May be starting my 42" Pompeii in NYC this week...

[NYC]

Re: May be starting my 42" Pompeii in NYC this week...

Today I did the rebar grid, poured the slab and in the evening formed and poured the vermiculite. My friend is a pool builder so he gave me 16 cubic feet of the fine pool base stuff. I poured a 4" slab and a 4" vermiculite layer.

[NYC]

Re: May be starting my 42" Pompeii in NYC this week...

This morning I decided to raise the forms and add an inch and a half of V for a total of 5.5" of floor insulation. Brick yard is closed on Sundays so needed something to do.

[NYC]

Re: May be starting my 42" Pompeii in NYC this week...

Question: once the forms are removed in a few days can I start building or do I need to pour concrete around the vermiculite to lock it in place?

[rodeair]

Re: May be starting my 42" Pompeii in NYC this week...

Nice job NYC. My experience was that the ends of the insulation layer would come loose when hit with tools, etc. I used homebrew, so if I had extra after a mortaring session, I covered the ends with that. I finally mixed up a big batch and did the rest so I didn't have to worry about it. It worked great.
Leigh

[NYC]

Re: May be starting my 42" Pompeii in NYC this week...

Great, thank you. I will mortar around the edges after removing the forms. I hope it hardens more because right now I can press an indent into the vermiculite layer and it's going to hold 3,000lbs on top.

[NYC]

Re: May be starting my 42" Pompeii in NYC this week...

By the way, I used 3.5 bags of vermiculite and only 2/3rds bag of portland. Seems like too little portland based on some of the mixes I've read here. It did seem to coat well when I dry mixed it and did seem to begin hardening. Will this cause an issue with crumbling under the weight of the oven?

[Faith In Virginia]

Re: May be starting my 42" Pompeii in NYC this week...

Nope.... a 5 to 1 mix comes out quite strong. I did a test piece 2" thick and let it cure. I beat the snot out of it and it got a few dents but still held together great. So build away!

Your project is looking great!

Faith

[NYC]

Re: May be starting my 42" Pompeii in NYC this week...

Well, my point is that it probably was less portland than 5:1 ratio as the V bags are much much larger than a portland bag. I don't want to beging an oven only to have it crumple with 5.5" of stuff underneath it that may be structurally sound.

[Faith In Virginia]

Re: May be starting my 42" Pompeii in NYC this week...

How did you measure your mix? A 5 to 1 mix should have been by volume.

[rodeair]

Re: May be starting my 42" Pompeii in NYC this week...

NYC - I would be sure your vermicrete was mixed properly before you start building on it. I know it's recommended to have a 5:1 mix for the insulation layer, I don't know how a lighter mix would hold up. If your bags of vermiculite were 4 cuft each, your mix was approx. 15:1. A 94 # bag of portland is exactly 1 cuft. So if you used 14 cuft of vermiculite, you would have needed almost 3 bags of portland for the 5:1 ratio by volume.
Leigh

[NYC]

Re: May be starting my 42" Pompeii in NYC this week...

It dried pretty hard today. The edges are brittle but the center is dense. I can put a dent in it with my finger but when I press with my hand it seems pretty strong. I'm thinking to martyr up around it this way it is all held in around the edges. Thoughts?

I'm also going to post photos of today's work in a minute.

[NYC]

Re: May be starting my 42" Pompeii in NYC this week...

Got some firebricks and laid out the floor, marked the 42" diameter and cut the edges round. Next I need to measure and cut the vent landing floor but will take tomorrow off to rest.

Forms removed.

130 bricks picked up this morning to start floor.

Laid out and marked.

Cut and ready.

[NYC]

Re: May be starting my 42" Pompeii in NYC this week...

Thanks a lot. I appreciate the kind words. I trusted a "professional" on my dime and got a dud. Not gonna happen a second time.

[Faith In Virginia]

Re: May be starting my 42" Pompeii in NYC this week...

Well the point with the ratio by volume is for the maximum insulation value. Vermiculite is the insulation the Portland cement is the binder. The common ratio is 5 to 1 or 6 to 1. I used a large ice cream bucket as my standard unit of measure.


Edit I re- read the amounts of vermiculite to portland that you actually used and that does sound right. the more it cures the stronger it gets.

Faith

[NYC]

Re: May be starting my 42" Pompeii in NYC this week...

If it doesn't rain tomorrow, I hope to lay the floor in place and maybe do the first course. Can I use the premixed bucket of refractory cement from my local masonry yard?