Can more water be added to grout for masonry walls after it is mixed initially?
You can add some water to grout to increase the slump, as long as the grout is still in the mixer and has not begun to set up. Adding water to grout after it is removed from the mixer is not practical because it cannot be mixed thoroughly. As with mortar, the grout should be discarded after 2 1/2 hours. Grout may need to be discarded earlier than 2 1/2 hours in very hot weather because it will set up faster.