Jeremy Harris Posted September 20, 2017 Share Posted September 20, 2017 (edited) It looks odd to me, too. One thing that springs to mind is that I remember once, years ago, mixing up some concrete that was far too wet, and as I tried to level it out something like this happened. I think that what happens is that when tamping it down, if it's got too much water in it the aggregate and cement sink and the fine sand floats up, with a lot of water. You then end up with a very wet surface, that "dries" to a slightly shiny finish, might well develop surface cracks and is very weak because there isn't much cement in it. Not sure if this is the case, but the shine in the top photo makes me suspicious. There are others here that know a heck of a lot more about the practical stuff relating to laying concrete - I only know a bit about the chemistry of the stuff really - and with luck they might chip in and say whether or not too much water in the mix can have this effect or not. Edited September 20, 2017 by JSHarris Link to comment Share on other sites More sharing options...
Crofter Posted September 20, 2017 Share Posted September 20, 2017 Agreed, you can get this if you over-vibrate or otherwise work the concrete, it settles out too much with all the fines and water coming to the top forming a very weak crust. It'll need chipped back to something solid. Link to comment Share on other sites More sharing options...
Nickfromwales Posted September 20, 2017 Share Posted September 20, 2017 This guy has an unenviable task ahead of him. When is he due back on site as this removal needs doing sharpish before it gets much harder? That friable top crust is not good. Those areas will need to have copious applications of very weak primer / water mixes, saturating the area so it penetrates as far as possible BEFORE any levelling takes place. Link to comment Share on other sites More sharing options...
oranjeboom Posted September 20, 2017 Author Share Posted September 20, 2017 (edited) Thanks @JSHarris , @Nickfromwalesand @Crofter. Probably not what I wanted to hear though. There are two main sections where it's 'gone bad', both of which were supposed to be approx 85mm depth in A142 mesh with UFH tied to that. The slab is not meant to be structural, just a final finished floor. Where this concrete was poured the makeup is: 85mm concrete Elevated mesh with UFH DPM (purely to stop concrete contacting the celotex) Celotex Radon barrier EPS 150mm re-inforced piled slab Just rang the supplier and it was c25 concrete that was poured. No poker was used. Expect it was just due to these areas being too wet and he should have ensured that the mix was drier. Although it was an internal pour, there was planty of ventilation through open doors and gaps around the windows (they're all hung externally of the reveals if you're wondering!). Other areas of the house were all EPS insuation so I did not bother with a barrier on top of the insulation layer. The builder did mention that he noticed the difference with the water coming up more on the areas where I had the DPM on top. And it's these areas that have been affected. I may call the building inspector out also, to hopefully get agreement from him also that this needs to be rectified then. Just wary of this crap concrete being gouged at with the UFH pipework!! I'm hoping it's not crap all the way down to the pipework and that hopefully just the first 20mm or so. Area in lounge: 1.5m x 2.5m: Not too difficult for a bit of graffiti: Bedroom area 2mx2m Edited September 20, 2017 by oranjeboom Photo Link to comment Share on other sites More sharing options...
Nickfromwales Posted September 20, 2017 Share Posted September 20, 2017 How long since the pour, and you being able to mark the slab with 'text' ? Link to comment Share on other sites More sharing options...
Onoff Posted September 20, 2017 Share Posted September 20, 2017 I'd be more worried about the dining room: Link to comment Share on other sites More sharing options...
oranjeboom Posted September 20, 2017 Author Share Posted September 20, 2017 27 minutes ago, Nickfromwales said: How long since the pour, and you being able to mark the slab with 'text' ? Pours were over 2 days (last week Mon/Tuesday). And graffiti appeared this morning (easily with a bit of slate). Creating @Onoff's beach scene this afternoon. Link to comment Share on other sites More sharing options...
Onoff Posted September 20, 2017 Share Posted September 20, 2017 Theres no magic concrete hardener out there that works is there? Over on my post there's all those SBR recipes for concrete repair mixes. Link to comment Share on other sites More sharing options...
Nickfromwales Posted September 20, 2017 Share Posted September 20, 2017 Repairs can only be over a solid substrate Link to comment Share on other sites More sharing options...
Nickfromwales Posted September 20, 2017 Share Posted September 20, 2017 Oh, and if it was the promised 35 mix you'd probably not be in such a bad shape. Over working or over wetting the 25 mix would magnify the problems. Link to comment Share on other sites More sharing options...
