Field of the invention

A building block which contains two interlocking block parts separated from each other by an insulating material.

Background of the prior art

United States patent 4,551,959 of Schmid discloses a building block with two spaced supportive parts separated from one another by a quantity of insulating material posi¬ tioned between the parts. When Schmid's block is sub¬ jected to conditions which will tend to degrade and/or weaken the insulating material (such as those one might encounter in a fire), the Schmid block will tend to lose its structural integrity.

It is an object of this invention to provide an insert which may be used to produce a building block.

It is yet another object of this invention to provide a building block with good structural integrity that does not contain thermally conductive webs or bridges between its wythes.

It is yet another object of this invention to provide a manufacturing process in which an insert may be used in place of a mold and the insert becomes an integral part of the molded product.

Summary of the invention

In accordance with this invention, there is provided a an improved building block.

Brief description of the drawings

The present invention will be more fully understood by reference to the following detailed description thereof, when read in conjunction with the attached drawings, wher¬ ein like reference numerals refer to like elements and

wherein:

Figure 1 is a perspective view of one of the preferred building blocks of applicants' invention;

Figure 2 is a top view of the building block of Figure i;

Figure 3 is a cross-sectional view of the building block of Figure 2;

Figure 4 is a top view of the interlocking block parts of the building block of Figure 1;

Figure 5 is an illustration of one preferred process of applicants* invention;

Figure 6 is a perspective view of one preferred em¬ bodiment of a corner building block;

Figure 7 illustrates one means of joining the building block of Figure 1 with the building block of Figure 6;

Figure 8 is a perspective view of another embodiment of a half-block building block of this invention;

Figure 9 is a top view of one means of joining the building block of Figure 1 with the building block of Figure 8;

Figure 10 is a top view of one means of joining two of the building blocks of Figure 1;

Figure 11 illustrates a construction wall;

Figure 12 illustrates a building panel;

Figures 13 and 14 illustrate one preferred embodiment of the insert of this invention;

Figures 15, 16, 17, and 18 illustrate a process in which a cementitious mixture is poured over the insert of Figure 13;

Figure 19 is a top view of a block prior to splitting which may be used to prepare one preferred embodiment of applicants' building block;

Figure 20 is view of a ribbed building block made from the split block of Figure 19; and

Figure 21 illustrates a process for producing a build-

ing block structure comprised of reinforcing rods. Description of the preferred embodiments

Figure 1 is a perspective view of one preferred em¬ bodiment of the building block 10 of the invention. Build¬ ing block 10 preferably has a rectangular shape and is comprised of two interlocking outer supportive parts, 12 and 14, and an inner insulating portion 16.

Outer supportive part 12 and outer supportive part 14 may be made by conventional means from any cementitious material, baked clay, or other material.

In one embodiment, outer supportive parts 12 and 14 are made with a Besser Vibrapac V3R block machine (avail¬ able from the Besser Manufacturing Company of Alpena, Michigan) with a hydraulic cement. As is known to those skilled in the art, hydraulic cements are produced by burning an intimate mixture of finely divided calcareous and argillaceous materials and grinding the resulting clinker to a fine powder, usually with gypsum to retard the set.

In one preferred embodiment, outer supportive parts 12 and 14 each consist essentially of concrete.

The building block 10 is preferably sized on a multiple of 2 inches and preferably has the same dimensions of concrete blocks in common use.

In one embodiment, building block 10 has a length 16 of from about 15 to about 24 inches and, more preferably, from about 15.3 to about 15.8 inches. In this embodiment, the height 18 of building block 10 may be from 3.5 to about 9 inches (and, preferably, from about 7.4 to about 8.2 inches) or, alternatively, from about 3 to about 4.5 inches (and, preferably, from about 3.3 to about 3.8 inch¬ es). In this embodiment, the width 20 of building block 10 is from about 7 to about 14 inches and, preferably, from about 7.3 to about 7.8 inches. In another embodiment, not shown, width 20 may be from about 4 to about 12 inches.

