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  #21  
Old 08-28-2012, 02:41 AM
david s's Avatar
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Location: Townsville, Nth Queensland,Australia
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Default Re: Vermicrete Layer Advice

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Originally Posted by david s View Post
When making vermicrete or perlcrete you require about double the content of water that you would normally use in a regular concrete mix. Given that a regular concrete slab still contains a fair proportion of mechanical water that eventually escapes to the atmosphere a vermicrete slab has proportionally a huge amount to be removed. This can easily be demonstrated by making a test slab and weighing the dry ingredients including the water, then weighing the slab daily to calculate the water loss over time. If I have time I'll do it and graph the results for you.
Here are the results of my test.
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File Type: zip Vermicrete insulating slab.doc.zip (74.4 KB, 50 views)
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  #22  
Old 08-28-2012, 10:04 AM
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Default Re: Vermicrete Layer Advice

It is so easy to make the structural slab slope slightly away from the middle there is no reason not to do so.

The vermiculite can be poured dead level and the hearth can be dead level.
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  #23  
Old 08-31-2012, 11:02 PM
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Default Re: Vermicrete Layer Advice

I re-weighed my vermicrete slab after it had been standing vertically in the sun for 12 cloud free days. It weighed 11.0 Kgs. The test clearly demonstrates the large quantity of water that has to be removed. It also shows that there was next to no water loss on cloudy days. I feel the slab is now completely dry but might just leave it a while longer as i thought it was perfectly dry at day 18. Water loss of 6 litres represents about 75% of the original water added.
I'm sure if the slab had been left sitting on top of a supporting slab and especially if it had been covered over with floor bricks most of the water would still be there. It is probably impractical for many builders to use the weather to dry their vermicrete, but the results are interesting (to me) nevertheless. Hope some others can benefit from them.

Last edited by david s; 09-01-2012 at 02:06 AM.
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  #24  
Old 09-01-2012, 08:58 AM
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Join Date: Jun 2012
Location: London, UK
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Default Re: Vermicrete Layer Advice

I stupidly left my vermicrete uncovered due to the nice weather... so while it had been drying nicely, after yesterday's shower it will need to start again... grumble..
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