CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and the benefit of the filing of U.S. Patent

Application Serial No. 12/554,191 , entitled "Products Made from Recycled Cardboard", filed on September 4, 2009, and the specification and claims thereof are incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not Applicable.

INCORPORATION BY REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

[0003] Not Applicable.

COPYRIGHTED MATERIAL

[0004] Not Applicable.

BACKGROUND OF THE INVENTION

Field of the Invention (Technical Field):

[0005] The present invention relates to methods and products for use in the building trades, which methods and products utilized recycled paper waste, including recycled cardboard, for use in making building structural and wall materials.

Description of Related Art:

[0006] It is necessary that recycling of waste be expanded in our society beyond what is currently done, for many obvious reasons. In one preferred method of recycling, waste materials can be reprocessed and used to produce new products. [0007] There is a need for technologically simple methods to produce building material utilizing recycled waste and particularly recycled paper waste. The prior art methods disclosed in U.S. Patent Nos. 5,102,596, 5,302,331 , 5,729,936 and 6,216,967, incorporated herein by reference, each disclose methods and products, but each method suffers from significant limitations, requires complex processing steps, or the like.

BRIEF SUMMARY OF THE INVENTION

[0008] The present invention is of a method of making a structural component (and such a structural component), comprising: mixing together wood pulp, water, bentonite clay, and calcium chloride; and forming the mixture into the structural component. In an embodiment, the mixture consists essentially of wood pulp, water, bentonite clay, and calcium chloride. In another embodiment, the mixture consists of wood pulp, water, bentonite clay, and calcium chloride.

Forming can comprise employing a wire screen, rebar, and/or interlocking blocks. In a further embodiment, the mixture additionally comprises one or both of borax and boric acid. In another embodiment, the mixture consists essentially of wood pulp, water, borax or boric acid, bentonite clay, and calcium chloride. Bentonite clay preferably comprises about 10% of the structural component by volume. Calcium chloride preferably comprises about 10% of the structural component by volume. In addition, plastic waste (or other, preferably non-hazardous, waste, preferably shredded) can be incorporated as a strand reinforcement for structural components of the invention.

[0009] Further scope of applicability of the present invention will be set forth in part in the detailed description to follow, taken in conjunction with the accompanying drawings, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0010] The accompanying drawings, which are incorporated into and form a part of the specification, illustrate one or more embodiments of the present invention and, together with the description, serve to explain the principles of the invention. The drawings are only for the purpose of illustrating one or more preferred embodiments of the invention and are not to be construed as limiting the invention. In the drawings: [0011] Fig. 1 is a schematic diagram of components according to the invention used to make a shed;

[0012] Fig. 2 is a schematic diagram of components according to the invention used to make a wall;

[0013] Figs. 3(a) to (e) are views of components according to the invention attached via clips;

[0014] Fig. 4 is a schematic diagram of filler material according to the invention used in conjunction with rebar;

[0015] Figs. 5(a) to (c) are schematic diagrams of use of "blown in" insulation with walls made according to the invention;

[0016] Figs. 6(a) and (b) are top perspective views of molds useful with the invention;

[0017] Fig. 7 is a flow diagram of uses of waste cardboard according to the invention;

[0018] Figs. 8(a) to (c) are views of a corner wall clip according to the invention;

[0019] Figs. 9(a) and (b) illustrate panel and block embodiments of walls according to the invention; and

[0020] Figs. 10(a) to (c) are further examples of walls made according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0021] Paper and cardboard products are one example of materials that can be reprocessed in used to make new products. This can be done, according to this invention, with a minimum of specialized equipment. In one embodiment, cardboard waste from a paper or cardboard plant may be employed. This waste is called "press cake" in the industry, and is gathered after the processing of used cardboard boxes that have been brought to the mill for recycling. This press cake is typically loaded onto a waste transport vehicle and hauled to a landfill and buried. Cardboard not rejected, and thus not forming press cake, is typically used again in manufacturing cardboard boxes. The reject material or press case contains a large percentage of paper elements, but also includes other elements, such as plastic, tape glue, strands, etc. The press cake is thus typically a mixed waste, though consisting primarily of paper and paper products. The press cake may be employed in this invention, providing that the materials other than paper and paper products do not interfere with subsequent processing and manufacturing steps.

