12 mm bond breaking neoprene sheet

[struct4me]

Dear All..

why this bond breaking material is used around steel pipe and embedded backfill concrete.

Thanks!!

 

[BridgeSmith]

Presumably, it's added to allow the pipe to move independently of the concrete. Whether that's longitudinal movement or transverse, depends on the conditions. If it's 12mm thick, I would suspect it's to allow the concrete to move transversely relative to whatever is adjacent to it that the pipe goes into, without shearing the pipe or spalling the concrete.

 

[coloeng]

Because of the difference in the coefficient of expansion between the two materials.