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Re: seaint Digest for 3 Sep 2003

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The high water content of mortar is necessary to achieve adequate bond with the masonry unit. Unlike concrete's homogenous mix, masonry assemblies are a combination of wet mortar and dry units. In many instances brick with high absorption ( high IRA) are wetted before laying. With CMU work the units are required to be dry when laid. Mortar testing is a real crapshoot . Prism tests of the entire assembly are most reliable.

Dan Murray
On Thursday, September 4, 2003, at 03:00 AM, admin wrote:
----------------------------------------------------------------------- --- 6 Message:0006 6 ----------------------------------------------------------------------- ---
From: "Alden Manipula" <amanipula(--nospam--at)>
To: "SEAINT Listserve" <seaint(--nospam--at)>
Subject: Low mortor prism test results

I have test results for mortor in an 8" CMU wall as 800 psi for type S

I was told by a local masonry representative that he wasn't concerned
because the mix they used was pre-approved/pre-packaged as type s mortor =
that they are allowed to add as much water as needed to make it =

This doesn't seem right.  Wouldn't adding water incrase the w/c ratio =
decrease compressive strength?

Also, ACI 530-02 Section says "Compressive strength of masonry
shall be considered satisfactory if the compressive strength of each =
wythe and grouted collar joint equals or exceeds the value of f'm"

So shouldn't there be a concern if the mortor test results are so low if =
specified f'm=3D1500 psi? ACI318 is clear on acceptance criteria, but =
530 is

Any advice appreciated.



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