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Re: Masonry: Epoxy-injection for shear repair?

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Livingston, Michael wrote:
> 
> I'm evaluating a 10-story masonry apartment building built in the early
> 70's where the walls sustained cracking from both the Loma Prieta
> earthquake and differential settlement.  About 5 years ago, it was
> "repaired" using epoxy injection.  I'm trying to track down which
> product was used without much success.  Apparently the criterion was to
> fix all cracks you could stick a credit card into and call the rest
> "cosmetic".
> My question:  Are these epoxy injection methods effective for restoring
> shear capacity of masonry walls?
> I've talked to some manufacturers who say it is great, stronger than the
> surrounding masonry, etc. but who were not forthcoming with test data.
> A colleague of mine suggests that for every crack, there are many more
> micro-cracks just waiting to open up nearby.  And where there is a
> visible crack, the steel may have yielded, reducing the capacity of the
> wall if steel was used to resist shear.
> Does anyone have any opinions/data on this method of repair?
> 
> Michael Livingston, SE
> michael.livingston(--nospam--at)intres.com
> 
Michael, I havent done any epoxy injection on a masonry building but
have been involved in over 40000feet of injection on concrete walls. You
didnt mention whether or not the walls are solid grout. If there not,
you can forget any capacity from the epoxy. If they are, you should see
if you can get copies of the inspection reports and test reports. If
there are none available or it wasn't done forget it. The results of the
testing we have done resulted in shear failures in planes other then
that of the epoxy plane. Hope this helps. Mark Harper PE