I put some rice flour in my adobe mix. Makes it very sticky and seemed to help with the cracking. Now I have so much ash in my forge it doesn't matter. I remember I tried the rice flour to repair a big chunk that had cracked off and I fired it up right away. Didn't let it dry more than an hour. Worked good with no cracking on the repair. I'm not sure if it will translate if you do a whole lineing without letting it dry. Came up with the idea after watching the Discovery channel. They used rice flour on some parts of the Great Wall and those places were less inclinded to crumble. Just figured I'd recycle an old idea.

Lensman