concrete column retrofit 3

[NGW]

A client needs to fix a failing concrete column. The problem is corrosion. It appears that moisture from a very humid indoor environment has started corrosion from the bottom and is working its way up the column. The bottom 18" of reinf. is severely corroded, allowing the column to crush and spawl. I was thinking of removing the damaged material and encasing the lower half with a reinforced concrete jacket. It's 14" diam., about 8' tall, supports a concrete beam and is on a 48" sq. pad foundation. It's in a utility room. Using the pad dimension to assume the column load, the column design seems to be more that adequate. It's not part of the lateral force resisting system. The plans provided aren't enough to determine the applied loads.

'Anyone have advise?

 

[csd72]

The development length on epoxy bars is much greater, I believe ACI requires twice the development length. May not be an issue but needs to be considered.

There are proprietary sacrificial anodes that can be embedded into the concrete to avoid the above mentioned corrosion. Once again I would recommend you seek advice from a reputable manufacturer.

 

[RHause]

look into Delta Structural Technology - they perform concrete repairs using various forms of fiber wrapping. good luck

 

[InDepth]

NGW, sorry for the late response.

On preping I would recommend chipping to sound concrete and then coating the surfaces with either a latex bonding agent or a epoxy based agent. I use SIKA products for these sort of repairs, like Sikatop 123 and Sikadur. You'll need to consult their spec sheets for application. Sika also has epoxy products for coating the reinforcement which has corrosion inhibitors in them. Ferroguard is the pucks.

Use Guide.

http://www.sikaconstruction.com/con/construction-applicationguide.htm

http://www.sikaconstruction.com/con/construction-factsheets_in_construction_name.htm

http://www.sikaconstruction.com/app-cpd-mortars-us.pdf

yes, be careful with using epoxy coated bars and pucks...you may just shift the corrosion problem to another part of the structure....maybe even right next to the repair. I highly recommend finding out what is causing the corrosion.

 

[InDepth]

Oh, and since it is a pool area, you may want to find out the depth of chlorine penetration into concrete. I would recommend placing a new flooring or concrete sealer to mitigate further chlorine penetration....but you have to be careful not to lock in moisture and chlorine under the sealers...because this may even accelerate corrosion.

 

[NGW]

Thanks InDepth,

Your advise has been helpful.

I think I'll recommend finding an expert in this field for the corrosion investigation and mitigation. I lack the expertise.

 

[csd72]

NGW,

The manufacturer such as Sika will give you the options, but it will still be up to a structural engineer such as yourself to do the final specification as it needs to be structurally adequate.

The structural adequacy you understand, the chemical and durability considerations will be addressed by their rep. I see no need for you to offload it to someone else.

Also, manufacturers like Sika usually have a list of approved repairers who know what they are doing, so the site work should not be an issue.

 

[csd72]

An interesting link I came across:

http://www.arup.com/_assets/_download/download192.pdf