[0022] Press cake if received from a paper or cardboard mill is typically saturated with water from processing. The actual cake is typically approximately 1 to 2 inches wide by 2 to 3 or 4 inches long by ¼ to 1 inch thick. However, the size will vary, and sometimes is in the general size and shape of a wood type "chip" used in landscaping, and sometimes is a much larger "patty".

[0023] Utilizing the methods of this invention, the press cake is processed further by soaking it in water and mixing with various chemicals. In one embodiment, the water-soaked press cake is mixed with a variety of reagents, including borax or boric acid, which serves as a flame retardant, with bentonite clay, which serves in part as a bonding agent, and with calcium chloride, which adds strength to the mixture. The specific chemicals used and the amounts or quantities can vary depending on the composition of the press cake or other waste paper source, the desired reaction or reactions, and the specific uses to which the resulting building material will be put.

[0024] While this invention may be employed with material that is convenient and readily available, such as press cake obtained from a paper mill, the processes and methods can also be employed with recycled paper or cardboard obtained from any source.

[0025] Once the mixture of cardboard and reagents is at the desired consistency, the resulting slurry can then be poured into a mold forming either a "block", tip-up wall section, or any other of a number of shapes and sizes required or requested. After initial setting, the resulting product may optionally be removed from its mold to facilitate drying. Utilizing this method, either no pressure or very low pressure is used to compress or form the block.

[0026] In one embodiment, the form has a wire screen on one side, which supports the block and allows air circulation thereunder to facilitate drying. The wire screen may also be employed as a permanent component, to increase adhesion of subsequent plaster coats. In yet another embodiment, the form itself may be composed of a wire screen or other air and water permeable material.

[0027] A "slab" or wall section intended for use as a wall product, depending on the desired application, may optionally include a frame as a permanent part of the slab, to aid in installation or provide additional strength. The frame may be built of wood, metal, plastic or any other material with the required structural strength.

[0028] Beside use in the building trades, the resulting material can be shaped into any of a wide variety of forms for other uses, such as for example shaping into forms for use as a protective shipping cover for products, or to restrain and cushion fragile items in shipping containers or cartons.

[0029] In one embodiment, larger size blocks in various sizes and shapes are made, thereby reducing both the amount required for a project and the need for handling, and thus resulting in lower costs of labor. The blocks may be designed in different ways depending on the application; in some applications an interlocking system is employed, wherein the blocks interlock one with another. In another application blocks with a continuous cavity or cells are provided, for use as a permanent formwork for concrete or other structural materials. The blocks may also be solid. The blocks may form a part of a formwork, for forming a permanent insulated concrete form, which may employ metal or other retaining or strengthening members, such as Polysteel® forms. In such forms the paper-based material of this invention is used instead of styrofoam or other expanded plastics or foams. The blocks are structural and load-bearing, with or without concrete inside the blocks, and whether installed inside a building or on the exterior.

[0030] Wall units may be created using slab, with the slurry mixed and then poured into various size forms to accommodate its individual application. Once dried, the wall unit can then be removed from its form, and optionally cut to fit as necessary. Using the method and processes of this invention, it is possible to produce wall units of various thicknesses, shapes and sizes. In one embodiment, the form employed as a mold forms a integral and permanent part of the resulting product, and may be optionally installed utilizing clips or other fasteners designed specifically for the wall unit (preferably an interior tip-up wall).

