Upcycling waste plastics into construction materials
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2026-02-03
- Publication Date
- 2026-08-13
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Figure US2026013712_13082026_PF_FP_ABST
Abstract
Description
60980 15916TITLE: Upcycling Waste Plastics Into Construction Materials INVENTORS: Hamed Khodadadi TirkolaeiMasum ShaikhEdward Kavazanjian Jr.CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to, and the benefit of, U.S. Provisional Patent Application Serial No. 63 / 754,349, filed February 5, 2025, entitled " UPCYCLING WASTE PLASTICS INTO CONSTRUCTION MATERIALS." The foregoing application is hereby incorporated by reference in its entirety for all purposes, including but not limited to those portions that specifically appear hereinafter, but except for any subject matter disclaimers or disavowals, and except to the extent that the incorporated material is inconsistent with the express disclosure herein, in which case the language in this disclosure shall control.TECHNICAL FIELD
[0002] The present disclosure generally relates to plastic waste management, and particularly, to systems and methods for converting and upcycling waste plastics into usable materials.BACKGROUND
[0003] The subject matter discussed in the background section should not be assumed to be prior art merely as a result of its mention in the background section. Similarly, a problem mentioned in the background section or associated with the subject matter of the background section should not be assumed to have been recognized in the prior art. The subject matter in the background section merely represents different approaches, which in and of themselves may be inventions.
[0004] Plastic materials are widely used across various industries due to their durability, low production cost, and versatility. As a result, global plastic production has increased significantly over recent decades, leading to a corresponding increase in postconsumer and post-industrial plastic waste. Managing this plastic waste presents an ongoing technical and environmental challenge.
[0005] Conventional recycling processes for plastics are limited in several respects. For example, many recycling methods require separation and sorting of plastic waste by polymer type, color, or additive content, which can be labor intensive, costly, and technically complex. In addition, repeated recycling cycles can degrade the mechanical and / or chemical properties60980 15916of plastics, thereby reducing the quality and utility of recycled materials and limiting their suitability for further downstream recycling.
[0006] Alternative plastic waste management approaches, such as landfilling and incineration, also present challenges. Landfilling requires substantial land resources and generally does not recover the material or embodied energy value of the plastic. Incineration can reduce waste volume and generate energy, but may produce undesirable emissions and suffer from challenges related to the disposal of incinerated plastic residues.
[0007] Other alternatives to plastic waste management, including chemical recycling and pyrolysis, have been developed to convert plastic waste into fuels or chemical feedstocks. While such techniques may recover energy or raw materials, they often require high temperatures, complex processing equipment, and may not be suitable for all plastic waste streams, particularly mixed or contaminated plastics.
[0008] Accordingly, there remains a need for systems and methods that enable the upcycling of waste plastics, including mixed plastic streams comprising different polymer types, into useful resources without requiring extensive sorting or energy-intensive processing. There is a further need for solutions that transform such waste plastics into materials suitable for long-term, load-bearing, or structural applications.SUMMARY
[0009] Disclosed herein is a method for upcycling plastic materials, the method comprising: providing a plastic feedstock; combining the plastic feedstock with solid constituents to form a mixed material; introducing the mixed material into a plastic-melting and forming module; heating the mixed material to soften, partially melt, or fully melt at least a portion of the plastic feedstock; homogenizing the mixed material; and forming the mixed material into at least one of a shaped article or a structural element.
[0010] In various embodiments, the plastic feedstock may be provided in shredded, pelletized, granulated, flaked, powdered, or other forms, and no particular particle size is required, provided the plastic feedstock can be introduced into the selected plastic-melting and forming module. In various embodiments, the plastic feedstock may comprise single-polymer plastics or mixed plastics, including hard-to-recycle plastic streams, and may be processed without sorting by polymer type and with minimal or no cleaning. In various embodiments, the method may further comprise reducing a size of the plastic feedstock by shredding, grinding, milling, granulating, or combinations thereof prior to combining the plastic feedstock with the solid constituents.60980 15916
[0011] In various embodiments, the plastic feedstock comprises mixed plastics containing two or more polymer types, such as polyethylene terephthalate (PET), polypropylene (PP), low-density polyethylene (LDPE), high-density polyethylene (HDPE), or combinations thereof. The plastic feedstock may be processed without sorting by polymer type and with minimal or no cleaning, thereby enabling direct utilization of mixed or contaminated plastic waste streams.