Building block 10 preferably has two opposite planar sidewalls 22 and 24, two opposite planar ends 26 and 28, a planar top 30, and a planar bottom 32.

It is preferred that endwalls 26 and 28 have substan¬ tially the same width and, preferably, be from about 6 to about 12 inches. Thus, each of endwalls 26 and 28 may be 6 inches, or 8 inches, or 10 inches, or 12 inches.

In one preferred embodiment, each of outer supportive parts 12 and 14 are so shaped that they contain curvilinear interlocking structure associated with them.

Referring to Figure 4, each of outer supportive parts 12 and 14 are preferably integral pieces having at least one internal section, 34 and 36 respectively, so shaped to enable a portion of each of parts 12 and 14 to project within the confines of the other block part. The centerline between block parts 12 and 14 is line 38.

Outer supportive parts 12 and 14 are laterally interlockably connected to each other. When forces are applied in lateral directions 40 and 42 tending to pull parts 12 and 14 away from each other, these block parts 12 and 14 will travel only a certain distance until the in¬ terior surfaces of projections 34 and 36 contact each other and prevent further lateral movement. Thus, referring to Figure 4, interior surfaces 44, 46, 48, and 50 of projec¬ tions 34 will contact interior surfaces 52, 54, 56, and 58 of projections 36 and preclude further lateral movement of block parts 12 and 14.

A simple test can be used to demonstrate this inter¬ locking feature. Referring to Figure 9, in this test building block 10 is placed upon a flat surface 60, and the insulating portion 16 is then removed from the block with¬ out disturbing the relative positions of block parts 12 and 14. The insulating portion 16 may be mechanically removed from the block. Alternatively, or additionally, it may be burned out of the block by heating the block for a time and

temperature sufficient to vaporize most of the material in the insulating material.

Once insulating material 16 has been removed from the block 10, force is applied to outer block part 12 to lift it in the direction of arrow 40 until it is at a height of 3.0 feet above surface 60. The lifting of part 12 above surface 60 will also result in the lifting of part 14 above surface 60.

The projections 34 and 36 are not rectilinear, that is, in no portion of these projections is a right angle defined by intersecting surfaces. By the same token, the insert 16 which fits within the space between the block parts also is not rectilinear but is curvilinear. The inner surfaces of building block 10, thus, preferably includes a multiplicity of corners, each of which is rounded. Thus, referring to Figure 4, it will be seen that none of the intersecting surfaces 62, 64, 68, 70, 72, 74, 76, 78, 80, 82, 84, 86, 88, and 90 of projections 34 of block part 12 are rectilin¬ ear.

Figure 3 is a cross-sectional view of the block of Figure 2 showing that each of block parts 12 and 14 contains pro¬ jections (34 and 36) which extend from the top 30 to the bottom 32 of block 10. Each of the projections is wider at the top 30 of the block than at its bottom 32; converse¬ ly, the insulating portion 16 is wider at the bottom 32 than at the top 30.

Figure 5 illustrates one means of constructing the build¬ ing block 10 of this invention. Each of outer supportive parts 12 and 14 may be disposed with regard to each other so that the tops of projections 34 and 36 are separated from the interior opposing surfaces 92 and 94 of parts 14 and 12, respectively, by a distance approximately equal to or slightly larger than the top width of insulating materi¬ al 16. Thereafter, insulating material 16 is inserted into and between block parts 12 and 14, snugly fitting into the

wedge-shaped crevices formed by projections 32 and 34 and locking parts 12 and 14 together.

In one preferred embodiment, insulating material 16 has a maximum width which is slightly less than the maximum space formed between the interior walls of block parts 12 and 14. In this embodiment, it is preferred that the maxi¬ mum width of insulating material 16 be from about 0.95 to about 0.99 times as great as the maximum width of the space between such interior walls. It is preferred that insulat¬ ing material 16 be substantially uniformly undersized, being from about 0.5 to about 25 percent smaller than the corresponding space between the interior walls of the block parts.

