Air entrainment
Air entrainment
(OP)
We have a project where the specifications call for 4%-5% air entrainment for an underground concrete water tank. Testing during the pour showed air content greater than 12% for some of the batches. The site isn't subject to freeze/thaw. Based on my research, other than the concrete looses about 5% of strength per 1% of air, what other issues might be of concern?





RE: Air entrainment
With a high air content, there is also a concern about abrasion resistance. All those little air voids just don't have any strength.
Please don't let this scare you away from using air entrainment for this application. Entrained air is very effective as a consolidation aid to reduce honeycombing and larger entrapped voids.
Greg
RE: Air entrainment
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RE: Air entrainment
RE: Air entrainment
The concrete also shrinks more and is more susceptible to greater volume change from wetting and drying.
A little air is a good thing...a lot of air, not so good.
RE: Air entrainment
RE: Air entrainment
RE: Air entrainment
RE: Air entrainment
RE: Air entrainment
Excessive air content is a result of improper dosing of the AE agent. You can't do anything in the delivery or placement of the concrete to increase the air content to those levels.
RE: Air entrainment
Greg
RE: Air entrainment
RE: Air entrainment
Sorry I missed looking at the mix design you posted. I've never worked with the Eucon NW, but I have worked with the Plastol 341 and AEA-92. Based on the dosage rate using our materials here, I would expect high air. The AEA-92 is one of the more effective air entrainers I've worked with, and with the Plastol 341, I will usually cut the air dose at least in 1/2 because of the synergy of the two in entraining air.
Greg
RE: Air entrainment
We CAD geeks are stuck in the lab, wondering what happens when the numbers don't add up in the field...?
RE: Air entrainment
Greg
RE: Air entrainment
RE: Air entrainment
Where is the project located? Materials and fly ash can vary widely (especially for short term by-product fly ash results), with short term results. Since it seems strength is your real concern and not just a air test.
Did you start with a mix design that was very similar (same properties, materials and admix additives) to your specifications. This provides a history and shifts the performance to the supplier. Most good ready mix suppliers do not just switch admixtures and and dosage since many admixture suppliers actually own the dosing equipment and the supplier has a good record of the individual batches.
The job site tech conducting sampling and tests and preparing samples can have a bigger effect than you think on the tests results.
How did the cylinders test for strength since freeze/thaw was not a problems but just "specification boiler plate".
Banging around a cylinder for a 5 break day test leads to many variations including site curing, sample preparation and handling. the 3 Day breaks can be even more misleading unless you have some information on the strength gain curve.
RE: Air entrainment
RE: Air entrainment
Greg
RE: Air entrainment
RE: Air entrainment
RE: Air entrainment
Seems commons sense that test cylinders should be cured exactly as the pour is, yes/no? But I've been on sites where the test tech is putting the samples away in the construction trailer, or the crew cab of his truck, etc... WTH?
RE: Air entrainment
RE: Air entrainment
Greg