Concrete powder will fall when there is a non-solid block beneath it. If it falls on a player or mob, the player or mob will suffocate. Creating concrete : If a concrete powder block comes into contact with water, it will solidify into a block of concrete. Specifically, the block has to fall into or be placed in a space that water occupied, or the water has to flow into it, whether from the side or above. It will also solidify if it's adjacent to water that isn't flowing into it. The exception to this is that it will remain concrete powder if an isolated block of water with nowhere to flow is used. Rain or splash water bottles also have no effect on concrete powder.