In one preferred embodiment, the insulating portion 16 also contains one or more crushed ribs and/or projec¬ tions. In this embodiment, the insert may be made by means well known to those skilled in the art. Thus, for example, one may score and/or mark the interior surface of the mold used to make the insert. The insert made from this mold will then contain a multiplicity of ribs and/or projections corresponding to the scores and/or marks made on the mold. It is preferred, in this embodiment, that the insert con¬ tain ribs which may (but need not) extend the entire height of the insert; thus, for an insert which is 8" high, the crushed ribs may be from about 7.5 to about 8.0 inches high. The depth of the crushed rib (the distance it pro¬ trudes from the side of the insert) may be from about 0.063 to about 0.375 inches; as will be apparent to those skilled in the art, this depth is a function of how deeply the mold is scored. The insert may have from about 1 to about 100 crushed ribs. Alternatively, or additionally, it may have from about 1 to about 100 projections.

The dimensions of the projections will vary depending upon how one marks the interior surfaces of the mold. In general, the projections will have a width of from about

0.01 to about 0.25 inches.

When the insert 16 contains from about 1 to about 100 crushed ribs and/or projections, it is preferred that its width be from about 0.95 to about 1 times the correspond¬ ing space between block parts 12 and 14. In this embodi¬ ment, the width of insert 16 is measured from opposing faces of the insert and does not take into account the depth of the crushed ribs and/or projections. Thus, the insert itself is not substantially contiguous with the interior surfaces of the block parts, but the crushed rib(s) and/or the projection(s) are.

Insulating portion 16 of building block 10 is preferably so dimensioned so that it extends slightly beyond the con¬ fines of endwalls 26 and 28, block top 30, and/or block bottom 32.

Referring to Figure 2, it will be seen that insulating portion 16 preferably consists of an integral piece of insulating material and extends the entire length of the block 10 and beyond planar endwalls 26 and 28 of block 10. Ends 96 and 98 of insulating portion 16 preferably extends from about 0.1 to 0.4 inches beyond endwalls 26 and 28, respectively.

In another embodiment, the insulating portion 16 extends from about 0.2 to about 0.6 inches above the top of the block 10.

Two or more of building blocks 10 may be joined end to end by mortar to form a construction wall which contains a continuous barrier of insulation throughout the wall and provides an impeded thermal path for the travel of heat from sidewall 22 to sidewall 24 (see Figure 10).

Building blocks 10 are preferably so constructed that, regardless of how one endwall of one block is joined with another endwall of a second block, the resulting structure will have a continuous barrier of insulation throughout it. In one embodiment the name of the building block

manufacturer (or of another entity) is inscribed onto the insulating insert 16 where it may be seen by a mason after the insert has been connected to block parts.

The ends 96 and 98 of insulating portion 16 which extend beyond walls 28 and 26, respectively, are preferably sub¬ stantially at the center of said walls 28 and 26. Refer¬ ring to Figure 2, a centerline 100 can be drawn between sidewalls 22 and 24, and the portion of the insulating material 16 which extends beyond the endwall is preferably substantially centered on both sides of the centerline.

The term substantially centered means that at least some portion of end 96 and of end 98 is on each side of the centerline 100. Thus, referring to Figure 2, the distance 102 between centerline 100 and the distal portion 104 of end 96 is preferably from about 0.25 to 4 times as great as the distance 106 between centerline 100 and the proximal portion 108 of end 96. Similarly, the distances between the distal and proximal portions of end 98 (not shown) and centerline 100 are preferably from about 0.25 to about 4 times as great as each other.

In the block of Figure 1, the thickness 110 of ends 96 and 98 at their midpoint of insulating portion 16 is pre¬ ferably such that the distance 112 from wall 24 to the inner wall 114 of end 96 is from about 0.8 to about 1.2 times the distance 116 from wall 28 to the outer wall 118 of end 96. Similarly, the distance from wall 20 to the inner wall of end 96 is preferably from about 0.8 to about 1.2 times the distance from 18 to the outer wall of end 98. At the point at which ends 96 and 98 extend past the ends of walls 26 and 28, the width of insulating por¬ tion 110 at its midpoint is preferably from about 1 to about 3 inches.

