Expanded polystyrene formwork for cast in place concrete structures

Abstract

A formwork for use in constructing concrete structures is made out of expanded polystyrene coated with an epoxy hard coat on the surfaces of the formwork against which concrete is applied or poured in the construction of concrete structures. A method of making the formwork involves constructing the expanded polystyrene to a desired shape and applying the epoxy to the surfaces of the polystyrene to be used to contact concrete and allowing the epoxy to cure. A method of constructing concrete structures involves using the formwork described.

1 . A formwork for cast in place concrete structures, comprising: 
 a formwork structure made of expanded polystyrene; and    an enamel coating on at least one surface of said formwork to be in contact with poured or applied concrete which will make up at least a part of a concrete structure.    
   
   
       2 . The formwork of  claim 1 , wherein said expanded polystyrene has a density of at least about 1.35 pcf.  
   
   
       3 . The formwork of  claim 2 , wherein said expanded polystyrene has a density of at least about 1.35 pcf to about 1.79 pcf.  
   
   
       4 . The formwork of  claim 1 , wherein the strength properties of said expanded polystyrene comprises: Compressive 10% Deformation Strength of at least about 15 psi; Flexural Strength of at least about 40 psi; Tensile Strength of at least about 18 psi; Shear Strength of at least about 26 psi; Shear Modulus of at least about 460 psi; and Modulus of Elasticity of at least about 320 psi.  
   
   
       5 . The formwork of  claim 1 , wherein the strength properties of said expanded polystyrene comprises: Stress at 10% Compression of at least about 30 psi; Flexural Strength of at least about 58 psi; Tensile Strength of at least about 62 psi; and Shear Strength of at least about 70 psi.  
   
   
       6 . The formwork of  claim 1 , wherein the enamel coating is polyurethane.  
   
   
       7 . The formwork of  claim 6 , wherein the polyurethane coating is made from a two component unfilled epoxy mixed with a catalytic hardener, the resulting polystyrene having tensile strength properties of about 25,000 psi and comprehensive strength properties of about 40,000 psi.  
   
   
       8 . A method of manufacturing a formwork for cast in place concrete structures, comprising: 
 shaping a piece of expanded polystyrene into a predetermined formwork shape;    applying an enamel coating on at least one surface of said formwork to be in contact with poured or applied concrete; and    curing the enamel coating.    
   
   
       9 . A method of manufacturing a concrete structure comprising: 
 shaping a piece of expanded polystyrene into a predetermined formwork shape;    applying an enamel coating on at least one surface of said formwork to be in contact with poured or applied concrete;    curing the enamel coating;    applying or pouring concrete into contact with the cured enamel coating to have the concrete assume a desired shape;    allowing the concrete to cure; and    removing the formwork after the concrete has cured sufficiently to result in at least a portion of a concrete structure.