Patent ID: 7396495

Claim:
A method for producing a block having a bottom, a top and sidewalls which extend between the bottom and the top, said method comprising producing an open top mold having a shape which corresponds with that of the bottom and sidewalls of the block by assembling at least two cooperating mold parts on a first plate, the assembled mold parts having interior surfaces which conform with the shape of the sidewalls of the block, and include at least one recess or protrusion so that a block produced in the mold can not be separated therefrom while the cooperating mold parts are assembled, tops, bottoms which match the shape of the part of the surface of the first plate on which they are assembled and enclose a portion of the surface of the first plate which conforms with the shape of the bottom of the block, clamping the assembled mold parts together, introducing into the interior of the assembled mold parts a concrete which is hardenable by hydration of cement therein, working the concrete as required into close proximity to the interior surfaces of the mold parts and to the plate surface inside the mold parts, introducing into the interior of the assembled mold parts a quantity of a foamable composition capable of forming a body of a thermoset, closed cell, foam with urethane crosslinks which fills the interior of the assembled mold parts above the concrete therein and has a density of about 10 to 60 pounds per cubic foot, and closing the mold by clamping a second plate to the assembled mold parts, wherein the second plate has a clamping surface with a shape corresponding with the shapes of the tops of the mold parts, and is urged against those tops when the second plate is clamped to the mold parts, and a closing surface which is inside the clamping surface and has a shape which corresponds with that of the top of the block, with the proviso that there are small openings between the interior and the exterior of the mold through which excess water in the concrete and air displaced by the expanding foam can flow without appreciable loss of solids from the mold, opening the mold, disassembling the cooperating mold parts, and removing the block.