It is preferred that the ratio of the width of the insulating portion 16 at its midpoint and at the points at which ends 96 and 98 extend past the ends of walls 26 and

28, to the distance between sidewalls 22 and 24, be from about 0.10 to about 0.5.

Referring to Figure 6, there is shown an alternative building block 120 which is suited for use at a corner of a wall construction. Building block 120 preferably has two opposite planar sidewalls 122 and 124, two opposite planar ends 126 and 128, a planar top 130, and a planar bottom 132.

Insulating portion 134 is preferably an integral arti¬ cle extending from endwall 128 to sidewall 122. Insulating portion 134 preferably extends beyond planar walls 122 and 128. Ends 136 and 138 of insulating portion 134 preferably extends from about 0.1 to 0.4 inches beyond walls 122 and 128.

Referring to Figure 7, the use of both block 10 and corner block 120 is shown. It should be noted that, at point 140, there is a continuous insulative path formed by the contact between insulating material 16 and insulating material 134.

Referring again to Figures 6 and 7, in the embodiments of the building blocks shown, mortar notches are provided which preferably extend the full height of block 10 and block 120.

Figure 8 illustrates another, smaller-sized version of the building block of Figure 1.

Figure 9 shows one means of connecting the building block of Figure 1 with the building block of Figure 8. It should be noted that, at point 144, there is contact bet¬ ween the insulating portions 16.

Figure 10 illustrates one embodiment in which mortar 146 connects two building blocks 10. In the embodiment depict¬ ed in Figure 10, the middle block also may be connected to the two outer blocks after it has been rotated 180 degrees.

The building block 10 of this invention may be prepared with materials, machines, and processes well known to those

skilled in the art. Thus, by way of illustration and not limitation, one means for preparing a lightweight building block 10 is described below.

In this preferred embodiment, one may use 1500 pounds of pumice, 2,500 pounds of sand, 530 pounds of 1-A cement, and water. The ingredients may be loaded into a mixer (available from Standly Batch Systems, Inc.) and mixed therein until a substantially homogeneous mixture is ob¬ tained. Thereafter, the mixture is then loaded into a hopper (available from Lithibar Matik, Inc.) which feeds the Besser block making machine described in a prior por¬ tion of this specification. The mixture is then shaken into a mold box (available from Rampf Mold Industries, Inc.) around a metal sinuous mold (available from Therma- Lock Products, Inc. of North Tonawanda, New York) which is adapted to form the mixture into the shapes of block parts 12 and 14. The mixture in the mold is then pressed and vibrated while in the mold to facilitate the settling of the mixture to the proper desired block height. The "green block" so formed in the mold is then removed from the mold and fired in a kiln (Johnson Gas Appliance Company) at a temperature of 180 degrees Fahrenheit for at least about 6 hours. Thereafter, the fired blocks are allowed to cool. Thereafter, as is shown in Figure 5, insert 16 is pressed into place between fired block parts 12 and 14.

In another embodiment of the process, the sinuous mold used is insulating portion 16, which is fastened within the mold box prior to the time the mixture is poured therein. The structure thus formed, containing insulating material 16, is then pressed in a similar manner, the green body is removed from the mold box, and the green body is then fired at a temperature of from about 125 to about 200 degrees Fahrenheit and then cooled. This embodiment in is il¬ lustrated in Figures 15, 16, 17 and 18.

In this embodiment, the insert 16 used is generally

serpentine in cross-section. One may produce such a ser¬ pentine insert by any of the means well known to those skilled in the art. Thus, e.g., one may use a process similar to that described in U.S. patent 4,551,959 of Schmid to prepare a serpentine insert.

In one preferred embodiment, where the insert consists essentially of expanded polystyrene, the insert is made by a steam chest molding process in which beads of expandable polystyrene are exposed to heat in a confined space config¬ ured to produce the desired shape. The preferred medium is steam; it is directly diffused through the preexpanded beads in a mold cavity.

In one preferred embodiment, insert 16 is a wedge-shaped structure with inwardly extending sides which are wider at the top 156 of the insert than at the bottom 158 of the insert.

