I am not greatly experienced with concrete restoration but have paid attention thru the years...

As you have received from others, there is the "impressed current galvanic protection" (active) and the "discrete anode" (hockey puck) (passive) methods. Both require physical access to the steel and only affect a relatively small area of steel so many access points are required. When I was with TT Engineers, another project team did one project to protect portions of the structural steel but the stone cramps have continued to corrode and spall the stone. The project manager would definitely be able to provide more info. I have not worked with the discrete anode method but it seems straight forward. The down side is the hockey puck will ultimately be fully used up and we cannot know how long as this is dependent on the rate of corrosion. The impressed current must be maintained and if the electricity is disconnected, then the system is not doing anything.

Some time ago there was a big push to use phenolphthalein to test for depth of carbonation of the concrete and then spray the concrete with a penetrating chemical to restore the passivation layer if/where needed call "Realkalization". I have not heard much on this approach for some time and I not sure if it is due to its performance or other reasons. It sure seemed promising when presented. Remember, we can get silane treatments to penetrate fairly deep although the literature on realkalization chemicals touted much greater penetration. 

Vector Corrosion Technologies uses all these processes.

Good luck!

Eric Hammarberg
Branch Manager
Brisk Waterproofing Company
720 Grand Avenue
Ridgefield, NJ   07657
D (201)945-0210
C (917)439-3537
[log in to unmask]
http://www.westerngroup.com

-----Original Message-----
From: The listserv where the buildings do the talking [mailto:[log in to unmask]] On Behalf Of Bruce Marcham
Sent: Wednesday, April 04, 2012 10:06 AM
To: [log in to unmask]
Subject: [BP] Concrete Passivation

We have a situation where I'm told they want to try "concrete passivation." We have rebar close to the surface on vertical wall panels on one of our buildings and I gather they are concerned about spalling (or more spalling) of the concrete if the rebar rusts (or continues to rust). 
 
To me it sounds like snake oil. Can you really get enough chemical into the concrete to neutralize it enough to stop corrosion that is already taking place? I could see it if you put it in the mix when the building is built but this is 45 years later. 
 
Do any of you have experience with this sort of thing?

A structural engineer friend of mine suggested that Grace makes a DCI admixture for the concrete mix during construction. 

http://www.na.graceconstruction.com/product.cfm?mode=c&id=4&did=1


Or this could be a case of the engineer managing the project being sent on a snipe hunt by the contractor or architects...

Bruce

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