Dual direction pre-stressed pre-tensioned precast concrete slabs and process for same

Abstract

A precast roadway slab is pre-tensioned longitudinally and transversely, and may also be post-tensioned. A casting bed has the capability of permitting pre-tensioning of a concrete cast to be carried out within the casting bed in both the longitudinal direction and in the transverse direction. Slots are provided at regular intervals within the side walls and jacking heads of the casting bed for tensioning wires to pass therethrough for pre-tensioning. The process utilizes a multilayer grid of pre-tensioning wires disposed within the casting bed, prior to pouring of the concrete. The cast concrete product can also be made with optional tubular ducts, laid parallel to the longitudinal wires, for post-tensioning subsequent to the cast of the concrete. The post-tensioning of the hardened cast, if called for, takes place at the job site.

1 - 11 . (canceled) 
     
     
         12 . A dual direction pre-stressed roadway slab which comprises:
 (i) a casting of concrete;   (ii) a plurality of spaced, first pre-tensioning elements extending in a longitudinal direction of the slab, the first pre-tensioning elements being bonded to the concrete and in a detensioned state; and   (iii) a plurality of spaced, second pre-tensioning elements extending in a direction substantially perpendicular to the longitudinal direction of the slab, the second pre-tensioning elements being bonded to the concrete and in a detensioned state,   said concrete having a compressive force transferred thereto by said bonding of said detensioned first and second pre-tensioning elements to said concrete.   
     
     
         13 . The slab of  claim 12 , further comprising a plurality of tubes disposed within the casting of concrete for receiving tensioning elements for post tensioning of the concrete slab. 
     
     
         14 - 20 . (canceled) 
     
     
         21 . A dual direction, pre-tensioned and pre-stressed concrete slab which comprises:
 a one-piece casting of concrete   a plurality of longitudinally spaced, first pre-tensioning elements which are bonded to the concrete and in a detensioned state; and   a plurality of transversely spaced, second pre-tensioning elements bonded to the concrete and in a detensioned state.   
     
     
         22 . The concrete slab according to  claim 21 , further comprising a plurality of spaced ducts disposed within the slab, the plurality of spaced ducts being configured to receive therein a corresponding plurality of post-tensioning elements. 
     
     
         23 . The concrete slab of  claim 22 , wherein a plurality of the spaced ducts extend in a longitudinal direction of the slab, and a plurality of the spaced ducts extend in a direction substantially perpendicular to the longitudinal direction of the slab. 
     
     
         24 . The concrete slab of  claim 21 , wherein the first pre-tensioning elements of the slab are located at a first elevation thereof and the second pre-tensioning elements of the slab are located at a second elevation thereof. 
     
     
         25 . The concrete slab of  claim 24 , wherein the second pre-tensioning elements are located at a second elevation of the slab that is spaced above the first elevation, and at a third elevation of the slab that is spaced below the first elevation. 
     
     
         26 . The concrete slab of  claim 25 , wherein said concrete has a compressive force transferred thereto by said bonding of said detensioned first and second pre-tensioning elements to said concrete. 
     
     
         27 . The concrete slab of  claim 22 , wherein the plurality of the spaced ducts of the slab are at a first elevation thereof. 
     
     
         28 . The pre-stressed roadway slab of  claim 12 , wherein said first pre-tensioning elements extend at a first elevation of said slab and said second pre-tensioning elements extend at a second elevation of the slab that is spaced above or below the first elevation. 
     
     
         29 . The pre-stressed roadway slab of  claim 28 , wherein said second pre-tensioning elements are also located at a third elevation of the slab on the side opposite of the first pre-tensioning elements to the second elevation.