Minimum Air Entrainment 3

[LPPE]

Is there a minimum air entrainment requirement for concrete? I specified a 4,000 psi NO AIR mix, and the submittal I received says "4,000 NO AIR", yet an air entraining admixture is listed, and the air content listed as 0-3%.

 

[SlideRuleEra]

Concrete without "added" air entrainment is used from time to time. However there is often some air that is unintentionally "entrapped" in concrete. Test procedures will show this as entrained air - a "zero percent", per the test, may not be obtainable.

Here is an article that may be of interest
ftp://imgs.ebuild.com/woc/J00J040.pdf

http://www.SlideRuleEra.net

 

[jdonville]

LPPE,

The supplier probably kept the admixture on the list as an oversight or laziness. From what I understand, there is no minimum air requirement. However, the supplier may also be covering himself in case someone tests and finds a small air percentage in the delivered concrete.

The best way to find out is to ask your supplier why the admixture and "0 to 3%" language is on the mix.

Jeff


Jeffrey T. Donville, PE
TTL Associates, Inc.

http://www.ttlassoc.com

 

[JAE]

There is usually a small amount of "natural" air entrainment that occurs in concrete - even if no admixture is added.

 

[emmgjld]

It has been my experience (and many years back I remember the 'reps' from cement suppliers saying) that entrapped air and some natural entrained air usually results in 2% to 3% measured air.

I specify no entrained air additive for interior slabs, to reduce potential delamination. I believe that is fairly commen.

 

[Ron]

Air entrainment is an admixture that allows a producer to make a little profit (volumetrically extends the mix)and reduce workability complaints as well (air entrained concrete has better workability, in general).

If you specified no air entrainment and you received a mix design submittal with air entrainment, reject the mix design. Get what you ask for, but ask for the right thing!

Entrapped air is larger and less effective for any material properties. It usually accounts for about 1 to 2 percent of the total air content, depending on the mix design and the type/duration of mixing.

 

[LPPE]

Ron- I see how the contractor would add the air entraining to get a little more out of the mix, and on this particular job, we're pouring about 3,400 cubic yards just to get out of the ground. On a large job, 3% air would certainly add up. But would the cost of the air admixture equal out the benefits of concrete saved?