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RE: Mortar Testing

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Rich -

I've been reminded on the shape of the grout test specimen. Thanks for
confirming.

In the hypothetical, if the grout tests came back less than satisfactory, I
agree, the next step would be to take a prism test. I don't think I ever
said that I would reject the work based on the grout test results.

Regards,

T. William (Bill) Allen, S.E. (CA #2607)	
ALLEN DESIGNS	
Consulting Structural Engineers	
http://www.AllenDesigns.com	
V (949) 248-8588	 .	 F (949) 209-2509	

-----Original Message-----
From: Rich Lewis [mailto:sea(--nospam--at)lewisengineering.com] 
Sent: Wednesday, April 06, 2005 10:05 AM
To: seaint(--nospam--at)seaint.org
Subject: RE: Mortar Testing

Bill,

The field test for grout doesn't make round cylinders, it makes rectangular
cube type specimens.  I don't recall the ASTM off hand, but you use 4 blocks
to make a mold and pour the grout.  The blocks absorb the excess water so
the cube is supposed to be representative of the grout strength.

Nothing beats a prism test if you really want to know what the strength is
like.  I would find it difficult to reject work based on solely a grout test
or a mortar test.  A savvy contractor could make you look pretty bad if you
did.

Rich Lewis


-----Original Message-----
From: Bill Allen, S.E. [mailto:T.W.Allen(--nospam--at)cox.net] 
Sent: Tuesday, April 05, 2005 4:05 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: Mortar Testing

This thread reminds me of a question I've been meaning to ask.

With regards to grout, when should it be tested? The w/c ratio has to be
really high (producing an 8-9 in slump) so that the block has some water to
absorb when placing the grout and doesn't suck it all out. However, with a
w/c ratio so high, I doubt if a satisfactory sample can be cast. After all,
the in-situ condition of grout has a w/c ratio which is more normal range
once the excessive water is removed by the block. It would seem to me that
the sample should be cast before the water is added, but that sounds like a
complicated process.

Any enlightenment would be appreciated.

T. William (Bill) Allen, S.E. (CA #2607)	
ALLEN DESIGNS	
Consulting Structural Engineers	
http://www.AllenDesigns.com	
V (949) 248-8588	 .	 F (949) 209-2509	

-----Original Message-----
From: Sherman, William [mailto:ShermanWC(--nospam--at)cdm.com] 
Sent: Tuesday, April 05, 2005 1:38 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: Mortar Testing

I just finished typing an email to a co-worker on this very subject.
Following is what I wrote: 

I have deleted testing of mortar during construction from the project
specifications for the following reasons: Sections 3.1 and 3.3 of ASTM
C270-03 state that this standard is not to be used for field testing of
mortar or to determine compliance of field sampled mortar with the
specification; ASTM C780 provides methods for field testing of masonry
mortar but it also states that such testing should not be used to
determine compliance with compressive strength in ASTM C270. The reason
mortar is generally not field tested is that the mixed mortar has a
higher water content than the mortar in the constructed wall, due to
absorption of water by the CMU. Thus, compressive strengths of field
mixed mortar alone would be expected to be lower than laboratory tests
that use defined water contents. 

Therefore, one should generally not specify field testing of mortar. UBC
does have a special test method using masonry units and mortar - but if
we are really concerned with strength of masonry, we should specify
prism testing. However, prism testing is not required by the code if the
specified compressive strength of masonry is within the permissible
requirements for the "Unit Strength Method". 


William C. Sherman, PE 
(Bill Sherman) 
CDM, Denver, CO
Phone: 303-298-1311
Fax: 303-293-8236
email: shermanwc(--nospam--at)cdm.com
 

> -----Original Message-----
> From: Kestner, James W. [mailto:jkestner(--nospam--at)somervilleinc.com] 
> Sent: Tuesday, April 05, 2005 2:30 PM
> To: SEAINT
> Subject: Mortar Testing
> 
> Why does the ACI 530, 3.7B, require only lab compressive 
> strength testing (ASTM C270) for acceptance of mortar? Field 
> testing (ASTM C780) is only to verify consistency of 
> materials and procedures, NOT FOR MORTAR STRENGTH. Yet, the 
> ASTM C780 tests for compressive strength.  This seems like 
> the mason and mortar suppliers have lobbied hard for this 
> provision to remove any checks and balance on their in place 
> work. Other than a prism test, what other basis do we have to 
> evaluate the strength of mortar that we are actually getting 
> in the field?  
> 
> I realize that I'm really only interested in the strength of 
> the entire assembly, but if it is cost prohibitive to test 
> the prism assembly, then if I test each component 
> individually and it comes up to strength, than I would think 
> that the assembly is acceptable.
> 
> 
> > Jim K.
> > 
> 
> 
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