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RE: Mortar Field Test

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The lab is correct - field tests for compressive strength of mortar cannot
be compared to lab test values. (The lab test is at a specified water
content but the water content in the field will vary. Some of the water is
absorbed into the CMU during placing, so the actual water-cement ratio is
less than in the test specimen.) ASTM C780 does provide for field testing of
mortar before and during construction, but only for an indication of mortar
consistency, not for an absolute value of compression strength. I do not
recommend specifying field mortar testing, as I also consider it a "wasted
test". 

> -----Original Message-----
> From: Todd Hill [mailto:thill(--nospam--at)tkarch.com]
> Sent: Tuesday, October 02, 2001 9:12 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)tkarch.com
> Phone	 816-842-7552
> Fax	 816-842-1302
> 
> 
> 
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