Just looked at the floor slab in the shower area that we laid 2 weeks back.

I was laying it with an assistant doing the mixing - basic C20 (1:2:4) mix.

Unfortunately some of the mixes went down too wet - seemed fine in the
barrow, but once it had been sitting on top of the DPM sheet and been
tamped down, a couple of mm of water appeared on top.

The end result is that the surface is quite weak - as in the surface can be
abraded with hard finger pressure.

The same mix was also used outside the DPM to fill some small voids under
the adjoining old floor slab and these bits are as hard as iron as
expected - I presume because the excess water could drain away into the
base sand.

Not really wanting to lay this again... Is this likely to be a surface
problem or is the whole slab likely to be weakened?

The aim is to put celotex on top then screed to 60-70mm - so 2nd question -
is any of this likley to matter that much? My default opinion is to wash
some dilute PVA over the top to firm up the surface then proceed as
planned. There is mesh in the slab and it's 100mm thick on a well packed
base so I can't actually see it going anywhere.

Opinions? Shame because I'd got it *very* level

Cheers

Tim