Steel tank but what's in the bottom?!?

I'm just cutting up the 3rd and final galvanised steel water tank in the loft, but the base has what looks like cement in it. It's super heavy.
It doesn't look grey like the asbestos cement things get built with. It's actually
Did people ever pour some cement in for ballast or something ?!?
I'm just looking to find out if this is safe to break up and remove.

Is the underfelt shot? Could be a build up of crap from the roof tiles, solidifies over time .
Or maybe leaked and someone pour rapid cement in to seal .

foxhole said:

Is the underfelt shot? Could be a build up of crap from the roof tiles, solidifies over time .
Or maybe leaked and someone pour rapid cement in to seal .

Click to expand...

I looked underneath and there was indeed a hole !!
Cement just looks pink so I'm thinking there's nothing to worry about.
Good knowledge!!!