Cracking Concrete Basement Wall

[BearcatEngineer]

My brother has a 8" & 10" basement walls poured with #4 at 12" o.c. both horizontally and vertically. It is a rectangular basement, 28'x45'. The walls are 9' to joist bearing from basement slab. The 8" wall is the 45' wall and has developed a vertical crack @ 20' from the side wall on both the front and back walls. It is visible on the interior and exterior or the house. No wall deflection or settlement difference is noticed at the cracks. i am assuming it is a shrinkage crack, but was wanting to seek others opinions on this matter. The house was premanufactured and set 4 days after the basement was poured. ANy thoughts would be appreciated.

 

[dik]

Vertical cracking at mid wall is likely shrinkage induced. Wall is restrained at corners. Any idea of the concrete mix used? slump?

 

[BearcatEngineer]

No, I can try and see if he as any info regarding that. I doubt it though, he couldn't even remember if it was reinforced and i showed him the pictures we took.

 

[Barbicane]

45 feet is a long way for concrete to go without a joint. It sounds like it made itself a joint. Cracking can get exaggerated when water is added to the concrete just before it is poured. Even a cocrete block wall could not take such long distances without a joint. I wonder if the crack in the wall aligns with a similar crack in the footing directly under it. I would not get too excited about the crack unless it was unusually wide. Sometimes, contractors do not alternate lap splices and it creates weak spots in the reinforcing. That could be another reason why the crack ended up where it did. Every other line of reinforcing should be continuous at a splice. But, that means you have to cut a perfetly good 20 foot long bar in half to get started and that is extra work and extra time.

 

[VBI]

Just because the picture shows reinforcing does not mean it was actually done. How did the contractor not remember?

Is the soil clay? Is the property poorly graded? This could add stress to an 8" 45' long wall...and raise concern.

 

[fndn]

I have encountered couple of years ago such cases on residential basements. As barbicane has pointed out and also in ACI paper that I can't recall the authors, 38 feet is the magic length of basement wall that doesn't have jogs or perpindicular beams tying into it before cracks. The exterior lateral earth pressure in the center span is just too much. Four days of curing is also early for sufficient concrete strength gain.

I would clean the surface, epoxy the cracks and replace the upper 4 feet of backfill soils(only along the 40' sides)with pea gravel and 1 foot of soil cap. Just make sure that the drains at the bottom are working.

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