Alchemical Cement

You mix this fine gray powder with water and a cubic foot of sand or gravel to form a durable stone-like material. Until it cures, it has the consistency of thick mud, and you must hold it in place (typically with a frame of earth or wood) if you want it to harden in a specific shape. It takes 1d10+10 minutes for the cement to partially cure, gaining hardness 2 and 5 hit points per inch of thickness. After 1d6 hours the cement is fully cured and as hard as true stone.