coldpatching

i submitted several ?s before but i did it on the reply line.i need a written source that i may refer to on the subject of cold patching.i recently observed a apt.building being built.on the walls there were deep cracks,starting at the top and running at a long angle to the bottom.you could also tell this was not all poured at the same time.is this what they refer to as cold patching,and what does this do to the strength of the wall or foundation.ithink these walls were not for a basement,but a crawl space.i think.then along the top of the walls where the floor would be tied into ,it looked as if they took big piles of concrete and just stuck this concrete on top in the indentations,where maybe some of it came off when they pulled the forms off.not smooth at all,proutruding rock etc.
these are the same walls i refer to above on the cracks also.they (the walls)come out of the ground about 1-3 feet.

is this common contractor work.what does this do to the strength of the walls.i need toget your opinion as well as a written source to refer to on this point,of so called cold patching. please excuse my typing.

 

[ishvaaag]

If the cause is just lack of care in some cases their structural effect may well close to nil. However it being too evident even if not targeting it to be close to architectural concrete means some degree of miscare.

Shrinkage, bad preparation of the forms, bad practices in their use or removal, lack of study of the reinforcement details, temperature change, degree of vibration when fresh, nature of the mix of concrete, settlements, mechanical impact all these may contribute to these ubly joints appearing. Some are irrelevant structurally, but not aesthetically or for the building envelope.

 

[pevans]

It appears that what you are describing is a 'cold joint'. Such joints occur when fresh concrete is placed against hardened concrete. Most structural drawings include a detail for cold joints, which are triggered when placements are interrupted. If the crack appears to be at an angle nearly that of the angle of repose for the fresh concrete, then a cold joint would possibly explain the observed cracking. Sometimes, it seems, concrete doesn't need an observable reason to crack. Any judgement as to the structural stability would then best be determined by a structural engineer, preferably the designer. It would be clear that lateral pressures could be poorly supported.

 

[ishvaaag]

The formulas for shear friction are used normally with different frction coefficients depending upon the surface at the interface old/new. You can see some of this in the ACI code or whenever shear-friction is talked about.

 

[Imagineer]

BigBam,
Could you tell us your involvement in this? Are you the building owner, a structural engineer called to investigate, a contractor doing extra work on the building? This would give us a direction to help you.

Imagineer