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Re: Repair of reinforced concrete members.

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I presume you are excavating a minimum of one inch deeper than the
bottom of the bar to insure the bar is coated completely with the
corrosion inhibitor.  Then applying epoxy to the excavated surface and
filling with concrete *might* create a patch that is electrically
iscolated from the existing concrete (except for the bar running through
it) and an anode/cathode might develope between the old and new
concrete.  An electrically conductive bonding agent might be a better
choice.

Regarding your original question regarding cracking, if you are
excavating to an inch below the bar then I would assume that future
corrosion of the bar would result in cracking similar to before the
patch is done.  But in my experience the future cracks nearly always
occur adjacent to the patched area because of the battery effect - which
is nearly impossible to mitigate (but we have to try).

Lew Midlam, P.E.
http://www.lcm.com
============================

Dr. Ravi Sinha wrote:
>  
> The most popular method that I have observed is to clean the rebars,
> apply corrosion inhibitor on the surface of the bars, apply epoxy
> on the concrete patch, and then replace the excavated concrete with
> polymer concrete with similar strength as the original.
> 
> This engineer (who probably speaks from many years of experience
> in this field) has expressed his apprehension that the presence of
> epoxy would make the concrete amenable to some change in volume.
> So, if the rebars corrode again in future, the tell-tale sign of
> surface cracks parallel to the rebars may not apper.  This will imply
> that the structure may deteriorate without any visual warning.
> I have not seen any such apprehension in literature and was wondering
> if there is any truth to this view.
> 
> ------------------------------------------------------------------------------