SLC Drying times

[Rich Midge]

Hi all, was just wondering out of pure curiosity how long people leave slc before they tile? Tilemaster's Rapid 30 is the only one I tile on same day. Most others state they cure in around 3 hours and are good to go. Others say cure in 3 hours but don't tile for 8. I always tile next day, don't feel comfortable laying same day but don't know if this is just habit.

 

[Andy Allen]

I use weber and always leave till the next day..

 

[widler]

I leave till next day, even with rapid 30, just tell customer " aye, can't tile over it for at least 12 hours"
Early dart [emoji41]🙂

 

[Ian]

Yeah I always leave til the next day.

 

[Ajax123]

Curing and drying are different things.

 

[CJ]

Next day.

 

[kimboslash]

Never tiled on top of SLC the same day.

 

[Rookery]

It depends on thickness but generally next day.

 

[Rich Midge]

Curing and drying are different things.

Presumably slc, screeds etc are dry enough to tile after x amount of time without being fully cured? Though I imagine its a different answer for different screeds.
Anyhow, glad it's not just me leaving leveller a day!

 

[Ajax123]

Presumably slc, screeds etc are dry enough to tile after x amount of time without being fully cured? Though I imagine its a different answer for different screeds.
Anyhow, glad it's not just me leaving leveller a day!

Curing involves retaining the moisture in the screed in order that the cement can hydrate properly. Therefore, from the technical purist point of view, the screed cannot dry whilst it is being cured. once it has been cured it can then be allowed to dry. It is not really possible to determine if it is dry enough to tile without carrying out moisture test but being reasonable a day should generally do it. There are screeds that use chemical means to tie up the water which will be dry enough earlier. Some say 4 hours. My concern is that if the cement is still hydrating at this time then it is shrinking and could crack or curl and part company with the sub floor. Leaving it 24 hours is almost like having a safety net so that is any cracking or curling is going to happen it is likely to have already happened after 24 hours and you can decide if it is mechanically safe to tile to.

 

[Rich Midge]

Curing involves retaining the moisture in the screed in order that the cement can hydrate properly. Therefore, from the technical purist point of view, the screed cannot dry whilst it is being cured. once it has been cured it can then be allowed to dry. It is not really possible to determine if it is dry enough to tile without carrying out moisture test but being reasonable a day should generally do it. There are screeds that use chemical means to tie up the water which will be dry enough earlier. Some say 4 hours. My concern is that if the cement is still hydrating at this time then it is shrinking and could crack or curl and part company with the sub floor. Leaving it 24 hours is almost like having a safety net so that is any cracking or curling is going to happen it is likely to have already happened after 24 hours and you can decide if it is mechanically safe to tile to.

By 'eck that's how to answer a question! If I could pick your brain still further, how are levellers "shrinkage compensated"? Obviously this is necessary or every bag wouldn't say it, but without wishing to sound like my 3 year old lad, why? Please feel free to be as technical as you like!

 

[Ajax123]

By 'eck that's how to answer a question! If I could pick your brain still further, how are levellers "shrinkage compensated"? Obviously this is necessary or every bag wouldn't say it, but without wishing to sound like my 3 year old lad, why? Please feel free to be as technical as you like!

I will be honest and say Leveling compound chemistry is something I am not an expert on, However there are various ways of achieving shrinkage compensation including expansive fillers and fibers. I think though that most leveling compounds will use brute force as it is the cheapest way to do it.

By that I mean that they are generally quite a high cement content and high polymer contents which means that the rate of gain of strength is very fast. Shrinkage compensation is used to maintain dimensional stability and to reduce the propensity for cracking during the setting process. This cracking usually happens because the tensile strength is not high enough to overcome the internal pressures caused by shrinkage. It happens whilst the screed is still plastic hence the term plastic shrinkage cracking... If you have a very fast strength gain the reaction will give enough strength for the material to overcome its desire to pull itself apart as it shrinks.

 

[widler]

Ive got a little geo bathroom to slc and tile/grout tomorrow, tilemaster 30 is wonderfull stuff [emoji106]

 

[Stef]

I used Rapid 30 & started tiling an hour later, no problems so far, that's was 5/6 months ago.
It's great stuff..

 

[Rich Midge]

Absolutely agree with the comments above. First used it this January, small toilet floor in an empty property so was cold! Had a bit of a panic when the 2 bags I'd poured were still wet after 45 mins. At 60 minutes it had set solid. Brilliant gear and flows great.