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Re: Corrosion-Damaged Brick Wall

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Nels,

How about:

1. Remove the outer wythe of brick to a level below lowest crack.
2. Remove effected grout and horiz. steel, clean vert. steel.
3. Install new wall anchors thru inner wythe & grout, terminating in outer
wythe space.
4. Form, reinforce and pour concrete that takes the place of the outer wythe
and parapet and engages newly installed anchors. Set 3/4" plywood form at
exterior of wall flush with exterior face of brick (form a ledge).
5. Strip forms, stucco exterior face taking advantage of the ledge.
6. Convince self and owner that this is less expensive than the injection
path.
7. Convince self and owner that this results in a repair that removes bad
material, arrests continued corrosion of existing rebar and permanently
mitigates water intrusion.

Regards,

Mark

----- Original Message -----
From: Nels Roselund <n.roselund(--nospam--at)worldnet.att.net>
To: <seaint(--nospam--at)seaint.org>
Sent: Wednesday, September 20, 2000 9:18 AM
Subject: Corrosion-Damaged Brick Wall


> I'm working on the design of a repair to a building with reinforced brick
> walls -- the walls were built with two wythes of brick separated by 1-1/2"
> to 2" thick reinforced grout.
>
> The project started out as a seismic anchorage project, and expanded when
I
> discovered longitudinal cracks at the tops of the parapets.
>
> Corrosion of the horizontal reinforcing in the top of the parapet has
> resulted in expansion of the reinforcing steel that has split the wall
from
> the top of the parapet to a bed-joint level that level that is about 16"
to
> 20" below the roof.  The separation is at the brick-grout contact plane,
> varies in width 0" at the lowest level to a width that varies from 1/32"
> 1/4" at the roof level.  The separation wanders from being adjacent to the
> inner wythe and being adjacent to the outer wythe of brick.  The general
> effect is that the outer wythe is tilted outward from the lower bedjoint
> level of the separation.
>
> I had the damaged portion of the parapet removed to the roof level.  I do
> not want to remove any more of the wall since more removal will affect the
> wall anchors and shear bolts, effectively disconnecting the walls from the
> roof diaphragm.
>
> I tested two repair procedures:
> 1) injection of cementitious grout.  This requires saturation of the brick
> to keep the grout fluid enough to flow, and in any case probably will not
> reliably fill separations finer than 1/16".  I abandoned this approach
> because of the large quantities of water that needed to be injected into
the
> wall to achieve grout flow -- I expect that undetected corrosion damage is
> already progressing into the wall, and additional water may accelerate the
> process.  (Another structural engineer recommended a grout consisting of
> only superfine grout, water and a shrinkage control admixture with which
he
> says he obtained good results in a similar repair.  I have not tested this
> procedure since injection of large amounts of water is also required in
> order for this material to flow in the wall).
> 2) injection of epoxy.  Sikadur 35 is very low viscosity and seems to be
an
> effective repair material.  In this test, I had the contractor drill
> vertical holes intersecting the separation and 3 to 4 feet apart and
> injected the holes with gel epoxy to form dams that will confine the
> low-viscosity epoxy to narrow zones that can be monitored.  The low
> viscosity epoxy flow out of the wall into the attic through pin-holes in
the
> mortar joints -- I think this is because the inner mortar joints were not
> tooled, but just struck off by the mason, so those mortar joints have not
> been consolidated.
>
> Question: what is a good material to seal the unconsolidated mortar
joints.
> I'm considering something like Henry's lap cement, painted on with a stiff
> brush used to work it into the mortar.  The contractor wants something
that
> can be spray-applied.  Any suggestions?
>
> Has anyone solved this problem in another way?  Reinforced brick buildings
> are getting old, and I expect that this will become a very important
> maintenance and repair issue.
>
> Nels Roselund
> Structural Engineer
> n.roselund(--nospam--at)att.net
>
>
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