getting cement off quarry tiles

any idea how to get cement off quarry tiles?

we've recently lifted a really badly laid laminate floor at ours & found a beautiful (if slightly neglected) quarry tile floor beneath it. only problem is there also used to be a gas fire in the room, looks like the hearth for this was kept in place with a few dabs of cement onto the tiles

I've tried chipping it off with a bolster but aside from not wanting to risk smashing tiles, its not coming off via this method anyway. I've tried caustic soda, and i've tried the trusty dremel, no joy so far.

i failed A level chemistry, but something tells me there should be a reagent that'll react with this to allow it to be lifted, anyone got any ideas or experience (or a chemisrty teacher in the family?)

I used sds on hammer only , keep at obtuse angle. then wire brush.

cheers fella!

(i'm now kicking myself for not thinking of wire brush)