Concrete floor grinder

gixer1

Well-Known Member
Anyone have any experience with these? Specifically for taking a bad layer of paint off a 100sq.m floor and keying it prior to repainting.

any input appreciated.

regards,
Gixer
 

Jagare

Well-Known Member
We used a flail type machine to remove floor coatings and scarife the surface. May be a bit OTT for what you need. For smaller areas a needle gun works well.
Google, concrete flail plane.
 
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Mike_E

Well-Known Member
rented a triple head (heavy duty wire brushes) floor sanding/grinding machine from HSS in Aberdeen a few years back for taking a soft layer off a newly poured concrete pad. was about £120 for the machine and £90 for the brushes from memory. did a good job and took it back to the aggregate layer. was only 20m2 mind... but it did hardly any damage to the wire brush heads and they would have done another 50m2 at least.
 

Alantoo

Well-Known Member
The machines may have changed over the years but I hired a floor grinder thirty years ago to try and remove a hump in floor and was really disappointed...it just polished the surface...it may work on your paint layer if you can stop it clogging. I still have the coarse grinding blocks I had to buy somewhere.

I learnt later that a "scrabbler" (which sounds a bit more aggressive than the flail machine @Jagare referred to) would have been better for my job...but the hire people advised badly/didn't have such a thing. I was told that scrabblers are used to resurface milking parlours, where the milk apparently rots the concrete surface, so they may be too aggressive for your purpose. Maybe smoothed with a grinder afterwards?

@Mike_E 's wire brushes sound like a good solution for paint.

You may be limited as I was by what your local hire companies have available...

Alan
 

Jagare

Well-Known Member
The machines may have changed over the years but I hired a floor grinder thirty years ago to try and remove a hump in floor and was really disappointed...it just polished the surface...it may work on your paint layer if you can stop it clogging. I still have the coarse grinding blocks I had to buy somewhere.

I learnt later that a "scrabbler" (which sounds a bit more aggressive than the flail machine @Jagare referred to) would have been better for my job...but the hire people advised badly/didn't have such a thing. I was told that scrabblers are used to resurface milking parlours, where the milk apparently rots the concrete surface, so they may be too aggressive for your purpose. Maybe smoothed with a grinder afterwards?

@Mike_E 's wire brushes sound like a good solution for paint.

You may be limited as I was by what your local hire companies have available...

Alan
You can get a scabbler head to fit in a kanga. I.ve used one many times works well on plain concrete a flail plane with th right flails in would be better for removing coatings and preparing the surface. Part of the work I did in the concrete repair game was specialist coating and floors.
 

gixer1

Well-Known Member
The problem being I applied a sealer, and then a polyurethane floor paint to an etched floor- after several days I noticed it isn’t hardening properly, spoke to the paint supplier and they reckon the level of etch was insufficient and grinding would be the only way to remove the bad paint and restart the job.

they have agreed to supply new paint as their procedures mentioned etch…the problem is floor grinders are not all that common around here and I really don’t want to mess up the finish on the concrete - not sure if it will just clog up with the tacky paint.

regards,
Gixer
 

Alantoo

Well-Known Member
You can get a scabbler head to fit in a kanga. I.ve used one many times works well on plain concrete a flail plane with th right flails in would be better for removing coatings and preparing the surface. Part of the work I did in the concrete repair game was specialist coating and floors.
That sounds good advice to arm the OP against the Hire shop, wish I'd known you thirty years ago.!

You sound like the man to ask.

What sort of depth of concrete can you remove with a scabbler / floor plane? I needed (still need, I never resolved the problem) to take off a hump/crown which was up to 25mm over 70m2. The result of a disastrous concrete pour which was thinned down to go through a concrete pump and as it was going in we suffered a deluge of a cloudburst. Never seen rain like it before or since. The concrete was then so wet it just flowed under the tamping beam.

Alan
 

Jagare

Well-Known Member
Depending how tacky the paint still is it would be best to scrape off as much as you can. Try a bark spade save all the bending. After scraping wipe over with a suitable solvent. Get your self a large angle grinder with a diamond floor grinding disc. After all the old coating is removed re etch the floor with hydrochloric acid. Let the floor dry and then re apply your coating. Was it a two pack polyurethane coating? Often its poor mixing or lack of hardener that cause it not to set. Poor degreasing and etching will cause the coating to lift
 

Jagare

Well-Known Member
That sounds good advice to arm the OP against the Hire shop, wish I'd known you thirty years ago.!

