Atlas™ brick are not normally tested in the same manner as concrete block (CMU). Because of the lower compressive strength of the material, CMU can be tested in a 16" length using testing machines with capacities of 250,000 lb. ratings. Structural brick have unit strengths 4 to 5 times that of concrete block and therefore must be cut into smaller rectangular sections. This is done by cutting the unit in half and removing the 'dog ears' flush with the web to create a rectangular unit. Prisms are also done in the same manner. Testing machines must be rated in excess of 450,000 lb. capacity in order to break the brick within the elastic range of the testing machine. Machines with ratings lower than this may cause premature failure.
The testing machine must also have a spherically seated head that adjusts for slight distortions in the material. A gypsum capping compound is used to cap the units and the prisms to also level out any non-uniformity in the units.