Crack on Civil Raft! suggestion please urgent:

BABU_SMIT Hope someone will answer your question, meanwhile if you can edit your profile and change your location to India (or whereever you are from) instead of Indian.

thanks,

Thanks you sir,

i will do it.

BABU,

If you are concerned about the crack, you can inject it with epoxy and it will have adequate strength. It is not necessary to re-do the pour.

I assume the crack is on the top of the footing. Is the footing reinforced only on the bottom? Will the footing carry a column at its centroid? Can you provide a photograph of the cracked footing and post it on CR4?

For recommendations on curing concrete, review these links.

Dear Sir,

Thanks for ur valuable suggestion, as u assumed the crack is on top of the raft.

Reinforcement on both top and bottom.

Shortly i send u the pics of the cracked raft.

With regards,

Babu.

Thanks for the photos. I reproduced them in Post #5 so the rest of the forum can see them too.

I think you should definitely inject epoxy into the crack.

The last photo indicates rectangular blocks at the bottom edge of the raft. Are these bricks? What is their purpose? This photo suggests to me that the vibration was not very good as there appear to be gaps in the concrete. Was a vibrator used to consolidate the concrete?

Just for clarity, this is not a raft this is a pad foundation i.e. it does not have continuity with the rest of the foundations but is separate.

The column will tend to bend the foundation and so the upper part will work in compression and thus stress the concrete. This is assuming, from the photos, that there is no further foundation beneath what we see.

BAEL is right to inject with epoxy (to the same strength as the concrete as a minimum) so that the concrete can work in compression.

Are these not shrinkage cracks caused by dehydration of the concrete? Was this the reason for having sacks near the foundation so as to cover it up to prevent evaporation of the water?

Finally, did you take a concrete cube test piece which you can now send for testing as it may be that you had too much water in the concrete which exacerbated the cracking due to dehydration?

However, having said all that, it might be judicious to replace the footing completely depending on the results of the cube tests. The cube should have been cured in the same conditions as the foundation itself and not, for instance, in the shade somewhere.

Dear Babu,

No need to be panic abt this crack on surface,this nothing but only shrinkage cracks and developes due excessive vibration in concrete, more water comes on surface and after evaporation of water cracks developes, mason didn't finish this surface properly.You only do ,cover the surface with polythene sheet and avoid water loss from concrete.Even after covering no need of regular curing bcz by covering heat developes will keep the surface of concrete.This not construction failure and no need of using epoxy and other things.

Regards

Mohinder Kochar

I would say that this is incorrect.

The top of the concrete pad is in compression and the forces should go through the concrete and not the reinforcement.

Secondly, the original post states that they are upto 40mm deep and so will almost certainly have an effect on the durability of the reinforcement: spalling etc.

Dear All,

I thanking you for giving me a valuable suggestion.

With Regards,

C. Babu

Hello

First, from the picture, this is a Pad foundation. Firstly, curing can start after the initial setting time of the concrete used is attained; normally curing may start after 6 hours of concrete casting. it may be early in case of hot weather conditions.

The cracks you are concerned about can be from many reasons, ranging from improper concrete proportioning, high slump, high concrete temperatures [over 35 Deg Centiggrate], to improper on insufficient vibrating eqpt used during concreting pouring, early side supports removal to even structural failures. If you can send a picture of the cracks it would be easier to comment on. However, after curing for 20 days, if you see any cracks increments, then its sign of problems. If not, normal grout can be used to fill up these cracks. If you happen to see [visual inspection] re-bars from the cracks then structural grouting to expansion grouts may be required.

Hope this helps.

Fareed