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RE: Carbonation

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I would not perceive carbonation to have much direct effect on bonding to uncarbonated concrete.  Indirectly, by lowering the pH and allowing rebar to corrode, localized bonding might fail due to the mechanical action of the expanding steel. 
This is not too unusual in the old days with precast plant heaters in the winter.  The precast was carbonated, but the topping was not.  I can not recall of any direct bonding issues other than what I have already mentioned. 

Harold Sprague

From: tiger(--nospam--at)
To: seaint(--nospam--at)
Subject: Carbonation
Date: Thu, 8 May 2008 01:07:12 +0900



I am trying to figure out what role carbonation may have played in a structure that has experienced debonding of a 2 inch thick concrete topping that was placed on 4 inch thick precast planks (roof structure).

I had a lab do analyses on a number of samples including ones in which the debonding had occurred and one sample where the topping and plank were still bonded.

The staining with the phenolphthalein indicator solution showed significant carbonation depths for the debonded topping and plank interface surfaces (debonded a while ago and carbonation occurred), but for the still bonded sample it showed carbonation on the top plank surface and NONE on the bottom topping surface.  In other words, the plank top surface appeared to carbonated prior to placement of the topping.

I am wondering if anyone has dealt with the effects that carbonation may have on the ability of fresh concrete to bond to a carbonated surface.  Would it reduce the potential bond, or have no discernable effect?


I’d welcome comments if you have any.





Terangue *Tiger* Gillham, PE
GK2, Inc.

tiger(--nospam--at) <


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