If you want “Lightweight Blocks” (in this locality commonly known as “Haydite Blocks”), specify that the aggregate shall meet ASTM C331.

If you want “Normal Weight” blocks (in this locality commonly known as “Concrete Blocks”), specify that the aggregate shall meet ASTM C33.

Note:
For Split Face and/or Colored Block, add that they shall be manufactured with an integral water repellant, and the mortar used with them shall contain a water repellant.

When using Split Face and/or Colored Block add that blocks from two or more cubes shall be mixed as they are being laid to assure that color and/or face variations will be divided.