We have removed a room and hallway of ceramic tile from the floor. This tile was on the cement slab. The tile adhesive in one area looks like it is black and a little brown. You cannot see the cement slab color in this area. In the actual bathroom the floor only has a brown colored adhesive on it and you can see the actual color of the cement slab. Both areas have some of the netting that was underneath the tile stuck to it. So, if this helps, it looks like it goes cement slab, brown and or black adhesive (depending on area) or a mixture in the one area and then the netting. I hope that is a decent description. What can I use to remove this adhesive to lay down new ceramic tiles?

Hi. You may want to try using a chisel or putty knife to remove the adhesive from the cementboard in the areas where its possible. This could be a lot of work if you need to do this along the whole floor.

Another option is to use a belt sander equipped with a medium grit sanding belt or an angle grinder to wear away those hard to remove spots. Be careful not to remove the cement board itself though. Wear adequate respiratory protection with this method as a lot of dust and loose particles will be kicked up. Cover the furniture and things.

Finally, if none of this works to your satisfaction just replace the old cementboard with new ones and start fresh.