Plaster reacting with screed

[Jilly]

Just had the very messy plasterers in (one more room to go!) and have noticed this morning that the screed has reacted with the plaster which has got splashed all over it and has become slightly pitted. I  see after googling,  it would have been better to do the jobs the other way round (yet another thing learned retrospectively!!).

 

I have no idea what was in the screed, it was done by three Romanian lads, they hardly spoke any English, but it looked a nice job, but I'm guessing an anhydride mix. It was arranged by my helpful part time builder who works on a day rate. Is there anything I can do to stop the reaction, aside from wetting it?  There are micro splashes of plaster all over the place. 

[Mr Punter]

I thought the anhydrite screed was gypsum based anyway?  If you are tiling you need to lightly sand off the laitance and that should get rid of any other imperfections.

[Russell griffiths]

Go and buy 20 sheets of that cortex plastic £3.50 a sheet in wickes and cover the whole floor, tape it together with gaffer tape. 

You will save the 60 odd quid in the long run by not having to scrape the floor off and having problems with tiles sticking if it’s covered in plaster dust. 

[Jilly]

I did buy them but they didn't use them properly as I didn't know it was an issue ?. I'll do it for the last room but there's still plaster all over the place. Does really all have to be removed...?

[Jilly]

How much do I need to sand off, just the gypsum it self, the etched bits or the pink stained bits?