Declan52 Posted September 20, 2017 Share Posted September 20, 2017 By any chance where they running low on concrete and threw a load of water in to the mixer to spread it out. How deep can you push a pencil/pen into it??? Link to comment Share on other sites More sharing options...
oranjeboom Posted September 20, 2017 Author Share Posted September 20, 2017 1 minute ago, Declan52 said: By any chance where they running low on concrete and threw a load of water in to the mixer to spread it out. How deep can you push a pencil/pen into it??? This was the first area that was poured. I just think the mix was too wet and seeing that they weren't able to spill the wet over the side of the slab like you would over a conventional slab where you have no walls/doors yet, meant it just sat there, creating an area of pooled water. He may have spec'd a wetter concrete as he knew I wanted this to be my finished layer (bamboo straight on top). Also meant that it was easier to push around. Can't really push a pencil into those areas. With a lot of effort you can push a screwdriver a few mm into it. It's very similar to limestone. Link to comment Share on other sites More sharing options...
jamiehamy Posted September 20, 2017 Share Posted September 20, 2017 11 minutes ago, oranjeboom said: This was the first area that was poured. I just think the mix was too wet and seeing that they weren't able to spill the wet over the side of the slab like you would over a conventional slab where you have no walls/doors yet, meant it just sat there, creating an area of pooled water. He may have spec'd a wetter concrete as he knew I wanted this to be my finished layer (bamboo straight on top). Also meant that it was easier to push around. Can't really push a pencil into those areas. With a lot of effort you can push a screwdriver a few mm into it. It's very similar to limestone. How big an area? Was it pumped in? Link to comment Share on other sites More sharing options...
oranjeboom Posted September 20, 2017 Author Share Posted September 20, 2017 12 minutes ago, jamiehamy said: How big an area? Was it pumped in? Yes, all pumped in over 2 days. 150sqm. Affected areas are around 2-3sqm (see pics above) and are only those areas that had DPM directly on top of PIR. The other areas (bare EPS) had capacity to absorb more of the 'wetness'. Moderators @Nickfromwales: It may be worth moving these last few posts from here onwards as they relate less to UFH and more onto my latest headache/fiasco. Link to comment Share on other sites More sharing options...
jamiehamy Posted September 20, 2017 Share Posted September 20, 2017 Hmm, if it was one area only, I would suggest that the pump crew did not dispose of the priming cement before pouring the concrete. When we were getting our pump done, I watched out for this and noticed that they were poised to fire the priming/hose grout cement in the walls until I told them to aim it over the side until the corner concrete came through. This would mean you have a small area of fairly weak mix of cement mixed with concrete rather than the spec mix. Not sure if it's this in your case tho. Link to comment Share on other sites More sharing options...
jamiehamy Posted September 20, 2017 Share Posted September 20, 2017 Sorry - if over two days then if it's two areas, see if they match where the pour started on each day. Link to comment Share on other sites More sharing options...
oranjeboom Posted September 20, 2017 Author Share Posted September 20, 2017 5 hours ago, jamiehamy said: Sorry - if over two days then if it's two areas, see if they match where the pour started on each day. @jamiehamy I was too busy rushing around looking after the UFH pipework inside to notice where they primed the stuff. However, I have no skip and there's nothing left on the front drive, so you may well be right with your thinking. They used at least 1 bag of cement to prime it each time (cleared up the rubbish afterwards). And where I have the issues is indeed in the same rooms that they started the pour on each day. Link to comment Share on other sites More sharing options...
oranjeboom Posted September 20, 2017 Author Share Posted September 20, 2017 Okay apart from potentially having to break up/scrape those crap concrete areas, I will also have to get the concrete depth reduced in many places. My laser tells me an average of 20mm needs to be removed in certain areas. How straight forward is that? How long would it take to reduce 1sqm by say 20mm? Something like this do the job? http://www.jewson.co.uk/tool-hire/concrete-cutting-equipment/floor-preparation/products/2045/floor-grinder-110v/ I'd probably need a hand held one for next to walls. Link to comment Share on other sites More sharing options...
jamiehamy Posted September 20, 2017 Share Posted September 20, 2017 3 hours ago, oranjeboom said: @jamiehamy I was too busy rushing around looking after the UFH pipework inside to notice where they primed the stuff. However, I have no skip and there's nothing left on the front drive, so you may well be right with your thinking. They used at least 1 bag of cement to prime it each time (cleared up the rubbish afterwards). And where I have the issues is indeed in the same rooms that they started the pour on each day. Hmm, that's a bummer. I reckon that's the cause. That grinder looks like what you need. Not used one but far better than handheld. Is a pourable self levelling compound an option here I wonder? @Nickfromwalesthe area is probably too big? Would be far easier and cleaner and quicker? Link to comment Share on other sites More sharing options...