Insert 16 is an integral, relatively lightweight struc¬ ture adapted to form a multiplicity of interlocking pro¬ jections with curvilinear structure. Thus, referring to Figure 12, if insert 16 is placed into a rectangular mold 148 and concrete is poured into the mold and allowed to cure, a building panel 150 will be formed with interlock- ably connected building panel parts 12 and 14. Each of these building panel parts will have an interior interlock¬ ing shape defined by the exterior shape of the insert 16.

Referring to Figure 13, insert 16 is comprised of at least one projection 152 which is curvilinear. It also preferably is comprised of at least two thumb holes 154 which facilitate the lifting of building block 10 once the insert has been wedged into place between block parts 12 and 14.

Insert 16 preferably consists of material with a density of from about 0.5 to about 4.0 pounds per cubic foot, a flexural strength of from 25 to 125 pounds per square inch and a shear strength from 25 to 175 pounds per square inch.

In a more preferred embodiment, insert 16 consists of material with a density of from about 1.0 to about 3.0 pounds per cubic foot, a tensile strength of from about 27 to about 125 pounds per square inch, a compressive strength of from about 11 to about 92 pounds per square inch, a melting point not lower then about 140 degrees Fahrenheit and an R value of at least 3.5 R per inch. In an even more preferred embodiment, the material in the insert has a density of from about 1.0 to about 2.0 pounds per cubic foot, a tensile strength of from about 42 to about 80 pounds per square inch, a compressive strength of from about 20 to about 53 pounds per square foot, a melting point not less then 160 degrees Fahrenheit, and an R value of at least about 5.5 R per inch.

In one preferred embodiment, the foam material used is "STYOPOR", which is an expanded polystyrene bead material available from BASF Corporation of Parsippany, New Jersey.

By way of illustration and not limitation, the material in insert 16 may consist essentially of urea formaldehyde, phenol formaldehyde, polystyrene, phenolic resins, polyur¬ ethane foam, and the like.

In one embodiment, the material in insert 16 consists essentially of at least one foam material. The term foam, as used in this specification, refers to a material with a spongelike, cellular structure and includes materials such as polystyrene foam, polyurethane foam, flexible foamed thermoplastic elastomers, and the like.

Referring to Figure 15, in the preferred process of this invention, insert 16 is disposed within a mold box. The mold box may contain one or more molds.

Figure 15 shows one mold 157 in the mold box. Insert 16 may be disposed within the mold 157 so that it is substan¬ tially centered within mold 157. Alternatively, it may be so disposed that it is off-center.

In one embodiment insert 16 is secured to mold 157 so

that, when cementitious material is poured around it, it stays in the same position. One may secure insert 16 within mold 157 by means well known to those in the art such as, e.g., by holding the top of insert 16 with suitable holding means (such as pins, e.g.) during the pouring of the cemen¬ titious material.

Once insert 16 has been placed within mold 157 and secured therein, a mixture comprised of aggregate and a bonding agent is preferably poured around insert 16.

The mixture which is poured around insert 16 is prefer¬ ably comprised of at least about 30 weight percent of aggregate. It is preferred that the mixture contain at least about 40 weight percent of aggregate. As is known to those skilled in the art, the term aggregate refers to one or more inorganic materials such as such as sand, gravel, clay, exploded shale, glass, pumice, granite, and the like.

In one preferred embodiment, the aggregate is exploded shale material.

In addition to the aggregate, the mixture which is poured around insert 16 also preferably contains at least about 5 weight percent of cement (also known as Portland cement) . It is preferred that the mixture contain at least about 10 weight percent of such cement.

The mixture poured around insert 16 also may contain other inorganic material such as, e.g., glass. In this embodiment, the glass used in the mixture preferably is so sized that substantially all of its particles have a lar¬ gest dimension which is smaller than about 1.0 inch. In this embodiment, the glass may be used to replace some or all of the aggregate; thus, the total amount of aggregate plus glass in the mixture is at least about 30 weight percent.

