Concrete Tanks

[justinh44]

What are the advantages/Disadvantages for using prestressed concrete versus regualr reinforced concrete for cylinrical tanks?

 

[dbuzz]

The most obvious benefit, for mine, is that prestressing and post-tensioning of tank walls can significantly reduce or eliminate the circumferential tensile stress, which, with concrete being a relatively weak material in tension, is a significant benefit.

 

[justinh44]

Are there advantages to using regular reinforced concrete?

 

[jike]

Concrete must crack before conventional tensile reinforcement carries the load. These microcracks need to be limited in size for a tank not to leak.

A prestressed tank will not crack until the tensile stress overcomes the precompression plus the cracking tensile strength.

Obviously a tank with no cracks is desirable.

 

[JStephen]

When you get into prestressed tanks, you are looking at more of a specialty item, rather than an "anyone can do it" item. Look up websites for Natgun, Preload, Crom Corp., Prestress(?), DYK, etc., for more information on the products they sell. There are several others across the county whose names escape me at the moment.

One difference also is that AWWA has standards on various prestressed tanks, but not on cast-in-place tanks. Typically, on modern tanks in the US, I've seen non-prestressed cast-in-place tanks used mainly for raw water or water treatment; that is, places where leakage doesn't really matter that much. Most of the CIP tanks I've seen used for potable water were also very old.

Another difference is that the prestressed-tank people generally want to do bigger tanks, and not, say, a 50,000 gallon tank. The prestressed tanks are generally aimed at circular tanks, also.