalt rock. E manufacturing of BF is similar to that of glass fibre, with less energy consumption and no additives, which makes it cheaper than glass or carbon fibres Other advantages such as a high modulus, heat resistance, good resistance to a chemical attack [5], and an excellent interfacial shear strength [6] enable BF to be a good alternative as a reinforcing material in a concrete composite [7]. Fibres can effectively improve the mechanical properties of shotcrete and enhance the engineering properties, fatigue wear strength, postcracking toughness, and load-bearing capacity [17, 18]. To reveal the influence of BF on the mechanical properties and microstructure of shotcrete, specimens for a four-point-bending test were shot and cured underground to ensure the real processing and curing environment. The underground roadway in a coal mine is supported by the recommended mixture ratio of the BFRS. e roadway convergence was monitored for 80 days to evaluate the BFRS performance
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