In the railway sanding, the sand particles are firstly crushed into finer fragments in the inlet zone of wheel/rail contact. Therefore, two kinds of particles act in the sanding process: the initial sand with large sizes and the final fragments with micro sizes. To learn which kind of particles is more crucial for the sanding performances, standard sand particles (0.6-2.0 mm) and its micro fragments (0.1-30 mu m) were used as two types of adhesion enhancers. The results indicated that the application of micro fragments had advantages on reducing the wear and surface damage, without losing adhesion enhancing capacities compared to the standard sand particles. However, the fluid-driven rolling contact fatigue (RCF) damage occurred when the micro fragments were used.