I am going to make some small concrete block planters, only 3 courses high and wide. I understand you can use construction adhesive rather than a mortar mix. Any recommendations as to the best adhesive to use.
Well, if you get yourself a tube of GripFill (green), Pink Grip, etc and a caulking gun you'll be able to see for yourself why it is probably an inappropriate material. The water-based versions such as GripFill solvent free (yellow) might be an easier option, but they are still expensive and I'm not so sure that you'll be able to find an effective release compound for your casting form(s)