metal pipes backfilled with flowable fill

huangyhg

metal pipes backfilled with flowable fill
i have a specification for flowable fill that prevents metal pipes from being backfilled with flowable fill unless coated with some sort of manufacturer coating material or plastic casing. the question has arose from a contractor as to why this is the case becuase the contractor wants to use plain cast iron with no coating or covering. does anyone know if this will harm the flowable fill (cementious, flyash material)? thank you.
you might try the materials engineers section of this forum.
i would suspect it is to protect the pipe.  steel pipe can be mortar-coated, which presumably protects the steel surface.  perhaps the intent is that flowable fill shouldn't be assumed to provide this kind of protection.
cast iron pipe and fittings normally have an asphaltic coating on the outside, and in addition is often covered with polywrap in corrosive soils.  is his material really bare metal, or is it the standard black asphaltic coating?