Beam screeder - Tamping

[potatoman]

Hi,I am using a double beam screeder with an engine for leveling a 5" deep concrete slab,can i get away with only going over it once

Thanks inadvance

[msh paving]

once will be fine , take it steady and keep some concrete in front of the front screed bar. if your not happy and it rides up run over it again , twice will give a better finish. MSH

[lutonlagerlout]

^^ also make sure you shuttering is solid
LLL

[TheRockConcreting]

There are much easier ways of screeding concrete than using a monstrosity like that. I get the impression people like the idea of using oversized cumbersome tools to deal with concrete because it makes them look like they know what there doing, and if it goes wrong they can blame the oversized tool.

If thats the only tool you have for the job i would take it apart so your left with just 1 screed bar, have a man at either end and just screed the concrete normally.

All this nonsense about you much vibe the concrete surface is crap, a bullfloat will clear any jagged agg and cream up the surface just fine.

[Brucieboy]

All this nonsense about you much vibe the concrete surface is crap, a bullfloat will clear any jagged agg and cream up the surface just fine.

Aren’t you forgetting one important issue – compaction, i.e. the removal of air voids from the concrete. Whilst a simple hand-dragged screed may be suitable for slabs up to 100mm, even possibly 125mm, anything thicker requires proper compaction. It also depends on the slump of the concrete.

The Department for Transport Specification for Highway Works (Volume 1 - Series 1000 – Section 1025) states that for hand-laid pavements, the concrete shall be compacted by vibrating beams with vibrating pokers used adjacent the side forms. Where the concrete is greater than 200mm thick (or less if necessary), internal poker vibration is required at points no more than 500mm apart over the whole slab – drawn in front of the vibrating beam. A bull float may be used for finishing (if necessary) followed by brush texturing. Hand tamping beams can only be used for short lengths, infill bays or tapers.

Volume 1 of SHW is accessible via http://www.dft.gov.uk/ha/standards/ghost/mchw/vol1/index.htm and Volume 2 - Notes for Guidance – Series NG 1000 - Section NG 1025 – via http://www.dft.gov.uk/ha/standards/mchw/vol2/

You may argue that this method is applicable only to highway construction, but the vast majority of external concrete slabs I’ve been involved with over the years, i.e. big shed car parks, urban roads etc, the contractors have used vibrating beams in one form or another. For large internal slabs, it’s usually been high slump concrete followed by laser screeding then power-trowelling.

To generalise that the use of a vibrating beam is unnecessary and crap is not applicable to all concrete slab work.

[msh paving]

^^^^^That seams the proper way to lay concrete brucieboy,
compaction is one off the most important steps in concrete laying,if not done it will crack and give a poor quality job
MSH

[lutonlagerlout]

I like the twin beam screeders
LLL

[mickg]

why would anything go wrong Jay when you using the correct tools for the job - vibrating beam screed and a powerfloat ?

[msh paving]

Another point is not to take a hired tool to bits and use it that way as it will cause lots of charges from hire co. MSH

[TheRockConcreting]

Aren’t you forgetting one important issue – compaction, i.e. the removal of air voids from the concrete. Whilst a simple hand-dragged screed may be suitable for slabs up to 100mm, even possibly 125mm, anything thicker requires proper compaction. It also depends on the slump of the concrete.

Bruce I'm sure you know that vibrating the surface does nothing for the body of the concrete, i always recommend vibrating concrete over 125mm with a high frequency poker with a head size of at least 45mm, slabs that or under its not needed as the simple act of walking in and raking concrete will compact it plenty.

Screeding with a screed bar promotes flexibility to handle concrete on many different situations, slabs are not just long bay pours, in fact its actually better to pour a continuous slab than split it into bays.

The screed the OP is suggesting is a cumbersome bit of kit, i am simply pointing out there are much easier ways to go about it.

My experience in the industry is vast every thing from laying, pumping, batching to even dabbling in mix design. There's not alot i ain't used when it comes to tools for concreting, and I've seen been 100s of epic fails whilst working on the pumps from untrained contractors trying to have a pop at laying concrete.

[Brucieboy]

Bruce I'm sure you know that vibrating the surface does nothing for the body of the concrete

Jay, I disagree with your statement. Surface vibration will, without doubt, adequately compact a slab up to 200mm thick providing enough surcharge is maintained ahead of the beam(s) at all times and the concrete is of the correct slump. The use of a vibrating beam also provides a flat surface that enables finishing to take place with minimal effort.

As I’ve said before, edges will require additional compaction with a poker and, where the slab is over 200mm thick or it’s heavily reinforced, additional vibration with a poker is needed to supplement (not replace) surface vibration. You can of course use a poker at thicknesses less than 200mm if considered necessary.

The British Ready Mixed Concrete Association (BRMCA) guidelines on compacting concrete state that for slabs of 150mm or more, a vibrating beam should always be used – see http://www.brmca.org.uk/documen....008.pdf

The Cement, Concrete & Aggregates of Australia (CCAA) guidelines on compacting concrete slabs are similar to the above – see page 5 http://www.concrete.net.au/publications/pdf/Compaction.pdf

I agree that slab thickness of 100mm (possibly 125mm), which are more typical of the DIY market, don’t generally require the use of a vibrating beam. Hand tamping / screeding, raking and walking on the concrete is normally sufficient to provide the necessary degree of compaction.

[GB_Groundworks]

the twin beams are heavy and cumbersome use the smaller hand held vibrating screeds or a roller striker, if using a twin beam need to be on well staked road forms or serious shuttering as itll shake it to bits

[lutonlagerlout]

we have used 8 by 2s with the twin bean before with success
obviously an element of can do vs experience on this thread but for a diyer a twin bean should work wonders
LLL