Suggest a solution to our predicament!

 

We have a 200mm slab that was poured with self levelling concrete, the result was ok, not great, pictures attached. 

 

I would like a solution to give the appearance of a concrete slab. What would you suggest?

 

Approx 90sqm to cover.

 

My idea is Aturo Mistral https://uk.arturoflooring.com/design/resin-flooring-design-options/arturo-mistral

 

Rep says that with our current slab it'll be a lot of work to prep it. I don't doubt it.

 

Anyone have similar issues, and find any other solutions please?

Microcement, or maybe ask a good grinding / polishing company to sample one small room and see what results that yields. 
 

Prep for adding layers to this will need to be robust, and would probably need some amount of grinding. The hope would be, to grind and area and see if it looks ok, then if so repeat throughout. 

That's a good suggestion, I'd like to bring in a team to do the work, but the cost is prohibitive.

 

Is it crazy to suggest that a self levelling compound, over the whole slab could be a finished floor?

 

Would have to look at the spec of a product to find a minimum viable thickness.

12 minutes ago, Duncan62 said:

That's a good suggestion, I'd like to bring in a team to do the work, but the cost is prohibitive.

 

Is it crazy to suggest that a self levelling compound, over the whole slab could be a finished floor?

 

Would have to look at the spec of a product to find a minimum viable thickness.

SLC is friable, so won’t last 5 mins. 

14 minutes ago, Duncan62 said:

but the cost is prohibitive

Not if it turns out cheaper and faster than prepping and re-covering with xyz.
 

Especially if you’re still on shaky ground as to whether that’s then still robust. 

Most of them will grind out if say, there'll be little big aggregate in the humps anyway so it might be straightforward enough. 

1 hour ago, Duncan62 said:

our predicament!

I am pretty sure they have added water to the mix, causing these very visible shrinkage cracks.

If you have the delivery ticket, they will have had to sign an instruction to add water as it absolves the supplier.

 

It is a common mistake but utterly misguided and you could ask for some recompense.

 

These cracks will be right through the depth so taking the surface off will not remove them, although the crack widths may reduce. It's possible that only the top few mm was hideously wet and overworked.

Are there contraction joints elsewhere, and what has happened there?

 

It's ok for any overlay as it won't move again.... unless overworked. I'd try chiselling a bit off the surface to see if it is well bonded to the mass.

 

Re the tamping ridges, that may not matter for tiling but has to be ground off for anything else.

It's a diy job with a grinder made for the very purpose.... but hard work.

 

A new poured surface is possible but would be very expensive.  It would involve taking all the pasty surface off then laying a granolithic or resin material. It might not crack if very skilfully done.

Best to decide that you really like tiles or vinyl.

 

If you must have a concrete finish then you could regard the existing as a base layer and pour a new floor, 100 thick, with reinforcement  and careful attention to detail 

BUT all concrete crazes and my opinion is that it is for commercial buildings.

 

You could also consider grinding down about 20mm into the stone, so you will se the matrix of stone and sand/cement. then you'd have to seal it as it will show stains. Again, this will cost an awful lot.

Edited January 24Jan 24 by saveasteading

You can get a self leveling compound designed for forklift traffic in warehouses 

I don’t know what it looks like, probably grey and boring looking if that what you are looking for. 
you could do one room with expansion gap at a door way as a tester. 

40 minutes ago, Russell griffiths said:

self levelling compound designed for forklift traffic in warehouses 

I have been out of that industry a few years now, but last i knew, it was an epoxy or polymer, not concrete. So it's a paint really, in any colour, but not at all interesting.

If you want your house to look like a garage....

 

16 hours ago, saveasteading said:

I am pretty sure they have added water to the mix, causing these very visible shrinkage cracks.

 

It's possible that only the top few mm was hideously wet and overworked.

Are there contraction joints elsewhere, and what has happened there?

 

Yes it was raining when it was poured so the top got too wet. 

The self levelling concrete doesn't like that, and as a result it cracked on the surface. 

 

The tamping marks are because it started to go off because the crew doing it weren't very good. 

 

Looks like I will be hiring a grinder and doing the dirty work.

 

Guess I need this for a week?

https://www.hsstoolshop.co.uk/diamond-floor-grinders-for-hire-12022-p.asp

 

 

1 hour ago, Duncan62 said:

Guess I need this for a week?

That's posh with the handle and standing up. That will do it rather quickly as a diamond grinder is OTT for that soft surface. But better that than struggling. 

Are you just smoothing it or taking a mm or two off?

