Thanks for the input,
Having researched the major constituents of both GGBS & CEM1 the only thing that comes close colour-wise is the Iron Oxide in the cement. Once the concrete goes off, the black staining seems to disappear.
The finished surface looks very dusty which ties in with the...
Thanks for the replies.
No fly ash in the mix, almost none existent in UK nowadays since all coal power generation has ceased. Also no microsilica, so as far as powder addition goes it's OPC + GGBS only.
We have had instances on this project where lignite has been present in the dredged...
Hi,
Can anyone confirm what the black material is on the attached photo.
Photo taken after finishing of basement floor slab. It's a blended CEM1 & GGBS F5 flow mix which, upon inspection of the placement records, was regularly in excess of maximum flow limits and hence exhibited excessive...
Thanks for the replies,
The particular circumstance is a raft slab pour approx 1.2m thick with an high density of rebar in the bottom 500mm with no room for vibrating pokers. The get around has been to specify SF2 self-compacting concrete for the bottom 500mm reverting back to the original F5...
Just one other point to mention, the water/cement ratio is calculated on the amount of free water in the mix and does not include the absorbed water in the sand and aggregate.
As mentioned previously there is no EN standard for mix design as such, the closest you will get is BS-EN 8500.
Hi,
I have come across a few instances where different grades of concrete have been placed during the same pour opearation, eg C40 concrete for the main slab & c60 concrete below where the columns will sit, also similar with waterproof & non waterproof mixes. The latter presumably being most...
