What is Fireclay?

[glennb]

Hi guys,
I've got a bucket of firebrick clay (all the dust/sludge removed from the wet saw after cutting the bricks), and want to know if i can use this to make my own mortar?

Is this stuff the same as Fireclay? The bricks are proper Al-Si Firebricks.
If not, i'll have to buy another bucket of pre-mix to get my entry arch finished.

[tigersmith]

Re: What is Fireclay?

Hey glennb,
I frequently read here that folks say to keep the cleanings from your rock saw. It is actually fire clay and can be used to make your own mortar. The formula can be found on this site somewhere...I'm sure someone else more knowlegable than I will chime in here shortly.

George

[glennb]

Re: What is Fireclay?

Thanks Tiger,
The recipe for home made refractory mortar includes Fireclay, Cement, sand, and Lime, but no explanation of what the Fireclay part actually is.

I was hoping the collection from the saw is the same thing and was looking for confirmation.

[glennb]

Re: What is Fireclay?

Ok,so a bit more research shows that firebricks are pretty much made out of fireclay, however brick dust from the saw has already been fired once already to make the bricks.

Will this stuff still work as a fireclay mortar?

[Archena]

Re: What is Fireclay?

Sure!

The clay doesn't change composition when fired - it's more akin to changing states. (Bad analogy alert! It's nearly 10 pm and this is the best I can come up with.) Kinda like when water converts from a liquid to a solid (ice); the state changed but it's still H2O.

Prove it to yourself - take a small amount and soak it in a bucket for a few hours and see what it does (you want it like a soupy dough otherwise you'll end up with a sludgy suspension). If it turns to gunk you're in business; if it stays like sand you're sunk.

You should get gunk. (<- technical term for a solid with plastic properties... )

[glennb]

Re: What is Fireclay?

Chris, I'm not sure what you are doing to cut bricks, but if you are using a wetsaw, the dust/mud that collects in the water tray is essentially fireclay. I have (as have many others), re-purposed that stuff into the mortar recipe.

If you are using a dry saw, with all of the dust flying into the air, I think you'll be out of luck.

Ok, I think i've found the answer to my question.
I've finished my main dome, so will only be using this stuff for the entry, vent and outer arch, so should be fine. Off to buy cement, sand and lime now. Can't wait to get this finished and start burning stuff..... i mean cooking stuff.

[glennb]

Re: What is Fireclay?

Sure!

The clay doesn't change composition when fired - it's more akin to changing states. (Bad analogy alert! It's nearly 10 pm and this is the best I can come up with.) Kinda like when water converts from a liquid to a solid (ice); the state changed but it's still H2O.

Prove it to yourself - take a small amount and soak it in a bucket for a few hours and see what it does (you want it like a soupy dough otherwise you'll end up with a sludgy suspension). If it turns to gunk you're in business; if it stays like sand you're sunk.

You should get gunk. (<- technical term for a solid with plastic properties... )

Definetly Gunky!! Never thought i'd be so happy to play with gunk!
Pretty much goes back to a clay like substance with more water and is quite workable.

[christo]

Re: What is Fireclay?

I agree with Archena as far as using brick dust as a substitute for fireclay. I'm not sure it's optimal for substitution in homemade refratory mix when building our ovens, but based on data here, it works.

If you want know more - and I suggest you find a cigar and put on your smoking jacket if you continue, cause I may ramble...

There are several mechanical and physical phases that occur when clay or bricks are fired. The most important one is where the temp is high enough where stuff melts and some of it turns to glass and bonds with the other non glass stuff.

Before I posted this I went to the net to look for something more technical than my memory. This is a better explanation than I just gave: What Temperature Does to Clay - How Temperature Changes Clay

The microscopic physical properties brick dust is likely a bit different than clay. Brick dust feels slimy (but not as slimy as wet unfired clay) and and under a microscope probably looks like a mix of clay and bigger chunks (of fired clay. for our purposes - I'm still not sure it matters.

Our ovens typically don't get hot enough to go through quartz inversion to fire off the fire clay or remelt brick dust. If we use a portand/clay or portland firebrick dust mix and the oven has been fired several times - it's likely if the oven is exposed to the elements long enough the mortar could wash away.

I had a higher demands for bonding than most builders and went with Refrax which later was renamed Refmix... and when I ran out I went with Heatstop 50 and then finished with more Refmix..... If I was building another oven in the standard pompei method - I'd likely still use Refmix but in a pinch I'd probably mix up a the homemade stuff and use my brick dust with fireclay and portland and use it up.

Christo

[gjbingham]

Re: What is Fireclay?

Just for a backup, you can buy large bags of fireclay from many places. Mutualmaterials.com might be a good start. Many others sell the stuff. Inexpensive too!