Refractory hearth

[theDarbster]

Hi there,
My local supplier suggested pouring the hearth with castable refractory. I've read contrary opinions on how well it works. Some say it cracks, some say it gets too hot.
I decided to try it out by casting four hearth 'tiles' with uni-cast 70 and laying them on top of the firebrick. This way they are removable and if it blows apart or scorches the bottom, I can remove them.
I'll let you know how it works, but if anyone has experience or info I'd love to hear.

[shuboyje]

Re: Refractory hearth

Does the method you used to cast them fall within Unicast-70's recommended instructions? I would personally expect them to crack the way you've formed them. They are thinner then most castables are rated for, have been trowel which is a no-no for most castables, and have lots of air entrapment from a lack of vibration. Maybe Unicast-70 has special properties to overcome this, but I doubt it.

Now to your original question. In my opinion if a castable is used with a low enough thermal conductivity, and it is properly cast in multiple sections AND properly fired all per the manufacturers spec, I would not expect to have issues with a castable hearth.

Most castles have a thermal conductivity too high to be used as a pizza oven hearth, are not cast properly by hobbyists, and are not fired following the manufacturers firing schedule due to lack of the proper equipment to do so. In that situation a castable hearth will be a failure is multiple ways.