Strengths
of CMU
Strength is expressed in two distinct ways:
Cmu compressive strength is the psi calculated from the net area of the individual unit. The minimum average net compressive strength per ASTM C 90 is 1900 net psi.
f'm, specified compressive strength of masonry, is the value used in design of the masonry wall. This is the strength specification that really matters, as it is the strength upon which the engineer's design is based. When the design utilizes prescribed minimum strengths of cmu and grout per their respective standards, the given f'm is 1500 psi based on net area. Notice it is the strength of masonry, not units. It is the compressive strength of the assemblage of masonry units, mortar, and grout.
[See next page for provisions for compliance with the specified f'm value.]
