Help with what concrete to use for an usu ( aka a giant mortar)?
I've never worked with concrete before but I have a burning passion to make an usu which is more or less a giant mortar about 1 1/2 foot deep and 2 feet wide in the inside diameter that uses giant mallets as a pestles to pound sweet rice into mochi. What I need to know is what kind concrete will be able to hold up to hot steaming rice and constant impact with wooden mallets without cracking or chipping. My idea is to cut a garbage can down to the height I need and to use a styrofoam mold that are the diamentions of the hole I need. Do I need some kind of release agent or will the water evaporating from the concrete shrink it enough to allow the styrofoam to be taken out?