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Placing concrete on 1:2 slope

Placing concrete on 1:2 slope

Placing concrete on 1:2 slope

(OP)
We have to place 30 000m2 concrete at a slope of 1V to 2H and the price is not fantastic.Consequently we want to try and place it without formwork, sliding or otherwise.In my experience unformed surfaces steeper than about 1v to 3.5 H cause problems with "bumping" as the bleedwater migrate to the surface and cause quick conditions or cold joints as the finishing is delayed too long or a poor wearing surface due to overworking.
Has anybody constructed something like this before.
The boss is adamant it can be done

RE: Placing concrete on 1:2 slope

It depends on what kind of finish you want. Concrete facing on the upstream side of rockfill dams can be placed using very low slump concrete, conveyor distribution and bunyan or vibrating screeds. On the other hand I don't think you'd want to screed spillway ogees or canal linings steeper than 1:4. Either way it takes some preplanning, trial concrete batches and a good delivery system to place and finish low slump concrete properly.    

RE: Placing concrete on 1:2 slope

Here in the USA we do this all the time, particularly at fill slopes for bridge abutments.

I've never seen anything special being used for it or special preparation.  We use a mix with about 8 sacks and a slump of no more than 3".  This is normally pumped as is the convention here only due to labor savings.  The overall area on the ground is broken into strips of about 4-6' and only alternating strips are poured on a single day.  When the contractor has the pumper out again for something else, he schedules the remaining strips to be poured.

Hope this helps.

RE: Placing concrete on 1:2 slope

You also need to consider the amount of reinforcing steel close to the surface, as this helps to keep the concrete in place while it is being placed.

We have successfully placed concrete on a 1 in 1 slope on a large pipe (6 m diameter) encasement job.  The mix design was carefully worked to a very low slump, and there was no surface finishing after the initial striking off.

RE: Placing concrete on 1:2 slope

(OP)
Thanks for the info gents.A bit more info required though.
krd,it is a waterway and the surface is steel floated. The trial panel 10m x 4m high x 1m thick was successful in that we managed to achieve the specified tolerances. It took however an inordinately long time to finish.
Qshake can you please give some idea on the rate of advance of the face on the abutments. I do not know how to place concrete with a free sloping surface at more than about 600mm high in 1hour  without it flowing during compaction.
On the thinner slabs (400mm) we place rebar at 100centres for the reason stated by RiBeneke

RE: Placing concrete on 1:2 slope

YEs, the slabs are generally on 2:1 slopes.  Two horizontal, 1 vertical.

the reinforcing in those slabs  is meshing and sometimes though not often a shear lug (or pavement lug)(concrete beam poured below the surface) is used to keep the slab from creeping.

RE: Placing concrete on 1:2 slope

(OP)
Thanks Qshake. It would appear that a very slow rate of advance is a given for thick slabs.

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