Using Crusher As A Fireclay Subsitute?

[cobblerdave]

Gudday all
Spoke to a bloke last week by phone...Brother of a friend who is casting an oven shell over a sand mold. He is using a mix of Ciment fondu and crusher dust.
Crusher dust is basically the small washed particles.. dust and up to sand grain size left over from washing gravel for road ways. Road base is another term I heard used. I have used road base to pack down a base under pavers...add a litle cement powder water a wack down and its like cement..and very stable.
My question...could crusher dust be used as a substitute for the fired component...the fire clay in the home brew fire proof mortar mix. Its crushed basalt fired in the earth not just a kiln so on the temp stakes that should be enough?
Any thoughts

Regards Dave
PS this blokes ovens now has under hearth pealite insulation plans a fire brick hearth and is to have ceramic insulation over the dome so in all other aspects should be a worker

[david s]

Re: Using Crusher As A Fireclay Subsitute?

My refractory supplier tells me it is quite common to line industrial chimneys with a mix of cracker dust and calcium aluminate cement (fondu) How well it would work for WFO and for how long is anyone's guess. It should also be noted that the temps we fire to are insufficient to convert the material to a permanent fired material. Any attempt to try to fire the material high enough with wood is counterproductive because of the lack of consistent temp rate rise.The 450-600C range must be slow and controlled and this is not possible with a WFO.The material is unstable in this temp range.

[shuboyje]

Re: Using Crusher As A Fireclay Subsitute?

On the ciment fondue web page it lists aggregates and their service temperature ranges. One that jumped out to me was crushed house brick. Don't remember the rating but it was much higher then we need for pizza.

[david s]

Re: Using Crusher As A Fireclay Subsitute?

You need to break them up until the bits are no bigger than about 1/4" That's a lot of work. I've just been through that process with insulating firebricks (about 20L) which are way easier to break up, but still an extremely arduous task.

[shuboyje]

Re: Using Crusher As A Fireclay Subsitute?

Yeah I envisioned some form of home made hammer mill, but I know not everyone has the access to scrap and metal working skills I do.

[cobblerdave]

Re: Using Crusher As A Fireclay Subsitute?

Gudday all thanks for your replies...
DaveS
"It should also be noted that the temps we fire to are insufficient to convert the material to a permanent fired material."
Could you explain about "permanent fired material" a bit more It seems I have never really understood the role of fireclay in the homebrew mix.
Understand the portland cement is the temp glue to set the mix till finally burnt away. The Lime supplies the long term "glue"at high temps and the sand...an agregate. The fireclay????

Thanks for you input as always

Regards Dave

[david s]

Re: Using Crusher As A Fireclay Subsitute?

Clay only becomes permanent (won't turn back to mud if wet) when it reaches 573 C beyond that temp it becomes harder the higher it is fired. In the case of calcium aluminate cement ( fondue) it goes hard but it is still not properly fired until it is sintered which begins from 573 +

[cobblerdave]

Re: Using Crusher As A Fireclay Subsitute?

Thanks for the input fellas
Result to date on the cast oven is that he has used a mix of Ciment fondue crusha dust and fire clay. He built it on a base of firebrick with cement/vermicule insulation. He is to insulate with 2in ceramic insulation and cement/vermucile over that but as you can see there is not much room left on the slab. looks to me also that the oven was cast onto the support slab not the insulation.



Sorry for the scant detail I have only spoken to the bro and had these pic sent to me MMS.

Regards Dave

[david s]

Re: Using Crusher As A Fireclay Subsitute?

"Ciment fondue being aluminium silicate cement,"

I think you mean calcium aluminate cement, Dave.

[cobblerdave]

Re: Using Crusher As A Fireclay Subsitute?

David s Wotavidone
Thanks heaps for the imput.....being asked for advice on a cast oven was hard for me as I had no experience with one. Especially hard as I only knew the Brother so everything was a little "3 hand" so to speak. Hope to actually see the finish in the future...I'll keep you posted

Again Regards Dave