I have used, used masonary cutting discs.
They are a bit finer grain than normal discs & a bit harder too, great for thin stuff that moves a bit when you grind it.

They are normally left over from worn huge discs as by the time they get to 7 inch dia they have stopped cutting or are too small Dia to make a deep cut into masonary or road surfaces.

Just make sure the cutting speed is correct. The 'metres/second' thing on the outer edge of the disc.