By way of illustration, one may use a mixture comprised of 1,300 pounds of exploded shale (sold as said "Haydite"), 1,400 pounds of limestone, and 335 pounds of Portland

cement .

In another embodiment, the mixture poured around insert 16 is comprised of at least about 10 weight percent of fly ash.

Cementitious material 158 is preferably poured into mold 157 until said material 158 substantially fills said mold. Then, as shown in Figure 17, the cementitious material is pressed and/or agitated to help it settle within the mold 157.

Referring to Figure 17, pressure is applied in the direc¬ tion of arrows 159 upon stripper shoes 160 and 162 until the density of all the materials within mold 157 is from about 80 to about 150 pounds per cubic foot. This pressure may be applied continuously, or it may be applied intermit¬ tently.

In one embodiment the pressure is applied intermit¬ tently. In this embodiment, it is preferred to apply pressure to the mixture 158 through the stripper shoes for from about 3 to about 6 seconds.

In one preferred embodiment, while pressure is being applied to the mixture 158, said mixture is also agitated to help it settle within the mold.

The pressure and/or the agitation are preferably continued until (l)the density of the material within the mold box 157 is from about 80 to about 150 pounds per cubic foot, and (2)insert 16 extends above the material 158. It is preferred to compress the mixture 158 until the insert 16 extends at least from about 0.2 to about 0.6 inches above the material 158. It is more preferred to compress the mixture 158 until the insert 16 extends from about 0.3 to about 0.5 inches above the material 158.

After the material 158 has been compressed to the desired extent, the block is removed from mold 157 by means well known to those skilled in the art. Thus, it may be pressed out of the mold 157 by first removing the bottom

164 of the mold and then pressing the block 166 out of the mold.

The block 166 thus removed is then cured. The curing is effected by heating the block 166 to a temperature of from about 75 to about 250 degrees Fahrenheit for from about 4 to about 10 hours.

In one embodiment, illustrated in Figures 19 and 20, a split block 190 comprised of inserts 192 and 194 is split along line 196 to yield a ribbed, split- faced units 198 and 200. Thus, by this process, one may prepare an insulat¬ ed building block of this invention which is three score, five score, three-wide score, etc.

The building block produced by the process of this inven¬ tion, regardless of whether it has a split face or a rela¬ tively smooth face, may be coated with glaze. In one aspect of this process, block parts 12 and/or 14 are coated with glaze, heated to a temperature of about 1,100 degrees Fahrenheit for from about 1 to about 5 hours, and then joined by having insert 16 be inserted between their in¬ terior faces.

In one embodiment, the face of the building block s coated with an inorganic coating known to those in the trade as "MINERALITE" (a coating consisting of aggregate which is available from Mineralite Limited, Bridgewater House, Surrey, England. ) . The coating is an aggregate (such as granite and glass) mixed with cement and non- resinous additives.

In one preferred embodiment, a process is provided for making an insulated concrete block assembly which can be laid dry or with mortar joints. This process is described in U.S. patent 4,584,043 of Monte Riefler. In the first step of this process, there is provided at least one inner concrete block having upper and lower load bearing surfaces and inner and outer faces extending between said upper and lower surfaces. This inner concrete block may be substan

tially identical to the block depicted in Figure 1 of this application.

In the second step of this process, there is provided at least one outer concrete block which is spaced from and registering with said inner block and which has upper and lower load-bearing surfaces. In this outer concrete block, the inner and outer faces extend between said upper and lower surfaces and a central crossweb extends between said upper and lower surfaces and has ends integral with said inner and outer faces.

In the third step of this process, there is provided a board of insulating material which is sandwiched between and adhesively bonded to the outer face of said inner block and to the inner face of said outer block. This board has an upper edge registering with the upper surfaces of said blocks.

