vermiculite to portland cement

[mrgweeto]

Is a 4 cubic foot bag of cement to one bag of 94lb portland cement too little?
Also because the insulating floor is not structural I assume no rebar is used.
G

[papavino]

Re: vermiculite to portland cement

G,

It all depends on the ratio of vermiculite to cement you use. I used about 7:1 for my insulating layer and I used about 6 cu. ft. of insulating material to a little less than one 94 lb. bag of cement. As far as rebar is concerned, you should have that in the concrete layer beneath your insulating layer, so you don't need to add it here.

[mrgweeto]

Re: vermiculite to portland cement

Papavino,
Thank you for the info. How many cubic ft total did you get out of 1 bag of portland cement with the 6-7 parts vermiculite added. I know the answer should be 7 but don't know if the vermicullite expands.
G

[papavino]

Re: vermiculite to portland cement

I didn't really see any expansion of the vermiculite. It just soaks up the water.

[Lars]

Re: vermiculite to portland cement

G.
I used 4:1 portland with a little bit of lime. Essentially, this means four coffee cans of vermiculite, one coffee can of portland, and about a gallon of water... and about 1/4 can of lime. I mixed about 6 batches for my underfloor layer. Later on I got more liberal with the mix and made about 5:1 (vermiculite: portland) and sometimes lime, sometimes not.

For a full hod of stuff ( in my case 10 coffee cans of vermiculite, 2 coffee cans of portland, and maybe 1/3 coffee can of lime) it took about 2 1/2 gallons of water.

No steel in this layer. If you press a bit with a steel trowel, you can get a waxy sort of surface on there ( very smooth)

Just use it in a similar ratio to these and if you run out of Portland, buy another bag --if you run out of vermiculite, buy another bag of that. (menards has it in the loose insulation section for 9.95 for 3 cubic ft.)

good luck.

lars.

[mrgweeto]

Re: vermiculite to portland cement

Good info. We just got through pouring our hearth today.
will let it cure till Sunday and then layout for the insulation area pour. I am going to boarder the vermiculite & portland mixture with brick to keep the mixture nice and compacted if it decides to crumble a little around the edges while we are working. So far so good. The hardes part of all this up to this point was to put the 80 lb bags into our trailor. Glad there is only going to be a couple of bags portland. I'll have my nephew carry those and I will take the vermiculite.
Thanks and have a great 4th
G

[Lars]

Re: vermiculite to portland cement

G.
I poured the corners in regular concrete too, then filled the middle with vermic./port. the next day. Lining with brick is a good idea.

Lemme' see if I can find a picture here...

[mrgweeto]

Re: vermiculite to portland cement

Lars,
Thanks for the pictures.
good to know that my brother and I are on the right track. We are going to put up the brick perimeter today and then get the vermiculite and portland and do our pour this Tues (weather permitting....CT is the wet state so far) and then the fun begins this weekend with the dome. How long did it take for your insulation hearth to cure ?
Thank you for the info,
G

[mrgweeto]

Re: vermiculite to portland cement

Thanks for the pictures.
good to know that my brother and I are on the right track. We are going to put up the brick perimeter today and then get the vermiculite and portland and do our pour this Tues (weather permitting....CT is the wet state so far) and then the fun begins this weekend with the dome. How long did it take for your insulation hearth to cure ?
Thank you for the info,
G

[Lars]

Re: vermiculite to portland cement

G.
I poured the rounded corners one day, the vermiculite the next day, and pretty much laid the floor the next. The light weight of a layer of bricks would not interfere with the curing of the vermiculite layer. In fact, they help keep the moisture in ( ALWAYS COVER any POUR using PORTLAND with plastic or water repellent tarp for a few days and keep it hydrated).

Lars.

[Neil2]

Re: vermiculite to portland cement

I used a 6:1 mix under the hearth and a 12:1 mix over the dome.

Mix "gently" by hand. If you mix in a machine you will tend to break down the vermiculite particles resulting in a denser and less insulating layer.

[mrgweeto]

Re: vermiculite to portland cement

Layed the brick form Sun and hopefully will get the ver/port poured tomorrow. We are going to end up with a 3" layer of insulation hearth. I think that is going to be fine. Our hearth stand is not going to be used for wood but for storage of tables etc and will be closed off with a door. We may even insulated the ceiling and walls. I know this doesn't add much but it won't take away either and because I can get the insulation for nothing it is a mute issue. We are making the 42" oven. I know the door height is critical and should be 60 percent of the inner height of dome. In this case it will be 12.5" high by 20". Seems low but I can see how you want to keep the heat in.
Thanks for the info.
G

[pizza_bob]

Re: vermiculite to portland cement

Thanks for the pictures.
good to know that my brother and I are on the right track. We are going to put up the brick perimeter today and then get the vermiculite and portland and do our pour this Tues (weather permitting....CT is the wet state so far) and then the fun begins this weekend with the dome. How long did it take for your insulation hearth to cure ?
Thank you for the info,
G

Hello mrgweeto,
I have a triplet brother named Guido. I'm building a 42" Pompeii style oven.
I live in Ct too - Oxford - and just poured my vermiculite layer Saturday (July 4th). I picked-up my vermiculite from New Haven Masonry. They stock the smaller granular size stuff for filling cement block cores. If you want the larger "attic type" vermiculite, which is what I used and it looks great, call them ahead of time and a distributor from upstate CT delivers to them twice a week.
I went with a 5:1 vermiculite-Portland mix but went through 8 cubic feet of vermiculite and 1 90lb bag of Portland. The cavity I wa filling was only 5.5 cubic feet - not sure why it used that much vermiculite but it looks really good.
Where in CT are you?

[mrgweeto]

Re: vermiculite to portland cement

Bob,
Thanks for the reply.
So you're the person he special ordered the attic vermiculite for. I spoke to Tony at New Haven Masonry and my only concern was that the vermiculite was treated with silicone which keeps the moisture out. Our insulation hearth was framed out with brick to keep it from crumling on the sides. It is 5' x 5' x 3" ( 6.25 cuft ) so I am getting 1 bag of portland and 6 cuft of vermiculite. Am going to have to use the vermiculite down the line so any left over is that much less I will have to get later. We are from Hamden. Plan on doing the mix tomorrow after work weather permitting. Can't tell with this wonderful CT weather. Felt like fall Sunday morning. Made me want the pizza oven finished even more.
G

[pizza_bob]

Re: vermiculite to portland cement

G-
If you plan on going with 5:1 or 6:1 ratio I would consider getting an extra bag of vermiculite and possibly Portland. You will need it for the dome if you don't use it for the hearth. If you look closely at my pictures, I actually ran out of Portland and did not want to make the trip to Home Depot to get another 90lb bag. I decided to not completely fill the form and stopped approximately 1/4" below the top. I had to spend some extra time ensuring the top surface was level but it seems to have come out really nice.
Did you purchase the vermiculite from New Haven Masonry? Tony and Andy hvae been really good to me. I'm probably gonna' buy my bricks from them too. The vermiculite comes from The Schundler Company. I just called them to see if they silicone coat the vermiculite and they said "...absolutley not! It's pure unaltered vermiculite"...Here is the MSDS link:
VERMICULITE MATERIAL SAFETY DATA SHEET--- SCHUNDLER COMPANY