Glass bottles in base

[Monilee]

Is it possible or recommended to lay down a layer a glass bottles in my vermiculite floor insulation layer? Try to create a taller base and keep it as insulated as possible. This is the layer before the floor bricks would go down.
Thanks for any input.

[UtahBeehiver]

Any thing is possible but empty glass bottles are very old school and old tech.(Alan Scott era) and I cannot say how well the insulation properties are. You do not say what you vcrete mix ratio will be. Typically a 5 to 1 is recommended for floor insulation so the sequence should be min. 4" standard concrete mix with rebar, min 4" 5 to 1 vcrete 6-8" would be much better, then firebrick. Here is a chart showing the K or thermal conductivity of vcrete by ratio. Not vcrete alone does not have the structural strength to support an oven.

[Monilee]

I was going to mix 6:1 vermiculite. We are on a tiny island off Puerto Rico and supplies and resources are limited. I was just trying to get the most air space in my flooring. I will pour about 6” of flooring. I also have glass blocks that I could use as well.
Thank you so much for your help. It’s an intimidating project.

[Monilee]

I also have a 3” floor poured with a grid of rebar. The Crete floor will go on top of that.

[UtahBeehiver]

There is not much K value difference between 6 and 5 to 1 ratios but the upper end of 5 to 1 strength value is substantially higher. IMHO go with 5 to 1 on floor and up to 8 -10 to 1 on dome insulation. 6" of 5 to 1 is a fair amount of floor insulation. I am not sure you gain much by placing glass bottles or block between the vcrete and the concrete hearth unless you need to raise the working height of the oven. Rule of thumb for the oven height is elbow height.

[Monilee]

Perfect. I did up the concrete closer to a 5:1. I did need to raise the floor height so it all worked out great! It’s such a strange mix though. It seems so dry and not strong. I could only finish half the pour today so tomorrow will get the next/final couple inches.
Thanks again!
Question about the dome insulation-do I mix the vermiculite with the high heat mortar For the insulation layer?
After the 2-3” insulation layer, I also need to skim coat it all with regular plastering concrete, for it to be more weatherproof, correct?

[UtahBeehiver]

It will take a few days for the vcrete to hardened, also it contains a LOT of water and your being in the subtropics it will take a while for the water to work it's way out. A good couple weeks in the sun and covered up good if it rains would be prudent before laying the floor down, it will take several curing fires to finish the job. On the vcrete dome insulation, regular portland cement/vermiculite (8 - 10 to 1) is fine for the insulation layer over the firebrick dome. You need at least 4-6" of insulation, preferably in 2" thickness for ease of drying. Pictures of your project or sketches of your design criteria would be helpful for the members who can give you tips and insight. Also, start a build thread under Pompeii Oven Construction rather than Ask Me section. It will get more exposure to the members.

[Monilee]

Ok. Thanks!