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Re: Substitute concrete for grout?

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I have an article dealing with this. I will try to dig it out when I get back to the office later this week.

Grout is very fluid so that it can be pumped and will consolidate around embeds and rebar. Mortar is very stiff because its function is to bond 2 masonry units together. It would not flow into the spaces without creating a lot of voids.

The extra water in the grout is drawn off of the grout in the masonry units. Grouts reduction in volume immediately after placement is due to this loss of water.

Regards,
Harold Sprague





From: "Jordan Truesdell, PE" <seaint1(--nospam--at)truesdellengineering.com>
Reply-To: <seaint(--nospam--at)seaint.org>
To: seaint(--nospam--at)seaint.org
Subject: Re: Substitute concrete for grout?
Date: Mon, 26 Feb 2007 20:55:28 -0500







I've heard that too (water absorption preventing full hydration) but
can't remember where. 



As a follow up what about the substitution of mortar for grout?


Jordan




Will Haynes wrote:
I thought I remembered something about the reason why you
shouldn't allow substitution of concrete for grout was because of the
wetness of grout compared to concrete and the porous nature of cmu,
which would absorb and bond to the grout much better than to concrete.
But maybe I just dreamed that one night.




Will H.



  On 2/26/07, Scott Maxwell <smaxwell(--nospam--at)engin.umich.edu>
wrote:
  Will,



Keep in mind that technically grout is concrete.  It is just concrete
with

a large slump and thus rather high water to cement ratio.



To my knowledge, there is nothing that specifically disallows the use
of


concrete in filling reinforced CMU cells (if so, then technically grout

would not be allowed either).  The MSJC specification (ACI 530.1/TMS

602/ASCE 6-05) does state in Article 2.6B.2:



"Unless otherwise required, mix grout to a consistency that has a slump


between 8 and 11 in."



Article 2.6B.1 states:



"Unless otherwise required, proportion and mix grout in accordance with

the requirements of ASTM C 476."



In the end, grout is just concrete that is "flowable" enough to
properly


fill voids without undue segregation.  This is typically done with high

slumps.  Thus, grout is just typically a VERY wet concrete (but with

typically smaller aggregate than "typical" concrete...i.e. rare to get


aggregate greater than 3/8" for course grout).



HTH,



Scott

Adrian, MI





On Mon, 26 Feb 2007, Will Haynes wrote:



> I seem to remember that ACI does not allow you to substitute
concrete for


> grout when filling reinforced cmu cells, having something to do
with the

> water absorption from the grout into the units. But I can't find
where this

> is stated. Does anyone know if this is correct?


>

>

>

> Will Haynes, P.E.

>



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