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RE: Corrosion-Damaged Brick Wall

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Nels,

Re: "Strengthening and Durability of Decayed Brick-Masonry Repaired by
Injections", Binda, Baronio, Fontana; Proceedings from the International
Brick Masonry Conference, 1991.  In this paper they used an epoxy based
putty for the larger cracks, and then painted the surface with a waterproof
synthetic paint for all of the fine cracks.  The paint was removed after
injection.  There is a good discussion of injection pressure in this article
as well.

If the cracks are wide and there are a lot of them, you might want to
consider shotcrete.  If the cracks are small enough, you could consider
using a breathable masonry coating like Conservare by ProSoCo.

You might want to discuss this with Mike Schuller at Atkinson-Noland
http://www.ana-usa.com/masonry.htm.

You could also consider vacuum injection.

Regards,
Harold Sprague


> -----Original Message-----
> From:	Nels Roselund [SMTP:n.roselund(--nospam--at)worldnet.att.net]
> Sent:	Wednesday, September 20, 2000 11:18 AM
> To:	seaint(--nospam--at)seaint.org
> 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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