How do Interpret Table 2 in TMS 602-16 in order to get the required net area compressive strength of an individual block for a specified f'm?
I have included an article below explaining the increased block strength. It includes a copy of Table 2 so that you can reference it as you read this.
The values of f'm are listed in the left most column and are labeled "Net area compressive strength of concrete masonry". Values are given in psi.
The right hand two columns give the required Net area strength of the individual unit to achieve the given f'm. The far right column is to be used if Type "N" mortar is used to lay up the wall and the middle column is used if Type M or S mortar is used in the wall.
Thus, an individual block with a net area strength of 2000 psi gives you an f'm = 2000 psi.
An individual block with a net area strength of 3250 psi gives you an f'm = 2500 psi.
And an individual block with a net area strength of 3900 psi gives you an f'm = 2750 psi.
Links to additional information:
Update on Increased Design Strength of CMU 1-3-18 with Attachment 1.pdf
We are bidding a job where the project engineer is requiring a 2500 psi block to meet an f'm of 1500 psi. We know that the new code allows a 2000 psi block to have an f'm of 2000 psi. What can we do?
Lets be clear, the project engineering can call for any strength block they desire - as long as it is called out in the project specs that are bid with the job. So if your project specs call for a 2500 psi individual block strength and an f'm of 1500 the 2500 wins and that is what you need to supply to the job.
On the other hand, if the specs ONLY call out for a masonry unit that meets 2000 psi f'm they MUST accept the current code and accept a 2000 psi individual unit strength. Requiring a higher strength unit than is required by the code, and not called out in the bid documents, would constitute a change to the project.
Don Beers, PE, GC