While concrete is in it’s plastic state (wet), a standard method of measuring the “slump” of the concrete is used.
The tool used is pictured below. Fill the device with wet concrete, remove the cone, measure how much the concrete slumps from the top of the cone. If the concrete only slumps 2″ after removing the cone, that concrete is really DRY, and is not very workable. On the other end of the spectrum, if the cone is removed, and the concrete spreads across the floor, the slump is beyond 10″ from the top of the cone, the the concrete is too WET. More water = more slump.