dusty concrete

[gaz_moose]

It rained on the day we poured my concrete slab and as a result it has gone dusty. i did try and cover it over with some DPM but it went windy and blew it into the concrete 🙄

Its been about 4 months and its still dusty and i can grind a rut into it with a screwdriver so i know its not the best.

SO

what are my options?

Ive seen concrete hardener Everbuild 403 Concrete Hardener & Dustproofer 5 litre | eBay should i coat it in something like this and then self level over the top? its for a garage so will need to be able to withstand car jacks etc.. 

i di google it but then reached a conclusion i should just burn it down 😁

[Onoff]

It is likely laitance. Attached PDF:

 

I'd wire brush the surface, I used a cup brush in a grinder on my double garage floor. Then vacuum the floor and paint.

 

 

 

 

137-concrete-floors-laitance_web (1).pdf

[Russell griffiths]

If it’s for a garage look up a self leveling compound designed as the finish layer. 
you will need lots of primer. 

[saveasteading]

How thick is this weak layer? Is it just sand and cement, with the stones below it?

[gaz_moose]

it was proper concrete out of a volumetric truck. 

there was a decent amount of that laitence creamy stuff on the rear part. I scraped it all off with a shovel. I dug down about 5mm with the screwdriver with not to much pressure applied. I only really stopped as i didn't want to ruin the screwdriver, i suppose i could see how deep a groove i can dig to see how bad it is tomorrow morning. 

If needs be i could bring the height of the floor up a maximum of 20mm.

I just wondered if that concrete hardening stuff was the answer to my problem. 

 

[saveasteading]

I expect it will be hard at that 5mm depth.

Stones are the strength in concrete, with cement and sand gluing it together.

I'd try a gallon of hardener. It will at least form a varnish on the surface that will stop dust for a while. It may permeate and harden enough for your purposes.

If that works then a floor paint will seal it.

Otherwise you hire a floor scraper to take that 5mm off.

 

One further thought. The slab surface  may have dried too quickly. Was it wetted or covered in the weeks after? Is it in the dry now?

[Onoff]

I'd try the Everbuild 403, I have good, longlasting results with their products. 

 

I use their 202 integral waterproofer for most cement based mixes. Their Forever White and 825 (buff) silicones are excellent too. 

[gaz_moose]

we basically poured it when it was dry and then the 20% chance of rain actually rained for the afternoon. it was open to the elements for about 3 months during the summer and now has a roof over it for about the last month. it has a dpm etc.. underneath it.

i think all the stones etc.. have sank to the bottom and the sand has risen to the top.

can i use the 'just add water' type levelling compound over the top or will it be too fragile for a garage floor?

[saveasteading]

First try this.

Wet the floor and put plastic over it for a week or so. There may well be cement in there which has not chemically bonded through being too wet/dry variously.

Then let it dry.

Next try the sealer stuff.

Next I wouldn't use screed but a garage floor paint, assuming it will stick. This won't break or crack, and can be recoated if it wears off under wheels.

It looks good and is easy to clean as a plus.

It might be that you do all of these.

[Onoff]

Two pack floor paint is generally tougher than single pack.

 

If your worried about the stones having sunk to the bottom you could always hack out a foot square sample with a bfo grinder or core drill. You'd need to tip a liquid DPM in before re-concreting.

[gaz_moose]

over the past week whilst its been raining outside ive been painting the walls inside and using some offcuts of DPM on the floor to catch any drips. its not been damp underneath any of it so im confident the slab is dry inside. ive also had some decent sized offcuts of EPM on the floor.

 

I do need to put some kind of leveller over the top as when i sheeted it over when the rain started i put old bricks around the sides which then got flung into the concrete when the sheet took off in the wind, i trowelled these area the best i could but they are a bit wobbly.

 

Im annoyed that it hasn't turned out as my last garage floor was like the surface of the moon so i wanted this one to be amazingly flat.

[Russell griffiths]

you need a floor leveling compound that is designed as the finished floor

there are lots available 

do not use the cheap shite it will just wear away. 
you will need to hoover the floor spotless and soak it in primer, you will then need to prime it before the leveller goes on. 
 

read instructions on leveller and buy the appropriate primer. 
 

do you want it flat and level and smooth or shit but painted a nice colour. 
 

wont be cheap going to cost you£3-400. 
 

no miracle paint or surface hardener will get rid of the crap surface, they will just stop it dusting up. 

[saveasteading]

1 hour ago, gaz_moose said:

I do need to put some kind of leveller over the top

I fear that domestic screed will fall apart under car wheels. 

