self levelling bubbles

[sWe]

hi mate 'bubbles' come from the substrate being dry, before laying slc dampen the floor first 'not wet damp' and then you shouldn't get any if not as many bubbles :santa_cheesy:

Some SLCs, especially rapidly curing ones, do not react well to the substrate being damp. It's best to simply follow the manufacturers instructions, but as a general rule, it's doesn't hurt to prime.

 

[DHTiling]

I actually thought that the bubbles were caused by air entrapment when mixing...

Woodie can you elaborate more on your theory please...

 

[woodie]

i was informed that the slc obviously dampens the concrete causing it to release air that is trapped in its surface so by dampening the floor first you release this into the air instead of into the slc:santa_cheesy: i didn't dampen the floor when i first laid the stuff hence i had air bubbles everywhere since then i don't get any trouble

 

[div]

1st ive heard about dampening floor proir 2 layin slc..!!!!:santa_cheesy:
bubbles usually appear because off mixing at high rpm ...:rant:

 

[woodie]

considering my mixer is called my arm i can't see that:santa_cheesy:

 

[sWe]

Pouring SLC directly onto concrete, which is porous, ie absorbant, lets the concrete absorb some of the water in the SLC, which pushes the air in the pores out, into the SLC. Hence, bubbles.I've observed similar things happen to plaster and some adhesives. The water acts as a low tech primer substitute, filling the pores, if temporarily.

Essentially, wetting the substrate before pouring SLC or whatever onto it, feeds the substrate with water, pushing the air in the pores out, so that when you pour SLC onto it, the air in the pores is already (mostly) gone. But watch out, not all SLCs react well to the added water. Some rapidly curing ones can crack as they cure.

 

[sWe]

Using the old concrete/cement method of laying tiles, you usually wet/slurry the subsrate first to better the adhesion, excessive drying through absorbation, etc.

 

[woodie]

Pouring SLC directly onto concrete, which is porous, ie absorbant, lets the concrete absorb some of the water in the SLC, which pushes the air in the pores out, into the SLC. Hence, bubbles.I've observed similar things happen to plaster and some adhesives. The water acts as a low tech primer substitute, filling the pores, if temporarily.

Essentially, wetting the substrate before pouring SLC or whatever onto it, feeds the substrate with water, pushing the air in the pores out, so that when you pour SLC onto it, the air in the pores is already (mostly) gone. But watch out, not all SLCs react well to the added water. Some rapidly curing ones can crack as they cure.

i was hoping someone would find the right way of saying it, my brains not quite functioning properly tonight:20:

 

[DHTiling]

Thanks guys......i prime , so don't have probs with air pockets....but mixing at too high a speed with a paddle mixer entraps air as well.......so a combination of both would deffo cause this...

 

[woodie]

Thanks guys......i prime , so don't have probs with air pockets....but mixing at too high a speed with a paddle mixer entraps air as well.......so a combination of both would deffo cause this...

cheers Dave i'll keep that in mind because i've been considering buying one of those things for a while now :8:

 

[sWe]

i was hoping someone would find the right way of saying it, my brains not quite functioning properly tonight:20:

It's friday, no one's going to blame you

cheers Dave i'll keep that in mind because i've been considering buying one of those things for a while now :8:

You refering to a paddle mixer? Highly recommended. It'll save ALOT of time, and you'll get a more homogenous mix. Buy one with High wattage and high torque though, because you want to be able to mix at relatively low RPM to avoid trapping air. You can't go wrong with Collomix, Festool, Flex, or Rubi. Remember that different paddles are good at different things.

 

[kaharrison9]

Cheers all for your experiences and experience.
Hopefully back on track.
Spoke to the Mapei technical dept and very helpful.Suggested using ultraplan slc over the bal multibase to level the floor,it goes from 1-10mm and use the Keraflex maxi 3-15mm bed and doesn't set as quickly,allowing myself a bit more time.
Have ordered a spiked roller from trade tiler,will certainly be on low revs when mixing and follow instructions regarding damping.
It does actually say on the multibase to prime,allow to dry then dampen the substrate.
Dave mentioned he is looking into suppliying spiked soles as well.
Is there a specific paddle swe for slc?I used my adhesive paddle.
Kev

 

[sWe]

Generally, adhesive paddles work quite well on SLCs, but some, specifically the thin flowing/semi-liquid ones, need paddles which generate higher sheer forces to avoid lumps. They can look like this:

But it varies. Generally though, you'll be ok with an adhesive paddle, as long as you take your time to mix it properly.