The Collaborative International Dictionary of English v.0.48:

Ferro-concrete \Fer"ro-con"crete\, n. (Arch. & Engin.)
   Concrete strengthened by a core or foundation skeleton of
   iron or steel bars, strips, etc. Floors, columns, piles,
   water pipes, etc., have been successfully made of it. Called
   also armored concrete steel, and most commonly reenforced
   concrete.
   [Webster 1913 Suppl. +PJC]

WordNet (r) 3.0 (2006):

ferroconcrete
    n 1: concrete with metal and/or mesh added to provide extra
         support against stresses [syn: reinforced concrete,
         ferroconcrete]