Hello: I found this site while searching for an answer and then searched here before posting.
I have a poured concrete driveway that touches and runs the down the side of my all brick home. The joint between house and driveway appears to have been sealed at one point but has settled about 1" or so judging by the line of of Grey Rubber-like Caulk still attached to the house.
It depends on how wide the joint is. If it's a half inch or less, clean it out well. Remove all of the old caulk. Install a non-absorbant backer rod and fill it with a gun grade urethane caulk. Keep the caulk bead within the dimensions recommended by the manufacturer for depth and width. If it's wider, clean and remove all of the old caulk. Install the backer rod and fill it with a pourable urethane sealant.