ASR

[dik]

I've encountered ASR in concrete mostly with slabs. The effect is mostly cosmetic. If surficial ASR is evident on a large pile cap, does it have an impact on the overall strength or seriviceablilty of the pilecap?

Thanks...

 

[jhnblgr]

like rust on rebar it expands causing cracks that leads to delamination that further exposes the interior of the concrete which will break down further until nothing solid is left. So in away it’s likely worse than rust since it is throughout the concrete. Id say it’s concerning, quantify it likely difficult.

 

[HTURKAK]

ASR causes internal pressure and results random cracking patterns called “map cracking” . In long term , cracks allow water to penetrate the concrete, accelerating the corrosion of reinforcing steel and further degrading the structure.
But you can manage the ASR with painting the concrete surfaces to minimize the moisture .

Summer 2008 - Volume 1, Issue 3 - Reactive Solutions - ASR - Concrete - Pavement & Materials - Pavements - Federal Highway Administration

www.fhwa.dot.gov

 

[lexpatrie]

Alkali-Silica Reaction? It would have the potential to penetrate and if it's on the top surface, likely the whole batch has the problem, so it would progress.

Isn't that moisture driven? I'd have a tough time convincing myself that moisture could somehow be precluded on a foundation, because the water won't necessarily be coming from above and it's tough to paint the bottom side of a footing or a pile cap.

The people who really seem to know about this is the Las Vegas Building department. Or maybe that's sulfate soils.

"cover" is generally predicated for a fifty year life, then the carbonation reaches the rebar and the neutralized concrete doesn't protect it. There have been protruding roof elements that "died" from rain exposure, with possible oxide jacking forces from rebar expansion contributing.... (this is a bit of an esoteric topic and is mostly recognized in nuclear facility designs, for whatever reason). Wikipedia kind of misses the Nuclear research, but it's got some leads for scholarly research if you are interested. https://en.wikipedia.org/wiki/Oxide_jacking

 

[dik]

Thanks, gentlemen (a binary term for PC).

 

[dold]

ASR is typically (or at least in part) a result of deleterious material in the aggregates. We have issues in our region (the aggregates) with this in regard to the strict ASR testing for FAA P-501 rigid pavement. I suspect you could find some reference material from the FAA.

 

[LittleWheels]

Reactive aggregates and moisture is the main driver for ASR and eventually the structure may need to be demolished. Many times, ASR is slow-moving but implacable. Cementitious replacement generally damps down aggregate reactivity compared to CEMI but that is no good after the fact.

 

[BridgeSmith]

ASR occurs when alkali in the aggregate reacts with the silica in the cement (and water) to form a gel on the surface of the aggregate. The effect is far more than cosmetic - it breaks the bond between the aggregate and cement. As you may realize, this results in a substantial reduction in tension and shear capacity wherever the reaction occurs. So, given enough moisture and time, it can compromise the structural integrity of the entire component.