foam concrete

[david s]

Re: foam concrete

Just bumping this thread. I continue to use the foamcrete, but have to admit that I usually use 50/50 volume with vermiculite and perlite mix which makes the mixing process easier. The result is that I end up with a product that is cheaper than vermicrete alone and has less absorbency as well as using less water in the mix, meaning less water to remove. Win/win I reckon.

[cobblerdave]

Re: foam concrete

G'day Davids
What's the stuff like to handle. Vcrete/ pearlcrete a devil to get to do what you want. Get a flat surface for a base or get to stick to a dome. I like the term"Devils porridge" it about sums it up.
Regards dave

[david s]

Re: foam concrete

G'day Davids
What's the stuff like to handle. Vcrete/ pearlcrete a devil to get to do what you want. Get a flat surface for a base or get to stick to a dome. I like the term"Devils porridge" it about sums it up.
Regards dave

Dave,
I've mixed up tons of vermicrete so I'm pretty used to it, but have found a few tricks to help it work better. Getting a good working mix is difficult and lots of people add more cement in order to get it to stick together more. This is a mistake if you want it to insulate well as the extra cement reduces the insulating capacity by increasing density and thermal conductivity. The correct amount of water is also crucial. I've found that 1/3 of the volume of vermiculite is the correct amount of water to add ie for every 10L add 3L water. Also a mix of 50/50 perlite and vermiculite works way better than either of them alone. I also throw in a handful of powdered clay for every 10L batch.This helps give it good workability.
When using foam it takes more careful mixing and it needs to be folded in gently like stirring in egg whites in a cake mix.the stuff needs to be mixed evenly, but if over mixed will start to deflate.

[Gulf]

Re: foam concrete

David,
I intended to refer back to this thread last night. But, my eyelids got a little heavy. I'm still very interested in your homemade foam generator and the foamcrete. I keep saying to myself that I am going to experiment with it myself. I'm fixin to have a little more time on my hands. Maybe, that will be one of the projects that I get to play with .

I'm looking forward to more of your experiments with the product.

Joe W.

[david s]

Re: foam concrete

David,
I intended to refer back to this thread last night. But, my eyelids got a little heavy. I'm still very interested in your homemade foam generator and the foamcrete. I keep saying to myself that I am going to experiment with it myself. I'm fixin to have a little more time on my hands. Maybe, that will be one of the projects that I get to play with .

I'm looking forward to more of your experiments with the product.

Joe W.

Joe,
My eyelids were a little heavy last night too, but I think it was the Prosecco.
With all the interesting things Italians do with concrete, I'll be renewed with enthusiasm to experiment more with the stuff myself. Thinking of casting blocks of the stuff to carve and recoat maybe. Back start of May.
Dave

[MeGiaJoe]

Re: foam concrete

Hi All,
I have been following this thread and I'm very interested in the lightweight concrete. I came across this foaming agent recipe on another blog I wonder if this will help you maybe make your own and save some money. David love your generator!
Chris

[david s]

Thanks Chris,
I have to admit that I don't always use the foam generator. Because I don't have a compressor I have to drive 600 m to the service station to use theirs. If making a small batch (around 5 litres), i simply place around 10 ml of concentrate, 100 ml water in a 5 L container with half a dozen bits of 6mm aggregate which act as agitators. Screw on the lid and shake the thing for around a minute. It works pretty well, but does not generate as much foam as the compressed air version. The most difficult part is folding the foam into the mixture because it wants to float it takes some time to get the mix consistent.

[fej]

Hi David,

I built a foam generator and want to make a perlite/foamcrete insulating hearth. Can you tell me the ratio of water/cement/foam/perlite you have found to be most successful?

Thanks!
John

[david s]

Hi John,

I have found that a 5:1 vermicrete with half the volume of vermiculite replaced with foam does a pretty good mix. But as previously posted it is essential to make sure the foam is well mixed in or you will get inconsistent strength. Using a mixer is likely to lead to deflation of the foam so better to fold the foam in using a barrow and spade. The rest is just practice/trial and error.

[Boogie-D]

david s Quote “Also a mix of 50/50 perlite and vermiculite works way better than either of them alone. I also throw in a handful of powdered clay for every 10L batch.This helps give it good workability”... aloha David is this your go to formula for the insulating home brew.??? I have access to both vermiculite and perlite and clay... I have the ability to make this.. I am planning my hearth and insulation now for my build and was just going to use the 5:1 perlite mix... but I could go with a 1/2 1/2 perli vermiculite mix with a dash of clay?? My concern with the vermiculite is water absorption and living in Hawaii... as well as strength under the oven... but I will follow your lead on my build.. thanks for all your insight aloha.

[david s]

The insulating slab under the floor bricks requires a richer mix (5:1) for strength. I make batches of 5L vermiculite, 5 L perlite, 2 L cement powder and 3 L water. Because it contains a fair amount of cement you don't need the clay to make it stickier. For the brew over the dome, where strength is not an issue and you want good insulation, go leaner and use 10:1, in which case you need the clay to make the mix more workable.

The attached vermicrete insulating slab doc is useful as is the attached table of strength/insulating values for various vermicrete mixes.

Some holes cast into the supporting slab greatly assist the drying and draining of the vermicrete slab.Moisture under the cooking floor is the most difficult to eliminate.

[Boogie-D]

Got it David.. thanks so much.. sorry I didn’t get the notification for this post... and I did a big post on my build thread... since both perlite and vermiculite are both readily available in Hawaii I will follow your lead on a home brew mix of both... greatly appreciated..

[david s]

I find the rate of water absorption and drying of perlite and vermiculite similar. I wonder if your perlite is the silicon coated stuff (not available to me) they use for filling cores in concrete blocks. The silicon slows water absorption and I would guess drying also.

Attached is some tests I did with different insulating aggregates. What surprised me was the similarity of the absorption and drying characteristics of most of the materials. The highest water absorption was actually the dry perlite. I didn't test dry vermiculite. Bags of both left in the rain weigh pretty much the same when wet though.

absorbtion and drying rates of insulating samples.pdf

The first column is time in hrs and the first row is % weight of dry material.
The second row is a 5 second immersion % of dry weight
The third row a 24 hr immersion % of dry weight and the others daily % of dry weight.

Regarding the foam, I haven't used it for a while because it takes time to generate the foam and then to mix it in with the other materials. There is some loss of volume when doing this which interferes with the volume calculations. If i were casting on a larger scale though I'd definitely be using it.