To get proper CEB compression you need materials with sufficient water. Depending on the soil 600 psi compression can yield 2000 psi finished material. Inverse, 5000 psi compression on insufficient wet materials will result in a 30 psi break. Labs can do soil compression testing that will give how much water is needed as a percentage of the soil. The test run about $150. You can do several test blocks instead using a 7 day to break. Put the CEB on a sturdy table, lightly score the block about half way. Hit it sharply with a hammer. It should break clean, not crumble, along the score line.