Lava rock

[dnno215]

New to this forum, so forgive me if this has been covered. Has anyone ever used lava rock as an aggregate for the concrete base and if so, does it provide good insulation> Thanks in advance.

[thickstrings]

Re: Lava rock

Don't know if its been covered,but, it may be slightly more insulative,BUT, it is certainly NOT a good enough insulator for a oven....There are proven methods,mainly ceramic fiber insulators that are used for a reason, they work...If you havn't built a oven before I suggest that you look at the Pompei Forno Bravo plans...A lot of work and money goes into these things and it would be a shame if you went through it all only to find it was a dud..just sayin..

[cobblerdave]

Re: Lava rock

Don't know if its been covered,but, it may be slightly more insulative,BUT, it is certainly NOT a good enough insulator for a oven....There are proven methods,mainly ceramic fiber insulators that are used for a reason, they work...If you havn't built a oven before I suggest that you look at the Pompei Forno Bravo plans...A lot of work and money goes into these things and it would be a shame if you went through it all only to find it was a dud..just sayin..

Gudday thick strings
I agree that there are better insulation options that are cheaper and more readily available than lava rock. But if that's what you have ,why not . Check out Lancers Phillipino build in the Australian section. He is using what is locally available. He is using plumice for insulation local fired brick for the dome and will slake his own lime for the homebrew mortar.
I say good on him, the most important thing is that he will be able to produce a viable oven still using the forno methods.
Regards dave

[thickstrings]

Re: Lava rock

Dave, that is a fantastic build by Lancer and I applaud his determination in getting the job done. I for one am all about using what you have....[ redneck engineer] I was congratulated once here by the locals for using a tupperware bowl as a roof vent shroud. This guy, I assume, is talking about the rock that one would put in a gas grill.....not pumice....He lives in Chicago..a major U.S. pizza city , urban sprall 90 miles in all directions.The right stuff IS available... Local Chicago joke....Why are all the [fill in the blank] leaving the city?.......They think Mount Prospect is gonna blow... Mt. Prospect is a NW suburb, not a volcano... P.S. I don't know Brisbane from Perth....

[Danthepizzaman]

It would seem as though lava rock would be a better insulator then say vermiculite since it is a lot more airy and heat resistive than vermiculite or pearlite and extremely lite. I also was thinking of using the "landscape" type lava rock to make my insulating slab which is much smaller pieces than gas grill rock and extremely cheap.
Any input here ?

[david s]

There are a number of types of lava rock eg. basalt, scoria and pumice, however all are denser than vermiculite or perlite which should make them less insulative. Whilst their higher density produces a stronger product it is less insulative. A better material is LECA (lightweight expanded clay aggregate) which is manufactured from clay producing small spheres with a hard exterior and softer air filled cores, but it is still denser and not as good an insulator as either perlite or vermiculite. Vermiculite and perlite will withstand temperatures up to 1100 C, which is around double that of a WFO. Both have densities around 1/10th that of water. A 100 litre bag weighs around 10 kg, 1 kg/10 litres or 100 kg/ m3.
Check out the relative thermal conductivities (opposite of insulation values) of your material with that of vermiculite and perlite. Also once you start mixing any aggregate with cement the insulation value drops further.
https://www.engineeringtoolbox.com/t...ity-d_429.html
https://hal.archives-ouvertes.fr/hal-01110505/document