Watertight concrete repair

[WiSEiwish]

Hello,

There is a concrete conduit that has failed with major spalling to the point where there is a hole in the wall. I have traced the source of the problem to poor joint maintenance, and that problem will be rectified in the repair. The question I have is how to ensure or specify a repair that is watertight. It seems like any proper concrete repair (per ACI or other reputable organization) should be watertight else it wouldn't really be a proper repair. Is this correct or is there something more specific that needs to be mentioned with regards to the repair?

The walls of the conduit will have constant fresh water contact and the new concrete will obviously be cast against existing concrete.

My question is a general question with a case specific application, so if there is any more information that is needed for a good answer then please let me know.

 

[JedClampett]

If your wall is less that 8 inches, you're going to have a problem no matter what.
Concrete is porous. So concrete can never be really bottle tight, especially when the water has a head. You can attempt to make it water resistant. If there is a repaired hole in the wall, the most critical point where water might leak in is at the joint between the old and new concrete. You can add retrofit waterstop or a hydrophilic (swells upon contact with water) waterstop at the joint. If it's too rough to do this, you might need to smooth it out (like saw cutting it larger), which seems counter intuitive. Another weak spot is at the top of the repair, where the concrete pour might have an air bubble. To avoid this, a bird's mouth type chute might be required.
Make sure the repair is doweled in to the existing concrete to prevent it from shrinking right at the joint. Use a low water to cement ratio concrete, like .45 w/c.