Backfill materials used to fill underground mines are a type of engineered material whose particle size distribution (PSD) directly affects their mechanical and physical properties. According to the authors' review, there is no comprehensive standard for the properties of aggregates used in underground mine backfill materials. In this paper, the particle size ranges and particle size distribution curves of various mine backfill materials, including hydraulic backfill, paste backfill and rock backfill, have been reviewed. The available data on different types of backfill materials were collected. Based on the collected data, the smallest particle size, the largest particle size and the PSD curve ranges for each type of backfill material were determined. Then the characteristics of the particle size distribution curve of each backfill material, including the mean particle diameter (D50), the uniformity coefficient (Cu) and the curvature coefficient (Cc), were calculated. The results of the analysis of the PSD curves for paste backfill, hydraulic backfill and rock backfill materials showed that the particles in rock backfill and paste backfill had the largest and smallest sizes, respectively. Finally, the particle size distribution characteristics of a new backfill material prepared from construction and demolition waste (CDW backfill) are presented and compared with the particle size distribution of each of the conventional backfill materials. The results indicate that the PSD curve of the CDW backfill lies at the upper limit of the range of the particle size distribution curve of hydraulic backfill and at the lower limit of the range of the particle size distribution curve of rock backfill.
