Having some building work done and am concered about the concrete for the
floor.

After 9 days it looks very sandy and sweeping it brings up lots of loose
sand. An electrician either dropped something or put his steps on part of
it and the "crust" broke showing a crater that looked like a poor quality
beach.
My gut impression is that there is was enough cement in the mix.

The bottom slab and the kingspan insulation and DPC were inspected by the
Building Inspector.

The builder will be here on Sat morning after being off site for 2 days. I
have told him on the phone that there is a problem.

What should the top layer spec be? What do you think is wrong?

Thanks