[0012] In various embodiments of the method, the mixed material is shaped to create structural or non-structural components, including but not limited to blocks, bricks, slabs, panels, piles, aggregates, containers, liners, modular elements, and other engineered components. In alternative embodiments of the method, the formed material is placed or injected into at least one of a borehole, an excavated space, a formwork, a container, or a defined void to form a structural element. The geometry, size, topology, and function of the formed components are not limited and may be selected based on structural, geotechnical, hydraulic, or functional requirements.
[0013] In further embodiments, the method comprises injecting or depositing the mixed material directly into soil or ground formations to create in-situ structural or functional elements, including piles, anchors, reinforcement elements, geosynthetic-like components, and interconnected subsurface networks. Such embodiments enable formation of components with complex geometries and topologies directly within the ground, analogous to three-dimensional printing in situ, thereby enabling novel foundation systems and foundation types with customized shapes, spatial arrangements, and load-transfer mechanisms.
[0014] In various embodiments of the method, the solid constituents comprise at least one of soil, sand, gravel, fly ash, coal ash, mine tailings, or glass, and the plastic feedstock comprises at least one of polypropylene, polyethylene terephthalate, high-density polyethylene, or polystyrene. In various embodiments of the method, a ratio of plastic feedstock to solid constituents is between 1:1 and 2:1. In various embodiments, the ratio of plastic feedstock to solid constituents is selected such that the plastic feedstock functions as a binder to encapsulate or bond the solid constituents.
[0015] In various embodiments of the method, heating the mixed material comprises heating the mixed material to about 250° C. In various embodiments, forming the mixed material comprises cooling the mixed material via at least one of ambient temperature air or water immersion to consolidate the formed material.
[0016] In various embodiments of the method, the shaped article or structural element is configured with a compressive strength of between 27-35 MPa. In various embodiments, the shaped article or structural element is configured with a splitting tensile strength of between60980 159162.6-6.7 MPa. In various embodiments, the shaped article or structural element is configured with a tensile strength of between 10-20% of the compressive strength.
[0017] In various embodiments, the plastic-melting and forming module comprises an extrusion device, including a single-screw extrusion device or a twin-screw extrusion device; however, other melting and forming systems may be used. In various embodiments, forming the mixed material comprises at least one of molding, pressing, injecting, or extruding the mixed material. In various embodiments, the plastic-melting and forming module is configured to displace the mixed material via a pressure generated by a screw, a hydraulic ram, a piston, a mechanical press, a gear pump, gravity-assisted flow, or combinations thereof.
[0018] Also disclosed herein is a system for upcycling plastic materials, the system comprising: a feedstock handling module configured to receive a plastic feedstock; a mixing module configured to combine the plastic feedstock with one or more solid constituents to form a mixed material; and a plastic-melting and forming module configured to soften, partially melt, or fully melt at least a portion of the plastic feedstock, and to form the mixed material into a shaped article or structural element by at least one of molding, pressing, injecting, or extruding the mixed material. In various embodiments, the system may optionally comprise a size-reduction module configured to reduce a size of the plastic feedstock.
[0019] In various embodiments of the system, the solid constituents comprise at least one of soil, sand, gravel, fly ash, coal ash, mine tailings, or glass, and the plastic feedstock comprises at least one of polypropylene, polyethylene terephthalate, high-density polyethylene, or polystyrene. In various embodiments of the system, the ratio of plastic feedstock to solid constituents is between 1:1 and 2:1. In various embodiments, the ratio of plastic feedstock to solid constituents is selected such that the plastic feedstock functions as a binder to encapsulate or bond the solid constituents within the formed material.
[0020] In various embodiments of the system, the plastic-melting and forming module is configured to inject or deposit the mixed material into at least one of soil, a mold, formwork, a borehole, or an excavated space to form a shaped article or structural element. In various embodiments, the plastic-melting and forming module is configured to displace the mixed material via a pressure generated by a screw, a hydraulic ram, a piston, a mechanical press, a gear pump, gravity-assisted flow, or combinations thereof.
