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I've the necessity for f'm=2500 psi in the design of some slender walls

I'm attempting to write a spec which will result in f'm=2500 psi which leads
to the following :

Am I reading Table 21-D correctly? For a specified compressive strength of
masonry, f'm=2500 psi for Type M or S mortar, the corresponding compressive
strength of concrete masonry units is 3750 psi. I am interpreting this
compressive strength to be that of the individual block, not the grouted
assembly, yes?

Footnote 4 of Table 21-D states that the compressive strength of grout shall
be equal to or greater than the compressive strength of the concrete masonry
units so... I should specify a grout compressive strength of 3750 psi, yes?

Finally, Table 21-15-A of UBC Standards gives the minimum average compressive
strength for Type S mortar as 1800 psi (read also Section 21.1505). Should
the mortar compressive strength also be up at 3750 psi?

I have exhausted my office resources on this issue, any comments would be
greatly appreciated.


Mark D. Baker
Baker Engineering