Efflorescence Build-up

[sedesigner06]

Attached is a picture of what I believe is efflorescence build up on the exterior wall of a tunnel. It builds up to almost a 2" thickness (iv never saw eff. build up like this, hints the "I believe" clause). I believe it is a concern based on what I have read to this point as it can be harmful to the longevity of the concrete based on the water coming through the wall and degrading the concrete of minerals.

Would you agree this is a viable concern?

My first thought on fixing is a spray on water barrier as some claim to be able to be applied on the inside face of a wall and keep water from "flowing" through as I believe is the issue here.

Thanks in advance for any help.

 

[dik]

Can you clean it off and use a Xypex type of topical application? What is the source of the water? Do you have a proper waterproof membrane on the outside of the tunnel wall? The expansion of the efflorescence can cause failure of the concrete in the long term. What is the crystalline material? Have you had it analysed to possibly determine the source? Lots of questions...

Dik

 

[OldBldgGuy]

That appears to be a much more active deposition than efflorescence. I might not be able articulate the difference clearly but efflorescence should be over a surface, powdery and easily wiped away, whereas your problem appears to be a hard calcareous build-up at a crack, indicating an active leak and evaporation or deposition from a supersaturated solution. Efflorescence occurs from diffusion through concrete or masonry, not a leak through a crack.

You can try patching it, but pushing water back through a joint is not easily done. I think you have to chase out that joint as deep as you can, then use a Xypex type of repair material in the joint followed by a surface coating in the local area.

 

[dik]

OBG... I was thinking that it's important that he determine the source of the water... I've seen large efflorescence buildup where the expansion products have actually damaged the concrete.

Dik

 

[hokie66]

I wouldn't call that efflorescence. It is the product of leakage through a crack/joint, and is like the process of autogenous healing. Is it still leaking?

A "spray on water barrier" on the inside won't help.

 

[dik]

that's why suggesting Xypex... it migrates towards the source of the water and seals the area using it's crystalline structure. Works well and used it for decades... only problem is the crack cannot be active.

Dik

 

[sedesigner06]

Thanks for you guys input, to answer some of your questions:

-I will have to research the design drawings to see if there was a water membrane to be on the outside of the wall. I would hope so, but my gut feeling is that there was not or it has failing hints what we are seeing. It would be nearly impossible to treatment on the outside of the wall at this point.

-I did not collect a sample, could possible make an additional site visit to collect and see if that will help me more.

-I believe this is an active crack, so seems like it may limit my solutions.

-There is a roadway over the top (approx. 15' above) of this so not sure if deicing salt would play a role in this seeping through the soil and into the tunnel crack.

 

[Canuck65]

Trying to fix this by putting a spray on water barrier on the interior face is doomed to fail. Xypex may help under the right conditions (lots of surface prep, attention to detail on installation, good curing, etc..) Repairing from the exterior, i.e. where the source of water is coming from is the best option, however, I do understand that this may not be possible.

Looks like it could be a good candidate for crack injection.

 

[dik]

Agreed... But, if an active crack duped will not work... Look into a polyurethane injection.

Dik

 

[Ron]

Yes, this is a form of efflorescence. Based on the accumulation, it is from relatively slow crystal growth.

Yes, it depletes minerals in the concrete, most notably calcium, the largest elemental component of portland cement.

Your issue appears to be localized to a crack or joint. It is caused by recurring moisture migration through the concrete.

You do need to test the residue. It will help solve the problem.