[0021] In various embodiments of the system, the shaped article or structural element comprises a material with a tensile strength of between 27-35 MPa and a splitting tensile strength of between 2.6-6.7 MPa. In various embodiments of the system, the shaped article or structural element comprises a material with a water absorption percentage of less than 1%.60980 15916
[0022] The foregoing is intended as a simplified introduction to the disclosure, and is not intended to be used to limit the scope of any claim.BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The subject matter of the present disclosure is particularly pointed out and distinctly claimed in the concluding portion of the specification. A more complete understanding of the present disclosure, however, may best be obtained by referring to the following detailed description and claims in connection with the following drawings. While the drawings illustrate various embodiments employing the systems and methods disclosed herein, the drawings do not limit the scope of the claims.
[0024] With reference to the following description and accompanying drawings:
[0025] FIG. 1 illustrates a method for upcycling waste plastic, in accordance with various exemplary embodiments;
[0026] FIG. 2 illustrates a system for upcycling waste plastic, in accordance with various exemplary embodiments;
[0027] FIG. 3 illustrates stress-strain behaviors and failure patterns of plastic foundation material samples under a compressive load, in accordance with various embodiments;
[0028] FIG. 4A illustrates the unit weight of various plastic foundation material samples, in accordance with various embodiments;
[0029] FIG. 4B illustrates the water absorption percentage of the various plastic foundation material samples corresponding to FIG. 4A, in accordance with various embodiments;
[0030] FIG. 5A illustrates stress-strain behaviors and failure patterns of various plastic foundation material samples under compressive loading, in accordance with various embodiments;
[0031] FIG. 5B illustrates stress-strain behaviors and failure patterns of various plastic foundation material samples under compressive loading, in accordance with various embodiments;
[0032] FIG. 6A illustrates the peak strength of various plastic foundation material samples under compressive loading, in accordance with various embodiments;
[0033] FIG. 6B illustrates the strain at peak strength of various plastic foundation material samples under compressive loading, in accordance with various embodiments;
[0034] FIG. 6C illustrates the modulus of elasticity of various plastic foundation material samples under compressive loading, in accordance with various embodiments;60980 15916
[0035] FIG. 6D illustrates the energy absorption capacity of various plastic foundation material samples under compressive loading, in accordance with various embodiments;
[0036] FIG. 7A illustrates strain rate dependent stress-strain behaviors of various plastic foundation material samples under compressive loading, in accordance with various embodiments;
[0037] FIG. 7B illustrates strain rate dependent stress-strain behaviors of various plastic foundation material samples under compressive loading, in accordance with various embodiments;
[0038] FIG. 8A illustrates strain rate effects on peak strength of various plastic foundation material samples under compressive loading, in accordance with various embodiments;
[0039] FIG. 8B illustrates strain rate effects on the modulus of elasticity of various plastic foundation material samples under compressive loading, in accordance with various embodiments;
[0040] FIG. 9 illustrates strain rate sensitivity of various plastic foundation material samples under compressive loading, in accordance with various embodiments;
[0041] FIG. 10 illustrates the relationship between strain rate sensitivity and modulus reduction of various plastic foundation material samples under compressive loading, in accordance with various embodiments;
[0042] FIG. 11A illustrates the creep-related response of various plastic foundation material samples under compressive loading at 0.5% strain, in accordance with various embodiments;
[0043] FIG. 11B illustrates the creep-related response of various plastic foundation material samples under compressive loading at 1% strain, in accordance with various embodiments;
[0044] FIG. 11C illustrates the creep-related response of various plastic foundation material samples under compressive loading at 2% strain, in accordance with various embodiments; and
[0045] FIG. 11D illustrates the creep-related response of various plastic foundation material samples under compressive loading at 3% strain, in accordance with various embodiments.DETAILED DESCRIPTION
[0046] The following description is of various exemplary embodiments only, and is not intended to limit the scope, applicability, or configuration of the present disclosure in any way.60980 15916Rather, the following description is intended to provide a convenient illustration for implementing various embodiments including the best mode. As will become apparent, various changes may be made in the function and arrangement of the elements described in these embodiments without departing from principles of the present disclosure.
[0047] Plastic waste management technologies currently encompass mechanical recycling, chemical recycling, energy recovery, and disposal-based approaches. Mechanical recycling processes typically involve collection, sorting, cleaning, and reprocessing of plastic materials into secondary products, often requiring segregation by polymer type such as, for example, polypropylene (PP), polyethylene terephthalate (PET), high-density polyethylene (HDPE), and polystyrene (PS). Chemical recycling techniques, including depolymerization and pyrolysis, are used to convert plastic materials into fuels or chemical feedstocks. Other approaches, such as landfilling or incineration, are employed for waste handling and volume reduction.
