Cold Joints in residential basement walls

[Kosmo]

Problem: New construction where the basement wall forms were pumped full of concrete and cold joints formed due to not vibrating the concrete. Water is presently leaking through the cold joints.

Question: What is the reduction in structural strength of a wall with cold joints. Wall is 10ft high by 50ft long and the cold joint runs along most of the wall at about 5 ft above the basement floor.

 

[JAE]

If there is reinforcing extending across the joint (at about 90 degrees) and the joint is where you say it is, there should not be a strength problem.

For shear, the rough nature of the joint, and the reinforcing, should work OK.

For moment, the bending in the wall will still engage properly on the compression side, and the reinforcing still work properly on the tension side (center of the wall?) so the flexural strength should still be fine.

These problems remain:

1. The wall is less stiff as you have created a "cracked" joint in the flexural element of the wall.. However, this may not be a huge problem if there is plenty of axial load on the wall itself.

2. The wall (as you report) now allows moisture to penetrate. This will eventually cause a problem with rusting reinforcing and a mess inside.

I would take steps to inject epoxy or grout into the joint or attempt to waterproof it from the outside if possible.

 

[jheidt2543]

If the wall has not been backfilled as yet, I would have a membrane waterproofing system installed. Not the roll-on or spray-on black coatings, but an actual membrane. Most of your local roofing contractors handle a system of this sort and it is the most positive way to end your water worries. Make sure the heavy equipment stays 4'- 5' away from the wall during backfilling! Use only hand compactors close to the wall so it isn't damaged any further.

If the wall has already been backfilled then the epoxy injection is the way to go.

Good luck.

 

[Sean2]

Kosmo,

Further to JAE's reply, I wonder if JAE has considered the effect of not vibrating the concrete.

As I understand it, a cold joint forms when concrete is poured on top of concrete which has already begun its initial set, and the fresh concrete is not vibrated into the older concrete. You then fail to get a continuous pour, and the joint between the two pours has not been designed or prepared.

However, you have not mentioned this situation. You say the "cold joint" formed because the concrete was not vibrated. If the concrete was not vibrated at all, perhaps you have a more serious problem throughout the height of your wall. I don't wish to frighten you unnecessarily, but if your cold joint is not as I understand it (the first decription above), you should inspect the wall in detail, and use a tool, such as a screwdriver, to test any suspect areas for weakness. If you find anything more than merely small air bubbles close to the face, you should try to quantify the problem a little better before deciding the best course of action.

I suggest you consider the risks:

What are the consequences of the water coming in?
What are the consequences of the wall losing strength?
What are the costs of the different options for remedial action?
How reliable are the options you are considering?
What impact will the remedial work have on the project? (Such as delay to occupation of the building, delay to other works, reduced enjoyment of the building.)

If you consider the above, you will probably find the best answer/solution for YOUR circumstances.

Also:
If the reinforcement rusts, it will (in time) expand and spall off some of the concrete in the corresponding wall face. The reinforcement will (obviously) also lose strength.

I hope you find some answers among all my questions, and I hope it works out well for you!

Sean2.

 

[Kosmo]

Thanks for all of your responses.

Sean2: You are correct on the way the wall was poured. They took to long between pours resulting in the cold joints forming. They poured on top of a wall that had already began to cure. Without the vibration to mix the two layers together the cold joint formed. As for using a screwdriver to investigate the wall, it is visibily obvious that there are holes and dry spots around the rocks in the concrete. It is almost as if the liquid concrete ran down the wall and left the rocks sitting without any cement around them. I am not sure if epoxy or other coatings will cover this as I suspect there are numerous paths for water to run through.

JAE: As for structural re-bar running vertically in the walls the only thing I remember is the ties that hold the forms together and 3 or 4 lengths of re-bar running the length of the wall (laid across the ties). I do not recall any running vertically in the wall. I would assume from this that the force of the house sitting on the wall could create enough shear force to collapse the wall. Are there any specific equations which pertain to structural strength of a wall with cold joints?

Thanks for all of the information

Kosmo

 

[Qshake]

We have address this issue many times before. Check the Concrete Engineering forum or ACI Code forum.

Aside from all of the technical information, if this is your residence...get a lawyer - no matter what the contractor says he is going to do with it. This work is below standard for the industry and it should be repaired to the point of demolishing the wall and replacing it. Any repair may become suspect in the future and water may leak into the basement destroying who knows what of who knows what value. In the absence of such an error, the wall would not leak.

If this is an industrial application, then do the same as above except involve your company attorney.

Your attorny will likely advise you to have the situation evaluated by a engineer who can and has experience in providing expert opinions.

 

[Kosmo]

QSHAKE: Thanks for the advise. I am currently looking into having a structural engineer come out and take a look at the wall to see if it meets Wisconsin code and find out what my options are. I am also contacting a lawyer and I will review the two other forums that you suggested.

Thanks to all that have responded.

Kosmo