Anhydrite adhesive test.

[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!

 

[Gazzer]

Well at least its not just me. At lunch time today I will know the readings from the latest test. If its not 85% then its not getting done and I am losing money now with all this running around. It has to stop !

 

[bugs183]

I know mate, its a right pain!
The thing is no one has ever said 'use this, it works, i've done thousands of meters and i am really impressed'
It just feels like the common story of the builder and his pva 'well i did a couple of jobs with it and didn't have any issues'. But we all know the risks.
There's plenty of reps telling us their adhesive is ace, but not many tiles confirming these as facts. But Creative Impressions seem to be getting the thumbs up at the mo, so i'll try those next.

 

[Ajax123]

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.

Gbta recommends me at of primer gbc01. Gypfix recommends a primer if the screed is particularly porous or dusty. I shall speak with sab at creative to see if th have tested primerless and let you know.

To be fair though two different anufactureres givin different instructions for their own unique systems is hardly confusing. Just flow the instructions on the bag.

 

[Ajax123]

Well at least its not just me. At lunch time today I will know the readings from the latest test. If its not 85% then its not getting done and I am losing money now with all this running around. It has to stop !

How long between the last test and this one? If it was 96 last week it will not be down to 85 this week. That is probably about three weeks away.

 

[bugs183]

It may look odd that we get confused about priming or not Ajax, in fact it could make us appear stupid. But aometimes you need to step out of the technical mindset and see things from the tilers perspective which is more practicle.
We don't look at a bag of adhesive and see the chemical makeup, we see it as part of a tiling system, and wether we have the right ro confidently approach each job.
So being used to priming everything gypsum based and to a degree now cement based we are conditioned to prime. Being told different information regarding the same system rings alarm bells, especially in a system that we are worried enough about.

 

[bugs183]

Right kids, i've just spoken to Sav from Creative Impressions and i've got to say he's the first adhesive rep to inspire about tiling to these screeds. He knew the product inside out and also what we as tilers want.
He insists you prime with their primer before using GBTA.
Looking forward to trying their product very soon.

 

[Ajax123]

Sab was specialist technical manager at Tarmac for twenty odd years. He was in on anhydrite screeds right from the beginning. I agree that there is ot much if anything he does not kow about the screeds. Creative also have cement based topping materials that stick like wotsit to anhydrite which he has designed. I know his gear is a little more expensive but really the failure rate which to date is zero as far as I am aware (that's in the five years or s that I have been dealing with creative) surely makes it worth while.

 

[Ajax123]

It may look odd that we get confused about priming or not Ajax, in fact it could make us appear stupid. But aometimes you need to step out of the technical mindset and see things from the tilers perspective which is more practicle.
We don't look at a bag of adhesive and see the chemical makeup, we see it as part of a tiling system, and wether we have the right ro confidently approach each job.
So being used to priming everything gypsum based and to a degree now cement based we are conditioned to prime. Being told different information regarding the same system rings alarm bells, especially in a system that we are worried enough about.

Not trying to belittle anyone bugs but is thing about prime or don't prime is down to the adhesive manufacturers and they surely put it on their insrptructions. Norcross and granfix also say no need to prime.

 

[Gazzer]

How long between the last test and this one? If it was 96 last week it will not be down to 85 this week. That is probably about three weeks away.

So here is why I am confused, last week when i commented on here it was 91% 96% and 93% all tested in different areas but according to the instructions on the Ball Hygrometer which is place on floor leave 4 hours, switch on and read after 4 hours or overnight.
This time I have done it your way, on floor ( yes sealed with the tape) 24 hours later turn on, 24 hours later read.....its now 81%.........you dont think that is confusing ?

 

[Ajax123]

I don't think it is at all confusing but then I know these screeds much more intimately. I said that screeds take longer than four hours to reach equilibrium. This is simply not long enough for the mini ecosystem within the test chamber to stabilise. I know from my own tests it takes up to 24 to 48 hours. The original test was done "incorrectly" (allbeit it was according to balls instructions) so presumably yielded incorrect resiults. The instruction is something that neds to be taken up with balls though. i beleive it comes from the old analogue hygrometers which did equillibrate much quicker. I am quite surprised that it dropped that much in a week though. Have they had plenty of ventillation going on?

cant remember off the top of my head what the tta document says in terms of time scale but if you speak to technical reps from the soft flooring side where moisture tests are done routinely they will say 24 hours.