#11  
Old 07-23-2010, 02:36 AM
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Default Re: S.E. Quensland Suppliers.

Thanks David,
is this vermiculite stuff waterproof?
If not how does one render it without trapping moisture inside?
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  #12  
Old 07-23-2010, 05:18 AM
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Default Re: S.E. Quensland Suppliers.

Try to let it dry for as long as possible before working over the top of it. It takes ages to dry out, maybe about 7 firings even after the oven has been cured. Because moisture is trapped under the floor, this seems to be the hardest to remove.
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Old 07-23-2010, 05:28 AM
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Default Re: S.E. Quensland Suppliers.

If you lay the 4" of vermicrete, leave it uncovered for a couple of weeks to let it dry as much as possible. No it is not waterproof quite the opposite it sucks up water really well because it's full of air. You need to add approx double the amount of water that you would normally use in a normal concrete brew. By the way if you want to make your hearth strong you should keep the concrete moist for at least a week, not just three days..
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  #14  
Old 07-23-2010, 02:16 PM
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Default Re: S.E. Quensland Suppliers.

Are you sure on those figures David?
100L of vermiculite will require 40L of water!
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Old 07-23-2010, 06:15 PM
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Default Re: S.E. Quensland Suppliers.

Yes 4L water/10 L vermiculite is what I use when also adding 4 L sand for strength. When doing the mix for the dome I use 10:1:3 vermiculite,cement, water. This mix is a little drier so it can stand up vertically.Yes it is a lot of water and it needs to be eliminated by evaporation and curing.
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Old 07-24-2010, 04:16 AM
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Default Re: S.E. Quensland Suppliers.

Quote:
is what I use when also adding 4 L sand for strength.
Adding sand to vermiculite concrete isn't recommended. It reduces it's insulation properties, and I don't see how it would make it any stronger.
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  #17  
Old 07-24-2010, 11:59 AM
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Default Re: S.E. Quensland Suppliers.

Vermiculite Insulating Concrete--The Schundler CompanyYes sand does decrease the insulation properties, just as cement does. It is all to do with the resulting density. The sand does contribute to increasing strength when combined with cement because the cement has something more solid to bind to. Look at the data on the following site. Also of note is the data showing exactly the same insulation value of fine and coarse vermiculite.
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Old 07-25-2010, 03:42 AM
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Default Re: S.E. Quensland Suppliers.

Thanks David,
very intersting read.

I mixed and poured my vermiculite today.

I did a 1 cement 1 sand to 10 vermiculite and added 4l of water for every 10 l vermiculite. I did find that the consistancy was slightly dry. I was temtped to add more water, however I refrained in the knowledge that more water makes for a weaker bond.

I have covered it with a tarp as we have rain showers forecast for the rest of the week. So it looks like I will have to wait a further week before I begin to place my fire bricks on it.
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Old 07-25-2010, 08:07 PM
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Default Re: S.E. Quensland Suppliers.

Spoke to the owner of Warwick bricks today.
They are the oldest brickworks in Australia.
He said they still make their bricks the old fashioned way and the bricks that his kilns are made out of are the bricks his grandfather made. I think he said he was 6th generation to be making bricks.
Anyway I asked about refactroy bricks and he said as all his bricks are made with clay and hard pressed and then wood kiln fired, that they would all withsatnd anything a pizza oven threw at them. His bricks are only 86 cents a go. As a side note as nothing has changed since they opened 160 years or so ago, the bricks still come in inches. Their standard brick size is 9 inches x 4.5 inches x 3 inches.

Even with the freight cost to Brisbane it still works out $300 cheaper to get them from him. The only thing that is nagging me is will they hold the heat as well as firebricks?
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  #20  
Old 07-25-2010, 08:59 PM
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Default Re: S.E. Quensland Suppliers.

Sounds good. I used clay pavers for the hearth, and they hold plenty of heat. As long as the bricks in your dome don't start dropping bits into your pizzas, they should be fine

Cheers,
Mick
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