Castable ingredients

[Prescott]

Howdy gang.

I'm much more relaxed about my measurements, and taking a similar approach to my castable mix, ingredients. That said, I am still awfully curious about a few things.

I can't find fire clay in stores, not sure i want to order it online and pay for all that shipping to the far eastern corner of America, so looking at other options.

I have a bunch of firestop but that isn't structural, hard as all get out, but won't support itself.

I have some noxcrete, and clearly comfortable using that by itself, but it's not insulated. My thoughts are to get that mixed right, then mix it with a 50:50 blend of the firestop and vermiculite. Maybe toss in a bunch of the thinnest stainless fasteners I can find (the noxcrete comes with stainless needles)

Would it ruin the castable?

I am not cobbing but building a container of concrete blocks and filling it with vermiculite around the core, so that won't offer much support, but PLENTY of insulation.

Looking for thoughts, ideas, rants and reflections. If you have ANY refractory experience I'd love to hear from you or read shared links.

Thanks so much and y'all keep up the great work!

[Prescott]

Just me adding the notification feature I neglected to on the original post

[matt walker]

Prescott, I just googled Noxcrete and it seems that that name is a manufacturer with a bunch of products. What noxcrete product do you have?

I would say, that if you have a pre mixed castable refractory, don't mix it up with the firestop. You'll be adding active ingredients, which in firestop I think is Sodium Silicate, and you might mess with the refractory's balance. I have had no problems adding perlite/vermiculite to high density castables to create an insulated castable. You definitely weaken it, but high density castable refractories harden to somewhere in the neighborhood of 5000 psi, so there's a lot of leeway to make a durable/insulated firebox.

I've played with quite a few homebrew refractories at this point, and have had varied success with them. For sure the safest bet is to just buy an off the shelf low density castable, but there are other ways. Unfortunately, most of them involve a lot of fireclay. Keep in mind, fireclay isn't really anything that special, it's clay. You might try a locally sourced clay or a potters clay, and do a small test batch of a mix and throw it in an outdoor fire. See what happens.

[Prescott]

Hey Matt!

Thanks for the feedback, sort of my gut there too but I greatly value experience.

You're going to love this, and since I needed to do the photobucket thing eventually, here is what is on my noxcrete bag

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Hopeful this works. And yes, all the bag says is Noxcrete! No mixing directions or anything, warnings on the back... (In case the photos don't load...)

Can you give examples of light versus heavy castables?

If I go with a pure castable mix and the core is then highly insulated, I am not looking at that much loss of efficiency am I? (That's the relaxation talking!)

Which castables have been most successful for you?

What ratio would you loosely recommend for the vermiculite?

Thanks and keep at the good fight~p

[matt walker]

Nice! Okay, those ingredients do point to it being a castable refractory indeed.

Okay, let's start with a little detective work. I noticed a maker on your bag's label. Call these guys tomorrow..

http://www.nockrefractories.com/

Tell them what you have, ask for a product sheet, especially density, mix instructions, and dry out recommendations.

Also, ask them if they have any additives to lower density (insulation) or if they recommend a lighter density product. Typically heavy, strong castables are in the 130lb/cu. ft. range and up. My insulative castable is 60 lb/cu.ft.

All the manufacturers will tell you the low density is no good in a fire box due to wood impact, but keep in mind they are talking about use in huge biomass plants where loaders throw in the fuel, and similar uses. I've been pleased with the low density stuff, and I've tried the high density stuff as well. It works fine, but is uninsulated and also ends up being way more expensive, since a 50lb bag goes half as far, or less.

I have been using Spar products, specifically sparlight 60. As for vermiculite ratio, I would just go by feel. Add it in until you feel it has a considerable amount but the stuff is still sticking together well. That's the relaxing homebrew approach, anyway.

I think a pure refractory core is a fine choice, especially if it's low density. High density will still probably be way less mass than a firebrick core since it will most likely be thinner in section. Run what ya brung, I say!

[Prescott]

Bitchin' Bro!

I'll ring them up mañana.

I was going to line the feedtube with keyed half firebricks, some on the bottom (and tuck a little {say 1/4 inch or so} Roxul around them between that and the core for a little flex, breathing room. Silly idea?) Two reasons, for a little momentum (like how you saw your bad boy doesn't coast) and of course toughness. The latter is shifting as the ingredients are looking to be very much in the castable category!

Guess I oughtta get another bag of the stuff, or two?! How far would two bags go (roughly speaking of course) and since we are talking a different ball of wax, what thickness do you recommend for this castable stuff. No, I'll not hold you liable for any of your fine, free advice/thoughts/brainstorms.

Time to hit up Ray in NH, he did an all castable core!

Getting time to fold, come Monday I am doubling my already 30 hour work week for the rest of the school year, it's going to be a grind and somehow I'll get me rocket flying!

Cheers~p

[matt walker]

It's true, mine doesn't coast. If you use the castables I again would caution against the firebrick in the actual casting. Even with the gasket, it will be hard to not bind up and crack the casting in my opinion. If you think you want that type of construction, I'd make the mold so you can drop in the roxul/brick liner later. That way it's replaceable as well. I do think that even lightweight castable will be right in between my homebrew insulated mix and firebrick, so I think you'd coast just fine without the brick. But hey, it's your baby, and firebrick is a common theme.

Thickness, yep, we better get Ray in on this one and see how he felt his core turned out. I do know that 2" is a fairly thick castable section, folks go even thinner than that, but I think 2" is a nice even number and a fair thickness.

As for how much, we're back to the density of your product. You need to figure volume of your mold, then you can figure how much castable via the density rating. That's why I said the light stuff is cheaper. You can see that you'd need one + a little 50lb bag of 60lb/cu.ft. stuff to fill a 1 cu. ft mold. You'd need almost three bags of heavyweight 130lb/cu.ft. stuff.