Tieing levels

[Big Neil]

Morning one and all. For anyone who has already poured or are planning to for this construction type, in stages, have you employed a mechanical method to tie in one pour to the next, such as bar poked into the top of one pour which would then come through into the next?

[Russell griffiths]

In the first pic these bars are not just pushed into the wet concrete, they are actually resin set into the foundation, and the concrete poured around them. 

Random placing of rebar was dictated by window openings and small pillars of wall between windows. Has your structural engineer not specifically asked for anything, 

i put 16mm bar at the sides of all openings and at 1200mm spaces, if a small pier 3-400mm I have 2 vertices as you can see in first pic. 

 

We have just just done our first pour at 2.7m above ffl and installed 12mm bar at 1m centres around the whole perimeter, but changed this out for 16 mm bar at window reveals for the second lift. 

Hope that makes sense. 

Edited December 28, 2018 by Russell griffiths

[Big Neil]

bang on taaaaaaaa

[Vijay]

SE said I needed 600 bars every 600, 300 in and 300 poking out

[Big Neil]

Seems like a prudent thing to do even if the SE doesn't require it. @Vijay other than around the openings and as you have described above, are you throwing any reinforcement at it. I know polarwall don't require it, but I can't myself get away from thinking that there's no harm in (figuratively speaking of course) throwing some in there, with the guidance of an SE, as a belt and braces approach.

[Vijay]

nope, only on the joins between pours and to make lintels

[Big Neil]

I guess for me it's just another of those things I need to get over. I'm just struggling with it at the minute because I can't picture a circumstance in which concrete might crack but i'd be ok with it. Also no-one seems to use micro-rebar much over here where it seems a bit more widespread across the pond.

[PeterW]

2 minutes ago, Big Neil said:

Also no-one seems to use micro-rebar much over here where it seems a bit more widespread across the pond.

 

They do - they just don't call it that !!

 

Micro-rebar has a number of trade names over the pond, Helix being one of them. They are essentially stainless needles that get mixed into the concrete at the final mix, and are in certain circumstances a replacement for rebar. Over here, if you ask for fibre reinforced concrete then you may get either stainless needles or fibreglass needles in the mix.

 

The key reason for it not being used as much in structural elements such as ICF is that you cannot guarantee the mix for strength purposes. For example, it is assumed that when you chuck 4 boxes of fibre into an 8 cubic metre concrete load, that they become evenly spread through the mix resulting in 1/2 box per cubic metre. If you analysed the concrete you may find this is far from the truth as they tend to bunch and thicken the mix slightly, so box 4 will not be as evenly mixed as box 1. With that being the case, you can't guarantee the strength and therefore the rebar has to stay.

 

In a ground floor slab, not having a perfect distribution isn't an issue as long as its there or thereabouts. Now change that to a wall structure, and the cold joint between the two pours is virtually flat - there aren't 10,000 little fibres poking up so the mechanical jointing between the pours nears zero. Also, fibre reduces the flow characteristics of concrete so filling with fibre reinforced is more difficult.