Vermiculite Layer

[Mojoe]

Does the vermiculite layer require any particular curing method? Cover, wet cure, etc like concrete?

I mixed the vermiculite 5:1 and wet it enough to form a loose ball in my hand but no water came out and I wasn't very gentle with it, hoe and wheel barrow. Will it be okay?

[Unofornaio]

Re: Vermiculite Layer

It should be fine. Don't fool with it, its deceiving just when you think its not going to ever set up it does. Give it a few days

[Mojoe]

Re: Vermiculite Layer

Just poured it earlier today and there's a chance of rain so I threw a tarp over it. I think my problem is that I used the fine vermiculite and when I run my hand over the top it comes right off. No clumps, just small particles. But if I push on the layer it feels as most here have described, spongy,springy, etc.

[nissanneill]

Re: Vermiculite Layer

Yes, it is unusual material to work with. When I poured mine, I added enough water to squeeze just a little bit out with a clenched fist. See my post on:

http://www.fornobravo.com/forum/f8/n...-1-a-2005.html

permalink #2 for the description and pictures. It will set in a few days and will feel a little like a firm cork consistency

Neill

[Mojoe]

Re: Vermiculite Layer

The particles in mine aren't that big and my mix wasn't that wet. Mine is close to a really coarse sand. A day later and it is like a firm cork (perehaps harder) however if you gently and barely slide your hand across the surface the result is a hand full of small particles and a irregular finish. The finish on this layer is closer to cornmeal on a pizza peel than a rough concrete finish.

How long do I wait before I remove the forms?

[nissanneill]

Re: Vermiculite Layer

Mojoe
so long as the layer 'sets' over the next few days (should be close to set by now), it will be fine as the hearth bricks will sit directly on it. I wouldn't worry too much about the surface toughness BUT the vermiculite which will lie beneath the dome brick course (soldier bricks on the first course) will need to be quite firm in order to support the weight of the dome.
Are you planning on running your hearth bricks out and under the dome bricks or cutting the hearth to fit inside the first soldier course?

Neill

[Mojoe]

Re: Vermiculite Layer

Haven't decided yet, originally thought I'd run the bricks out and under. Should I give it a couple days before I pull the forms?

[Unofornaio]

Re: Vermiculite Layer

Yes wait to pull the forms. No need to do it now and run the risk of pulling off chunks of the sides. As I said before, don't fool with it and give it a couple of days. If its been raining there Id give it the better part of the this week, wed or thurs to be safe.

[Mojoe]

Re: Vermiculite Layer

Came home from work today to find out that my 2 1/2 year old did some excavating on the vermiculite layer, about a 6"x6" square. It appears I didn't add enough water as the top 2" easily crumbled upon removal. The bottom 2" that was closest to the fresh concrete was actually very hard, used a heavy piece of scrap 1/4" angle to scrap most of it off.

With the new batch I placed tonight I added enough water so that a little would ooze out when squeezed. Much more than that and the stuff wiggled like jello when placed and troweled. Feels like I got it right this time.

[james]

Re: Vermiculite Layer

Mojoe,

I'm sure it will set. Gravity is on your side as well.

I have always thought of the mixer as feeling like a grainy oatmeal.
James

[Archena]

Re: Vermiculite Layer

Move whatever the little one got up there with. Toddler versus DYI project - the project always loses!

[Mojoe]

Re: Vermiculite Layer

I've secured the perimeter of the oven with razor wire and pungee sticks so he'll have to pole vault over or repell from a nearby tree.

[Archena]

Re: Vermiculite Layer

:smile: LOL!



That only stops adults - toddlers are immune to anything they don't realize should kill them (unless Mom is there to scream in panic).

[Mojoe]

Re: Vermiculite Layer

My 2nd attempt provided much better results. It is stiffer than a cork partly because I lowered the ratio to 4:1 and I got the right amountof water. I lowered the ratio because I wanted to ensure I could lay brick over the upcoming 3-day weekend. The layer does give and according to this chart-> Vermiculite Insulating Concrete--The Schundler Company I haven't lost much thermal conductivity (K factor). Hearth is comprised of 4" vermiculite concrete, 4" regular reinforced concrete, and 1/2" backerboard underneath. I had some scrap backerboard laying around so I thought why not.

One definite plus to the lower ratio is the set time of the layer. I poured it Tuesday night and I stood and walked around on it this morning without a crumb being disturbed.