1. Varying concentration of concrete ingredients resulting in nonuniform proportions in the concrete mix. 2. The tendency for the coarse particles to separate from the finer particles in handling; in concrete, the coarse aggregate and drier material remains behind and the mortar and wetter material flows ahead; this also occurs in a vertical direction when wet concrete is overvibrated or dropped vertically into the forms, the mortar and wetter material rising to the top. 3. In aggregate, the coarse particles roll to the outside edges of the stockpile.