Anyone tried autoclaved aerated concrete (AAC)?

[David Dobbs]

For an article I'm writing for a builder magazine, I'd like to hear from
anyone on this list who has used (or seriously considered and then decided
against using) autoclaved aerated concrete in residential construction (esp.
single-family homes). Would like to hear pros, cons, pleasures and
challenges both expected and unexpected, general impressions, details of
use, etc.

Thanks much,

David Dobbs

[ultimobo]

David Dobbs wrote in message <380b...@news.together.net>...

>I'd like to hear from anyone on this list who has used (or seriously
considered and then decided against using) autoclaved aerated concrete in
residential construction (esp.
>single-family homes). Would like to hear pros, cons, pleasures and
challenges

This is relatively new to Australia - I checked it out and here's what I
found:

PROS:
lightweight, can cut with a handsaw, easy to cut grooves for concealing
wiring runs, etc; ~100mm thick equiv. to (Aust.) R1.5 thermal insulation
(better than normal bricks); once you have good full masonry footings, a
handyman can lay the bricks.

CONS:
bricklayers avoid it as it requires requires an accuracy in preparing
perfectly level footings with which they tend to be unfamiliar, and the thin
adhesive doesn't allow alignments to be fudged and corrected as you lay up
the bricks; ground movement may crack the entire wall as when bonded
together it acts as a solid sheet; the bubble structure seems more subject
to weathering and water infiltration unless you apply an external coat of
waterproof ?stucco/paint which may be relatively expensive; labour may be
harder to find and more expensive; as it requires the same full masonry
footings as a solid brick wall, the total materials and labour costs may not
save you over normal bricks; the external relatively expensive coating needs
to be reapplied every so many years to prevent water infiltration.

[Chuck Dinsmore]

The only usage with this material in my opinion is mostly architectural. I
wouldn't use it for any structural elements unless it can be reinforced.
This would be a concern in any earthquake prone area which I know there are
in AU and other places around the world.
___________________________________________________________________________
_
civ...@home.com Chuck Dinsmore P.E. R.A.
ci...@eskimo.com

ultimobo <ulti...@ausisp.com> wrote in message
news:94091341...@server.australia.net.au...

[ultimobo]

Sorry I don't have lambda or U-values handy as I did not yet use these
blocks.

Keyed blocks sound good, but I have not yet seen these in Australia yet,
only straight-sided rectangular blocks. Speaking of which, how does
autoclaved concrete sell in Germany compared to the standard structure I saw
in Munich a while back, which was say 200mm thick terra-cotta style blocks,
double thin-wall, with a big hole in the middle, which were then laid up
with a thick layer of thick ?glass wool insulation on both sides...?

Thanks for your comments.

[R. Phillips]

ultimobo wrote:

Sounds like 'Ziegeln' - sorry, I can't translate that, it is literally 'brick',
but refers to a fired clay block, with the clay made porous by mixing saw-dust
with the clay (this burn away leaving millions of micro pores in the material) -
trade name is Poroton. It can be simply hollow core, as you describe, although
this is normally for party walls, and filled with concrete to room height. More
common now is a honey-comb core, giving better structural and thermal
performance. Normally, these blocks are used as a single leaf construction,
with a 365mm wall thickness. With thermal render, this construction yields a
wall of about 0.31 W/m2K, and with an external insulation/cladding layer, 0.2
W/m2K or better is possible. Cavity walls are less common in Germany, although
they seem to be on the increase.

Porous concrete and Poroton are both very popular, and have many of the same
advantages: good thermal properties, thin joint mortar, keyed vertical faces,
easily cut on site, fast to build with and compatible with accurate and solid
building practices. It is possible to obtain a greater range of components in
porous concrete, such as roof and wall elements, stairs, etc., although Poroton
can be used to fabricate (on or off site) floors and roofs as well. Poroton are
slightly ahead on the environmental side, as saw-dust is used to achieve the
pores, whilst aluminum is used to do this for porous concrete - wood is
renewable, and burning aluminium emits toxic fumes.

I think they are both excellent materials, with a lot to offer the
architect/builder. For more info:

Poroton:
http://www.roeben.com (site in german, but they have an English broschure
- and a US factory)

Porous Concrete Blocks:
http://www.ytong.de (in German only, but good info)

[magicr...@gmail.com]

AAC blocks are the most cost effective and eco-friendly material used as substitute of traditional clay bricks. It is recommended by Indian Green Building Council (IGBC) as material of choice for LEED certification and offers cost savings up to 40% due to huge savings in structural costs and increase in floor space area. It is termed as the wonder building material.

http://www.magicrete.in/index.php