How do I remove thick old glue from concrete stairs ?

I am trying to get rid of thick, old glue ( not sure shat type ) which had been used by previous owners to glue carpet down to the interior concrete stairs leading up to a friend's flat.

I have tried using paint thinner and also using a chisel/mallet but to no avail.

Even if I manage to chip off the very thick lumps I would like to be able to remove it all so I can paint the steps for my friend as that is what they'd like doing. Some of it is really thin so just chipping away at it will take forever and still wouldn't really be a brilliant result.

Someone has suggested I buy a heat-gun but I wondered if there was a product available (at a reasonable price) in the Uk which I could just put onto the steps and it would dissolve the glue so it could be easily removed. The least physical effort for me the better as I have health issues which mean I can't exert myself too much (and my friend is even worse than me).

many thanks for reading this

K