concrete floor

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
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I only hope your telling us that you've put the copper piping and cables into a duct of some sort (?) as the chemical reactions between copper, electricity and the PVC coating of the cables with cement and aggregates in the concrete will wear them down to the point of breaking within a very short period of time.
The cable and pipework should be installed through galvanised trunking or nylon terrain pipe (the red pipe used for underground systems) to stop the reactions from happening and stop the need for it all to be dug back out to repair it.
Please read.
http://www.mg-assoc.co.uk/concrete.htm#_concrete-cathodic-protection
for more information on this.
You can cover the pipework and cables with a protective layer of roofing felt before filling, or place heavy duty polythene around them to give a protective coating, but this will also give rise to the need for a solid layer to prevent the new concrete from causing the pipes and cables from bending and breaking at the joints.
If the pipes and cable are directly on to sub soils under the floor, then this too can cause damage from chemicals in the soil and allows bending due to the weight of the concrete and people walking over them and the pipes and cables should be laid on top of a layer of sand to a depth of at least 30 mm which helps to cushion them.
Please be careful with this, as it may cost you dearly if not done correctly.
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If you are using plastic pipes just pour concrete. Although I would put them on a concrete base first just so they are completely enclosed. What you have done is the normal way of construction on the continent burying plastic cables and pipes in a concrete screed. The manufacturer of the plastic pipes should be able to give you some guidance.
However, as everyone has pointed out do not do this with copper pipes, they react with concrete and expand when heated and will fail quickly.
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cuckoo flower wrote:

Doesn't matter as long as it doesn't totally collapse.
If that is a worry, use a stiffer (less water) mortar mix.
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wrote:

The plastic pipes will expand even more than copper so will need some kind of all round space to allow for movement. If you don't allow for them to expand and contract then your joints will definitley just fall apart.

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|Doncaster, UK http://www.hepworthplumbing.co.uk |DN12 1BY
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I hate to be a wet blanket but maybe you should talk to my next-door neighbour who put his central heating pipes under his floor, and had to re-route them some years later when they leaked.
Rob Graham
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