Anhydrite adhesive test. - TilersForums.com

[Ajax123]

So i dunno what proves what really!
I'm totally aware that these compatible adhesives are disperive based, and about trapping the moisture, and also the priming considerations.
This was a test to what happened in as many scenarious as i create, albeit quickly.
But that in itself brings us right back the issue that you don't fix porcelain with dispersive adhesive.
Addressing one issue has woken another problem up!
i'm still none the wiser and certainly still have little confidence in tiling to these screeds.

Gypsum adhesives are not based on a dispersion mechanism. They are based on hemi hydrate calcium sulphate which when added to water hydrates to form gypsum. Gypsum needs to lose moisture in order to gain strength as the moisture sits at the interfaces between the interlocking gypsum crystals and effectively lubricates them. This reduces the amount of friction between crystals and reduces the compressive and flexural strength. The reason they work so well without primers is because there is no ettringite formation a the screed adhesive interface and the unprimed screed can pull the moisture out of the adhesive helping it to gain strength quickly.

 

[bugs183]

All i know is i have a limited capacity or need to retain so much information. I just want something that sticks!
I'm a tiler that wants to go work and be happy with what i've done and sleep at night.
Its a tad annoying having to work through different adhesives, but it dies sound like Creative Impressions were the biz so i'll get onto them.

 

[The D]

So are we now saying that cement based adhesive primed or not is not suitable for fixing tiles directly to this type of sub-straight ??????

 

[Rizzle from the Portizzle]

with so many types of these screeds comming on to the market its about time the screed surpler or the adhesive surplier gave us a spec in writing each seams to be passing the buck so who should be giving us the info and standing by it .i take my hat off to buggs for doing this test for us all putting in his own time and effort and sharing with us .its some think we all need to do .its a shame we are no wiser.

 

[bugs183]

God knows!
I believe if you use an Epoxy primer with cement based adhesives it should be fine, i couldn't test that one as i had no epoxy, but i may in the future.
Yet Norcross said if i were to use Ditra they don't recomend i use their gypsum based adhesive but prime with SBR and use cement based adhesives.

Any comments on the Agilia Horizontal Ajax?? That looked like impressive stuff.

 

[bugs183]

Cheers Ray!!
I'm probably making myself look pretty stupid in the process, but i just us tilers to be as happy as we can, i hate not being confident in what i do.
No one wants hassle, and the screeder from Lafarge agreed saying that so many guys he's spoken are bricking it over these screeds.

 

[Rizzle from the Portizzle]

buggs the last thing you look is stupid any body who looks for answers is at the top of the tree what i can tell you is from what i have found out so far these floors should be primed twice first coat should be watered down 75% water alound to dry then cross primed neat and allowed to dry before tiling but there are so many checks you have do first does the latice need to be sanded is it dry have you hovered up the debreis this is even before you have laid a tile .we make the least money but are asked to take the biggest risk

 

[Gazzer]

Gypsum adhesives are not based on a dispersion mechanism. They are based on hemi hydrate calcium sulphate which when added to water hydrates to form gypsum. Gypsum needs to lose moisture in order to gain strength as the moisture sits at the interfaces between the interlocking gypsum crystals and effectively lubricates them. This reduces the amount of friction between crystals and reduces the compressive and flexural strength. The reason they work so well without primers is because there is no ettringite formation a the screed adhesive interface and the unprimed screed can pull the moisture out of the adhesive helping it to gain strength quickly.

But here we are again, GBTA informed me a while back that the floor MUST be primed, with their primer of course. N&C say and state on the bags "No priming needed".
Is it any wonder the tiler is left confused...all we want is an answer that all adhesive, tile and screed manufacturers agree to and that what we tell the client.

 

[bugs183]

I know Sir, also why how can a tiny bit of moisture off priming be worse than the fast track method that Schluter recommends where you fix Ditra to damp floor???


What made me laugh was i discussing/moaning about all this with the client and builder saying how unconfident i was, and that really things need addressing with the manufacturers etc and all they could say was, well its a fast system to install and its good with inderfloor heating.
My reply was so what if the majority of tilers aren't happy sticking tiles to it, surely a system that is prone to failures is not really that good.
But that just doesn't seem to sink in with anyone.
i've got anther 60m2 next month with slate so i'll try the Creative Impressions and i'll do another test with that.

 

[bugs183]

I really need to win the lottery now!