On Aug 15, 6:59*pm, "Richb" wrote:
10 years ago I re-did my bathroom shower. I re-sheet rocked it with cement
board, then tiled it. My plumber at the time got me some sort of joint
compound that was I think acrylic based. I am re-doing another bathroom and
am no longer in contact with that plumber. Does anyone have any idea what to
use to fill in the joints of the cement board.

You shouldn't use joint compound. A typical installation would embed
the mesh tape in latex-modified thinset and then set the tile in the
same stuff. Some would coat all of the walls in a brush-on
waterproofing like Redguard.

R