Some 2 part epoxies will be thick enough to take out  a few mm, but they are expensive.

 

1 hour ago, Onoff said:

Two pack floor paint is generally tougher than single pack.

And 5 x (or 10x) the price.  I have built 5 or 6 or so big commercial garages.  In some we used the epoxy paint instructed by the dealership, at huge cost, once thick enough to call a screed.  It was really good.

 

In others we used single coat paint. It worked fine but wore out at repeat tyre scrubbing points. However the client had saved a fortune and was happy to retouch when necessary, which any of the mechanic s could do..

 

1 hour ago, Onoff said:

the stones having sunk to the bottom

Where else might they be hiding?   a 10mm paste on top is standard, resulting from tamping, and I assume that is the case here.  ie the paste rises, leaving solid concrete mix below.

 

1 hour ago, gaz_moose said:

so im confident the slab is dry inside.

I'm suggesting the opposite. let it be wet for a week.

[Onoff]

7 minutes ago, saveasteading said:

Where else might they be hiding?   a 10mm paste on top is standard, resulting from tamping, and I assume that is the case here.  ie the paste rises, leaving solid concrete mix below.

 

 

I meant so he could gauge how bad it is. Don't know how thick, if there was admix, fibres, mesh etc. 

[saveasteading]

5 minutes ago, Russell griffiths said:

do not use the cheap shite it will just wear away.

What is cheap? we found that cheap(er) , from a known brand, was just fine. I'm talking about garages with 30+ movements a day, some HGV too, and oil spills etc.. 

I expect there is some rubbish too.

[gaz_moose]

ive just ordered some everbuild stuff, i will dig at it in a bit when i get home to see how thick the soft top is.

[gaz_moose]

i went out and scraped at the floor in a few places until I hit solid stuff, seems the rear of the slab is the worst with a 5mm groove dug then it tapers off to 3mm by about the middle, then to solid.

 

i will look for a final finish floor leveller.

 

i live round the corner from a cement truck filling place, could i just get then to come and pour me something over the top if i put that everbuild stuff down? the internal dimensions are just under 30SQM so it would be a decent amount of leveller to mix in a bucket.

[saveasteading]

40 minutes ago, gaz_moose said:

cement truck filling place, could i just get then to come and pour me something over the top

No. you wold need to put at least 75mm on top or it will curl and crack. 

[Onoff]

Apparently Springfield had a better ring to it than Concrete.

[saveasteading]

43 minutes ago, gaz_moose said:

5mm groove dug then it tapers off to 3mm by about the middle, then to solid.

It  is very sad for me to smile at being right for once.

 

Does this make you you less concerned? Nobody else will notice the wobbly surface, unless it gets wet and puddles.

[gaz_moose]

TBh i knew i was forked when it started raining. 

I purposely left the creamy stuff on the top so it would catch all the mortar I was going to drop on it as I found it came up easily.

id still like to level it because ive only really got this chance to get it nice before I fill it full of stuff.

it does brush up fairly easily, should i just brush loads of it off.

[saveasteading]

11 minutes ago, gaz_moose said:

should i just brush loads of it off.

Yes. there are fancy machines for it, but they are expensive and sometimes a bit fierce.

do you have access to a pressure washer. (a £300 one, not a car wash model).they can be powerful enough to take this off, and then stop at the concrete.

otherwise get the radio on and knee pads and several wire brushes.

 

[Onoff]

14 minutes ago, gaz_moose said:

it does brush up fairly easily, should i just brush loads of it off.

 

Best best is a light going over with a cup brush in a grinder. The vacuum and vacuum again. 

[gaz_moose]

well the everbuild stuff was delivered about 8 am this morning. which is mad as i bought it about 1 pm yesterday.

ive got a broom that i bought from the poundshop that is solid like a scrubbing brush so will go and blast it with that. ive a bit of an agreement with my neighbour that i wont make noise before 10.

[gaz_moose]

Angle grinder with a cup brush did the trick to remove a lot of the top layer, after about 60 seconds i couldn't see as far as my arms due to the dust, so it was slow progress. could do with some rain to wash all the neighbours houses off 😄

 

the everbuild 403 says 5L covers 25 SQM of floor and want 2 coats 24 hours apart, so I bought 3 bottles, I managed an area the size of a supermarket car parking space with the first bottle so have had to order some more, seems they do a 25L barrel so went for that. Yesterdays coating has done a really good job, i rubbed it with my shoe and no dust came up, todays coating didn't absorb as much straight away but will see what its like tomorrow.