I have noticed that sometimes when concrete masonry units are broken during construction, the fractures do not break through the aggregate. Instead, whole pieces of aggregate are left on either side of the crack. Does this mean that the masonry has low strength?
This may be an indication that the block does not have adequate strength. Intentionally breaking concrete masonry units is a method of quality assurance that is recommended in the Reinforced Concrete Masonry Inspector's Handbook published by the Masonry Institute of America (MIA). This document suggests breaking a unit to examine the portion of broken aggregate in the failure plane and to look for evidence of internal moisture. If no aggregate is broken, MIA recommends that a check be made to make sure that the units have been tested in the laboratory to meet the required specifications. In many projects, concrete masonry unit strength is important to develop the proper strength for bearing and shear walls.