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RE: Determining F'm from Tests

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Bill,

 

The only really appropriate way to test the compressive strength of in place masonry is to saw-cut a square prism from the wall.  This is supported in both Amrhein and Schneider.

 

Core testing is appropriate for concrete, however as you pointed out the invasive nature of core testing usually results in separation of the face shell.  Add to this the fact that the wall is not loaded perpendicular to the face shells, and standard procedure for masonry strength testing is a prism.  Core testing can tell you about the relative soundness of constituent materials, or whether the materials were placed and compacted properly, but that is about it.

 


From: Bill Allen [mailto:T.W.Allen(--nospam--at)cox.net]
Sent: Friday, July 28, 2006 7:14 AM
To: seaint(--nospam--at)seaint.org
Subject: Determining F'm from Tests

 

I am trying to analyze an existing reinforced masonry wall. The wall consists of 10” thick CMU. A testing lab took two, five inch diameter cores. Due to the fact that one face shell separated from the grout, the testing lab tested the grout and face shells separately. The compressive strength of the grout was 1,990 psi and 2,290 psi for an average of 2,140 psi. The lab then conducted five cube tests of the face shells. The results are 2,170 psi, 1,550 psi, 2,640 psi and 2,820 psi for an average of 2,295 psi.

 

While the lab (a reputable one) has given me a method to determine F’m, I want to check to see if their method is the correct/best method by querying this list. I would be most appreciative for any guidance on determining F’m based on the data provided above as well as documented references for such methods.

 

TIA,

 

T. William (Bill) Allen, S.E.

ALLEN DESIGNS

Consulting Structural Engineers
 
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