i have just dug a channel in my concrete floor, through the kitchen,
lounge & hall, which is about 6 inches wide, 5 or 6 inches deep, and
10 meters long (sorry for mixing metric & imperial), in order to lay
the downstairs pipework for my new central heating system (i don't
want any pipes/surface conduit boxing visible), and i was just
wondering if any experienced builders out there could tell me the best
method to fill it back in again now all the pipes/conduit boxes etc.
are in place. The original concrete floor is about 4 inch thick, so
obviously i've broken right through this to the loose hardcore/earth
below, etc., so do i use sand, rubble, hardcore, some of the old
broken concrete, just new concrete mix, or am i thinking all
wrong...............all i want is to patch it up as it was before,
with no chance of it ever coming loose/rocking under foot etc.

sorry if this is a bit long winded, hope someone can help.
TIA