[0031] The resulting products will advantageously be insulating, having a high R-value, thereby resulting in lower overall energy bills, increased warmth in winter and enhanced cooling in summer). In certain embodiments, the material further has a U-value, and retains and transfers heat energy as a function of time. The resulting products will similarly be lightweight, and thus easy to handle, capable of being produced in larger sizes, and easily used in building projects. The resulting products will similarly be inexpensive. The material will result in decreased costs of building, since the insulation is integral to the product. No sheet rock or other wall covering is required on internal surfaces, since the resulting surface can be directly plastered, or alternatively may be painted, using a primer as appropriate. On external walls, stucco or other typical exterior wall covering material can be applied directly to the material, thus eliminating otherwise necessary steps and additional labor. The products can be cut with ordinary tools, such as saws, known to the construction trade. The product can also be shaped, grooved to allow for other installation needs, and otherwise formed as required.

[0032] In one example, press cake was added to water in a five-gallon container. Between

1 ½ and 2 ½ gallons of water was utilized, with the balance being cardboard waste, such as press cake, to a total volume of about four gallons. To this was added up to two quart of 94% anhydrous calcium chloride, as a free flowing powder. Up to two quarts of bentonite, sold under the trade name Aquagel by Baroid Drilling Fluids, was added. Optionally a fire retardant, such as borax or boric acid, can be added, and flammability tests have been very positive. An insect repellant may also be added. The resulting contents are mixed, thereby forming a slurry, and poured into a form.

[0033] Figs. 1 -10 illustrate embodiments of the invention, including methods and mechanisms for using products made by the described methods of the invention.

[0034] Fig. 1 is a schematic diagram of components according to the invention used to make a shed 10. The shed is preferably about 5'x8'x8' high, and comprises panels 12,14,16,18. Stucco finish outer walls 13 are employed, with plaster preferably to be applied for interior wall finish. Floor joists 15 are preferably 2'x10' with ¾" plywood flooring. Walls are preferably molded using 2'x4's 17 as a frame with rebar and/or wire mesh for wall reinforcement. Roofing 19 is preferably rafter type with asphalt shingles.

[0035] Fig. 2 is a schematic diagram of components according to the invention used to make a wall 20, with cutaway view 22. The wall comprises rebar 24 in frame 28. The frame is preferably 2'x4' or 2'x6' used as a mold when pouring slurry for the walls at the building site, thereby forming processed materials 26 according to the invention. Wood baseplate 30 is preferably redwood. Window 32 in window frame 34 can be employed. Panels 36 are nailed and/or bolted (e.g., via bolt holes 38) in place before the final wall cover is applied. A metal purlin or wood truss 40 is employed. If and where needed, tie brackets 42 can be employed for strength, on top, bottom, and/or sides.

[0036] Figs. 3(a) to (e) are side, top, end, perspective, and assembled views of components 50 according to the invention attached via clips 56 (with cutaway views 54 of walls (preferably interior tip-up walls). Clip attachment points 52 are for straight wall clips on top or bottom with attachment points shown. Clips 56 are but one of many possible ways by which panels can be attached to each other and/or other components, such as steel braces, concrete flooring, and concrete walls. Each panel, whether in its mold frame or removed from its mold frame, will accept such clips. Other attachment means, such as nails, bolts, staples, etc., can be employed.

[0037] Fig. 4 is a schematic diagram of filler material 62 according to the invention used in conjunction with rebar 64, and optionally in frame 66, to form panel 60.

[0038] Figs. 5(a) to (c) are schematic diagrams of use of "blown in" insulation with walls 70 made according to the invention. As illustrated, a slurry mix or shredded material can be placed in molds of any shape, size, or material to be included as part of the resulting product or, once poured in a form, left to dry by any method, and then taken from the mold to be handled from that point to its next step in its processing for its final form. Insulation can be made after the material is dried and then put in a machine to create the cellulose type product of the invention. Filler material 76 is preferably dried and stamped with a pattern. Wood frame 72 and rebar 74 are preferably employed, with blown-in insulation 78, wood or steel trusses 80, and dry wall or drop-in ceiling 82.

[0039] Figs. 6(a) and (b) are top perspective views of molds 90,100 useful with the invention. Fig. 7 is a flow diagram of uses of waste cardboard according to the invention. Figs. 8(a) to (c) are views of a corner wall clip 110 according to the invention, useful either on tops or bottoms during installation.

