Outdoor Fireplace Construction

[Julianjym]

Hello all....I'm building an outdoor fireplace similiar to the StoneAge Fireplace I've seen online.I've made forms to pour a concrete/perlite mix to form the blocks and I was wondering what you all would recommend for the proportions??? I've tried 50% perlite/50% quikcrete but I think I didn't tamp it enough because it was breaking off on the edges...I'm trying to achieve something lightweight but strong...These blocks will be 24" above the firebox floor (which will be covered, including sides with firebrick)...Many thanks in advance for your help....Julianjym

Good to be here.............
I've attached a pic of what I've made so far...this is the base and I made it with 90% concrete/10% perlite...weight wasn't an issue at the lower level but will be when I get further along...

[Julianjym]

photo of completed blocks:

[Julianjym]

Also, photo of the original construction schematic and finished product:

[dmun]

Well, good luck with your project: It looks good. There's a little problem. Perlite concrete is an insulating material: the perlite substitutes for the aggregates in ordinary concrete. It's pretty strong in compression, but it has no tensile strength.

When you say you're mixing perlite with concrete, instead of cement, I don't know what you mean. Are you mixing some perlite in with ordinary concrete mix, like sacrete?

Also, concrete, no matter what the aggregate, is not a refractory material. It will break apart quickly in direct flame. That's why we use firebrick and refractory mortar on the inside of our ovens. That commercial unit you've shown will no doubt be made from some form of castable refractory. You may need to consider a firebrick liner to your fireplace, if you plan to use it with any regularity.

[Julianjym]

Dmun...thanks for the reply. I am mixing it with a concrete mix and adding more portland and additives for strength....the firebox will be lined on all sides and deck with firebrick and high temp mortar...the closest block will be approximately 3'above open flame...I want to make these more manageable i.e. lighter...the whole thing I'm going to line with galv. lath and el dorado stone veneer....thanks

[dmun]

Let us know how that works. It's not a mixture I've ever heard of.

[Julianjym]

Does anyone know of a recipe for the "Castable Refractory" mix??? I've heard of Norlite...but don't know the mixture...thanks in advance for any help...