Monolithic Foundation Question

[hyphenme]

We have foundations at an electrical substation where all the foundations are round caissons with some having a rectangular or square top for the anchor bolt pattern. The concrete guys poured all the foundations in that substation partially up to where my rectangle/square top is suppose to start. The contractors usually pour the foundation in one go but this time they didn't, not sure why. We didn't specifically require that the caisson be monolithic but it has never been an issue until now.

What kind of issues comes up with concrete being poured in two stages like this? There are 3-4ft left in the pour. I know cold joints become an issue and we're tempted to require the contractor to pull up all the foundations and re-pour it. This might be very expensive and we're deciding if there an alternative solution. There are rebars in these foundations, some go as deep as 20ft. Thoughts? Opinions?

 

[JedClampett]

I'm not a believer that cold joints are all that serious. Code allows shear friction at joints. Unless the concrete work is very sloppy (dirt, laitance and junk on the joint), you should get good compressive strengths through the joint. And since the bars should be continuous through the cold joint, tension is taken care of.
Have the contractor clean, roughen and wet the joint. If you want to make him suffer, have him do some additional work (scab the concrete, bonding agents, etc.) just for fun.

 

[hokie66]

It is normal practice to cast the bored pier first, then the rectangular plinth. The reinforcement for the plinth should be developed into the bored pier, and the joint should be clean and rough.

 

[delagina]

what hokie66 said, our standard drawing for drilled pier has construction joint about 3 feet above top of pier.