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Dowel Bar Placement

Dowel Bar Placement

Dowel Bar Placement

(OP)
A lot of times when we have L-shaped slab-to-grade beam dowel bars, the contractors prefer to "wet-stick" them during the grade beam pour, instead of the tying them to the grade beam rebar before the pour.

Is there any reduction in dowel capacity that should be taken if the dowel bars are placed in this manner?  Does ACI comment on the matter?  Any help would be greatly appreciated. Thanks.

RE: Dowel Bar Placement

There was another thread on this a while back.  ACI 318, Section 7.5 requires that reinforcing steel be in place and adequately supported/tied PRIOR to concrete placement.

Wet sticking is not a good practice.  Bond can be severely compromised.

RE: Dowel Bar Placement

I also notice contractors placing starter bars into wet concrete instead of tying them to grade beam reinforcement.

RE: Dowel Bar Placement

If its simply the bars to be bent down into the slab I dont see a problem if its done in a timely fashion. As contractor you have to make a judgement based on the spacing and whether or not the alignment is critical.   Just would have to make sure there is not too  much congestion in with the grade beam rebar.  A good contractor would have a template for the bars to rest on while the concrete hardens, otherwise it may be hard for the bars to stand in place.  A good example when it is acceptable to wet stick is when bars extend from the top of a foundation wall into the slab.  We always wet stick these bars otherwise placing and finishing concrete in the wall becomes very difficult and even dangerous.

Dont misunderstand me though, wall dowels in a footing should always be tied before placement.  I am just trying to point out that there instances it is acceptable to wet stick.   

RE: Dowel Bar Placement

I don't think there are any instances where it is acceptable to wet stick. ACI doesn't condone it at all.

The dowels from a top of foundation to a slab could be very critical bars necessary for the structure to perform as intended.  By wet sticking you are ensuring that you won't know at all what sort of development you have in the bars.

I know wet sticking occurs, but it is never acceptable in my book.

 

RE: Dowel Bar Placement

Piling on here...I agree with JAE...it is not an acceptable practice.  Keep in mind that if some type of failure occurs, it won't matter whether it was the cause of the failure or not...it just indicates that your practices are poor and that concept will be extended to all your construction.  It's hard to defend an unacceptable practice.

RE: Dowel Bar Placement

Well Ron piling on a bit but.... I've worked for contractors for over 20 years and I also don't see advantages for "wet sticking".

For me the main disadvantage is that you're mixing up the trades, steelfixers fix rebar and masons place concrete. Of course we have all had cases where a few starter bars are out of position and we have to find a solution. But is there really any evidence that "wet sticking" avoids this problem.

RE: Dowel Bar Placement

Just laziness on the part of the contractor.  

RE: Dowel Bar Placement

Whether or not there are advantages to wet-sticking, it is not an acceptable practice and should not be permitted.     

BA

RE: Dowel Bar Placement

(OP)
Thanks for the responses.  It certainly seems tough to justify  allowing it if ACI clearly does not condone it.

Does anyone know if the the masonry code address this issue?  Wet sticking is also commonly done for masonry wall reinforcement splices during grout pours.

RE: Dowel Bar Placement

Wet-sticking nice term. It usually happens been to several places already and seen their construction practices. Sometime s it gets you thinking where did they get this idea.

But I agree with Sir Ron that it's difficult to defend unacceptable practices when worst comes to worst.

RE: Dowel Bar Placement

Has anyone ever seen a failure or problem due to bars being "wet-sticked"?

I'm not defending the practice, but wondering how big a problem this really is?  I know it is done all the time.  With so many instances, shouldn't there be many examples of problems?

RE: Dowel Bar Placement

Have seen several times the bars are not properly bonded with the concrete probably they sticked it a li'l bit late.

RE: Dowel Bar Placement

I have never seen a failure resulting from wet-sticking because the practice is usually confined to dowels which are not under much stress...i.e. dowels from a footing to a foundation wall.  If the practice were used in highly stressed reinforcement, the experience could be different.

