Scrabbler or grinder to knock 1mm off SLC?

[SuperPav]

So we've had the slab poured now (Agilia topflow self levelling concrete). In a few areas we've got a bit of crusty residue on the top, possibly where they sprayed too much activator. It's only about 1mm if that, but to scrape the whole 150mm by hand is too much.

 

Going to get a machine in for the day to just go over the whole floor and knock off a 1mm skim off the top. The whole slab will be tiled, so don't need an aesthetic finish, but equally don't want it super rough.

 

Do I get a scrabbler/scarifier (drum type thing with lots of teeth), or do I get floor grinder (round diamond pads that spin round)? Scrabblers seem cheaper, and lighter, but Ive never used either and don't know whether I'll just ned up with massive grooves all over the place?

 

Thoughts?

[Dave Jones]

why bother if its being tiled? lose 1mm easily in the adhesive

[jack]

1 hour ago, SuperPav said:

Do I get a scrabbler/scarifier (drum type thing with lots of teeth), or do I get floor grinder (round diamond pads that spin round)? Scrabblers seem cheaper, and lighter, but Ive never used either and don't know whether I'll just ned up with massive grooves all over the place?

 

I assume you can't just build up with adhesive, because the concern is more the loose crud on top than a little bit of unevenness.

 

If all you want to get is to get rid of the loose stuff on the top, I'd have thought a scrabbler would be the way to go.

 

I used a concrete grinder to grind the concrete floor in our garage (we had spalling for various reasons - very cold weather overnight, possibly a bit too much water in the site-mix that was used), and would caution against it. To remove only a few mm, I had to go over it repeatedly, and it cost a fortune in worn diamond pads.

 

Admittedly I was working with concrete that had cured for several years - if your slab is days rather than years old, it'll likely be easier on pads. But the main thing here is that you aren't trying for a smooth surface, you're looking to break up a thin friable layer. Scrabbling is much better suited to that task than grinding.

 

I wouldn't worry about grooves being left by the scrabbler. If anything, they'll provide some tooth for the adhesive.

 

 

[SuperPav]

Thanks both, yes it's just to knock off the "crap" off the top for adhesion purposes, as tiling onto it will just cause the adhesive to fail/unstick from the slab. The slab is level to within 3mm across the whole place, (except one corner where it drops off over a square metre which I can latex SLC over)

 

The slab will be 3 weeks old, and as it's self leveling concrete, the top layer is sort of half screed half concrete anyway, so it's nowhere near as hard as properly cured concrete, but I still might give the scrabbler a go first for the £70 it costs to hire (plus I can pick it up, unlike the 200kg grinder).

 

Off until Monday but I'll report next week how I'm getting on!

 

 

also I meant 150sqm in the OP, not 150mm!  doh

 

Edited January 25, 2023 by SuperPav

[jack]

6 minutes ago, SuperPav said:

The slab will be 3 weeks old, and as it's self leveling concrete, the top layer is sort of half screed half concrete anyway, so it's nowhere near as hard as properly cured concrete, but I still might give the scrabbler a go first for the £70 it costs to hire (plus I can pick it up, unlike the 200kg grinder).

 

Definitely give the scrabbler a go at that price. The grinder cost me several hundred quid in hire + wear, and that was with a discount due to my family having connections into the building hire trade. That was to do around 50 m², although as I said, the concrete was old and hard.

Treat yourself to a decent respirator too, if you don't already have one. Concrete dust is bloody evil.

[markc]

+1 on scabbler