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

Abstract

An apparatus, and a method of use of the apparatus, for forming a concrete slab are provided. A formwork may include a support element having a layer of active material bonded on each side to a backing sheet. The active material is chosen to slowly compress over time when placed under a load, and 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). 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 . A method of forming a concrete slab to be supported on a top surface of one or more load bearing members, wherein the formwork used to support the concrete when poured includes a support element having a support surface onto which concrete is poured to form the concrete slab, the method comprising:
 providing a load bearing member to support the slab when cured;   providing a formwork including a support element having a layer of active material that compresses progressively under the load exerted by the concrete over a time it takes for the concrete to cure;   covering a space around the load bearing member, including under the concrete slab when poured, with the support surface of the support element facing towards where the slab will be formed;   sealing any space between a 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 providing of the load bearing member comprises providing a load bearing member comprising at least part of a base isolation device, and   a surface of the base isolation device forms the top surface of the load bearing member.   
     
     
         2 . The method as claimed in  claim 1 , wherein the preparing of the formwork comprises forming the formwork such that an initial level of the support surface is at a same level as the level of the top of the load bearing structure. 
     
     
         3 . The method as claimed in  claim 1 , wherein the formwork comprises two support elements and the covering of the space around the load bearing member comprises placing the two support elements on top of one another. 
     
     
         4 . The method as claimed in  claim 3 , wherein an outer surface of each support element includes a smooth backing sheet having a coefficient of friction less than 0.4 with respect to a smooth backing sheet of another support element, and the covering of the space around the load bearing member comprises stacking the two support elements on top of one another with the smooth backing sheets in contact with one another. 
     
     
         5 . The method as claimed in  claim 1 , wherein the base isolation device comprises a first plate that forms the top surface of the load bearing member. 
     
     
         6 . The method as claimed in  claim 5 , wherein a first surface of the first plate is flat. 
     
     
         7 . The method as claimed in  claim 5 , wherein a first surface of the first plate is curved. 
     
     
         8 . The method as claimed in  claim 5 , wherein the base isolation device comprises a second plate having a second surface of complementary shape to the first surface of the first plate. 
     
     
         9 . The method as claimed in  claim 1 , further comprising:
 placing reinforcing elements in a volume to be filled by the slab prior to the pouring of the concrete.