The barn has a cobbled floor in the front section and compacted soil floor at the back. A damp proof membrane can either go above or below the concrete floor. I have decided to put a damp proof course under the concrete, but I may an additional one on top of it when its finished and then screed over it.
A concrete pump to pump the mix to back of the barn costs an additional 150 euros.
It seems common practice to put steel in concrete floors, but Roy and Roger say it’s not necessary as the floor is not structural. If I can get the C25 mix for less than 950 euros that Point.P have quoted for 6 cubic metres and 10 metre concrete pump then I might put some steel in just in case the floor becomes load bearing in the future.
6 Cubic metres of C25 concrete should be enough for 100mm thickness of concrete over the entire floor area. At some point in the future the floor should be covered with insulation and then another 100mm of concrete.
Concrete reenforcing bar (rebar) for french barn floor slab
When I return to France I will visit Leclerc and Reseau Pro to see if they can beet the Point.P quote for C25 Mix, Leroy Merlin in Poitiers also supply readymix concrete but I imagine the distance that they are from the barn will make them the most expensive concrete supplier.
On a non load bearing slab floor you could probably use a weaker mix than c25 and save yourself some money. Maybe look at using c7.5 as specified on this page (http://www.dts-uk.com/html/readymix_concrete.html) which has lots of info on different concrete mixes. It says ST1/Gen 2 for House Floor – topped with Screed. I believer that ST1 is another name for C7.5 concrete.
You can check all the different BS882 code (c7.5,c10,c20,c30 etc) concrete mixes on this site http://www.pavingexpert.com/concmix1.html , its also got some useful aggregate quantity calculators on there.
While stell and wire mesh are common practice in a concrete floor as of late we are seeing a lot of macro fiber being used to replace wire mesh and most steel in floors as well as walls.