Concrete Cover for Water Tight Concrete

[imsengr]

Hi everyone,

Does anyone know whether ACI has any provisions for concrete cover for water tight concrete? Section 7.7 of ACI provides for concrete protection for reinforcement in cast-in-place concrete and precast concrete. Section 7.7.5 also provides for corrosive environment. But how about water tight concrete? Is there a specific provision for that.

I am doing a review of some notes for drawings, and there seems to a set of concrete cover for water tight concrete, that seem to be slightly more stringent than ACI's concrete protection for reinforcement. (generally, about 1/2 an inch more than ACI's, but sometimes similar to ACI's as well.)

Thanks, y'all.

 

[miecz]

For environmental structures, ACI 350 has similar requirements to ACI 318. The cover for primary reinforcement for beams and columns is increased by 1/2" in ACI 350.

 

[vincentpa]

CIP Concrete
Cover is a minimum of 2" for walls.
For beams, 2" to stirrups and 2.5" to primary reinforcement.

 

[Gumpmaster]

Even with a large amount of cover, you'll still get shrinkage cracking and the concrete will leak. More important than cover in watertightness is controlling cracking. Design per the alternate design method of ACI 350 and limit the crack widths to .008in or less. This should reduce the amount of leakage. Epoxy injection will still likely be needed to fix what cracks do occur.

Also, limit the w/c ratio. w/c=.39 isn't unreasonable with a super plasticizer. Finally, look at Xypex as a coating to reduce leakage, or there are some crystaline admixtures that swell in contact with water and eliminate leaks.