Dust! You'll need masks etc and do you vacuum it up?

 

Whose decision was it to pour despite the rain? Or was it not forecast?

It's a very big decision to cancel a pour, so I appreciate the pressure to do it.

You can get a handheld version 

get that fora day as a tester. 
 

what are you actually try to achieve. 

Handheld ones can carve valleys into the surface in seconds, so beware to not do more harm than good.

 

I’d defo go for the upright and start with just taking a whisker off the surface, and remember to keep the machine moving at all times. Any time you need to stop, lift the machine.

 

This isn’t a job for the front-hearted btw, and we recently had to drop an concrete raft down about 15mm (door and window supply and fit company fecked the job up royally, setting the front door down way too low to the slab as it was too big, and when I laid a tile down dry the front door wouldn’t open inwards as it was hitting 90% of the 9mm tile!). 

 

My mate came to the rescue, and did 2 days of grinding and smoothing out, over around 30m2 to feather it out. 
 

He told me we’re not friends anymore, and not to call him the next time 🤣.

 

Hire the big machine for a day, try and area that you can sacrifice as a tester, and then remember you’ll need the smaller detail grinder to do corners and areas that the big machine can’t get to. 
 

Beware that the upright machine will chew through the job at a much faster rate than the detail grinder, so don’t make those areas then a load of grief by going to far with the upright machine.

 

Mask anything such as skirting or units so as to not damage them, with Antinox sheets / other. 

How old is the slab. What self levelling concrete did you use?

22 hours ago, saveasteading said:

That's posh with the handle and standing up. That will do it rather quickly as a diamond grinder is OTT for that soft surface. But better that than struggling. 

Are you just smoothing it or taking a mm or two off?

Dust! You'll need masks etc and do you vacuum it up?

 

Whose decision was it to pour despite the rain? Or was it not forecast?

It's a very big decision to cancel a pour, so I appreciate the pressure to do it.

 

I'm trying to level the substrate flat, to allow the finish epoxy resin to not crack.

21 hours ago, Russell griffiths said:

You can get a handheld version 

get that fora day as a tester. 
 

what are you actually try to achieve. 

We have approx 90sqm so think a stand up version is advisable?

16 hours ago, Adrian Walker said:

How old is the slab. What self levelling concrete did you use?

It's about 18 months now. 

 

https://www.heidelbergmaterials.co.uk/en/ready-mixed-concrete/self-compacting-concrete

 

With reinforcement fibres, which I didn't ask for, but got.

9 minutes ago, Duncan62 said:

We have approx 90sqm so think a stand up version is advisable?

1000%

 

10 minutes ago, Duncan62 said:

 

I'm trying to level the substrate flat, to allow the finish epoxy resin to not crack.

Ok, so the concrete is not your intended finished floor?

Let's go back a step.

Are we looking at the surface of a concrete slab (lots of big stones in it) or a screed?

 

Are you simply looking to get it smooth enough for covering with resin, as prev response?

 

1. I'm guessing that the surface is a few mm of surface "fat" in jargon. That is probably quite soft. Have you tried scratching or abrading it? If so, it will grind off very readily. You do not want a heavy duty grinder that can smooth the concrete with stones in it.

2. The fibres will look ugly but won't affect the surface you put over it.

3. Unless the resin is very hard and inflexible it should flex if necessary, but the crazing is almost certainly static now.

Ask the resin supplier.

How thick will the resin be?

1 hour ago, Nickfromwales said:

Ok, so the concrete is not your intended finished floor?

Given they put fibres in it when not asked to, I don't think I can grind and polish that. 

 

I'd prefer concrete finish but have got over it now.

You can grind it but the fibres will show.

5 minutes ago, saveasteading said:

Are you simply looking to get it smooth enough for covering with resin, as prev response?

 

Yes, due to the fibres in it.

 

Some of the tamping marks are 10mm high. Theses are hard. Other areas of the surface is quite soft and powdery.

Try a cold chisel or an old screwdriver. I reckon they will bash in a few mm... so it is  soft as far as grinding is concerned.

"After preparation the surface should have a fine-micro textured appearance with the aggregate visible."

 

Is manufacture recommendation before applying resin product.

 

 

Morning @Duncan62

Were you expecting the self levelling concrete to be your final flooring or adding another layer?

I sense that a concrete surface was / is your desired outcome.

If you have the time and energy I would recommend you do a test with a grinder.   The grinding discs or pads are the costly part.

I made some concrete worktops with fibres, lots of wet grinding and very pleased with the outcome.