Screed is this right

[Tonythecat]

I have recently cast some concrete and finished the top off with about 30mm of sharp sand screed. The concrete was mixed 4.2.1 and the sand screed was 4.1. the issue is that I'm not sure that is hardening correctly. Its been laid for a week now and gives of sand when rubbed.hard I've added a couple of pics to show the amount that comes off with about 5 hard scrapes with the edge of the float. Is this right or should it be much harder. First pick shows how much I can hack it out with a few hard blows with the corner of the float

 

[23vc]

The screed will take about a month to set based on the 1mm per day rule so won’t be that hard yet. 30mm sounds pretty thin for S&C, was it bonded to the slab?

 

[Tonythecat]

The screed will take about a month to set based on the 1mm per day rule so won’t be that hard yet. 30mm sounds pretty thin for S&C, was it bonded to the slab?

Ok so I laid it all at the same time with the screed going straight onto the concrete. So would you expect to be able to rub sand off it. Also if a wet it and rub I get a sandy/cement slurry as though it's not fully set but expected it to not do this after seven days.

 

[^woody^]

Yes screed surfaces are soft.

You can get a liquid to brush on the surface to harden it. Search for " Floor Dustproofer/hardener "

 

[Tonythecat]

Yes screed surfaces are soft.

You can get a liquid to brush on the surface to harden it. Search for " Floor Dustproofer/hardener "

I thought that sharp sand screed would result in a harder surface than soft sand is this not the case

 

[^woody^]

Not unless you tamp and trowel it smooth like you might with concrete.

 

[Tonythecat]

Not unless you tamp and trowel it smooth like you might with concrete.

Ok so pressume this is because tamping brings more cement up. Soi plan to tile this so will I need to chop out the top layer and re screed with tamping and trowelling