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Support for footing reinforcement 1

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IceNine

IceNine

Structural
Feb 24, 2006
282
At a recent visit to a job site, I was observing the reinforcement for a cmu cantilevered retaining wall with a concrete footing. The hooked dowels extending out of the footing were supported by tying an additional vertical rebar to each dowel, and embedding it in the earth.

This seems like a very poor practice in that it provides a path for water to enter the footing and corrode the reinforcement.

Should I make the contractor remove the embedded rebar and support the dowels with chairs or small cmu blocks? Anyone know of any articles addressing this concern?

Thanks

Ice
 
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Am I correct in saying that the footings haven't been poured yet? Then you noticed the dowels as you mentioned? I am not sure how much of a path this will create for water to enter the footing given that the footing is no more likely to crack at service loads with this sort of rebar support. As a general cost consideration I have to think it is more expensive to be throwing rebar into the ground to support rebar, rather than using chairs or small block as you mentioned above.
 
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We categorically reject any rebar supported this way that we find during our inspections. It is contrary to CRSI placing reinforcing standards and is downright stupid.

You should reject it immediately and have the contractor do it right.
 
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I would also say reject. he should be using rebar chairs or supporting the bars from above.
 
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I saw bars shown this way on the design for a school I reviewed recently. I didn't like it but was left wondering if there is an official position by CRSI which prohibits this practice.
 
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Technically it violates code.

In reality, unless the soil is very aggressively corrosive, by the time the entire length of rebar corrodes so that the rest of the steel can begin to corrode and cause a problem, the structure has probably lived its useful life anyway. I'd make them fix it since you saw it and it violates code and is another magnet you're wearing for liability.
 
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Thanks for the replies.

UcfSE- Where in the code is this prohibited?
 
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Contractors complained that chairs "sink" into base (compacted soils or aggregate), so I specified SOLID CONCRETE BRICKS for bar supports. The dimensions (I think 2.5-inch thick and 3.5-inch wide) of CONCRETE BRICKS do not provide 3-inch clear cover. Inspector needs to check clearances prior to concrete placement.

Good luck
 
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This situation has occurred for me in the past. I made contractors remove such bar supports and replace with either chairs or precast concrete bricks. Or, support the bars from above in some manner.
 
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It violates minimum clear cover provisions.
 
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If it is not reinforcement but merely support for the reinforcement do the cover provisions apply?
 
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i agree...it violates code, but as UcfSE states, in reality, it somewhat improbable to cause real problems. as a matter of practice, the contractor should do this. they could drive electrical conduit (since it doesn't corrode) into the ground periodically and then tie a horizontal bar above the top of and in the footing to tie the remaining vertical bars to. this should satisfy code and still allow the contractor to effectively secure his bars. i personally would make him fix it if it was more than just an isolated incident. if he doesn't want to do that, he could lay 2x4's across the top of the footing excavation then tie horizontal bars whereby he would then tie his vertical steel. it's really not any more trouble than driving pieces of bar into the ground...that's my personal experience as a contractor.
 
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imbedding the dowels into earth? am i reading that correctly? they can use bricks to sit the bars on.
 
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I've never let contractors get away with using brick or cmu.
As I see it they are porous enough to provide a path for water to get to the reinforcement, or at least compromise the concrete cover.
 
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CRSI allows the use of precast concrete bricks as long as the compressive strength is equal to or greater than the concrete being placed.
 
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It can cause problems with corrosion. The embedded bars form an electrical connection between the soil and the internal reinforcing bars. In some cases you can have an acidic soil and basic concrete which can create a galvanic cell resulting in corrosion.

I used to okay these sorts of things, but I have since learned that there can be problems with durability as a result.
 
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Concrete brick are compatible, but clay brick are a totally diiferent material with different long term properties.

Take a look at some of the reinforcement and spacing products available. They are not all thin wires that sink into the sand. There are a number of choices.

Poly Lock(sp?) has a complete line of supports for single and multiple layers at mutiple heights and many other very specialized situations. They are relatively open, but you can get some of them with a large enough footprint for granular or wet grades.
 
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