Old 08-01-2010, 09:17 PM
Join Date: Jan 2010
Location: Oceanside, CA
Posts: 50
Default Re: Vermiculite in San Diego

Well, for better or worse the hearth got poured today, both the structural and the insulation. It took nine(9) hours to do both.

The structural portion went uneventful. All the forms held. It took 1,350 lbs. or dry concrete mix (15 bags @ 90# ea).

The insulation portion was not quite as easy. I ran out of material and had to make a run to HD. I used 12 cu ft of coarse perlite (3 bags X 4 cu ft ea.), 1 bag of 3.5 cu ft vermiculate, and the 2 cu ft bag of medium perlite from HD. I also used a little more than 1-1/2 sacks of Portland (90# ea.) cement - about 140 lbs. or so total.

I never dreamed I'd use 17.5 cu ft of insulation. My hearth is about 6X6.

So I have a frankenstein hearth. I just hope it works.

Quick question: it the insulation suppose to be compacted? Maybe that's why I used so much.

A photo of the start of the insulation layer.

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Vermiculite in San Diego-hearth-001.jpg  
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Old 08-02-2010, 12:45 PM
Join Date: Aug 2009
Location: so calif
Posts: 6
Default Re: Vermiculite in San Diego

I used 6:1 pearlite and it worked well. The key to mixing it is to make a cement slurry separately and then pour that into the pearlite then mix with a hoe. To make the slurry I used a twirly type paint mixer in an electric drill.

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Old 08-02-2010, 08:09 PM
Join Date: Jan 2010
Location: Oceanside, CA
Posts: 50
Default Re: Vermiculite in San Diego

I mixed the perlite and cement dry until it was well-coated and than added water. It worked well, but I just used a lot more than I thought. I'm still trying to figure why. Maybe my hearth was bigger than others.

It's already setting up well, so in a week it should be rock-hard.

How do I get the finished concrete look. Right now it looks like Route 66 outside of Kingman, AZ. Perhaps just take a sand and cemet slurry?
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