Adding some structural integrity to perlite/clay-slip insulation?

Hi again, and thanks so much for the helpful replies to my previous first post.

Does anyone have suggestions how to beef up the structural integrity of the standard perlite/clay refractory insulation with a fiber additive?  I've heard of "cobbish" which incorporates lamb's wool, but it looks like a bit of a pain, and I don't have a good source.  I was looking at the fiberglass fibers in standard insulation, but they seem pretty tiny length-wise when pulled apart, at least in the sample I checked.

Has anyone found a decent, readily available refractory material to do this?

Thanks in advance,
Steve

I have used rock wool . It can take the heat.

Here in Germany there´s company that produces basalt fibres for composites, they sell their "waste" cut to 2.3" for cheap. Maybe there´s the same where you are if you google it.

Rock wool insulation (Roxul is one brand) is said to tolerate higher heat than fiberglass, and might serve well in your case.

If you are concerned about abrasion resistance, increasing the proportion of clay for the wear surface layer would help.

"Painting"with sodium silicate (water glass) will help with abrasion in the feed tube

Some say that the clay and Perlite face inside the riser  will sinster after enough use.

Yes, a long hot burn will fire the clay portion into pottery. It won't be very strong, but strong enough to hold up for a long time in the heat riser environment.

I was looking at the fiberglass fibers in standard insulation, but they seem pretty tiny length-wise when pulled apart, at least in the sample I checked.  

 I did read about someone using fibreglass.
I was thinking about doing this as well.  My thoughts on this: The fibers might be small, but that is not a bad thing, as you are looking for micro re-bar.  They will bind bit by bit throughout the mix.  Wear a mask.  Mix them into your dry mix so that you get them evenly distributed, and then add your water.  Make a mix of just the fiberglass fibers (in higher quantity with clay slip) and run that over the internal surface to give it super strength.