Old and new concrete bonding

[jambouk]

Revised idea for my outdoors pier. There are two options.

1. This plan would be to shorten the existing steel pole which is hollow, and then place a 10-12" pipe around that with the existing pole in the centre, and then fill the hollow pole and the rest of the pipe with new concrete to the desired height, and then set threaded bar into the wet concrete to eventually take a universal pier adapter. But how to best bond the old and new concrete? 

2. Find a steel pier which could tolerate living fully outdoors all year round and able to take say an EQ8 and C14. If there was room for the shortened pole to go inside the pier it could, else take the pole off to just below ground level (not easy but do-able). I presume the majority of piers available are meant to live inside observatories, not be fully exposed to the elements all year round.

Grateful for any ideas.

James

 

[Xsubmariner]

I would use a plastic pipe outer sleeve and you might want to consider drilling some holes in the steel inner to screw in some stainless steel screws to lock the concrete (prevent any possibility of outer sleeve rotating).

[Dr_Ju_ju]

I'd also echo the use of a plastic air-conn pipe, as they come in more usable sizes, and when filled with concrete are just as strong & robust. Also to aid the bonding of differing concrete slabs, rough\gouge the old concrete and add some external grade PVA to the mix... 

[Stuart1971]

3 hours ago, jambouk said:

Revised idea for my outdoors pier. There are two options.

1. This plan would be to shorten the existing steel pole which is hollow, and then place a 10-12" pipe around that with the existing pole in the centre, and then fill the hollow pole and the rest of the pipe with new concrete to the desired height, and then set threaded bar into the wet concrete to eventually take a universal pier adapter. But how to best bond the old and new concrete? 

2. Find a steel pier which could tolerate living fully outdoors all year round and able to take say an EQ8 and C14. If there was room for the shortened pole to go inside the pier it could, else take the pole off to just below ground level (not easy but do-able). I presume the majority of piers available are meant to live inside observatories, not be fully exposed to the elements all year round.

Grateful for any ideas.

James

 

I think your new idea, option 1, is perfect....and will be cheaper...but just as usable and strong... 👍😀

Edited September 12, 2020 by Stuart1971

[jambouk]

OK, so I am thinking a 10" diameter pier to ensure there is sufficient concrete around the pole and to really bond it all together with some rebar I'll put down into the slab beneath and into the pole itself coming outwards.

What qualities does the 10" diameter pipe need? I was just thinking of waste pipe like this stuff, and leaving it on after the concrete has set. Or are there advantages of taking the pipe off afterwards? Straight pipe of corrugated stuff? The fact I've not seen any corrugated piers would suggest straight pipe...

Thanks

James

 

[Stuart1971]

11 minutes ago, jambouk said:

OK, so I am thinking a 10" diameter pier to ensure there is sufficient concrete around the pole and to really bond it all together with some rebar I'll put down into the slab beneath and into the pole itself coming outwards.

What qualities does the 10" diameter pipe need? I was just thinking of waste pipe like this stuff, and leaving it on after the concrete has set. Or are there advantages of taking the pipe off afterwards? Straight pipe of corrugated stuff? The fact I've not seen any corrugated piers would suggest straight pipe...

Thanks

James

 

I would use a straight pipe, and leave it on, as long as it looks ok....as if nothing else it will add to the strength...and maybe even look better too.. 👍😀

[x6gas]

I couldn't find circular, rigid, plastic air-con pipe in anything bigger than 6" diameter.  I wanted 8" or 10" but now I've done the pier I don't think I would need anything bigger.  I poured the base (75 cm^3) and the pier at the same time, though, with rebar between the slab and pier and metre long M16 threaded bar sunk in from the top.

I've seen people using corrugated waste pipe for larger diameters.  Once the concrete has set you can always cut off the pipe and render it to get a smooth finish if you wish... and can be bothered.

[jambouk]

These lined cardboard moulds seem like a good option for me:

https://www.preconproducts.co.uk/products/monotub-dd/cardboard-column-formers

James

 

[inapottingshed]

You might want to consider adding a bonding agent to the mix, something like Everbuild SBR5L S.B.R. Bond 503.