Effect of particle gradation on properties of fresh and hardened cemented paste backfill

• Increasing of finer parts in CPB mixture is detrimental to workability of fresh CPB.
• Blending with finer tailing particles can improve gradation of tailings.
• Higher packing density of tailing particles benefits mechanical performance of CPB.

The purpose of this study is to assess the influences of the gradation of tailings on the qualities of coarse tailings used for cemented paste backfill (CPB). Two reference mixtures of tailings (T and W) with CPB and four blended mixtures of tailings with CPB with T/W ratios (the weight ratio of tailings T and W) of 8/2, 6/4, 4/6, and 2/8 were prepared. The moisture content in hardened CPB generally increased as the tailings fineness increased. The relationship among tailings fineness, packing density and unconfined compressive strength (UCS) is discussed. As the tailings fineness increased, the flowability value decreased.