Air-Entrained Concrete
Air-Entrained Concrete
(OP)
Hi Guys,
This has been a subject of debate in the office. I live in a country in the tropics (temperature is constantly in the 80-90 degree range), so no freeze/thaw concerns. Currently, the specifications for a project indicate to air entrain the concrete. I believe that these specifications are in place as a result of being copied over from US specifications, with little attention paid to the specifics of where the project is located. The engineer who wrote the specifications states that the air entrainment is required for workability of the concrete. This seems to be an issue of means and methods. Also, there are much more economical alternatives to improve workability where we are located. As this is not normally done, air-entraining concrete is vert costly. Are there any other reasons why one would air entrain concrete somewhere where there are no freeze/thaw concerns?
Thanks.
This has been a subject of debate in the office. I live in a country in the tropics (temperature is constantly in the 80-90 degree range), so no freeze/thaw concerns. Currently, the specifications for a project indicate to air entrain the concrete. I believe that these specifications are in place as a result of being copied over from US specifications, with little attention paid to the specifics of where the project is located. The engineer who wrote the specifications states that the air entrainment is required for workability of the concrete. This seems to be an issue of means and methods. Also, there are much more economical alternatives to improve workability where we are located. As this is not normally done, air-entraining concrete is vert costly. Are there any other reasons why one would air entrain concrete somewhere where there are no freeze/thaw concerns?
Thanks.






RE: Air-Entrained Concrete
RE: Air-Entrained Concrete
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RE: Air-Entrained Concrete
RE: Air-Entrained Concrete
RE: Air-Entrained Concrete
RE: Air-Entrained Concrete
I also have had contractors demand air in concrete when they have to pump it up several stories so the air does affect pumpability (i.e. workability)
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RE: Air-Entrained Concrete
"Reduces the weight of the trucks"? I had a chuckle about that one.
RE: Air-Entrained Concrete
Blistering is a finishing issue that can be properly handled by appropriate finishing techniques, even with air entrainment. The finishers often get on the concrete too quickly and seal the surface before the bleed water escapes. There are other impacts on blistering potential as well, but this is a big one!
RE: Air-Entrained Concrete
jayrod... the addition of air does improve the workability and flowability of the mix.
Missed the sarcasm...
Dik
RE: Air-Entrained Concrete
No sarcasm intended. I've never had a contractor ask me to add air to improve workability. More often than not, I've got contractors asking if the air is really required in the mix.
Air may help with workability, but I feel like there are other equally efficient and economical ways to improve the workability of the concrete.
My "Queue the angry mob" comment was about how I rarely specify slump. I let the contractor choose the slump but their desired slump must be on the sealed mix designs and truck tickets so I know they aren't screwing with the actual performance of the concrete.
RE: Air-Entrained Concrete
Makes sense though no? For most companies the benefit would be negligible, but if you have a fleet of a few hundred trucks then why wouldn't you reduce the loads they carry?
RE: Air-Entrained Concrete
Joe Bubba in his pick'em up truck would just do it wrong and we'd have blisters a-go-go all over the floor.
(Queue Mr. Bubba's lawyers for JAE defamation suit)
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RE: Air-Entrained Concrete
RE: Air-Entrained Concrete
Professional and Structural Engineer (ME, NH, MA)
American Concrete Industries
www.americanconcrete.com
RE: Air-Entrained Concrete
When we are doing construction consulting, we require a "Pre-placement Meeting" before any concrete is placed. Mix design, slump control, air content, vibration, grade control under slabs, finishing, curing, etc.....are some of the things we lay out. Another is that control joints must be sawn the same day as placement....they hate that one.
The "payload" of a transit mixture is essentially reduced by the air content......5% air>>>>>5% less weight. In my opinion, not enough to worry about. I concur with hokie66's assessment