anhydrite

[Gazzer]

I use a floor polisher with sanding disc, works a treat and does not create too much airborne dust due to its low rpm speed.

 

[AD Ceramics]

Would only use decoupler if it is heated and natural stone but with 800x800 it's up to you. It can't do any harm but is probably over engineered. If it natural stone then decoupling is essential.

yes it is heated and porcelain tiles.

 

[Mark S]

Check with Kerakoll, as they have an adhesive specifically for latge format tiles.
H40 is 'Ideal' for ceramics onto Gyvlon screeds, without the need to prime, although some still prime but only to prevent the adhesive drying too quickly.
As with the other posts sand using an orbital type STR machine and 60-7-grit paper, to remove any loose or friable surface material, and to open up the screed surface.
And deffo use a de-coupling membrane

 

[Stef]

Took readings from the hygrometer today,

This Gyvlon was 55mm deep & this is day 53.
Good to go me thinks.
Working right through the holidays.