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Corrosion-Damaged Brick Wall

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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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