10" concrete slab or is it? 3

[jechols]

We have a project with an elevated 10" concrete slab. Before the pour the contractor put the reinforcing in on chairs then a layer of 1" conduits side by side and then a layer of 2" conduits side by side with no room for concrete to get to the bottom of the slab not mention the area of concrete being displaced. The slab has deflected and in some places the little bit of concrete that made it to the bottom of the slab is just falling off. Does anyone think there is any alternative but to remove all the concrete in the affected areas and start over. I personally think the contractor should of known better than to do this.

 

[SlideRuleEra]

jechols - What you describe is totally unacceptable, IMHO. In fact, it sounds like the slab is "telling" you this by deflecting (under only dead load, I assume). Suggest that you take it out.

If necessary, one way to handle objections from the Contractor is to have him hire his own Engineer (at his expense) to prepare and submit a report to you on why the slab is acceptable - doubt if that will happen.

To post images, go to a free web site like this

http://www.imagecave.com/

(there are many others)
create an account, upload the photos and link to them.

http://www.SlideRuleEra.net

 

[TDAA]

If I recall correctly, doesn't ACI require a minimum of 3 times the conduit diameter for the space between. It has been years since I dealt with that, but I had a similar issue. We had the contractor move than before the mud though.

 

[cvg]

The contractor should also hire his own engineer to propose the method of fix (if anything other than remove and replace). Why should you have to spend your time telling him how to fix his mistake, or take the liability for some sort of remedial repair?

 

[Bagman2524]

ACI 318-99 Chapter 6:
Conduits shall not significantly impair the strength.
Conduits OD shall not be larger than 1/3 overall slab thickness.
Conduits shall not be spaced closer than 3 diameters or widths o.c.

 

[Ingy]

jechols, I'm curious, what did the electrical drawings show? Do they show those conduits routed together in the slab? Was there an inspection prior to concrete placement, e.g. a pour card? It is easy to blame the contractor, and maybe he is at fault, but it is also easy for an engineer or drafter to cram a bunch of lines on a drawing. Without drawing them to scale, the lack of space is not apparent.

 

[SlideRuleEra]

Here is a photo of jecheols' slab

http://www.SlideRuleEra.net

 

[cvg]

it doesn't look like the reinforcing stayed on the chairs...

This is incredibly amateurish, I can't believe this was a licensed contractor!

 

[Ingy]

Classic, thanks SlideRuleEra for the photo. As they say, a picture is worth a thousand words...

A smart contractor would have submitted an RFI because this was discovered while making a lift drawing. A regular contractor would have called the engineer out after the conduit went in and said "what do you want me to do now?" An incompetent contractor would do what was done.

Rip it out and fix it. No extra money, no extra time, just get it done and done right.

 

[Zambo]

I don't think "ripping it out" will take very long. It also looks as if the waste of concrete will be minimal (as hardly any was used in the original cast)It is a clear cut case of demolishing and starting again. The question I have is where are all those conduits going to go next time - spacing at 3 x diam doesn't seem to be the answer!

 

[Ron]

If that much conduit is required, it should be in a separate chase or use a false floor above the structural floor.


I agree...this should come out and start over.

 

[Ron]

I was too quick on the button!!...

If the conduits are anywhere close to the design, this is a case of design/construction incompatibility (constructability issue). If not, the contractor needs a new superintendent.

 

[jechols]

Thanks for everyone's comments!

Ingy,

Apparently the electrical conduits for all the floors go down until the floor in question and then travel horizontal thru the slab to a chase. The electrical drawings do not indicate this. You would think the conduits for each floor would travel through the slab at that level to a chase.

Again thanks everyone for your comments!

 

[samdamon]

Regarding the picture, Yikes!!

 

[TDAA]

OMG!

Who thought the concrete would get to the bottom of that?
I would be woried about the quality of your inspector, as well as your contractor!

 

[DTGT2002]

I would hope this slab is receiving some additional support/shoring for the intermediate time as who knows its actual structual capacity.

Prop that thing up!

As a side note, I have encountered many drawings, electrical or otherwise that refer to equipment to be installed by others with no grasp of the actual size of the embedded items. It can make a very fuzzy case with regard to responsibility. Ingy hit it on the head with his comments above. It never should have gotten this far...

Daniel

 

[archeng59]

just curious: was there a drawing or detail on any MEP or architectural drawing showing the conduit in the slab? why would the contractor choose to do this? because he always did it in slabs-on-grade? I would consider this contractor as inexperienced in elevated structural concrete construction. that's not a desirable condition.

 

[FSS]

Wow! Maybe they were trying to create an "aggregate filter."

That is one amazing picture.

 

[UcfSE]

Given the magnitude of the DUH in that picture, it's scary to think about what you haven't heard about or caught yet!

 

[JAE]

heh - hey UcfSE - do you suppose that CSI will begin to establish a DUH section in their standard specifications!

SECTION 01083
DUH AND OTHER STUPID TRICKS