You sound like the man to ask.

What sort of depth of concrete can you remove with a scabbler / floor plane? I needed (still need, I never resolved the problem) to take off a hump/crown which was up to 25mm over 70m2. The result of a disastrous concrete pour which was thinned down to go through a concrete pump and as it was going in we suffered a deluge of a cloudburst. Never seen rain like it before or since. The concrete was then so wet it just flowed under the tamping beam.

Alan
25mm over 70 sq mtrs would see me getting in one of the big diesel planes we used to use. Or it may be better to cut round and remove the high section of floor and relay.
 

gixer1

Well-Known Member
So for the purpose of taking the paint and as little material as possible off would I be better with the grinder of the scrabbler you mention?

thanks again for the input!

regards,
Gixer
 

gixer1

Well-Known Member
Depending how tacky the paint still is it would be best to scrape off as much as you can. Try a bark spade save all the bending. After scraping wipe over with a suitable solvent. Get your self a large angle grinder with a diamond floor grinding disc. After all the old coating is removed re etch the floor with hydrochloric acid. Let the floor dry and then re apply your coating. Was it a two pack polyurethane coating? Often its poor mixing or lack of hardener that cause it not to set. Poor degreasing and etching will cause the coating to lift
It was an Everest polyurethane paint, I mixed it with a paddle mixer so pretty confident it was mixed well. I’m reluctant to etch as the paint supplier stated the ground floor was the preferred option for penetration over the etch…

regards
Gixer.
 

Jagare

Well-Known Member
If that what they recommend just get back to a clean dust free surface and reapply the coating. Hopefully it will cure this time.
 

Jagare

Well-Known Member
I see they only recommend acid etching for self leveling and power floated floors. That makes sense. I have in the past use grit blasting or very powerful jet washers to remove the latence from concrete surfaces before coating.
 

Jagare

Well-Known Member

Try one of these most hire shops do them

Paul D
Those are good machines with the right flails in. The carbide flails are a bit heavy if recoating floors. I've use the same machine with carbide flails for resurfacing cattle yards so the cattle get a good grip.
 

gixer1

Well-Known Member
I see they only recommend acid etching for self leveling and power floated floors. That makes sense. I have in the past use grit blasting or very powerful jet washers to remove the latence from concrete surfaces before coating.
I don’t know if I would be better etching or grinding - the floor was power floated and etched but when I spoke to the paint supplier they recommend grinding - I said to them that the procedure mentioned etching and this is why they agreed to supply the replacement paint FOC. I loathe to have to go and knacker a floor with a bad grinding job as it’s a fantastic finish at the moment other than the paint not bonding…🙄
 

Buckaroo8

Well-Known Member
If you can find a concrete polishing contractor local to yourself they will be able to grind off as much as you want very quickly if you just need the paint gone. Or hire a scabbler or a floor polisher like a Husqvarna PG450 with suitable diamond tools.
I’ve done a 50M2 floor with a Festool Renofix RG130 but it’s a killer on your knees and back.
Hook up a dust extractor if you’re doing it yourself.
 

Sandyb

Well-Known Member
I had to take off some high points of a laid screed and fitted one of these to my 9" or 10" angle grinder.
Cupped disc


I bought it as a kit online with the seller also selling a dust cover / extraction shroud. Better than a scabller for small areas, cheaper too..
 

Buckaroo8

Well-Known Member
I had to take off some high points of a laid screed and fitted one of these to my 9" or 10" angle grinder.
Cupped disc


I bought it as a kit online with the seller also selling a dust cover / extraction shroud. Better than a scabller for small areas, cheaper too..
A 180mm cup wheel is ok for grinding off high spots on a screed but they can be a bit aggressive and in inexperienced hands could quickly and easily dig into the concrete causing more damage.
I think the paint supplier will recommend getting the power floated later off the top as it’s all “fat”and not actually very hard compared to the concrete underneath.
 
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