Investigating the influence of polypropylene fiber content and length on the properties of lithium slag cement backfill

This study examines the effects of polypropylene (PP) fiber content and length on lithium slag cement backfill (LSCB), which is of great significance for promoting the resource utilization of industrial solid waste and improving the engineering performance of mine backfill bodies. Fluidity tests show that increasing fiber content and length reduces slurry fluidity. Uniaxial compression tests reveal that fiber-reinforced samples exhibit similar stress–strain behaviors, with shorter fibers enhancing initial strength but offering limited large-deformation resistance. Under the same fiber content (0.2 % − 0.8 %), compared with short fibers (3 mm) and long fibers (19 mm), the reinforcing effect of medium-length fibers (6 mm, 12 mm) was more significant. When the PP fiber content was 0.6 % and the length was 6 mm, the 28-day compressive strength of LSCB was 31 % higher than that of the blank group (3.46 MPa) and reached 4.53 MPa. SEM analysis indicates that PP fibers provide a skeletal structure within hydration gels, while adhesion, friction, and cohesion between fibers and the matrix help resist crack propagation. An economic feasibility analysis, it was concluded that adding 0.6 % − 6 mm PP fibers is feasible in engineering applications.