Civil Engineers - Concrete Beams

[bigtomjaguar]

Hello all, sorry if this is in the wrong place,

I am currently doing an OU engineering degree and have managed to secure a work placement with a civil engineering company that specialises in groundworks and foundations. As part of this placement, I'm helping to put together some operating procedures and would really appreciate any help/advice from any PH experts! (I apologise if any of my questions are obvious, but I'm just starting out.)

My issue is with concrete beams cast in situ so;

Is a blinding layer always necessary for beams (especially when the beam is being cast across piles)?

When using the vibrating pokers, are there any industry standards (depth and spacing etc.) that need to be adhered to?

Are there any techniques/practices that are used to ensure that the concrete, once poured, remains level as it hardens and any bolts remain in place at the correct orientation? (Or is it just a case of pouring it, checking it and hoping for the best?)

This isnt an urgent project but it is quite important to me so any help would be brilliant! And no jokes about vibrating pokers...

Thanks.

[Rovinghawk]

[quote=bigtomjaguar]

Is a blinding layer always necessary for beams (especially when the beam is being cast across piles)?
As once told to me: The sole purpose of blinding is to keep st off steel.

When using the vibrating pokers, are there any industry standards (depth and spacing etc.) that need to be adhered to?
Common practice is to get an experienced guy on the poker & leave him to it.

Are there any techniques/practices that are used to ensure that the concrete, once poured, remains level as it hardens and any bolts remain in place at the correct orientation? (Or is it just a case of pouring it, checking it and hoping for the best?)
Check the bolts immediately after pouring then walk away.

RH

[ALawson]

I know this is from Oz, but concrete behaves the same over here!

http://www.ccaa.com.au/publications/pdf/ConcreteBa...

Some useful stuff, the illustation about the over lapping zones of influence is good.

I would always use blinding, check the spec its probably specified by any decent consultant engineer.

With holding down bolts, make a template, check the dimensions, if it is a large size put breather holes in the top. Set out centre lines of grid on it and then position around displaced reinforcement. If possible set out the bolts first so that the reinforcement doesn't clash. Survey prior to, during and following pour prior to striking template.

Depending upon the size of the HD Bolts and the thickness of the baseplate make sure the bolts are vertical as the hole for the bolt is only 2mm greater than the bolt up to circa 24mm.

Depending upon the slump of the concrete use screed rails to control the concrete level, and what ever you do make sure that you cure the concrete properly.

Make some cubes (and then a few extra) just in case.

P.S. Do not PM me as I cannot send you any operational stuff that is already written.

Edited by ALawson on Tuesday 18th September 07:48

[bigtomjaguar]

That's fantastic! Thanks so much for your help.

[ALawson]

Oh, don't forget the cover on the base and sides of the pour, use correct spacers between the formwork and the reinforcement. On the base if you are using spacer block then don't lie it in long lines, break it into 300mm lenghts. Long lengths increase the chance of water ingress in cracks finding its way into the reinforcement.

Make sure all tying wire is outside the cover zone or the correct amount of cover isn't worth anything.

Check the the lap is correct on the reinforcement and if Eurocode design make sure that the laps are in the correct places. Obviously check the grade or reinforcement is correct.

If you are pouring and its less than 5 degrees make sure that the temprature is rising, forms and reinforcement are free of snow and frost (as well as the normal cleanliness checks), if required ask the batcher to add heated water to the mix (they may not sign the ticket off though). Make sure you wrap it up in blanket.

Spray some curing agent on the top like AdoCure.

[MP85]

bigtomjaguar said:

Hello all, sorry if this is in the wrong place,

I am currently doing an OU engineering degree and have managed to secure a work placement with a civil engineering company that specialises in groundworks and foundations. As part of this placement, I'm helping to put together some operating procedures and would really appreciate any help/advice from any PH experts! (I apologise if any of my questions are obvious, but I'm just starting out.)

My issue is with concrete beams cast in situ so;

Is a blinding layer always necessary for beams (especially when the beam is being cast across piles)?

When using the vibrating pokers, are there any industry standards (depth and spacing etc.) that need to be adhered to?

Are there any techniques/practices that are used to ensure that the concrete, once poured, remains level as it hardens and any bolts remain in place at the correct orientation? (Or is it just a case of pouring it, checking it and hoping for the best?)

This isnt an urgent project but it is quite important to me so any help would be brilliant! And no jokes about vibrating pokers...

Thanks.

1 - blinding ensures there is correct cover to the steel
2 - no standard but generally every 3/400mm until bubbles stop rising, nb over vibrating seperates agg from cement. not good!
3 - you might think about using a screed to keep level, but if its just a capping beam it may have a fillet which you can use? Bolts -as above. check pre pour, and post pour. fix before it cures! most cones have plenty of play in them, but in the past ive made templates out of ply for bolt clusters which have center lines both N-S & E-W - easy way to make sure that they are square rather than checking each bolt!

where possible, use precast.