What does a CMU contain?

A concrete masonry unit (CMU), commonly referred to as a concrete block, is often reinforced with steel rods to enhance its strength and load-bearing capacity. This reinforcement is crucial in construction applications, especially in areas that require additional structural integrity, such as load-bearing walls or seismic areas. The inclusion of steel reinforcing rods helps resist tension and improves the overall durability of the structure.

Void space, while it may exist in certain types of blocks for insulation or lightweight considerations, is not a defining characteristic of what a CMU is or contains fundamentally. Joinery instructions are not part of a CMU; those would typically be found in guidelines for assembly or construction practices. Explosives certainly do not belong in a CMU, as that would negate its purpose as a building material and pose safety hazards.

The primary function of steel reinforcing rods in a CMU is to provide necessary reinforcement, ensuring that the unit can withstand forces and stresses that it may encounter in structural applications.