Aggressive water on concrete

[RMPE]

Looking at a 10 year old clearwell that has been exposed to an aggressive water with a Langlier Index of -1.3, Alk of 76 (mg/l as CaCO3), Hardness of 160(mg/l as CaCO3), and CO2 of about 50 mg/l. After 10 years the cement paste has been "dissolved" to about 1/4" in depth and only the sand remains. Has anyone seen this before and remedied the problem??

 

[DeltaCascade]

Looks like you need a new clearwell, that's for sure hay? ... with a different material or rubber or some other coating... or, although likely not feasbile, changing the water quality before it gets to the area in question...

 

Yes, its pretty commonplace in water and wastewater treatment, and arises from the original designer having no clue what they were doing. You can restore the surface if its not too bad structurally. I use materials from a company called xypex in water plants. It is NSF approved for contact with drinking water and resists chemical attack typical of water treamtent.

 

[RMPE]

Clearwell is fine structurally at this point but I'd rather not see it get any worse. I'm not sure it's a design problem because, heck, it's potable water with a pH of 6.7! And an air stripping tower was designed to remove the CO2 but never funded.

Have never used Xypex, spec'd it twice, but for water containment in an old concrete storage tank and in an underground elevator room that had moisture problems.

What I'd like to know, is what is the tolerable levels of CO2, etc that will not affect concrete. I.E. what are the limiting parameters to design new tanks without protection? I understand from a source at AWWA, there was a similar condition with a Langlier Index of +something that exhibited similar conditions. Thanks for the help.