[0048] While existing approaches to plastic waste management may be suitable for certain applications, they present limitations when addressing mixed plastic waste streams and contaminated plastics. Many recycling techniques require extensive pre-processing, including sorting and cleaning, and may be sensitive to contamination or polymer incompatibility. In addition, some recycling processes can degrade material properties, limiting the usefulness of the resulting products. As a result, mixed plastic waste materials are frequently diverted to lower value uses or disposal, presenting a need for novel approaches to upcycle or repurpose mixed plastic streams into additional, higher value applications traditionally devoid of plasticcontaining materials.
[0049] Accordingly, disclosed herein are systems and methods for upcycling plastic waste streams into useful resources, including materials suitable for structural and foundation applications. In various embodiments, mixtures of plastic materials are combined with soil or other particulate media to form composite structures capable of supporting loads and resisting environmental exposure and degradation. Foundation systems, including those conventionally supported by concrete, represent one potential application of the upcycled materials produced by the systems and methods disclosed herein; however, the disclosed embodiments are not limited in this regard. The upcycled materials may be employed in a wide range of applications, including energy infrastructure, foundations for solar installations, wind turbines, utility pads, retaining structures, or other civil or industrial uses. Further, while the disclosed embodiments reference waste plastic materials, the disclosed systems and methods are not limited to postconsumer or post-industrial plastics, and may also incorporate virgin, unprocessed, or partially processed plastic materials, alone or in combination with recycled plastics.60980 15916
[0050] With reference now to FIG. 1, a method 100 for upcycling plastic is disclosed herein. In various embodiments, the method 100 comprises: providing a plastic feedstock (step 110); combining the plastic feedstock with solid constituents to form a mixed material (step 120); introducing the mixed material into a plastic-melting and forming system (step 130); heating the mixed material to soften, partially melt, or fully melt at least a portion of the plastic feedstock (step 140); homogenizing the mixed material (step 150); and forming the mixed material into at least one of a shaped article or a structural element (step 160). In various embodiments, step 160 may comprise cooling or solidifying the formed material to produce a plastic foundation material.
[0051] In various embodiments, the method 100 may comprise providing or receiving a plastic feedstock for processing (step 110). In various embodiments of step 110, the plastic feedstock may comprise a plastic material stream. The plastic material stream may be sourced from post-consumer waste, post-industrial waste, or other suitable sources. In various embodiments, the plastic material stream may comprise waste plastics, while in other embodiments, the plastic material stream may include virgin, unprocessed, or partially processed plastics, alone or in combination with waste plastics.
[0052] In various embodiments, the plastic material stream may comprise one or more polymeric plastics, including, but not limited to. polypropylene (PP), polyethylene terephthalate (PET), high-density polyethylene (HDPE), polystyrene (PS), or combinations thereof. In certain embodiments, the plastic material stream may comprise mixtures of different polymer types, optionally including contaminated, multilayer, composite, thermoset, or otherwise heterogenous plastics that may be difficult to recycle or process using conventional mechanical or chemical recycling techniques. In various embodiments, the plastic material stream may not require sorting by different polymer types, and may reduce or eliminate the need to clean the plastic material stream, thereby reducing pre-processing.
[0053] In various embodiments, step 110 may optionally comprise subjecting the plastic feedstock to a size-reduction process (e.g., shredding, grinding, milling, granulating, or combinations thereof) to facilitate mixing, melting, handling, feeding, or forming. In other embodiments, the plastic feedstock is provided in pelletized, granulated, flaked, powdered, or other forms without performing size reduction. No particular particle size is required, provided that the plastic feedstock can be introduced into the selected plastic-melting and forming system and combined with the one or more solid constituents.
[0054] In various embodiments, size reduction, when performed, may produce plastic pieces having an average largest dimension selected based on the plastic type, the solid60980 15916constituents, and the melting and forming equipment used, and may range from fine powders to coarse pieces, without limitation.
[0055] In various embodiments, step 110 may be performed using any suitable sizereduction equipment, including, but not limited to, shredders, mills, grinders, combinations thereof, or other suitable shredding apparatuses known in the art. In various embodiments, step 110 may comprise multiple stages, such as a coarse shredding stage followed by a fine shredding stage, to achieve a desired particle size distribution. The target size range may facilitate subsequent steps of the method 100. In other embodiments, the average particle size may be adjusted outside of the stated range depending on the composition of the plastic material stream, the filler material or solid constituents used in step 120, or the configuration of the plastic-melting and forming module used in step 130.
