Crushed rock comes in sizes ranging from stones the width of baseballs to fine powder. The different sizes of rock allow different usages for each class of crushed rock. While the larger stones can be used as base fill and as filler stone to use with concrete, smaller stones mixed with dust are used as compacting gravel. Because each size of crushed rock is used for a different purpose, it is best to classify the crushed rock by size before purchasing it.
How to Class Crushed Rock by Size
Things You'll Need
Opaque plastic bag
Spread an opaque plastic bag across the ground to create an isolated work area that you will later use to examine the rocks.
Scoop out a small portion of the crushed rock with the bucket and gently lay it out onto the opaque plastic bag. Spread out the crushed rock using your fingers so that you can easily examine the stones.
Use a measuring tape to measure the diameter of the stones. You don't have to measure each stone, just enough to determine the average width. If the crushed rock you are using is very fine, shake it through a sieve.
Compare the average diameter of the stones with the Crushed Stone Sizes chart (see Resources). If you needed to shake the stones through a sieve, your stone size will be classified as "dust" or "sand." If, after shaking, you have a significant amount of dust on the opaque bag and still have gravel-sized stones in the sieve, you likely have sand that is used for packing gravel roads.