Enhancing flexural property and mesoscopic mechanism of cementitious tailings backfill fabricated with 3D-printed polymers

Abstract

Backfill mining, one of the most common methods for removing hazardous tailings, is performed on cementitious tailings backfill (CTB), which can be employed to fully discard risky tailings while diminishing the ecological effect on the surface by delivering them underground voids as backfill material. By counting mechanized mining tools, the downward backfill hexagonal approach mining method is an effective way to exploit surrounding rock with poor properties. With this innovative extraction technique, it is crucial to guarantee the safety, productivity and cost control of a solid artificial false roof. To further strengthen the toughness and strength of CTB structures, two new 3D-printed polymer (3D-PP) models (i.e., Models 1 and 2) were constructed in this study. The fracture toughness and flexural strengths of CTB were explored via 3-point bending tests and scanning electron microscopy (SEM) observations. Lab testing results showed that 3D-PP application considerably enhanced the flexural/deflection properties of CTB. The bending strength of the CTB structures fabricated with 3D-printed polymers was 1.72 MPa, which indicates a major increase of 409% when compared with that of the control specimens (N-3D-PP). The highest deflection value was 17.6 mm, which also showed a significant increase in CTB structures. One can also interpret from the SEM–EDS results that CTB structures presented many CSH products, which escorted with major elements: O, Si, and Ca. Applying 3D-PP results in backfill with good toughness and ductility, while N-3D-PP reveals brittleness. Moreover, the deflection enhancement effect of Model 2 is much greater than that of Model 1. Finally, this study urges that the development of flexural properties and mesoscopic mechanisms of CTB be ensured by 3D-PP models, maintaining a decreased failure probability of mine fills.