[0040] Figs. 9(a) and (b) illustrate panel and block embodiments of walls 120,130 according to the invention, with wood headers 122, wall panels 124, and molded blocks 132. Figs. 10(a) to (c) are further examples of walls 140,150,160 made according to the invention, including headers 152 (wood or material of the invention), wall sections 142, and garage door 162.

[0041] The materials of the invention were subjected to flame exposure/flammability testing, with comparisons to traditional adobe and polystyrene building materials. The testing approach was designed to mimic the flame exposure conditions of AST tests, but on a smaller scale. Flame testing was performed in an indoor firing vessel at Los Alamos National Laboratories. The vessel is capable of handling explosive charges up to 10 kg TNT equivalency.

[0042] ASTM standards exist for flammability testing and surface burning behaviors of building material. ASTM E84-092 describes evaluation of the surface burning characteristics of large exposed building material surfaces. Test 1 , described below, exposed the materials of the invention to a flame below a horizontal surface. The ASTM test standard also specifies a natural gas (methane) flame, but of a lower temperature than the flame conditions used here. The second ASTM standard, ASTM E 1 19-08a, describes fire testing of building and construction materials. The test is specified for walls, partitions, floor and roof specimens.

[0043] Here, a propane-based flame was used in all of the tests, though oxy-acetylene was considered. The maximum flame temperature for propane/air is 1990°C (or about 3595°F), which is higher than methanol, but lower than diesel, and comparable to gasoline. These temperature- exposure time guidelines were considered during tests, however based on the experimental results during testing and the limitations of the propane/air flame, the test was unable to achieve all of these conditions at the building block surface using the propane flame.

[0044] Two slabs of building materials of the invention were rigorously tested, "Block 1 " and

"Block 2," as well as additional tests using loose material, and a full as-prepared. Block 1 was a more finished block. Block 2 appeared to be less dense (more porous) than Block 1. In addition to these materials, adobe and polystyrene block building materials were also tested.

[0045] The building materials were exposed to the propane/air flame in two configurations.

In the first configuration, an approximately 1 " thick slab of building material was placed in a horizontal position above the flame. The flame standoff was varied while temperature readings at 8 positions on the sample were made, and visual observations were recorded with time. The flame was moved sequentially closer to the sample until it was in contact. In the second configuration, the sample slab was placed in a vertical position, similar to how the material would be exposed if used as a wall. The flame was then brought very near to the pristine slab surface. Follow-on tests used the vertical configuration to examine the materials of the invention, and the adobe block and polysytrene.

[0046] A brief summary of the tests performed is given in Table 1 . The first experiment was performed to gauge the response of the material to flame exposure, and enable planning of the instrumented tests. Loose building material was first placed on the floor of the firing chamber and the flame was brought to within 1 " of the material. No evidence of burning was observed. The flame was then brought in contact with the loose material, and the material was observed to smoke or smolder. The loose material did not sustain flame propagation when the torch was removed.

Table 1. Summary of flame tests performed on building materials.

Test # Material Exposed Configuration Summary of Results

N/A Loose Inventive Exposure of loose Material was observed

Material material to flame to smolder with flame in contact Test 1 Inventive Material Horizontal surface of Blackening, smoking slab

Test 2 Inventive Material Vertical surface of slab Self-sustained flame

Test 3 Inventive Material Vertical surface of Blackening, smoldering, block retained heat

Test 4 Polystyrene Vertical surface of Burning/disintegration block

Test 5 Adobe Vertical surface of slab Retained heat

[0047] Test 1. The first instrumented test was performed on Block 1 , a 1 " slab cut from the finished blocks of the inventive material. The block was then back drilled, using a slightly undersized drill bit, in eight positions to allow for placement of type-K thermocouples. The holes were drilled at varying distances from the test surface. Thermocouple 4, at the center was drilled all the way through the block so that the thermocouple tip was flush with the exposed surface. The remaining holes were placed in a manner to cover varying distances from the center, as well as distances from the test surface.

