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Masonry mortar: Low Compression Results (Text Err)

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Dear all,
 
I apologize for my rather ambigous encoded HTML posting. You bet, it surely didnt look too good! I am rewriting this in the standard format and I hope it comes out allright this time.
 
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Fellow Engineers,
 
Recently, I received many low compressive results for masonry mortar testing. Most of the low results were found with the brick mortar. I specified type 'S' mortar, which should have 1800 psi strength, and yet the result came back as low as 900 psi.
 
This project is an 8 story CMU structure with a brick facade. There is a relieving angle placed at every floor to carry the brick load.
 
The following are my questions:
  1. Since the brick is supported at every floor, should I settle with type 'N' mortar (750 psi)? What is the standard mortar type for a one floor brick wall structure?
  2. Is there any impact of the low strength compression in the long run? WIll lower mortar strength cause premature repointing?
  3. The material testing company used a plastic form, which doesnt allow any water absoprtion compared to brick, thus the plastic form resulted in a higher water content than the actual brick. Is it possible that the cause of the low compression is due to the method of the sampling?
  4. Is there any insitu testing that can be performed to verify mortar compressive strength other than winsor-pro?
  5. Did anyone encounter this situation before, and what was your couse of action as the EOR?  FYI, the construction is 95% complete.
Any comments and thoughts counts! Thank you as always,
 
Hadi Djohan, P.E.
Brooker Engineering, PLLC
Suffern, NY.
 


 


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