Bubbles/Craters in Cement Based Leveling Compound/SBR mix

Go down the B&Q and buy another brand. I've used three different ones and all were different. Wickes own brand being positively crap.

I got bubbles in all three but not that many.

Mark S.

Going to have to wait for the temp to rise a little...

It's hovering around 1 deg C out there at the moment....

Roy

Don't do what I did when I did it on a new conservatory floor. Tiny tiny hole between the concrete and the brick surrounding wall. Quite big enough for a bucketful of leveller to slurp down though....

OK. I have found the problem.....

Hands up all those who said it's coming out of the floor and go to the top of the class...

Here is what I have done...

I took half a 25bag and carefully poured it into 3L of water, mixing as it was being poured, a little at a time. No SBR - just water. And taking great care that there was no contamination :-).

I had in the back of my mind John Armstrongs post (above) about making sure the floor was wet... Well I overdid it a bit and put a bit too much water down. The mixture when laid on this was without doubt a bit too runny. Anyway - same problem - bubbles. However there did seem to be slightly less, and it did seem to respond better to the roller. When dry there were marginally less bubbles than my earlier attempts.

I then did the same but this time with SBR/Water mixture. But less water on the floor. Same old problem - bubbles. However this time it was a little thicker and rolling did not help.

Now I'm thinking to myself that I have not done a very controlled test - and how am I going to explain it to the NG. In fact I was feeling ticked.

I have the floor divided into three and there was one more bagfulls worth to finish off this section. I decided to lay this last bagfull - and decided to make it a little looser and with lots of water on the floor first. So I put plenty of water on the floor, swept it all over and got on with the mixing.

When I finished mixing I applied a bit more water, and sat down for a moment waiting for the mixture to stand. As I sat there I caught some movement on the wet floor where the light was shining. I could also hear some very soft clicking noises. On closer inspection I found that the whole damn floor was "leaking" like crazy.... Blowing bubbles through the water! Not just the odd bubble here and there - great long fizzes of the stuff!

So I left it for a bit and the clicking and fizzing slowly subsided, then added water and the bubbles started again but slightly less. I repeated this for about 20mins but the bubbles kept coming. I had to lay the mixture before it went off and sure enough the bubbles appeared as usual.

OK - so now we know where it's coming from - how do I stop it. PVA Sealer? Well that didn't work on the StoreRoom floor that I did earlier. I put a 3/1 PVA Mixture on that and it still produced bubbles... Hmmm...

Thoughts?

Roy

================= You could try an old-fashioned technique called 'grouting off'. This involved mixing a very thin mix of cement and water which was poured and allowed to spread. This was used (maybe still used) to bond new concrete to a previous day's pouring in shuttered constructions. In your case the effect would be to seal the 'worm holes' in the base concrete. Try a small area and see what happens.

Cic.

I think what you need is more PVA frankly. The surface should look almost shiny when you are done.

If the screed is very porous, it may need more than one application. What you are trying to do is to make sure the surface layer of the screed has replaced all air spaces by PVA.

Very porous crumbly screed is what you get when a screeder is skimping on cement, and making a very dry mixture as well. This means its easier to get a smoth surface (heck you can do that using sand alone) and has just used the cement to stop the sand shifting...:-)

This isn;t exactlyt WRONG, but it does malke for a structure that has loads of holes in it. Soaking it complertely fills them with water, but the PVA is better as it actually strengthens the top layer as well as making it waterproof - well water resistant anyway.

The SBR would be a much more effective sealer than pva

Hmm if its that porous I would now be wondering if a levelling compound was the best way to go. This is a garage? I would be tempted to dig a test hole to see what is underneath. You may only have a few inches of hardcore with a light screed on top. levelling compound will not fix that !

--- clip

Hmm... Many thanks for your help...

I now have Thanks, Roy

---clip

No no. I know exactly whats underneath. It's concrete beams. The concrete floor above the beams is quite thick.

Yes - this is a garage at the moment but I'm converting to a workshop...

Thanks for your thoughts.. Roy

I hope the joins between your sections don't give you problems. I remember those ridges being a bugger to even out.

---Clip

Stuart,

No - the one join I have done so far is OK'ish. Mind you I have been down on my hands and knees all day, fillings holes and smoothing with

Not really but it feels like it!

Roy

In article , RzB writes

You mentioned before about damping down, this means flooding the area and keeping it flooded for 24hrs and then sucking up any standing water. Priming is to seal the substrate not to act as a bonding agent

Yes - this is a very good suggestion I think. I have just spoken to the Antel technical dept. They have been very helpful. He has recommended doing exactlty as you suggest. I have some tanking slurry left over from a previous job and they have recommended using this. Interestingly the tech guy did in fact suggest this some time ago - but at that time I convinced him and myself that the bubbles were not coming from the floor because the very first lot I laid, I put a PVA mix down first. However that was a 3:1 Water/PVR mixture and obviously did not completely seal the floor...

I'll report back in a day or so and let you know how it turns out!

Thanks, Roy

Opps - a bit out of sequence..

- have spoken to the mfgr - see response to Cicero above..

Roy

This posted a little later when bubble mechanism understood..

I'm now very sure this is not a product problem - the bubbles are com Many thanks, Roy