Removing concrete remains

[Easrow]

As per the title, how would you guys remove the remains of concrete poured over our quarry tiles, and the rest of the downstairs, many moons ago. I've sorted the blue lias flag stones but I have quarry tiles and bricks to deal with. Any pointers? A wire wheel on a grinder doesn't touch it and nor does a rust removal wheel. I've tried a sander but not much luck. The quarry tiles are pretty soft so don't want to damage them. We have some acid cleaner, and alkali cleaner for tiles which fizzes nicely but leaves the concrete. I'm thinking I'll have to just be very gentle with a grinder.

 

[Cubist]

I've come across some YouTube videos in the past that touch on the topic but have no direct experience. Phosphoric acid seems to be the GoTo product for the job.
May be worth a try if you haven't done so already.

 

[88v8]

Well you could try this sort of thing which as Cubist says is probably phosphoric acid.

If that doesn't work, bear in mind that originality is great, but not everything can be saved. Removing old hard cement from soft tiles, hmmm.

Unless the quarries are something very special or there aren't many to deal with, you might look to replace them or at least those worst affected. You may be lucky finding old tiles on eBay, although one has to beware of buying tiles that are themselves contaminated with cement.

Ivor