Akali Silica Reaction - Residential foundation

[RHTPE]

All of you concrete gurus:

I am investigating a residential foundation that was constructed in 1988. Starting in 2005 cracks began appearing in the wall and got progressively worse. As of last month, the inside face shows a cracking pattern typical of akali silica reaction (ASR), along with carbonation on the surface of the wall. The homeowner just spent a tidy sum having the outside of the foundation coated, covered with a drainage fabric, and installed a positive footing drain system.

My question for those more experienced than I: Is there a way to mitigate the damage caused by ASR that would be less involved and less expensive than replacing the foundation walls?

The improvements to the ground water control will certainly help to slow down the ASR, but as I understand the phenomenon, it will continue as long as water is available in some form. At this point it's not of any major structural concern, but if it continues it will some day be of concern.

Please share your thoughts & experiences.


Ralph
Structures Consulting
Northeast USA

 

[Ron]

Ralph...whether the damage will be pervasive or superficial depends on the source of the ASR and the distribution of the offending aggregate.

For example, there are areas in the country of known ASR activity from the coarse aggregates. In some of those, the offending aggregates are simply minor contaminants in an otherwise competent aggregate matrix. There can also be ASR in the fine aggregate. Either can be pervasive and destructive.

You also need to determine if your reaction is ASR or ACR (Alkali-Carbonate Reactivity). I would suggest a petrographic examination of several cores to characterize the pervasive nature of the reaction, and from that you can make logical decisions as to a course of action.

Since you are in the Northeast US, I would suggest that you contact Simpson, Gumpertz, and Heger; or Wiss, Janney, Elstner, both with offices in Boston. Both have good petrographic capabilities. I fairly sure that SGH does their petrography in Boston, but I'm not sure if WJE sends theirs to Northbrook, IL (main office, Chicago area).

Good luck.
Ron

 

[RHTPE]

Ron,

Thanks for the input. The damage is a tad beyond superficial, but I don't think it's yet to the point of being critical to the structural integrity. I have reached out to both SGH and WJE to see how they could assist.

From what I have learned about ASR, it seems that keeping the concrete devoid of water would stop the reaction. The homeowner has taken one step in this direction by having the foundation drainage system reconstructed to provide positive drainage of all ground water and roof drainage. Temporarily supporting the addition to reconstruct its foundation is a cure that I hope to avoid.

Any input regarding mitigation will be appreciated.

Ralph

Ralph
Structures Consulting
Northeast USA

 

[Ron]

Ralph,
Keeping the water out is certainly a start, but keep in mind that there is interstitial water in the concrete that will still support some level of reaction.

Once you have the reaction occurring, you can slow the process down by preventing water intrusion, but there's not much else that will mitigate the issue after the fact.

In new concrete, there are several ways to mitigate, but those don't work in-situ. There is some research ongoing using lithium (normally used as an admixture to mitigate reactive aggregate conditions)in an injectable or saturant form to help reduce the reaction. I'm not sure how far along that is or the results thus far.

Ron

 

[Teguci]

I have heard of Lithium being used as a topical solution to ASR but thats not going to solve the problem. Considering Delaware's reaction to ASR (they shut down a piece of I95 and replaced it) I'd suggest letting the existing concrete crack and find some way to contain it.

I didn't think it took that long for ASR to begin?