My house is heated with hot water radiators fed from a boiler in through concrete trench through the middle concrete slab for the ground floor of the house and then back in a pipe trench along the perimeter of the house.
The main supply line rusted clean through and for weeks (months? years?) has been dumping water under the foundation (fortunately near the outside. I just spent the last 48 hours breaking the floor and exposing pipe allow me to replace about 7 feet of pipe. Now that the repairs are all complete, I need to cover back up the hole in the concrete floor.
Previously, the pipes were running in a hollow trench - about 8" tall and and 8" wide, in a bed of what looks like vermiculite or some sort of loose fill material. I know that the cement should come in contact with the pipes, so I am trying to figure out how to re-pack the new pipes put a 1-2" cement top back on to restore the floor.
I was thinking maybe some loose fill around the pipes, then a piece of rigid foam over the top to create a base for the cement and then cover with a couple inches of cement?