Nickfromwales Posted September 21, 2017 Share Posted September 21, 2017 10 hours ago, jamiehamy said: Is a pourable self levelling compound an option here I wonder? @Nickfromwalesthe area is probably too big? Would be far easier and cleaner and quicker? Depends on what's left low after the grinding has been done TBH as only then will you be able to determine what's got to be levelled. It doesn't sound as if the whole area needs to be levelled so there shouldn't be an issue imo, but if it's over 8-10mm with any decent area then I'd probably change to the fibre-impregnated pourable screed / leveller so it can flex with the subfloor. That should stop the two parting company. Started ripping this out yesterday. Never seen a slab or levelling done so badly before. Shocking. Liquid screed laid so low by the doors that the first layer you can see coming up nearly half inch thick was used to get the floor raised. Then up to another half inch of tile adhesive to get the tiles flat. I still don't know how someone can get it so wrong TBH. ?? Neat flexiprime going on and then a decoupling membrane, then fibre levelling screed then adhesive. Imo it should be completely ripped out but it's got UFH pipes and I've only got 6 days to do it ? Get the prep right folks or you'll be doing it twice I promise you. . Link to comment Share on other sites More sharing options...
oranjeboom Posted September 21, 2017 Author Share Posted September 21, 2017 @Nickfromwales You've only got 6 days on that job and then? You're coming to sunny Kent to sort out my mess?? 15 minutes ago, Nickfromwales said: Get the prep right folks or you'll be doing it twice I promise you. I had my prep done alright - big red datum lines with the words "that is the MAXIMUM concrete level". Hope I've calmed down by the time he comes back. The only reason I got a 'professional' in was to get a level floor. Again, another job that I should have done myself, room by room. Slower, but at least I would have ended up with a better job and in the long run would have ended up being quicker no doubt by the time this is all rectified. @jamiehamy - I don't appear to have a chance but grind down the vast expanse by the 4.5m slider. See earlier post: My FFL will end up above my threshold, so this area and other high spots will have to be ground down. No other way I think. There will be some spots that will need self levelling applied, but the main job is to get areas ground down by up to 20mm. Link to comment Share on other sites More sharing options...
Dudda Posted September 21, 2017 Share Posted September 21, 2017 2 hours ago, Nickfromwales said: Get the prep right folks or you'll be doing it twice I promise you. . Hard to tell from the photos but it looks commercial. Would it be an old matwell they infilled? That means it's a localised issue and not the whole floor. Link to comment Share on other sites More sharing options...
Nickfromwales Posted September 21, 2017 Share Posted September 21, 2017 36 minutes ago, Dudda said: Hard to tell from the photos but it looks commercial. Would it be an old matwell they infilled? That means it's a localised issue and not the whole floor. Nope, it's some poor sods kitchen diner. A big conservatory company, who's name rhymes with schneverest, did a total botch. I get to put it right. Lucky me. Liquid screed over UFH and I think I've just got to grow a pair and dig the lot out, pipes n all. Feck. Link to comment Share on other sites More sharing options...
Nickfromwales Posted September 21, 2017 Share Posted September 21, 2017 4 hours ago, oranjeboom said: Nickfromwales You've only got 6 days on that job and then? You're coming to sunny Kent to sort out my mess?? Was up West Malling ( Laybourne? ) a while back fitting my B+SiL's bathroom. This one belongs to your builder. Maybe he laid the shat that I've having to deal with here I just cannot fathom out how they couldn't lay a bloody liquid screed level . It levels itself for crying out loud!!!! 1 Link to comment Share on other sites More sharing options...
Onoff Posted September 21, 2017 Share Posted September 21, 2017 5 minutes ago, Nickfromwales said: Was up West Malling ( Laybourne? ) a while back fitting my B+SiL's bathroom. This one belongs to your builder. Maybe he laid the shat that I've having to deal with here I just cannot fathom out how they couldn't lay a bloody liquid screed level . It levels itself for crying out loud!!!! My chiropractor's in West Malling...spitting distance! Link to comment Share on other sites More sharing options...
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