I got a bunch of broken K23 bricks that I have been saving for a day I have time to make something with, and that day is approaching. I want to shape the pieces and cement them together and make a forge to give to my brother-in-law. What's a good 3000F cement to use? I tried some fireplace 2400F some time ago and it made a mess, and the seams cracked and ruined a bunch of bricks. In fact, some of my broken bricks are from this experiment gone awry, and I had to clean them up on a disk sander to get rid of the black flaky crude. I don't want a repeat.