How ? Cement based TERRAZZO on a calcium sulphate screed.......

[fergal]

How? Cement based Insitu Terrazzo on a calcium sulphate screed......

Recently done a calcium sulphate screed for client,who now wants a cement based insitu terrazzo floor covering and i was wondering...

1) Has anyone done it before?
2) Which is better-Epoxy based Terrazzo or Cement based Terrazzo?
3) Can there be issues with it?
4) Why is it so hard to find anyone wh wants to do Cement based Terrazzo?

If anyone can help, with any of the above it would be great! ​

 

[DHTiling]

What make of screed is it..?

 

[fergal]

I think that it Lafarge's,it's an anhydrate screed.

 

[DHTiling]

So it will be Gyvlon LL then..?

 

[DHTiling]

How long has it been down..?

Is is heated..?

 

[fergal]

It's Gyvlon but not the LL, and the screed has been buffed to remove any latance.

 

[DHTiling]

Ok.. so surface laitence has been sanded off..

Which ever terrazzo that you use , you will be stick it down with a suitable cement based adhesive be it single part or 2 part polyurethane one... so screed prep is crucial...

Have a read of this for a good epoxy primer if required.

View attachment Calcium Sulphate Tech sheet Apr10.pdf

And these are info pdf's on Gyvlon prep etc.

View attachment gyvlon screeds 2.pdf

View attachment Gyvlon screeds 1.pdf

 

[fergal]

It has been moisture tested, came back at 0.43% and it is a heated screed. The client has been told by someone that a cement based Terrazzo is a far better product than an Epoxy based Terrazzo. Do You Think This Is TRUE.....

 

[DHTiling]

If used externally then yes cement based is better as it does not lose colour but epoxy is more widely used as it is supposed to a much stronger product and less prone to cracking..

The epoxy terrazzo will come in a wider range of colour choice etc... So the choice is the customers really.. but as for using it on an anhydrite screed then again as i said prep is crucial..

 

[fergal]

When you say prep is crucial,would it be possible to to put down a DPM or can you stick Terrazzo to something like Detra mat, so that there is 100% no possibility of the two materials coming togeather,as the client is worried about the Gyvlon screed pulling the moisture from the Terrazzo mix, the Terrazzo contractor the client has been talking to, says on a sand and cement screed they flood the floor with water ,let it sit for a time then remove the excess with a wet and dry hoover, them put down a cement slurry before placing the Terrazzo mix.

 

[DHTiling]

The issue is keeping the wetting from the screed.. this is why i say prep is crucial.. The only way i would say to protect it is to epoxy sealer the surface.. but i have not done this before on an Anhydrite screed or laid terrazzo over one.. so your best bet is to contact Ajax123 on here who is the technical specifications guy for Gyvlon...

 

[fergal]

Would a good Acrylic primer do if it was done with two coats ,first 1-1 and the second neat,if we are doing a cement based leveling compound this is what we use and never have any problems with it.

Maybe the guy doing the Terrazzo would have to change his mix to allow for him changing the way he normaly works.ie not being able to wet up the sand and cement screed he usually lays on....

 

[DHTiling]

Only method after priming i would say will give a better bond is to slurry coat before laying terrazzo.. but check with Alan first.. as these screeds are his speciality..

 

[DHTiling]

You can pm him here or await his arrival.. Ajax123

 

[Ajax123]

this one is a little tricky as I am not familiar with Terazzo being laid this way. The only terrazo I have seen is done the old fashioned pressed wet bed method into fresh sand cement screed.

In terms of prep of the screed however if you are using a cement based adhesive I would always prefer a water dispersible epoxy primer as these act as a much more robust barrier to the migration of moisture borne sulphates which tend to be responsibl for the Ettringite delamination events. As you have the old fashioned stuff and have taken off the skin getting the epoxy into the screed would not be a problem as it can be on the newer low laitance screeds. I wonder if you might be better speaking to one of the gypsum based adhesive suppliers. Are you in Ireland by any chance Fergal. Laying the cement based levelling compound is the same as laying the cement based adhesive in terms of chemical incompatibility and I would always receomnd Gypsum levelling in preference to cement if possible. The heating MUST have been commissioned and run (it sounds like this has been done) The moisture sounds a bit borderline at 0.48%. I would probably be inclined to run the heating for another few days just to force out a little more moisture. I realise the general recomendations in terms of moisture but if you are using cement addy or leveller I would aim for about 0.3% moisture using the CM method.