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> The Danger of Autoclaved Aerated Concrete (AAC), Fragile walling material AAC

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TSimmigrant_at
post Apr 20 2014, 10:52 PM, updated 10y ago

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The biggest AAC factory in Malaysia already came on the market in Dec 2013.
Does any one know what is AAC?
If your developer uses AAC to make your house, good luck to you.

If you do not know how dangerous is AAC , this website tells the lawsuit against the AAC makers in Germany.
http://www.derwesten-recherche.org/2011/11...lstein-skandal/

Structurally, something 500-700kg/m3 cut cost building material AAC does not hold building weight much, the steel-reinforced concrete frame structure will still need solid walls holding up its beam weight.
Or the transfer weight from beam to AAC wall will make cracks.

The house made with AAC in Germany have many cracks. Even the good lime and cement or sand are used to make AAC, this type of low density material does not take building weight and becomes powders in hot and humid Malaysia.

AAC is being promoted hard by a few german companies worldwide. They will have some good starting years, but they will also pay out compensation at last.

Kevin Chan
post Apr 20 2014, 11:08 PM

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It's just suppose to be wall and not load bearing frame.

In a normal construction, there is always the frame then the wall.
I deal with mostly warehouse construction... So it's steel frame and the cladding wall.
You see that cladding don't give any strength at all... It's all the frame that does the carrying.

Is the construction doing something wrong with expecting AAC to hold weight?

We used AAC to make vault as it can be made with fire retardant ability and it's very light, so it's easy to fit those brick into existing building without jeopardizing the floor loading.

Don't blame the brick... Go after the construction or the supplier sales man.
TSimmigrant_at
post Apr 20 2014, 11:15 PM

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QUOTE(Kevin Chan @ Apr 21 2014, 12:08 AM)
It's just suppose to be wall and not load bearing frame.

In a normal construction, there is always the frame then the wall.
I deal with mostly warehouse construction... So it's steel frame and the cladding wall.
You see that cladding don't give any strength at all... It's all the frame that does the carrying.

Is the construction doing something wrong with expecting AAC to hold weight?

We used AAC to make vault as it can be made with fire retardant ability and it's very light, so it's easy to fit those brick into existing building without jeopardizing the floor loading.

Don't blame the brick... Go after the construction or the supplier sales man.
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What I mean is that the steel-reinforced concrete frame (beam) will still transfer weight to the AAC wall. Unless your AAC wall is not contacted with the beam.

The article I cited means that AAC will become powders after aging.
Fazab
post Apr 20 2014, 11:24 PM

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I am under the impression that in Malaysia, houses are built with the pillars and beams taking up the entire weight.

Unlike in Europe or US, our houses do not have load-bearing walls. So we can remove a wall as long as don't kacau the pillar or beam.

Please tell me this is still true as I just hacked away a 10 feet wall to extend my new house kitchen.

Also looking to build a double wall in front of my master bedroom to reduce heat from sun. AAC sounds like just the right material. Is it very expensive?


TSimmigrant_at
post Apr 20 2014, 11:37 PM

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QUOTE(Fazab @ Apr 21 2014, 12:24 AM)
I am under the impression that in Malaysia, houses are built with the pillars and beams taking up the entire weight.

Unlike in Europe or US, our houses do not have load-bearing walls. So we can remove a wall as long as don't kacau the pillar or beam.

Please tell me this is still true as I just hacked away a 10 feet wall to extend my new house kitchen.

Also looking to build a double wall in front of my master bedroom to reduce heat from sun. AAC sounds like just the right material. Is it very expensive?
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If above the 10ft wide wall has the steel reinforced concrete frame, I would really dare to remove this 10ft wide wall. But how do you know how many steel inside the concrete frame? How many bars inside there? Did you witness the steel reinforced concrete drying up construction process?

You do not need AAC panels to reduce solar heat gain on the existing wall like in your master bedroom. You simply buy the super lightweight XPS or styropor sticking to the external wall and apply fiberglass mesh, brush the surface with a mixture of fine sand, cement and colour pigment paint liquid. Then your wall is super insulated with plastic coat.

External AAC usage needs fiberglass mesh with 24mm special plastering almost like the grade of tile adhesive powdered cement.


Kevin Chan
post Apr 21 2014, 08:19 AM

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QUOTE(immigrant_at @ Apr 20 2014, 11:15 PM)
What I mean is that the steel-reinforced concrete frame (beam) will still transfer weight to the AAC wall. Unless your AAC wall is not contacted with the beam.

The article I cited means that AAC will become powders after aging.
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this powered after ageing is like saying steel structure get rusty after ageing. so you ban steel structure ?

you protect the structure from exposure. again i find the problem is people trying to used the product in "ingenious" manner, i call them "chikai" manner.

ACC is done by technically pumping air and creating air chamber [honey comb] in the material hence removing weight/density. the air structure provided "similar" structural strength. take completely solid rod versus a hollow rod. hollow rod is lighter but can also provide same strength as the solid rod ... IFF used correctly.

