David Swain Jan 25, 2017:

I know this thread is a few years old, but I've come across what I think is the correct term for this in English: "clear spacing". I found it in the glossary on p.7 of this document (http://www.dfi.org/viewpub.asp?tid=TM-CONCRETE2016) produced by the European Federation of Foundation Contractors and the Deep Foundations Institute. Hopefully this is useful for colleagues working in this area in future!

Didier Fourcot Nov 25, 2013:

Explanation of the French term I confirm Albena's view: this as a path allowing the concrete to flow properly among the rebars (that can be numerous and tightly packed in this industry), which is confirmed by the additonal point of allowing the concerte chute to be positioned, implying IMHO a conic shape (funnel) at top: the chutes I know of (concrete trucks) do not fit in 150 mm wide.
I am not English native, but I should understand a "placement chimney" this way with cheminée -> chimney and bétonnage -> placement