[0048] Block 1 was placed horizontally 6 1/8" above the surface of the torch, or about 1 -1 .5" from the top of the flame tip. The torch was then ignited and temperature readings were recorded at all 8 thermocouples. Within 2 min of flame ignition, T4, the center thermocouple flush with the surface, reached 2310 °C (approx. t=500 s). 10 min after exposure, the surface temperature reached a near-steady temperature of 300-320 °C. At this position, the flame exposure resulted in blackening of the surface of the building material, but no signs of burning or smoldering were observed.

[0049] The flame was then moved closer to the surface by 1 " so that the flame tip was in contact with the surface. The surface of the building material began to glow with an orange color, and the temperature at the center thermocouple ramped up to 590 °C. After direct flame contact, the building material was observed to ash, then re-light. The material reached a temperature of 660 °C where it was held for 5 min. This condition was chosen to simulate the temperature-exposure time listed in the ASTM standard test. The building material did not support or propagate a flame (i.e., catch on fire), however once the flame was removed, it was observed to smolder, and smoke was evolved. After flame removal, the temperature dropped to about 330 °C and leveled off, dropping more slowly over time, indicating that the block was smoldering internally. The surface of the material that had been exposed to the flame was also sunken, and no longer planar. 20 min after removal of the flame, the temperature had dropped to 100 °C. [0050] Next, the flame was brought in direct contact with the sample (moved closer by another 1 ") at the same position on the surface. The temperature at the center (T4) quickly spiked to 790 °C, which appeared to be the maximum obtainable temperature in this configuration. Here, the center of the block had diminished integrity, and appeared to be ash-like, as if the material had been burned (again no flame observed). The position was held for just 5 min [not the 10 min desired to simulate the ASTM conditions] as the sample lost integrity and appeared to be "burned" through the entire 1 " width of the slab. Again, temperature readings were recorded after flame removal. For well over 5 min after flame removal, the material got darker in color and evolved smoke. The temperature at the center position leveled off near 330 °C, similar to the previous flame position. The thermocouples were then removed, and the block was extinguished with water.

[0051] Test 2. The goal of Test 2 was to expose the building material to the harshest conditions possible using the propane flame. In this test, Block 2 was held in a vertical position, with the flame brought into direct contact with the pristine surface (not pre-exposed to flame as was Block 1 in Test 1 ). Block 2 was the more "finished" of the 2 blocks tested. For Test 2, the thermocouple positions and numbering were identical to Test 1. Here, the sample was held in the vertical configuration, as it would be positioned if used as a wall. This configuration also reproduces conditions in which drafts exist near the surface.

[0052] Within 2 min of flame exposure, the surface of the black had reached 350°C in the center. The temperature peaked at 370°C, at which point smoke was observed emanating from the back of the 1 " thick slab. After 10 min of flame exposure, the rear surface of the block ignited and a flame on the back surface was observed. There was evidence of self- sustained burning, and the flame took about 346 sec to extinguish after flame removal. Further, the block smoldered for over 20 min after flame removal with temperature levels of near 300-400°C. Drafting the panel soon after flame removal caused the block to "flare-up" and a flame was observed. The block was extinguished with water. The Flame was brought into contact with the front surface of the sample slab, resulting in immediate blackening and temperatures between 370-430°C at sample center. 10 min after exposure, a self-sustained flame was observed at the back surface. Removal of the propane flame at the front surface resulted in significant smoking and smoldering, and a hole was burned completely through the 1 " thickness. Drafting or fanning the block, with no flame present, resulted in flare-ups.

[0053] Overall, this configuration appeared to provide the harshest flame exposure conditions on the block surface. While the temperatures did not reach those observed in Test 1 , the material was exposed to the most intense flame (in contact) in a pristine (not pre-burned) state. In addition, thermal conductivity and drafting are significant factors in this configuration. While the slab did ignite, and a hole was burned through the center of the sample, the flame did not engulf or destroy the entire block. Because the 1 " thickness of the sample was burned through, Test 2 motivated Test 3, exposure of an entire finished block with a greater thickness.

