Moonshine Posted June 23, 2021 Posted June 23, 2021 (edited) Pretty much as the steel work is in, the BCO has been out and checked it and is happy and looking to do my concrete slab pour on Friday. its going to b a 300mm concrete (RC32/40) slab with two layers of mesh (bottom layer is 100 x 100mm grid) in it with 50mm cover, which will be pokered I have a booking for the concrete, and have been asked what a slump i want. I asked the ground work who has said 70-80, and when i told this to the concrete supplier they said it was too dry and won't go through the mesh and should have something more like 120. having never poured a slab i don't know which one to go with, or just split the difference and get 100, any ideas This guide recommends a slump of up to 90 for slabs and industrial floors https://www.geargb.co.uk/productpdfs/Guide to concrete floor applications.pdf Edited June 23, 2021 by Moonshine
tonyshouse Posted June 23, 2021 Posted June 23, 2021 Pokered 50 slump will be ok , for pumped will need to be thinner but not 120, all the stones will sink to the bottom 60 for me
Haylingbilly Posted June 23, 2021 Posted June 23, 2021 If you are pumping it, I would definitely check with the pump supplier.
Nick Laslett Posted June 23, 2021 Posted June 23, 2021 (edited) You have my sympathies. I had this exact issue with my foundation pour. 150mm slab with 200mm ring beam and thickenings, 1 layer of reinforcing mesh in the slab, 2 layers in the other areas, grade C25/30. The groundworkers said ask the Structural Engineer, they said it was up to the groundworkers! My understanding is that there is a minimum slump required for it to work with the pump truck, my supplier said that was S3, range 100 to 150, target 130. The ground workers seemed very happy with a slump of S3. Sorry I could not be more helpful. They did not have a poker. Edited June 23, 2021 by Nick Laslett
Happy Valley Posted June 23, 2021 Posted June 23, 2021 Just poured 28 cu meters of concrete this morning for our ground floor slab. Two layers of mesh plus L shaped rebar for the ICF. Slab is 280mm thick and used 190 C28/35 with Sika Water resistant additive.
Moonshine Posted June 23, 2021 Author Posted June 23, 2021 56 minutes ago, Andy brown said: If you are pumping it, I would definitely check with the pump supplier. its not being pumped, out of a mixer with conveyor for the first load to get to the back of the slab, and straight out of the mixer for the other loads.
Moonshine Posted June 23, 2021 Author Posted June 23, 2021 26 minutes ago, Happy Valley said: Just poured 28 cu meters of concrete this morning for our ground floor slab. nice, go on then where is your picture of your nice new slab?
Mr Punter Posted June 23, 2021 Posted June 23, 2021 1 hour ago, Moonshine said: its not being pumped, out of a mixer with conveyor for the first load to get to the back of the slab, and straight out of the mixer for the other loads. I don't think I have seen a concrete conveyor. Does it come with the concrete truck? Any pics?
Happy Valley Posted June 23, 2021 Posted June 23, 2021 (edited) 51 minutes ago, Moonshine said: nice, go on then where is your picture of your nice new slab? Th Edited June 23, 2021 by Happy Valley
Moonshine Posted June 23, 2021 Author Posted June 23, 2021 26 minutes ago, Mr Punter said: I don't think I have seen a concrete conveyor. Does it come with the concrete truck? Any pics? I believe its like these
Bitpipe Posted June 23, 2021 Posted June 23, 2021 I'd go with your ground worker's spec as they will be contractually responsible to you if it is incorrect. Get it in writing though. Are you ordering your own concrete? Any reason the GW didn't want to do that?
Ronan 1 Posted June 23, 2021 Posted June 23, 2021 Absolutely you want an S3 mix for a slab anything else is nearly unworkable and definitely wouldn't get through a pump. Target 120 ish and it's nice and workable, 70 slump is crazy low slump and will be damm near unworkable. P.s if it's going through a pump fell the plant you want a pump mix.
Ronan 1 Posted June 23, 2021 Posted June 23, 2021 Sorry only seen your using a conveyor ?. That's why the GW's are looking a low slump, can't run a high slump mix of a conveyor... Poor groundworkers ?
Moonshine Posted June 23, 2021 Author Posted June 23, 2021 36 minutes ago, Ronan 1 said: can't run a high slump mix of a conveyor... @Ronan 1 its the concrete supplier with the conveyor that is recommending the high slump of 120, so they must think they can convey it.
Ronan 1 Posted June 23, 2021 Posted June 23, 2021 Oh.. They must have a fast belt conveyor then so. Then in my humble opinion I wouldn't ask any of my concrete to pour a slab unless there was extenuating circumstances at anything less than 120 slump. It's unnecessary hardship that if you get hot weather and not enough help could facilitate a disaster. We pour circa 2000 -3000m3 a week at work as a rule. Chat to your GW's tell them what you've been advised in case there is some particular quirk to your slab but as I say if I said I was getting 80 slump concrete my crews would baulk at me ..... plus they will only end up flooding it with water to get it workable and weakening your concrete anyway 1
Moonshine Posted June 23, 2021 Author Posted June 23, 2021 19 minutes ago, Ronan 1 said: Oh.. They must have a fast belt conveyor then so. Then in my humble opinion I wouldn't ask any of my concrete to pour a slab unless there was extenuating circumstances at anything less than 120 slump. It's unnecessary hardship that if you get hot weather and not enough help could facilitate a disaster. We pour circa 2000 -3000m3 a week at work as a rule. Chat to your GW's tell them what you've been advised in case there is some particular quirk to your slab but as I say if I said I was getting 80 slump concrete my crews would baulk at me ..... plus they will only end up flooding it with water to get it workable and weakening your concrete anyway 120 it is then
Moonshine Posted June 25, 2021 Author Posted June 25, 2021 Slab laid, 120 slump, though the gw was complaining it was going off too quickly 2
markc Posted June 25, 2021 Posted June 25, 2021 If they complain its going off too quickly on a pour of that size its so they have an excuse for any imperfections or unevenness you pick up
Ronan 1 Posted June 25, 2021 Posted June 25, 2021 4 hours ago, Moonshine said: Slab laid, 120 slump, though the gw was complaining it was going off too quickly ??if he struggled to work it at 120 he'd have been in big trouble had he got it at 80 like he wanted.... I'm sure your just glad to have it poured, congrats ? 1
Moonshine Posted June 26, 2021 Author Posted June 26, 2021 On 25/06/2021 at 18:38, Ronan 1 said: I'm sure your just glad to have it poured, congrats ? Thanks, it's a big weight off my mind now it's done. Appreciate your informed help massively! 1
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