Experimental study on mechanical properties, microstructure and ratio parameter optimization of mixed fiber-reinforced rubber cemented coarse aggregate backfill

In this paper, the influence of basalt fiber, polypropylene fiber and rubber particles on the strength of cemented coarse aggregate backfill (CCAB) was deeply studied. Moreover, based on the engineering example, the optimal content of basalt fiber, polypropylene fiber and rubber particles is determined. The findings indicate that when utilizing mixed fiber and rubber particles to enhance the mechanical properties of CCAB, the reasonable content ranges for basalt fibers (BF), polypropylene fibers (PF), and rubber particles (RP) are 0.2 % to 0.6 %, 0.2 % to 0.4 %, and 5 % to 15 %, respectively. Among these additives, BF exerts the most significant influence on CCAB strength, followed by PF, while RP has the least impact. When BF content reaches 0.4 %, the addition of PF leads to a reduction in the compressive strength of CCAB. Fibers primarily enhance the macroscopic strength of CCAB by load dispersion and load sharing, while increased rubber particle content effectively fills void structures within CCAB, thereby improving its macroscopic strength. Based on engineering examples and fuzzy mathematics comprehensive evaluation model, the optimum content of the three types of admixtures is 0.4 % basalt fiber, 0.6 % polypropylene fiber and 5 % rubber particle.