Influence of fiber reinforcement on mechanical behavior and microstructural properties of cemented tailings backfill

Abstract Fibers are accountable for an increase of compressive and shear strengths, particularly at the post-peak and post-cracking stages. The level of the strength improvement is primarily based on several factors: fiber type and content; fiber geometry, fiber distribution within the matrix; and the fiber-matrix interaction. An experimental campaign consisting of uniaxial compression and scanning electron microscopy tests were carried out to realize the effect of fiber reinforcement on mechanical behavior and microstructural properties of cemented tailings backfill (CTB) prepared with different fiber types (e.g., polypropylene, polyacrylonitrile and glass fibers) and contents (0%-control sample, 0.3, 0.6%, and 0.9%). Experimental results exhibit that polypropylene fiber exhibited the strongest reinforcing effect, followed by polyacrylonitrile and glass fiber. The rate of strength increase of the three fiber-reinforced fills after curing of 28 days reached 39.6%, 34.8% and 23.1%, respectively. A fiber content of 0.6% in the mixture is considered as a critical point, and the compressive strength of fiber-reinforced CTB samples first increases and then decreases, the peak strain and the post-peak ductility properties are positively correlated with fiber content. The failure process of fiber-reinforced CTB samples is mainly divided into four stages: pore compaction, linear elasticity, strain softening and crack propagation. It has the feature of ‘cracking without breaking’. Besides, fiber-reinforced CTB samples have a dense microstructure and good adhesion, improved interface between the fiber and the CTB matrix, and suppressed crack propagation. Lastly, an empirical equation was developed to forecast the peak strength and elastic modulus of CTB samples with different curing times.