[0054] Test 3. Since Test 2 resulted in burning through a 1 " slab of inventive building material, the goal of Test 3 was to examine the effect of sample thickness in a vertical configuration. Here, the propane flame was brought within 0.5" of the vertical surface. A single thermocouple was inserted from the holes in the center of the block to be about 1/8"from the exposed surface. The temperature was also recorded using a laser-based temperature sensor, which was checked prior to testing for comparison to the thermocouple. The thickness of the block at the exposed position was 3". The block was the same block (Block 2) from which the slab was cut and used in Test 2.

[0055] Within 25 sec of flame exposure on the surface, the temperature rose to 400°C and it continued to rise to about 510°C at the center over -60 sec, measured using the laser sensor. T5 did not register a temperature rise under later. Blackening of the surface was observed immediately. After 3.5 min of exposure, the surface was black, but no smoking was observed. The maximum temperature (about 510°C) was maintained for 10 min. The flame was then turned off.

[0056] As to the temperatures recorded at the front surface of the block following flame removal, the characteristics associated with the drop in temperature over time are consistent with those observed in Tests 1 and 2. The temperature drops slowly and plateaus near 300-350°C. After several minutes, the surface retains its heat. In fact, the block was still warm (100°C) 6 hrs after flame removal, even though the flame exposure duration was only 10 min.

[0057] Tests 4 and 5. Tests 4 and 5 exposed a polystyrene block and adobe slab to the same propane flame. The tests were not instrumented, only visual observations were recorded. No evidence of blackening or burning of the adobe block was observed under direct contact of the propane flame to the exposed surface. However, the surface did get hot, and retained its heat for a long period of time following flame removal. The polystyrene, on the other hand, exhibited complete destruction under the flame exposure.

[0058] Next, the thermal conductivity of the inventive block material was determined using laser flash analysis (LFA). LFA is a technique in which a laser pulse is used to rapidly heat the front surface of a sample while a long wavelength optical detector monitors the temperature on the back surface of the sample. The pulse transit time through the sample is directly related to the material's thermal diffusivity. The thermal conductivity can be calculated from the thermal diffusivity if the heat capacity and density of the sample are known. All of these quantities are temperature dependent. [0059] LFA was carried out using a Netzsch Instruments LFA 427 system. This uses a defocused 1064 nm pulse from a Nd:YAG laser to heat the front surface of the sample. Heat capacity was measured using a Netzsch Instruments DSC 404 C differential scanning calorimeter (DSC). Heat capacity is calculated by comparing the heat flow into the sample to the heat flow into a sapphire sample under identical thermal ramp conditions. Density as a function of temperature was inferred by calculating the initial density of the sample from its mass and dimensions and then measuring the thermal expansion of the material over the temperature range of interest using dilatometry. Dilatometry was carried out on a Netzsch Instruments DIL 402 C.

[0060] Samples of the inventive material were mechanically cored from larger block pieces.

Several cores that had relatively flat surfaces and straight edges were chosen for analysis. The rough, inhomogeneous nature of the material made it difficult to obtain samples of the quality normally used for LFA and so the reported thermal conductivity numbers are rough values. The cores were nominally 12.5 mm in diameter by 4 mm tall. The end faces of the cores were coated with a thin layer of graphite powder, which is used to absorb the laser pulse and insure efficient heating. The graphite is applied in spray form and time is allowed for the aerosol propellants or solvents to evaporate before LFA measurement.

[0061] Heat Capacity. The material showed a significant variation over the 30 °C temperature range examined, with an average value of about 2.8 J/g K. Some of the variation could be due to changes in the physical contact between the sample and DSC pan due to the rough nature of the sample. Attempts were made to press it into the pan since the density does not usually affect the heat capacity measurements.

