Cable in concrete floor

[Watersider]

I have found a large number of cables of various sizes embedded directly in concrete between floors in a block of flats, has anyone any info regards the effects of cables(modern <10 yrs old) being in direct contact with concrete affecting the cable over a longer period of time - thanks

 

[Andy78]

The concrete will not do them any good as it can degrade the outer sheath, and eventually the inner insulation. Any cables through floors should have been routed through a rising duct, I am assuming it is far too late now and they are staying where they are.
This will probably take a long time to show any ill effects though, although testing more regular than normal intervals will keep an eye on them.
What sort of cables are they ? PVC twin and earth, SWA, MI ?

 

[Guitarist]

It sounds like another case of "do the quickest job possible, get paid, get out."
If you want facts, I suggest taking some pictures and e-mailing the cable manufacturers. As Andy says, should have been in ducting.

 

[Engineer54]

I can't see how concrete will have any effect on PVC sheath compounds, as they are pretty impervious to most building encountered chemicals/compounds. It's not something i would ever allow, just from the pure commonsense angle of these embedded cables not being able to be upgraded or replaced/rewired. A sleeve/duct or the like, is always the way to go for any such penetrations of concrete slabs, finished with a fireproof mortar sealing...

 

[Guitarist]

Concrete does affect PVC sheathing, but only during the chemical curing process. Additionally, as shrinkage occurs, sheathing can split. We've all seen cables buried in concrete which last for years, but then again, we've all seen entire installations with no main earthing...doesn't make it right.

 

[Knobhead]

I’ve installed 100's of cables and had them grouted through concrete floors to maintain fire integrity. It’s a standard practice.
The time you will get trouble is if the outer sheath has been damaged. Particularly with high alumina cement. The curing process for a grout is only a mater of a day and it should be made with Portland cement.

 

[Engineer54]

Concrete does affect PVC sheathing, but only during the chemical curing process. Additionally, as shrinkage occurs, sheathing can split. We've all seen cables buried in concrete which last for years, but then again, we've all seen entire installations with no main earthing...doesn't make it right.

That's a new one for me!! If anything was going to be detrimental to a cables PVC sheathing, it'll be the aggregate piercing the sheath during settling curing stages...

 

[Knobhead]

Regarding PVC cable or any other type for that matter, after 24 years working on cement plants I’ve never seen any chemical damage to cables. Heat damage from the clinker or physical damage, lots of times but never chemical.

Please post any relevant information about “cement” chemical damage. I’m interested.

 

[somersetsparks]

Round our way theres an entire 1966 block of flats wired with T+E direct in concrete, makes it a nightmare to work on, i.e. moving things about, however all the cables I have tested have been perfectly good, this is after 45 years +, So IMO no probs.