Air-Entrained Concrete Walls?
squibt
| Posted in Energy Efficiency and Durability on
Has anyone used air-entrained concrete for foundation walls in a cold climate? I don’t mean the “Krete” products. The reported R-values are R-3.9 as opposed to regular concretes R-0.08. For an 8″ wall you are going to get somewhere around R-30? From reading around a bit it seems you can get a 20mpa (3000#) air entrained concrete mix with 6% air. I wonder what the extra cost would be…would it be worth it from an insulation perspective?
Tim
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Air entrained concrete is very common in a cold climate. However it provides no different R value than standard concrete. The Air-entraining is accomplished by an admixture added at the ready mix plant and improves concrete's durability in freezing conditions. Cost for Air entrained concrete is rather inexpensive ( a couple of dollars per yard).
Are you thinking of Autoclaved aerated concrete (which does have a better R value)?
Is the air entraining even advisable, from a cost standpoint, in a wall? I thought the benefit of the air entraining was for freeze/thaw cycles, like when a slab in a garage will be heated now and then in a heating-dominated environment. I know very little about concrete; just asking.
Hi Pete, I understand how air-entrained concrete is used in a cold climate. Logically you would think the R-value of air-entrained concrete would have to be more than R 0.08 std concrete - due to the volume of insulating air. If an 8" concrete block has an R-value of 1.1, std concrete that is air-entrained to 6-8% has to be quite a bit more than R 0.08 but no where near R 3.9 ...how much R value?...I can't seem to find an answer. None of the reported values of "Air-Entrained Concrete" as being R 3.9 are identifying what product is being referred to...AAC...Light Weight Cellular Concrete...or any of the many other formulations. Cement.org says "A high air content gives ACC an R-value of 1.26 per in. (25 mm) of thickness". So these web sites that are saying air-entraied concrete has an R-value of 3.9 is like saying "Insulation has an R-value of R-20"....meaningless.
Some Canadian suppliers boast their air entraining admixture of 6% is standard mix at no extra charge.
Maybe Hempcrete (a mixture of concrete and hemp) is the way to go ;')
Just wanted to point out that concrete's R-value is 0.1 per inch, not 0.01 per inch. It's still minimal, just wanted to clarify the figure used in the original question.
http://coloradoenergy.org/procorner/stuff/r-values.htm ...and many other sites say concrete is 0.08...where did you get your figure from?
There's a phenomenal concrete house in Chur (CH) by Patrick Gartmann that utilizes expanded clay (liapor) to replace gravel, and expanded glass to replace sand. It's still not much in the way of insulation (~R-10 walls, ~R-14 roof I think). However, what makes it interesting is the entire projects is pretty much exposed concrete, larch or glass. No idea on how it performs, cost was approx. double typical concrete construction, but required no other trades, products, layers, etc.
http://mw2.google.com/mw-panoramio/photos/medium/16743828.jpg
vid here (english): https://youtu.be/WQ_XODbBSBY