[0062] Thermal Expansion. The expansion is reported as dL/Lo, which is the change in length (relative to the starting length) divided by the starting length of the sample. The sample length was measured with the dilatometer LVDT. For this measurement, the force applied to the pushrod was set to its smallest value (15 cN) to avoid influencing the behavior of this relatively soft material. The total expansion over the 30 °C temperature range is about 0.05%, corresponding to about 2 microns for the sample thickness used. The LFA analysis software uses this data automatically to correct for sample thickness as a function of temperature.

[0063] Thermal Conductivity. Diffusivity is calculated from time at which the curve reaches half of its maximum height. From the diffusivity and the parameters shown above for heat capacity and thermal expansion, the calculated thermal conductivity is about 0.16 W/m K. The thermal conductivity (also known as the 'k' Value) specifies the rate of heat transfer. The lower the thermal conductivity, the less heat the material will transfer. The value of 0.16 W/m K means that a cube of the material with 1 -meter length sides will transfer heat at a rate of 0.16 watt for every degree of temperature difference between opposite faces.

[0064] Calculation of R-and U-values. The thermal conductivity measured above is related to the R-value used in the building and construction industry to describe a material's ability to insulate against heat loss. The material's thermal resistivity is referred to as the Y value

(lowercase), and r = l/k. For the inventive material, then, r = 6.25 m K/W. The uppercase R-value refers to thermal resistance for a material of a given thickness: R = thickness / k. For the inventive block material with a thickness of approximately 1 foot (= 0.3 m), the R-value would be calculated as R = (0.3 m) / (0.16 W/m K) = 1.875 m ² K/W. Internationally, R-values are given in SI (or

International System of Units) units, typically m ² K/W or m ² °C/W, and these are the units used above. In the U.S. construction industry, R-values are usually given in units of ft ² °F h/Btu. To convert, one multiplies by 5.68 to get R = 10.65 ft ² °F h/Btu for a block that is 1 foot (= 0.3 meter) thick.

[0065] The U-value describes how well a material conducts heat. It is defined as U = 1/R.

Therefore, for the inventive material with a 1 -foot thickness, U = 0.09 Btu/ ft ² °F h.

[0066] The inventive building material offers potential as a "green" construction material prepared from recycled materials, including recycled paper. The small-scale flame exposure testing was designed to guide ASTM testing and evaluation of the material. Exposure of the building material to moderate conditions (stand-off flame, several hundred °C) resulted in "ashing" and smoldering of the material, but no sustained burning or flame propagation. In the harshest conditions examined, a flame was observed to burn through a 1 " slab of material, but the flame did not propagate outside of the flame exposure zone of the sample, nor engulf the slab. A thicker block of material, more similar to the thickness used in the ASTM surface burning test, was observed to smolder and retain heat for a long period of time (6 hrs after 10 min of flame exposure). The inventive building material appears to offer advantages to polystyrene block, and similarities to the clay-based adobe block. The inventive material was found to be more flame-resistant when compared with polystyrene, offering significantly greater structural stability under direct flame exposure. Similarly to adobe block, flame exposure resulted in retained heat at the exposed surface, a feature that is related to the thermal properties (specific heat, thermal conductivity) of the building material, and may be advantageous for thermal gain in "green" construction (e.g., for use in Trombe walls, etc.).

[0067] The thermal conductivity (needed to calculate R-and U-values) of the inventive block was measured to be about 0.16 W/m K, and this value or better (less) is achievable by the inventive materials. For a 1 -foot thick block, this gives R = 10.65 ft ² °F h/Btu and U = 0.09 Btu/ ft ² °F h. [0068] Note that in the specification and claims, "about" or "approximately" means within twenty percent (20%) of the numerical amount cited. Note further that plastic waste (or other, preferably non-hazardous, waste, preferably shredded) can be incorporated as a strand reinforcement for structural components of the invention.

[0069] Although the invention has been described in detail with particular reference to these preferred embodiments, other embodiments can achieve the same results. Variations and modifications of the present invention will be obvious to those skilled in the art and it is intended to cover in the appended claims all such modifications and equivalents. The entire disclosures of all references, applications, patents, and publications cited above are hereby incorporated by reference.