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RE: Mortar Field Test

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Mortar is generally tested in cubes not cylinders, but either can be used.
The appropriate test for mortar is ASTM C-780.    There is a good discussion
of mortar testing that was put out by the Minnesota Concrete Masonry Assoc.,
"Recommended Practices for Specifying and Testing Masonry Mortars for
Concrete Masonry".  In that document they state C-780 was not intended to
compare the field results with C-270 or UBC Std. 21-16.  The intent of C-780
is for monitor consistency.

ACI 530 puts you in a bind in the QA requirements.  They give you a bunch of
tests, but do not give you acceptance criteria as you find in ACI 318.

If compressive strength is a concern as opposed to consistency, you should
probably be doing prism testing as opposed to the unit strength method.

If you review ACI 530.1 Sect 1.4 B, you will find that masonry mortar
testing is not required under the unit strength method.  It is confusing.
That is why you are better off just referencing the QA requirements of ACI
530.1 and be done with it.

Harold O. Sprague

> -----Original Message-----
> From:	Todd Hill [SMTP:thill(--nospam--at)]
> Sent:	Tuesday, October 02, 2001 10:12 AM
> To:	SEAINT (E-mail)
> Subject:	Mortor Field Test
> I got a mortar test report from a testing agency on one of my projects.
> I actually have never received a mortar test report before.
> I've gotten block & grout tests, but never mortar.
> Anyway, ASTM C-270 & ACI 530.1 call for an Average Compressive Strength
> for
> laboratory prepared
> Type S mortar of 1800psi.
> However, there is no mention of a field test value.
> The testing agency tells me that this is actually a wasted test because
> there are no field values to compare to.
> Is this correct?
> The test values I got were 1210 psi & 1110 psi, for a type S mortar.
> Is there a field value for the mortar to compare testing to?  
> It also seems to me that a 3" diameter cylinder test will not tell what
> the
> real compressive strength of a 5/8" mortar joist is.
> Is this a reasonable assumption?
> TIA,
> Todd Hill, PE
> Project Manager
> TK Architects
> THill(--nospam--at)
> Phone	 816-842-7552
> Fax	 816-842-1302

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