Strength development and microstructure characteristics of artificial concrete pillar considering fiber type and content effects

The artificial concrete pillar (ACP) replacement technique is a safe and reliable method to safely mine orebody pillar in room and pillar mining. In contrast to traditional ore pillar, artificial pillar has recently received significant attention due to its applicability, stability and cost benefits. This study deals the influence of fiber type and content on uniaxial compressive strength (UCS) and microstructure characteristics of fiber-reinforced concrete (FRC) considered as an effective artificial pillar. A total of 3 non-FRC (NFRC) and 27 FRC samples reinforced with glass, polypropylene (PP), and polyacrylonitrile (PAN) fibers at a content of 0 wt%, 0.4 wt%, 0.8 wt% and 1.2 wt% were manufactured for examining their strength properties. After UCS testing, some microstructure tests including computed tomography scan and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy were done to better explore the morphology of FRC. Results illustrate that: (1) The UCS values of all FRC samples first increase and then decrease with increasing fiber content. The UCS increment ratio in FRC steadily decreases as the fiber content increases. (2) PP fiber was more effective than both glass and PAN fibers in increasing peak strain and strength performance. This was mainly because of an improved bonding quality within the matrix which allows to decrease the water absorption of FRC. Overall, the peak strain increases linearly with increasing fiber content. Finally, the findings of this study can offer a substantial reference in design and application of FRC to be used as artificial pillar in underground mines.