Casting concrete beams

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Casting concrete beams

This topic has 9 replies, 7 voices, and was last updated 3 November 2010 at 18:07 by Jeff Dayman.

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2 November 2010 at 12:00 #21747
John Lawson
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@johnlawson61116
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2 November 2010 at 12:00 #57996
John Lawson
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@johnlawson61116
Does anyone have any experience of casting steel reinforced concrete beams, we wish to replace the wood beams on our raised track with something more stable and would welcome any guidance as regards mix, casting etc.

Thanks

John
2 November 2010 at 17:26 #58007
Peter Tucker
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@petertucker86088
Hi John,

What size are your beams and what loading are they going to have?

Peter.
2 November 2010 at 17:37 #58008
bricky
Participant
@bricky
Hello John.

The size of the beam and the length is a factor.

If you have access to a machine to lift the beams then they can be cast in shuttering on the ground.If not they will need to be cast in situ in a supported shutter.

The mix for concrete for beams (shovels)10 gravel 5 Sharp sand 2 cement or if it is mixed ballast I use 7 ballast 1 cement.

The reinforcing bar needs 2 longitudal rods top and bottom with bar bent into a square at 300mm centres tied with wire to the 4 rods to form a cage.Keep the cage 25mm up from the bottom/side&top .Hire a vibrating poker to remove the air .Hope this helps

Francis
2 November 2010 at 18:50 #58011
Nicholas Farr
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@nicholasfarr14254
Hi John, Francis mix seems a little weak to me. The info I have gives a general purpose mix of ballest otherwise knowen as pre-mix of 4 to 1, however if it is out in the weather it would want to be a paving/driveway mix of 3.5 to 1. I have not got any info on a structual beam, but I would think it would have to be at least as strong as a driveway.

Regards Nick.
2 November 2010 at 19:52 #58015
Brian
Participant
@brian
Sounds like a lot of hard graft to me.

This link http://www.mexboroconcrete.com/brochures/ebeamsbrochure1.pdf may solve the weight and construction time problem for the straight section of trackway.

This would leave the curved section to be cast insitu, but it could cut out a lot of back breaking work.

Just a thought.

Regards Brian

No connection with this company, Honest.
3 November 2010 at 10:44 #58051
John Lawson
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@johnlawson61116
Hi Paul

As the beams are a direct replacement for the existing raised track they are 1.8mtr long 200mm wide and we proposed to make them fishbellied shape from 100mm at the ends to 200mm in the centre with 2 lengths of rebar in the bottom section.

As for loading ? how many fat people can you get on the 1.4mtr free span.

We will cast these on site and lift them in so we can keep the track available for use we have about 100 to produce.

John

Edited By John Lawson 1 on 03/11/2010 10:49:55
3 November 2010 at 11:40 #58054
DMB
Participant
@dmb
Do you have to have concrete beams? Many tracks have A shaped support pillars topped by all sorts of beams including wood. Worthing Model Engineers use 2 channel steel sections laid on sides with the `bottom` of the channels back to back. I dont know how the beams were bent. The passenger car bogies (cast ali. – frem) have an outboard steel drop – arm bolted on with a right – angled stubby bar which travels inside the channel, but not normally touching it. This arrangement serves as a very effective anti – tip device. I am anformed that the track was not originally planned in this way and that a member responsible for devising the anti – tip thought up this simple brilliant solution.

Solving the channel bending prob. would make a simple system for other tracks without recourse to many additional bars and tubes of steel added on under the track with the increased difficulty in grass cutting under the track.

Just a thought but hope it helps someone.

John.
3 November 2010 at 11:42 #58055
DMB
Participant
@dmb
Sorry, can spell! Previous post said “cast ali. frem” but this was meant to be “frame”,
3 November 2010 at 18:07 #58073
Jeff Dayman
Participant
@jeffdayman43397
Just FYI For the strongest possible concrete I have found a mix as below works best:

3 parts crushed 3/4″ stone

2 parts sharp sand

1 part cement

Use minimum possible water. If you can get some chemical plasticizer and air entrainer it will increase workability while using less water.

Good luck. JD
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