Spanish term (edited): forjados reticulares de bloques perdidos de hormig�n

forjado reticular = waffle slab (info below), but when you add bloques de hormigón to it, it sounds more like a rib and block suspended floor (also known as pot floor), but I'm also assuming the "perdido" means that it is hollow, which it might not mean at all.

Waffle Slab (diagrid floor)

. 1. A two-way concrete joist system. 2. Two-way slab or flat slab made up of a double system of narrow ribs or joists, usually at right angles to each other, forming a pattern of waffle-like coffers.

According to the building dictionary, a rib and block suspended floor is a lightweight concrete floor slab with stiffening robs formed by the spaces between hollow floor blocks

--------------------------------------------------
Note added at 1 hr 35 mins (2003-10-24 17:44:33 GMT)
--------------------------------------------------

hollow block floor is another possibility. If nobody else comes up with anything, then ask the client for a better description/possible translation.