Formwork of reducing thickness due to loading of slab cast in-situ

Abstract

An apparatus for forming a concrete slab to be supported on a surface of load bearing members, and a method of use of the apparatus, are provided. The apparatus may includes a support element having a layer of active material bonded on each side by a backing sheet. The active material is chosen to slowly compress over time when placed under a load of the concrete when poured onto the apparatus. The rate of compression is chosen such that the layer of active material continues to support the slab until such time as the slab becomes self-supporting (i.e., the concrete has cured/set) on the load bearing members. The active material is chosen such that the load supported by the active material reduces gradually from an original value of 100% when the concrete is poured to less than 40% of its original value after 10 days as the concrete cures. Another feature is the inclusion of a surface of the backing sheet with a relatively low coefficient of friction. When two support elements are laid one on top of the other with the surfaces in contact, the upper support element may slide over the lower support element, for example during a seismic event.

1 - 28 . (canceled) 
     
     
         29 . A support element for use as a component of a formwork for producing a concrete slab to be supported on a surface of at least one load bearing member, comprising:
 a layer of active material that compresses under load, wherein   a first surface of the support element is attached to a backing sheet and a second surface of the support element opposite the first surface can form a support surface of the formwork onto which concrete is poured to form the concrete slab, and   the active material is chosen such that the load supported by the active material reduces gradually from an original value of 100% when the concrete is poured to less than 40% of its original value after 10 days as the concrete cures and the load is gradually transferred onto the at least one load bearing member.   
     
     
         30 . The support element of  claim 29 , wherein the backing sheet has a coefficient of friction less than 0.4 when placed in contact with another backing sheet of the same kind. 
     
     
         31 . The support element of  claim 29 , wherein the layer of active material is sandwiched between two backing sheets. 
     
     
         32 . The support element of  claim 29 , wherein the layer of active material comprises an enclosed void and a surface of the enclosed void is flexible. 
     
     
         33 . The support element of  claim 32 , wherein the enclosed void comprises a fluid. 
     
     
         34 . The support element of  claim 33 , wherein the surface of the enclosed void is permeable to the fluid contained within the enclosed void when under a load such that, under the load of the poured concrete slab, at least some of the fluid escapes over a period lasting from 2 to 10 days. 
     
     
         35 . The support element of  claim 32 , wherein the layer of active material comprises a plurality of enclosed voids. 
     
     
         36 . The support element of  claim 35 , wherein the support element comprises a plurality of layers of enclosed voids. 
     
     
         37 . The support element of  claim 35 , wherein the layer of active material is formed from an array of air filled enclosed voids. 
     
     
         38 . The support element of  claim 29 , wherein the support surface is a backing sheet of the support element. 
     
     
         39 . A method of forming a concrete slab to be supported on a surface of at least one bearing member, wherein the formwork used to support the concrete slab when poured comprises a support element having a layer of active material that compresses under load, wherein a first surface of the support element is attached to a backing sheet and a second surface of the support element forms a support surface of the formwork onto which concrete is poured to form the concrete slab, the method comprising:
 preparing the formwork to cover a space around the load bearing structure and under the concrete slab when poured;   sealing any space between the top surface of the load bearing structure and the support surface to form a continuous surface onto which concrete can be poured; and   pouring the concrete over the continuous surface, wherein   the active material of the support element is chosen such that the load supported by the active material reduces gradually from an original value of 100% when the concrete is poured to less than 40% of its original value after 10 days as the concrete cures and the load is gradually transferred onto the at least one load bearing member.   
     
     
         40 . The method of  claim 39 , wherein the preparing of the formwork comprises placing two or more support elements on top of one another. 
     
     
         41 . The method of  claim 39 , wherein the support elements are chosen such that a coefficient of friction of the backing sheet attached to the first surface of the support element with another backing sheet of the same kind, is less than 0.4. 
     
     
         42 . The method of  claim 41 , wherein the preparing of the formwork comprises placing two support elements on top of one another such that the backing sheets of each structural element having a coefficient of friction less than 0.4 between them, contact one another. 
     
     
         43 . The method of  claim 39 , wherein the top of the one or more load bearing members includes a base isolation device.