The aggregate grading is a key parameter in the design of cemented paste backfill. In re⁃

sponse to the problem that original coal gangue is coarse and cannot be directly used for preparing coal

gangue paste，research on crushed coal gangue grading design and optimization for backfill are performed

through laboratory experiments and hydration simulation. The results show that the dry density of coal

gangue sampled on site is 1.614 g/cm3 ，with a specific gravity of 2.518. More than 70% of the particle diame⁃

ter is greater than 1 mm，belonging to block stones and gravel，and the grading is unreasonable. Using the

Taibol theory to design the grading of crushed coal gangue，within the Taibol index range of n is 0.3 to 0.7，

the packing density of the crushed coal gangue has a parabolic relationship with n. When n=0.35，the de⁃

signed crushed coal gangue aggregate has the maximum packing density of 2.222 g/cm3 ，with fine particles

below 75 µm accounting for 14.2%，which can meet the preparation standards of the paste. There is a clear

linear relationship between the Taibol index n and the featured particle diameter，while the relationship for

curvature coefficient cc and the non-uniformity coefficient cu is not significant. Using VCCTL hydration simu⁃

lation software，it is verified that the hydration degree of coal gangue paste with the grading of n=0.35

reached 0.78 after 28 days. The microstructure of the paste was denser，with higher predicted mechanical

properties，which are related to the filling and nucleation effects of fine particles. The rationality of gradation

optimization design is verified from the perspectives of indoor experiment and hydration simulation. The

study provides an important theoretical basis and guiding significance for the design and optimization of coal

gangue paste fill.

coal gangue, paste fill, pipeline transportation, grading, packing density, hydration simula?