What is this?

[TwinkleWings]

It's next to some paving slabs. Can't work out if it's another bit of paving slab but wondering if it could be asbestos cement? It's about an inch in thickness from what I can tell.

It's got kind of dimples in it which is what is worrying me. But so have the definite paving slabs but the dimples on them are smaller.

Thanks for the replies

Posted too soon.

I'm not sure why I'm worrying about it all because it's too late now. But asbestos has been on my radar since my friend had a garage roof removed that my kids played next to a lot. I'd researched it a bit and realised it was nothing to worry about as was all in tact when they did but I think when I noticed this, after spending most of the break not even noticing it as such, I then suddenly thought "shit that's got dimples on it and is broken!" and had a wee panic.

Im going to have to go with the concrete imprint suggestion I think as I can't find any evidence of paving slabs with dimbles in them. (As in inverted dimbles, not ones that stick out but please feel free to prove me wrong!)