Excessive Concrete Cover in Wall - Remediation?

[gmannix1000]

Hi All,

Have a 200 thick RC wall up through a six storey building and at ground floor level the contractor messed up the concrete cover. It should have been 25mm each face but at the bottom half of the wall we have 60mm on one face and 45mm on the other face, which is

What should typical remediation look like for something like this, as checking the calculation it would be required.

Thanks in advance if anyone has any advice or come across this before.

 

[Buddha01]

I guess the magnitude of the problem depends on whether the 6 storey's have been built as yet or the high cover has just been detected when surveying post striking? I've had similar before yes but with reasonably tall cantilever retaining walls and bridge abutments. You say the calculations need the bars closer to their original cover position, and I note 25mm is quite a low cover to specify, so that means it is a structural issue. I've tried things like re-analyzing with a characteristic concrete strength verified from a suitable number of site cube results, or cores extracted as usually better than the min. design requirement, and to include compression reinforcement in the resistance calcs - gives a little improvement but might just get you over the line. I've also had to drill and resin a run of additional bars into a footing in order to increase the wall thickness...break back new concrete....prepare face and recast for a wider section. This is not desireable and I appreciate this is not likely to be attractive to your Contractor. CFRP bonded to strengthen etc. or you review assumptions on the loading side. Not a great problem you've been asked (I hope very politely) to sort.

 

[hokie66]

What is the issue with the wall? In other words, what dictated the 25mm cover?

 

[dik]

Is this a doubly reinforced 8" wall? What is causing the reinforcement requirement?

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[KootK]

1) If you're feeling very helpful, you might use some of the more advanced concrete wall design methods in order to attempt to justify that the existing condition works. The tilt up wall folks use those methods are able to get surprisingly slender walls to calc out.

2) FRP reinforcement might be viable if you can solve the fireproofing issues sometimes associated with that.

3) If it would be architecturally acceptable to do so, a cost effective fix might be just adding 4" concrete thickness to the wall and a new layer of rebar.

4) You might attempt to study the wall as a four sided panel rather than simple spanning to make it calc out. If you need a stiff pilaster here and there to make it go, so be it.

 

[Greenalleycat]

The remediation entirely depends on what your problem actually is
Is it for some kind of cantilever capacity e.g. post-fire stability? Is it for midspan flexure for out-of-plane earthquake loading?

 

[MotorCity]

From a steel corrosion standpoint, too much cover is usually not a bad thing unless it gets really excessive to the point where you need to provide additional shrinkage and temperature reinforcing.

From another perspective, are the bars in the correct location relative to each other and the faces of the wall, or was the additional cover condition created by misplaced bars (i.e. the inner and outer curtains of reinforcement were placed too close together)?

Is the additional cover an issue because:

1. It adds additional weight to the structural?

2. It interferes with the finishes and facade?

3. Both, other?