Theoretically, wet-sticking could be done so that proper bond is achieved between steel and concrete.  The problem is that the inspector cannot tell after the fact what technique was used and hence how good the bond is.

BA

RE: Dowel Bar Placement

I've seen loose dowels in hardened concrete - wiggled easily when touched.   

RE: Dowel Bar Placement

Probably placed when the concrete had partially set so that the concrete matrix could not flow evenly to the bar as with totally wet concrete.  I have seen the same thing over the years.

Mike McCann
MMC Engineering
Motto:  KISS
Motivation:  Don't ask

RE: Dowel Bar Placement

If the bars were loose in the holes and wiggled easily when  touched, one would not expect to be able to develop much  tension in the bars but they may be effective in providing a key of sorts.

BA

RE: Dowel Bar Placement

Yea - a key that the bars were an after thought of a contractor with a hangover.  shocked

Mike McCann
MMC Engineering
Motto:  KISS
Motivation:  Don't ask

RE: Dowel Bar Placement

I knew people would disagree with me.  What I will admit is that it does make the inspection process harder.  How can an inspector verify embedment lengths and the state in which the concrete was in when they were placed.  

In my typical example you are dealing with bars that have to bend down to slabs.  I cant tell you how many times i see rebar detailers draw this bar being being bent before concrete placement.  As if we are going to knotch our forms for every foot on center. Similiarly, when you are placing a 12" wall and half rebar sticking up 3' past the pour it makes it a nightmare for the pump operator or the guys and the operator on the bucket (cant lower bucket as rods are in the way).  Now if you have someone right after the wall is being topped off wet stick staight bars into the pour, is someone here going to say there is a problem with that?
 

RE: Dowel Bar Placement

Yes, I would say there is a problem with that.

BA

RE: Dowel Bar Placement

The bars need to be tied into place.  The reasons this is frequently done are:
1) ability to strike a flat surface with the screed, then insert dowels - just to make it easy.
2) the dowels do not have intersecting bars which can provide proper support to the free-floating dowels.

The solution is the addition of carrier bars to hold the dowels, and a bit more work at the screed.  Otherwise, you have to use a have a piece of formwork to support the exposed portion of the dowels.

Tolerance on embedded length is -1 or -2 inches, depending upon bar diameter.  If the bar is intended to develop tensile capacity, bond and development is critical, and this is only assured by proper embedded length and proper consolidation around the bars.  Bars need to be placed and tied to prevent movement prior to concrete placement to assure depth of placement and that vibration can be carried out in fresh concrete with the bar inserted in its final position.

John Turner CSP PE
CRSI Greater Southwestern Regional Manager

RE: Dowel Bar Placement

doka1 - yes I'd have a problem with wet sticking bars.  The issues you present (as roadblocks to pre-tied bars) are overcome in thousands of projects by competent contractors.

If you have proper slump concrete (not soup) then stabbing a bar into properly placed concrete creates voids around the bars, limiting the pull-out strength.  For a structural slab/beam system, these bars may be critical - taking stress and providing strength/stability in the assembly.

If so, then as an engineer, I cannot allow wet-stabbing as I KNOW that this creates uncertainty in my structure.

Contractually the contractor is required to bid and build the job per the drawings and specs - the drawings and specs will refer to "in accordance with ACI...".  ACI requires pre-tied bars.

RE: Dowel Bar Placement

I had a builder ask me on Thursday whether they can "wet-stick" the starter bars for the blockwork walls into the footing which I disallowed.

If the footing is 20" deep and the starter bars for the cmu wall extends 24" out of the footing, then the total fall of the concrete is 3'8" which shouldn't be a problem for placement of the concrete. Likewise if the starter bars are required at 16" crs then wouldn't it be easy to provide ties at 16" crs so the wall starter bars can be tied to the cage.

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