Cracked concrete stem wall

[shacked]

I was called by a client to visit his home because he wanted to remove some interior bearing walls and other miscellaneous Structural issues. The house was built in the early 60's in Southern California, single story, conventionally framed with a raised wood framed floor supported on post and beams & small pad footings throughout. While in the crawlspace I noticed a rather significant horizontal crack in the concrete stem above grade of a 5 foot retaining wall. At some portions of the crack you could stick a wood pencil about 3 inches into the crack & I could see rusted rebar in the center. Although he did not call me out for this, since he was not even aware of it, I felt obliged to bring this to his attention since there is in adequate shear transfer from the wood stud cripple wall sitting on top of it, up to the first floor.
Just curious as what other might propose to repair this. At this point I am going to propose to infill the cracks with epoxy, as well as drill 1/2" diameter holes down the center of the stem, in plan view, & epoxy #4 rebar @ 24" o.c. along the length of the wall where the crack occurs. The rebar would need to extend at lease 6" below the crack in order to get adequate shear resistance as well as tie the upper concrete stem to the bottom of the wall. See attached picture of wall.

ANy thought would be appreciated.

 

[boo1]

kinda looks like a cold joint

 

[Ron]

Agree with boo1...cold joint. There was obviously several placements of concrete, looking at the variation of the concrete appearance just above the cold joint.

I agree with your repair method.

 

[shacked]

Yes it is a cold joint. From the inside of the garage you can see all of the lifts that they made. Very poor construction.
I am wondering why it cracked like it has, possible air void and when they took the forms off some of the aggregate that separated the crack could have fell out over time?

Thanks guys, I appreciate it.

 

[Ron]

shacked....multiple placements of concrete which are poorly controlled result in differential shrinkage and differently response to thermal movement. It is obvious that the mixes were not consistent, so you might have a high strength mix in one portion and a low strength mix in another....lots of differential movement potential