We are In the middle of delippig marble floor and after finishing grinding with metals grout in some places is already flush with the tile but in most places little  below. I was planning on filling it up with the grout Mixed with latex but I have concern about new grout Bonding to the old one.  Did anybody had problem with that?
Grout is non sanded and lines are 1/4" wide, 1/16" to 1/8" deep. Grinding deeper will take too Much time and I really don't think it make sense. Any suggestions?

Adam Bartos
BiO Tile & Grout Restoration
773-575-5515 (c)
847-438-0212 (o)
www.RestoreYourTiles.com