Here are a couple of sets I made using concrete as a glaze material. It was pretty simple to make. The project began after finding two concrete paving tiles in a construction rubble dump. The larger one I kept for the bases, and the other I busted with a sledge hammer into gravel sized chunks. The gravel went into a bisque kiln, and the remaining slab went into the brick saw to get cut in half. Once the calcined concrete came out of the bisque, the friable powder went into the ball mill and ran for a relatively short 8 hours. After sieving out the remaining sand and large pebbles, I had myself a pretty nice looking glaze slurry. Overnight I noticed a lot of settling, I added a small bit of epsom salt, and what I guessed to be about 1-5% by weight of bentonite. It still settled a bit, but not so much that you couldn’t use it. The application of the glaze was dipping, with a bit of spraying to build a thicker layer of glaze on the top half of each piece.
The clay I used was a bastard mix of Danish stoneware and high fire reclaim clay. The firing was a very straightforward 1180C in 12 hours with a 1 hour hold. Based on other high fire celadon glazes I’ve fired in the past I’m guessing this same glaze would come out a very pale celadon blue in a reduction firing. Who knows though, I only had time enough to test in oxidation. Whatever the case my be, this was the execution of an idea I’d been meaning to try for more than a decade after hearing or reading somewhere that you could make a celadon glaze out of concrete!