"Jeff Layman" wrote

I have been lifting up concrete that was in my back garden, and the
soil/clay under it is blue, sticky and doesn't allow the rainfall to
drain. Is there anything i can do to improve the drainage?




IMO, short of getting a JCB in to remove it and replace it with topsoil,
no. That's assuming you want to cultivate it. You can try land drains,
and digging in lots of good compost, leaf mould, etc. But they will all
disappear over time to be swallowed by the clay.

If you just want to get the rain to drain away without cultivating the
land, just dig out the top few cm and put down gravel or stone chippings
to the same depth. These will also get swallowed over time, but will last
many years.

--

Not my experience!
Are you looking to plant crops here?
I had a similar area 5m x 2.5m covered in concrete and gravel.
The clay below was blue-grey and slimey, came off the spade in "bricks".

After digging to 1-1/2 spades deep and adding much vegetable matter, it is
now a thriving plot!
Yes it's still not what you would describe as free-draining exactly, but
it's plenty good enough for a vegetable patch.

Phil