Investigating the influence of acid–base/KH550 composite-modified BFs on the fracture characteristics of fiber-reinforced asphalt mixtures via DEM

This paper studies the effects of acid–base/KH550 composite-modified basalt fibers (BFs) on the fracture characteristics of basalt fiber-reinforced asphalt mixtures (BFRAM) via the discrete element method (DEM), providing an experimental basis for further optimization. The semicircular bending (SCB) test was conducted on BFRAM, along with DEM simulation. This study revealed that (1) compared with those of blank group A, the fracture energies of BFA, BFA-H, BFA-N, BFA-NK and BFA-HK increased by 17.2%, 33.6%, 37.4%, 39.0%, 55.0% and 56.6%, respectively, and the flexibility indices increased by 18.8%, 55.8%, 58.3%, 45.3%, 63.9% and 73.3%, respectively. Fiber modifications, especially acid etching/KH550 composite modifications, are beneficial for improving the crack resistance and toughness of BFRAM. (2) The indoor SCB load–displacement curves of the BFRAMs are located mainly in the DEM simulation area where the fiber interface coefficient (FIC) is 0.6–0.9, which proves that the surface modification of the BF is conducive to improving the adhesion of fibers and asphalt. (3) The maximum contribution rate of the fiber units to resisting the external load in the DEM sample is 6.7% (FIC = 0.9), which is 2.09 times that of the DEM sample with FIC = 0.6. In the postpeak stage, the contribution rate of fiber units in the DEM samples remained at a high level of 3.5–6.7% (FIC = 0.9).