ACC is lousy at bearing static weight but provide similar impact integrity [you can hit it]. so for your situation, if weight is bare on to the ACC long term ... aka lousy structure, you are asking for trouble. but if the situation is sudden structure break, the ACC would have does it job of preventing total collapse fine.

YES those ACC does go powder. but if you does good wet work [water proof/ air proof] and paint job as you would protect steel structure. i don't really see much of a problem.

I would still chase after the ACC sales guy, what the heck he has promise you? the construction guy, does he know what is he doing with the product ?

I only used ACC for light weight and fire resistance. if its just a ground floor vault where floor loading can take ... i'll go for much cheaper, STANDARD fire brick !!

I have no opinion of those on site easy mix pour in version... never tried them before. notworthy.gif

is ACC getting popular ? i still see sand brick trumping everyone in term of total cheapness , sand brick degrade even faster...
TSimmigrant_at
post Apr 21 2014, 01:01 PM

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QUOTE(Kevin Chan @ Apr 21 2014, 09:19 AM)
this powered after ageing is like saying steel structure get rusty after ageing. so you ban steel structure ?

you protect the structure from exposure. again i find the problem is people trying to used the product in "ingenious" manner, i call them "chikai" manner.

ACC is done by technically pumping air and creating air chamber [honey comb] in the material hence removing weight/density. the air structure provided "similar" structural strength. take completely solid rod versus a hollow rod. hollow rod is lighter but can also provide same strength as the solid rod ... IFF used correctly.

ACC is lousy at bearing static weight but provide similar impact integrity [you can hit it]. so for your situation, if weight is bare on to the ACC long term ... aka lousy structure, you are asking for trouble. but if the situation is sudden structure break, the ACC would have does it job of preventing total collapse fine. 

YES those ACC does go powder. but if you does good wet work [water proof/ air proof] and paint job as you would protect steel structure. i don't really see much of a problem.

I would still chase after the ACC sales guy, what the heck he has promise you? the construction guy, does he know what is he doing with the product ?

I only used ACC for light weight and fire resistance. if its just a ground floor vault where floor loading can take ... i'll go for much cheaper, STANDARD fire brick !!

I have no opinion of those on site easy mix pour in version... never tried them before.  notworthy.gif 

is ACC getting popular ? i still see sand brick trumping everyone in term of total cheapness , sand brick degrade even faster...
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The crucial thing you may not know. The cement inside the 1m3 of AAC (600kg/m3) is about 20-25%, while FLY ASH is about 60%. Fly ash is a incomplete burnt coal waste containing heavy metals from power plant. It is to say AAC has very little cement bonding, too porous. The entire AAC is really good for fire resistance or insulation purpose. But why do we need this AAC being the wall.
In Malaysia, fine sand AAC is not yet the day. Fine sand AAC is still very similarly porous and fragile.
Fly ash AAC is about RM30-33/m2. Fine sand AAC is not known.
Cement sand brick is RM22-23/m2. Yet cement-sand work has more bonding cement than AAC.
The german people still dare to promote AAC and some people really buy the idea. In their case, AAC was 50% cheaper than their conventional blockwork cost. In Malaysia, unpromised performance AAC is more expensive than cement sand work.
I do not use AAC , I am smarter and would rather use cement sand masonry work if that is a low cost house.
halcyon27
post Apr 21 2014, 01:29 PM

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This is a case where a product is given a bad name by a dishonest manufacturer using incorrect materials.

From what I know, AAC only has 50% compressive strength vs concrete and yet lower heat mass due to the micro porous air pockets disrupting the heat flow into its mass. Manufacturer recommendations made it very clear that it's not meant to be primarily a load bearing structure or how to compensate by using thicker blocks.

Some places uses both masonry and AAC with the latter as a facade to disrupt heat gain from the sun. Of course, it's better to plant trees but the benefit for that is only reaped after 7-10 years.

In Sweden and Europe and now in the middle east, AAC is very favourable for being able to disrupt heat flow in and out of the thermal envelope of the building. Cools interior stays cool for long in the summer and warmer in winter so long as the thermal leaks are addressed. Humidity presents another challenge as our climate here very humid.

Due to it's porous nature, proper water proofing treatment is needed just like any masonry. I would not use it for areas subjected to a very high water table aka prone to flash floods - in that area it would have been wiser to built higher stilt-like structure.


The issue here would be ignorance of product and assumption that bricks are all the same. It's not easy to convert from masonry bricks to AAC - I imagine a civil structural engineer needs to recalculate the load distribution as well. But it's easier to build a new one with so long as the main bulk of the load is catered for by pillars and beams and that with a caveat that this structure should be no higher than 3 stories.

Perhaps with that that's why it's not easy to retrofit and renovate with it. Imagine a second owner wanting to convert the clay tile hip roof into reinforced concrete without knowledge that the current house has only catered for a specified mount of load and that the walls are half of that of equivalent masonry bricks. To effect an equivalent load bearing spec - the thickness and volume needs to be adjusted upwards.

This post has been edited by halcyon27: Apr 21 2014, 01:30 PM

 

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