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Re: Fiber Reinforced Masonry Grout

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Christopher,

I think that Bill and/or Harold basically answered your question...I would
have ask a question first: what is the purpose of the reinforcement in the
masonry/grout?  Is it for shrinkage/typical steel?  Or is it for definite
structural purposes such as vertical reinforcement for out of plane wind
loads or vertical/horizonatl reinforcement for in plane (shear wall)
loads?

I think Bill hits it right on the head.  If it is for structural purposes,
then I would say that you should NOT be using fiber reinforced grout.
Even in the concrete world (i.e. ACI 318), fiber reinforcing is not
permitted to replace standard rebar if it is there for structural
purposes.  The same would be true for masonry.

If you are looking at it for the purposes of shrinkage type situations,
then I really don't know how effect it will be for that any way.
Regardless, Harold is 100% correct...and is actually understating the
tendency of steel fibers to ball (in my opinion)...in my experience, steel
fibers WILL ball and they WILL be a real pain in the A$$ to work with.
So, getting a high slump grout to work with steel fibers and then pouring
that grout down empty cells is a LOT easier in theory then I believe it
will be in practice.

Typically, if one needs to get bars into an existing wall, one method used
is to cut slots in the face shells to get the bars in and then grout the
cell solid including the slot in the face shell.  You don't necessarily
have to cut the slot the full height of the wall...just enough to get the
bar into the cell.  Sometimes this will be done with a couple of shorter
bars that then get spliced in the cell (i.e. you can cut shorter slots but
get the full height of rebar will multiple shorter bars that get lap
spliced).

If you need to reinforce the wall in order to handle greater out of plane
wind loads (i.e. the unreinforced masonry cannot span the required
vertical or horizontal distance when carrying the required loads), you
could also leave the wall unreinforced and add in steel (or some other
material) backup that will act as girts (vertical span) or wind columns
(horizontal span) to cut down the span of the walls.

I guess it would be helpful to know WHY the wall needs to be reinforced
now.  Such information could help other come up with other suggestions.

Regards,

Scott
Adrian, MI


On Wed, 4 Jan 2006 bcainse(--nospam--at)aol.com wrote:

> If you check ICC Evaluation Reports for fiber reinforced concrete, you will find that fiber reinforcement is not allowed to replace "structural reinforcement."  Why would it be any different for fiber reinforced grout. Sounds kind of "dicey" to me.
>
> Bill Cain, S.E.
> Berkeley CA
>
>
> -----Original Message-----
> From: Christopher Haffner <chaffner(--nospam--at)gorge.net>
> To: seaint(--nospam--at)seaint.org
> Sent: Wed, 4 Jan 2006 11:01:29 -0800
> Subject: Fiber Reinforced Masonry Grout
>
>
> Two questions:
>
> I have a client that has requested the use of fiber reinforced grout to
> reinforce an un-reinforced hollow core masonry wall in lieu of using normal
> grout and mild steel reinforcing.  Has anyone used this type of grout and if
> so what was your experience?
>
>
> We are reinforcing an existing un-reinforced masonry concrete block wall
> (not normal CMU block but somewhat similar characteristics) building and
> need to get some reinforcing inside the voids and grout the reinforced cells
> solid.
>
> Does anyone have a suggestion (trick) on how to physically get mild
> reinforcing bars inside the 7.5"x12" voids (yes - they are a weird size in a
> weird system) prior to grouting?  This is why the fiber grout is being
> considered.
>
> Chris
>
> Haffner Consulting Engineering
> www.haffnerconsulting.com
> Office & Fax:  541-478-3052
>
>
>
>
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