Effect of Doped Glass Fibers on Tensile and Shear Strengths and Microstructure of the Modified Shotcrete Material: An Experimental Study and a Simplified 2D Model

Cunli Zhu,Qiangqiang Cheng,Yaben Guo,Meng Li,Nan Zhou

doi:10.3390/min11101053

Abstract

Shotcrete material has found extensive applications as a reinforcing material in the engineering sector. This study examined the effect of doped glass fibers on the mechanical performance of the modified shotcrete material composed of aeolian sand, fly ash, cement, quicklime, and doped glass fibers. Its tensile and shear strengths values were experimentally determined via a WAW-1000D computerized hydraulic universal tensile testing machine. Its microstructure was analyzed via a size analyzer, scanning electron microscope (SEM), and X-ray diffractometer (XRD). A 2D simplified mechanical model was elaborated to reflect the influence mechanism of the doped glass fibers on the mechanical performance of the modified shotcrete material. The experimental and mechanical analysis results indicated that, at the macroscopic scale, the experimental tensile and shear strengths of the shotcrete material doped with glass fibers were significantly higher than those of the undoped shotcrete material (by up to 310% and 596%, respectively). These results were in concert with the proposed model predictions, where the compound stresses in the shotcrete material were derived as the sum of the stress borne by the shotcrete material itself and the bridging stress exerted by the glass fibers. At the microscopic scale, SEM observations also revealed that the glass fibers were intertwined with each other and tightly enveloped by the shotcrete material particles within the modified shotcrete specimens, connecting the particles of different components into a whole and improving the overall mechanical strength. In addition, the relationships of the compound stress of the shotcrete material vs. embedment length, embedment angle, and cross-sectional area of the glass fibers were established. The research findings are considered instrumental in clarifying the mechanism by which the glass fibers influence the mechanical performance of shotcrete materials and optimize their solid waste (fly ash and quicklime) utilization.

Highlights

Coal is the leading energy source in China and occupies the predominant position in China’s primary energy consumption [1,2,3]
The surface microstructure of the specimens was observed to reveal the mechanism by which the glass fibers influenced the mechanical strength of by scanning electron microscope (SEM) to reveal the mechanism by which the glass fibers influenced the mechanical the modified shotcrete specimens
We further studied whether the doped glass fibers improved the shear Because shear strength is alsoisvital the for proper mechanical performance of shotcrete strength

Summary

Introduction

Coal is the leading energy source in China and occupies the predominant position in China’s primary energy consumption [1,2,3]. Along with the high-intensity mining of the coal resources, the shallow coal resources in Eastern China are on the verge of depletion. The depth of coal mines is extending at an annual rate of 10–25 m [7,8,9,10]. The high-intensity mining of coal resources is inevitably accompanied by the production of a large amount of solid waste. The in situ stress increases with the mining depth. Rib spalling and roadway floor heaving are more likely to occur under higher in situ stress, and reduce the service life of the roadway and coal mine [14,15,16]

Methods

Results

Discussion

Conclusion