Broken Concrete Footing Can Being Repaired? 1

[allanex50]

Proposed 4-story Building is supported by isolated footing rest on Bored Piles. A newly concrete footing was found to be inadequate due to low strength test results, so the consultant decided to remove the concrete. However, our project manager refused to do so, instead, he proposes to remove only portion of the concrete that seems weak which is located 1/3 of the thickness upper part of footing to keep lower part remain. Then using special cementious material and adhesive chemical and fill up concrete up to the required level. My question is, Does it satisfy to rectify the structural integrity of the footing? Please, any expert on this to give your opinion is highly appreciated.Thanks a lot.

 

[Ron]

What the project manager is proposing is possible, but would require some additional design considerations, including doweling of the existing concrete to tie to the new concrete.

Unless this is an exceptionally large footing, I would recommend against this approach. You will only have one opportunity to fix the problem...don't shortcut the process.

 

[allanex50]

Ron,
Thanks a lot..But one more thing to clarify. The shape of footing is triangle with equal three sides having dimensions of 3.2 m. Upper portion appears to be weak which is about 1/3 of thickness of 1.15 m. Our project manager wants to break the upper part only and rectify the concrete using cementious material and adhesive chemical for bonding between the old and new concrete. To me, once you break a concrete especially footing using jack hammer, that will harmful to structural integrity of the structure. Do you have different opinion on this? Please reply.

 

[Ron]

allanex50...you are correct. Utilizing a jackhammer to remove partial depth in concrete can and does introduce microcracking in the underlying concrete. Sometimes it "repairs" itself (autogenous healing from unhydrated cement particles); however, the potential damage is done.

You might allow it if the contractor does a full scale load test to twice the design load after the repairs are complete.

 

[hokie66]

Agree with Ron. This approach is foolish. Just pull it out and start over.