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Slab with Concrete Blocks

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There was a proprietary 16" wide, post-tensioned deck system in the late 50's 
and 60's which was called, IIRC, Rapidex or Rapidek or some other permutation 
of the name.  It was fabricated with special cmu that had round holes at the 
ends of each cmu into which a high strength rod could be inserted and 
tensioned by tightening down on nuts.  The rods were solid, and mortar was 
buttered on the cmu units for adhesion to the adjacent cmu.  Joints between 
deck units had shear keys of a sort and were grouted.  Parallel rods would be 
about 4" to 6" apart (adjacent deck units) or 10" to 12" apart for rods in 
the same deck unit.  The cmu were typically 8" deep, but frequently had 2" of 
topping on them.

If it is this system and I understand your description of the present 
condition, the rods have lost their tension and I would not classify it as 

I'm sorry, but I don't have anything in my files on this and this is all from 
memory.  You might find out more information by doing a Google search on 
Rapidex, Rapidek, Rapideck, etc., or finding a set of Sweets catalogs from 
the period.


A. Roger Turk, P.E.(Structural)
Tucson, Arizona

Shival Tailor wrote:

. > Trying to figure out a concrete slab system built around 50 years ago. I 
. > can see 
. > concrete blocks hanging on something made of steel (beams, covered with
. > concrete 
. > casing) one CMU o.c. Either they are really hanging (being supported by 
. > the steel beam 
. > covered with cement concrete or simply they are there because of the 
. > concrete bond 
. > only. It could be W section or something that I can't figure out. Need to
. > notch the 
. > section. At a couple of places I could see removed concrete casing and 
. > could clearly 
. > see rusted steel, the steel section looked hollow to me, and at many 
. > places the blocks 
. > have fallen and some of them are in progress of falling down.

. > I have pictures of the slab. The blocks have started falling down slowly 
. > and gradually. I 
. > can see the deflection in the slab clearly. People, residents of the 
. > apartment complex 
. > have their car parking space under the slab, and walkway + entrance of the
. > apartments 
. > over the slab. Looks, 25+ or - total span of the beam w/ around 30 + or -
. > beams. 
. > Couldn't figure out the total thickness of the slab. Must be more than a 
. > block height. 
. > Town building inspector has asked for the structural inspection and 
. > approval from a PE 
. > if this is still safe with this remedy.
. > Any thoughts ?

. > Much thanks for your time.

. > Shival Tailor

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