The ingredients for the binder course shall consist of asphalt, cement, portland cement or stone, dust, sand and gravel, or crushed stone mixed in the following proportions:
Bitumen, 4 to 7 percent.
Crushed stone or gravel passing 1¼-inch mesh, and retained on 1½-inch mesh, 30 to 50 percent.
Crushed stone or gravel passing a ¼-inch screen and retained on 10-mesh, 30 to 60 percent.
The balance of the aggregates from 10 to 20 percent, to be composed of sand and fine material of various sizes, from 10-mesh down to dust.