Make My Own Refractory Panels????

Anyone know a good concrete mixture formula to make my own replacement refractory panels?? My old Marco fireplace panels are about $600 now due to Marco being out of business. A local fireplace/concrete shop made me up some concrete replacement panels, but they have cracked after only a few months use. I've decided to make my own....any suggestions????

Try a ceramic site for the right mix of vermiculite ,gypsum and refractory cement.
It has been a few years since I last madethem for my kiln.

See if you can find a foundry supply outfit in your area. They can sell you a mix for a phosphate-bonded castable and ask for some stainless steel fibers to add to the mix for strength.

concrete will not do it,, it doesnt have any heat proofing or heat proofing

Do a google search on something called "Insboard." This product might just fit the application you have in mind. Of course, this material isn't exactly cheap, though you will come out way ahead if $600 is the price for the replacement panels.

You can use "castable refractory cement" by rutland.