deciphering air entrainment requirements
deciphering air entrainment requirements
(OP)
The summerized specs read:
for normal weight concrete air content =
•no entrained air for concrete placed in foundation
•5% +- 1.5% entrained air UNO
•3% +- 1.0% entrained air for mixes with compressive strength greater than or equal to 5000 psi
•4% +- 1.0% entrained air for mixes with compressive strength less than or equal to 5000 psi placed in aggressive
(Aggressive environment = Exterior)
So for slab-on-grade with interior exposure and placed with 4000 psi concrete the air requirement is ______?
By the specs given it's either 5+-1% OR the member is considered part of the foundation and thus no A/E required.
for normal weight concrete air content =
•no entrained air for concrete placed in foundation
•5% +- 1.5% entrained air UNO
•3% +- 1.0% entrained air for mixes with compressive strength greater than or equal to 5000 psi
•4% +- 1.0% entrained air for mixes with compressive strength less than or equal to 5000 psi placed in aggressive
(Aggressive environment = Exterior)
So for slab-on-grade with interior exposure and placed with 4000 psi concrete the air requirement is ______?
By the specs given it's either 5+-1% OR the member is considered part of the foundation and thus no A/E required.






RE: deciphering air entrainment requirements
I'd read your specs as having to conform to #1, 3.5 to 6.5. I think the spec writer has 1 and 3 confused. Should have higher for exterior exposure if freeze-thaw is an issue.
Dik
RE: deciphering air entrainment requirements
RE: deciphering air entrainment requirements
On the general notes page of the structural drawings under the FOUNDATION section there are notes on footings, foundation walls, drilled piers, s-o-g, retaining walls, soil density, bearing capacity, etc.
He must be considering s-o-g as "foundation", right? That's the only way his A/E criteria make sense. Also makes more sense considering the vast majority of interior slabs get trowel finish. 6 1/2% + trowel = delamination right?
What say you guys?
RE: deciphering air entrainment requirements
RE: deciphering air entrainment requirements
From what I've read, steel troweling of slabs with 5%+-1 1/2% air can contribute to blisters, finishing problems and weak concrete at the surface.
RE: deciphering air entrainment requirements
Dik
RE: deciphering air entrainment requirements
1. Is this project a building?
2. Is the project located in a a region where air-entrained concrete is typically specified for freeze-thaw resistance?
3. If the answer to the preceeding question is negative, do you know why air-entrained concrete was specified?
RE: deciphering air entrainment requirements
1, yes
2, yes
The given criteria do not cover all possible concrete members on the job. If the first criteria were changed to read,
•no entrained air for concrete placed in foundation or in slabs, walls, and columns with interior exposure
the specs would work better.
But if one goes "by the book" interior slabs could have as much as 6.5% air.
RE: deciphering air entrainment requirements
1. Gunite (dry mix)
2. Shotcrete (wet mix)
3. Cast in Place
If your using Gunite, I don't think an air entraining admixture can even be added.
RE: deciphering air entrainment requirements
RE: deciphering air entrainment requirements
If the footings (not the pedestals necessarily) are founded below frost, A/E would not be necessary. The slab could be subjected to freeze thaw and therefore needs A/E.
Even if it does not need A/E, it does not hurt. Never had trouble w/ finish w/ up to 7% A/E. I would define agressive as corossive. So if 4%+/- 1% is wanted, it should be clearly called out on the drawings. A/E is not that big a deal. Someone seems to be overthinking the problem. What does the engineer say?
RE: deciphering air entrainment requirements
RE: deciphering air entrainment requirements
I feel the spec should be able to stand alone as much as possible.
So does he consider the slab on grade to require A/E?
RE: deciphering air entrainment requirements
Going exclusively by the spec the interior s-o-g would require A/E. But since this element is not being subjected freeze/thaw, ACI318 does not require A/E. That's what I have been told.