In the fourth step of the process, there is provided a sheet metal tie. n the fifth step of the process, said inner and outer blocks are conveyed along laterally sepa¬ rated paths to stops; a set of one inner and one outer block is positioned with the outer face of the inner block presented to and in register with, but laterally spaced from, the inner face of the outer block; said set of blocks is then conveyed past two sets of adhesive guns which apply adhesive to the blocks; the adhesive-laden blocks are then stopped in register with and laterally spaced from each other, with the adhesive coated faces facing each other; the board of insulating material is inserted between and in registry with said adhesive coated faces; the blocks are then pressed together to compress the board between the adhesive coated faces of the blocks; a spot of adhesive is then applied to the upper surfaces of each of the blocks; and the ends of the sheet metal tie are then pressed against the adhesive-laden spots.

In another embodiment of this invention, the insulating

insert 16 is replaced by aerogel. As is known to those skilled in the art, aerogels are gel materials which are dried under high pressure and temperature and which produce one of the lightest solid materials.

Another embodiment of this invention is illustrated in Figure 21. In this embodiment, hammer 202 (or another similar instrument) is used to break away from building blocks 204 and 206 knockouts 208 and 210. In order to facilitate the breaking away of knockouts 208 and 210 from the building blocks 204 and 206, the building blocks 204 and 206 may be scored at points where it is desired to cause the knockouts 208 and 210 to separate from the blocks. Thus, e.g., one of such scores is illustrated at each of points 212, 214, 216, and 218. Alternatively, other means may be used to facilitate the separation of the knockouts from the blocks.

The space created by the separation of the knockouts 208 and 210 may be filled with one or more retaining rods 220 and 222. As is illustrated in Figure 21, these retaining rods may be passed through a multiplicity of building blocks which are offset from one course to the next.

After the retaining rods are placed through the orifices in the offset blocks, the blocks may be grouted or posten- sioned tightened.

In another portion of this specification, applicants have described the preparation of the insert 16 with expandable polystyrene. In one aspect of this embodiment, an aluminum tub comprised of interior aluminum surfaces is used to shape the insert. Five projecting dies extend upwardly from the wall of the aluminum tub and, when in contact with the expandible polystyrene, define the curvilinear projec¬ tions of insert 16. It is preferred that at least three of the five projecting dies be removably attached to the wall of the aluminum tub so that, if one desires to change the configuration of the insert 16, he may replace one set of

dies with another.

In another portion of this specification, applicants have described a process in which the building block of this invention is made by first preparing two block parts 12 and 14 and then inserting insulating insert 16 therebet¬ ween. The two block parts 12 and 14 may be prepared by inserting a metal mold into a mold box and placing con¬ crete around the mold. The metal mold may be made by a process in which a wooden pattern is made with substantial¬ ly the same shape as insulating insert 16. Thereafter, this wooden pattern is placed in sand and then removed, thereby leaving a cavity with substantially the shape of insert 16. This cavity is then filled with molten metal which is thereafter allowed to cool, thereby forming the metal mold.

The following example is presented to illustrate the claimed process but is not to be deemed limitative thereof. Example l

An insulating insert was prepared on a steam chest mold¬ ing machine from expanded polystyrene with a density of 1.5 pounds per cubic foot. The polystyrene was formed into a serpentine insert, with substantially the shape shown in Figure 13. Referring to Figure 13, this insert had a height 168 of 8.0 inches, a length 170 of 16 inches, a top depth 172 of 5.5 inches, a bottom depth 174 of 5.25 inches, a top wall thickness 176 of 1.3 inches, and a bottom wall thick¬ ness 178 of 1.0 inches.

1,300 pounds of exploded shale, 1,400 pounds of lime¬ stone, 335 pounds of Portland cement, and water were mixed until a substantially homogeneous mixture was obtained. The insert was disposed and centered within a rectangular mold which was 27 inches long, 20 inches wide, and 10 inches high. The shale/limestone/cement mixture was then poured into the mold until it was substantially level with the top of the insert. Thereafter, while the mold is

vibrated, the cementitious mixture was pressed at a pres¬ sure of 300 pounds to compress the mixture until its densi¬ ty is 100 pounds per cubic foot. Thereafter, the block so formed was removed from the mold and heated at a tempera¬ ture of 185 degrees Fahrenheit for 6 hours.