The cage is the wall. but the cage is not tied. the foam and plastic are not structural.

Posted By Roger R on 01 Jul 2013 07:15 PM
I appreciate all the comments very much. This 'to tie, or not to tie' question has been nagging me for some time. I'm still not quite clear how the vertices are held into place. I was at one job recently, and the contractor was just "dropping" the rebar into the empty wall... some were on the left side of the channel - some were on the right side.... some were slanted bottom left - top right & so on. How could they have made these vertices tight - in a correct place? In commercial building, "the cage is the wall", since concrete is a pretty weak material unless reinforced. I can not see 'why' in residential construction the cage would not be the wall, too....

If the contractor was dropping the rebar and leaving it crooked as you stated, then the problem is not with the ICF method but with the contractor.

Concrete is not "weak" as it is very strong in compression. The "weakness" of concrete is in tension, hence the reason for rebar.

Here is something to help you finally clear your worries:

Engineers have been using ICF structures in areas of earthquakes and the walls are 100% engineered strong and able to withstand earthquakes without any issues and all without metal wire ties. Engineers are signing off on designs without ties and they are not concerned.

Roger - it seems that either you have convinced your self or someone has convinced you that there is some magic about the crosses being tight or as you put it the vertices. This is incorrect. Concrete has tremendous compressive strength, rebar has tremendous tension strength. They need each other. Because the bar prevents the concrete from stretching, it pulls its share of the weight. It stops the concrete from stretching vertically and horizontally but the fact that the bars cross each other has nothing to do with it. Actually if the bars were an inch apart the wall would be stronger, however for convenience in open form work, to keep the bars standing, they are tied to each other.

When the contractor just dropped them in an empty cell, they provide the same tensile strength as when the are tied, however since the form holds them from falling flat, there is no need to tie them. The fact that they are slanted with in the confines of the 8" cell will not in anyway weakening their tensile strength, however if you watch a pour closely, the concrete tends to push the bar to the center, not that it makes any difference.

What is important is to make sure the bar is on the tension side of the wall. If you are pouring a basement that is backfilled, the bar goes on the inside of the wall so that when the dirt pushes against the wall, the bar will stop the wall from bowing in because it won't let the concrete stretch. If you are pouring above grade, the bar goes in the neutral position, i.e. the middle of the wall. If you are pouring a suspended slab, the bar goes in the bottom, again because the slab wants to sag and the bar will stop it.

If you always think of the which is the tension side and which is the compression side, you soon understand that how it is tied make no difference.

One more time: There is a gap between horizontal rebars.
Simply slide your vertical rebar between them.
It will not go anywhere.

There is a great network of experience here. It seems logical that the cage is built, when using wood forms, because there is no form or ties to hold the rebar - as you go. It also seems logical that the cage is far stronger and safer than floating rebar... otherwise why would commercial inspectors check the ties?

TexasICF is correct re non-contact lapped splices..... I have stood toe-to-toe with dozens of building inspectors on this one. The intersection between horizontal and vertical rebar is not a "lapped splice" so there is no requirement other than minimum concrete cover at that point.

What are you smoking today, Bruce? The compatibility of PVC with concrete has nothing to do with lapped splices in rebar. That issue may come into play when sleeving out the wall to pass utilities through, but certainly not regarding reinforceing.

Generally, the codes say "secured", not "tied", as most building inspectors assume. If your bar is secured per ACI 318 and has minimum concrete cover, you are fine.

I always suggest that lapped splices be placed in an "over & under" position, vs. side-by-side. This presents a smaller target for the concrete to hit, and lowers the opportunity for congestion to occurr.
DJB

Thank God you signed onto the forum, De'toxguy. Everyone was wallowing around in the darkness until you came along with the lantern of enlightenment.

Carry on, Bruce..... Give us the whole story on how a piece of PVC is going to disrupt a lapped splice in reinforcing. I seriously would like to know the basis for your assertion.

No dog in the fight here........

This is certainly becoming a P contest - love it.

Remember Sergent Joe Friday, "Just the facts"!!! Thus who has the facts, and can back those facts up.

I shall stay tuned.

OK. I watched a documentary on The Buddha last night and promised myself I would become a kinder person, so here goes: We're not talking about a lap splice, we're talking about catching the dowel with a vertical rebar. We're all about best practices at Polycrete. Concrete does not adhere to PVC, but it does adhere to steel. If you use a steel collar you get a more elegant solution. We don't like PVC and we don't like polypropylene. We like steel. It makes us feel good. Good and strong. Like Bull.

So when PVC sleeves are used for electrical conduit and other in-wall sleeves, does that create any problems?

Treat the sleeve as temporary formwork and knock it out when the concrete is cured.

The code commentary for IPC section 305.1 specifically mentions brass, copper, cast iron and steel as the only materials that are required to be protected from corrosion.
d

This from Concrete Construction mag:

A. According to Bernard Erlin, the principal chemicals in concrete that could conceivably attack plastics are calcium hydroxide, sodium hydroxide and potassium hydroxide. Erlin cites a table from Handbook of Chemistry and Physics stating that rigid PVC has excellent resistance to strong alkalies.

Reference

Bernard Erlin, "Embedded Metals and Materials Other Than Reinforcing Steel," Significance of Tests and Properties of Concrete and Concrete-Making Materials, STP 169C, ASTM, West Conshohocken, Pa., 1994, p. 179.

Maybe an easier way to think of this issue:

The rebar within a concrete wall that provides the strength is the bar that runs perpendicular to the force on that wall. In a basement, the backfill wants to push the wall inward (ie, if the force is too great for the wall, a complete failure would be in the form of a horizontal break along the length of wall). The horizontal bar only serves 2 purposes - to help control shrinkage cracks in the concrete and to hold the vertical bar at the tension side of the wall. This is why ICF product engineering keeps the horizontal rebar size/spacing consistent through all backfill heights/soil types, but the vertical bar is increased as backfill height is increased (ie, rebar cage is not needed).

As was mentioned earlier, tying the bar only serves to keep the laps from seperating too much (typically 1/5 of lap length to a max of 6"). Some forms allow for multiple bars to be locked into the same spot on a web, sometimes a non-contact splice can be used. The key is to keep the lap length/spacing within specs so the 2 lengths of rebar are still acting as though they are 1 continuous length of bar within the wall.

Also, Chris was correct in saying the vertical bar and dowels serve different purposed. Dowels provide shear strength at base of wall/footing, while verts provide strength against backfill, wind, etc. I would not place a PVC sleeve around the dowel, since this would prevent the concrete from being able to fully surround the dowel in concrete.

Excellent summary, ICFBdr.......all gospel from what I know.

We recommend that the length of any PVC sleeves not be included in calculating the over-lap ("development length) of the lapped splices. (d.bar x 40)
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