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RE: Mortar Testing

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Gentlemen:

Removing the mortar testing is a potential interpretation of the various
ASTM tests and yes it does give the Masons a free pass.

Here are my thought on the mortar and grout situations.

Mortar:
1.  Watch the mason batch a batch.  Test that batch.  Use that as a
guideline for the quality of other batches.
2.  Have the onsite make sure that the mortar hold time and re-tempering
requirements are met.  Don't let them go to lunch and then add water after
lunch to the same batch.
3.  Don't delete the testing.  Just realize that some low breaks are ok and
anticipated.  If it doesn't get to spec, physically check the batch
procedures, re-tempering and hold times and have the mason correct.  If you
have less than 1/2 of the specified strength YELL LOUDLY.  1500 of 1800 is
in a reasonable range for water absorption.  800 of 1800 is not.  Yes the
lab could be wrong, but based on my experience, I doubt it.
4.  Pull the samples from the mason boards etc.  Don't let them always make
a new batch just for the testing.
5.  Have the lab pull a sample of the masonry sand.  You'd be surprised at
how little of the sand actually meets the "spec".        The mason cannot
use "non-spec" sand unless a laboratory mix design has been developed for
the specific sand he's using.

This will usually get the masons attention right away and make him toe the
line.

If you really think the batch portions are off, run an acid dissolution test
of the mortar to determine the proportion sand and cement actually present.
If you want a w/c ratio you need a Petrographic point count.  About 650 to
850 dollars from a reputable lab.  You only need a wafer of the mortar for
the second test and

Grout
Grout should be tested either with a traditional pinwheel or with the new
Grout Sample Box (GSB) system at the time of delivery during placement.  Go
to www.deslinc.com to see the GSB system.  We use this in our laboratory and
have great success with this.  I prefer centrally batched grout delivered to
and pumped on the site from a qualified redi-mix.  Using cylinder molds may
be convenient for the laboratory but is not the best way.

If they batch grout on site.  Pull and test the stockpiles for gradation.

Specify grout by FLOW not slump.  Make the labs do the damn testing
right!!!.

Grout and re-bar hold masonry together, not the mortar.  If the grout is bad
you have problems.

Prisms
At least one prism should be made up and tested at the beginning of the
project to check the mason.  If you have concerns, cut a 1/2 size prism
about 14 inches tall from a non-critical section of the wall.  A cut prism
test should be less than a grand in most locations.  You fellas in CA may
need $1500.  Transport, handling of these are critical.  Most labs don't
have compression machines with enough capacity and head height to test a
full size prism.  You will need to make some adjustments and interpret the
test results.  Also, if they don't locate and load through the CENTROID of
the sample, the test results will be screwed.

Wall Jacking Test
This is a rare test.  I haven't actually done one but would love to try.

Impact Rebound (IR).
I've heard about a draft ASTM for Mortar (IR).  Our European brothers have
been using pendulum type impact rebound on mortar for years.  There is a
Windsor Pin test.


Just some quick thoughts.


Arvel




Make sure you get a grout test from each elevation of the wall.



Remember, for all intents and purposes, the grout and the re-bar are what
holds that wall together.  If the grout breaks low be nasty.

On site aggregates should be tested in the stockpile.  You'd be amazed at
the different "cheap" aggregates I've seen masons try and use in their
grout.  Also, some masons will purchase remix aggregate.  This is the sand
and coarse aggregate combined.    This seems to work good.





-----Original Message-----
From: Sherman, William [mailto:ShermanWC(--nospam--at)cdm.com]
Sent: Tuesday, April 05, 2005 3:38 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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