[0056] In various embodiments, the method 100 further comprises mixing the plastic feedstock provided in step 110 with one or more filler materials or solid constituents to form a mixed material (step 120). In various embodiments, the solid constituents may comprise at least one of soil, sand, gravel, fly ash, coal ash, mine tailings, glass, or other particulate or granular materials suitable for altering the physical, thermal, or mechanical properties of the resultant composite material. In various embodiments, additional additives may be included to modify strength, stiffness, density, thermal conductivity, hydrophobicity, durability, or environmental resistance of the resultant plastic foundation material. Such additives may include, for example, coupling agents, binders, pigments, or reinforcing materials. In various embodiments, the solid constituents may comprise a silica-based sand, such as a F60 silica sand having an average particle size of less than approximately 0.22 mm; however, the disclosed systems and methods are not limited to this or any particular filler composition.
[0057] In various embodiments, the filler material may comprise industrial byproducts or locally sourced materials, reducing transportation requirement and enhancing a cyclical waste management economy.
[0058] In various embodiments, step 120 may comprise combining the plastic feedstock and filler material in a suitable ratio depending on the desired properties of the resultant plastic foundation material. In various embodiments, the plastic-to-filler ratio may range from about 1:1 to about 2:1, measured either by volume or by weight; however, ratios outside of this range may also be employed, provided that a sufficient amount of plastic is present to act as a continuous phase or binder that encapsulates, coats, or bonds the solid constituents. The selected ratio may depend on the filler type, particle size, moisture content, processing conditions, and targeted mechanical, thermal, or durability performance. For example, higher filler content may be used to increase stiffness or compressive strength, while60980 15916higher plastic content may improve ductility or moisture resistance, such that each component may be added to formulate a plastic foundation material suitable for a desired application.
[0059] In various embodiments, step 120 may be performed using manual techniques, such as manual mixing, or using industrial mixing equipment, including, but not limited to, paddle mixers, auger-based mixers, continuous mixing systems, or other suitable apparatuses known in the art. The mixing (step 120) process may be conducted for a sufficient duration and under conditions effective to produce a substantially uniform distribution of the plastic feedstock and the filler material prior to feeding the mixed material into the plastic-melting and forming module in step 130.
[0060] In various embodiments of the method 100, after formation of the mixed material in step 120, the mixed material may be introduced into a plastic-melting and forming module (step 130). The plastic-melting and forming module may receive the mixed material via a hopper, feed chute, conveyor, ram, batch loading process, or other suitable feeding mechanism configured to deliver the mixed material into a heated region, mold cavity, container, or processing zone at a controlled or uncontrolled rate. In some embodiments, step 130 may be continuous, while in other embodiments step 130 may be batch-based or semibatch.
[0061] The plastic-melting and forming module may comprise any apparatus capable of softening, partially melting, or fully melting plastics with or without solid or synthetic aggregates, particles, or powders, including systems that perform melting and forming in situ within a mold, container, or defined space, and systems that discharge the resulting material under pressure through a die. nozzle, port, or outlet. By way of non-limiting example, the module may comprise an extrusion device, a heated press mold, a heated container with mechanical mixing, a heated injection vessel, a heated auger or screws system, or combinations thereof.
[0062] In various embodiments, pressure used to form or displace the resulting material may be generated by a screw (single or twin), a hydraulic ram, a piston, a mechanical press, a gear pump, gravity-assisted flow, or combinations thereof.
[0063] In various embodiments, once fed into the plastic-melting and forming module, the mixed material is heated (step 140) to soften, partially melt, or fully melt at least a portion of the plastic feedstock. In an exemplary embodiment wherein the plastic-melting and forming module comprises an extrusion device, the extrusion device may comprise a motor-driven extrusion mechanism, such as a single-screw extruder, although the present disclosure is not limited to this configuration. The plastic-melting and forming module may further comprise one or more heating elements, temperature controllers, and operating units configured to raise60980 15916the temperature of the mixed material to a level sufficient to soften or melt the plastic feedstock of the mixed material while maintaining the filler material in a substantially solid state. In various embodiments, the one or more heating elements may be configured to heat the mixed material to a temperature of at least 200° C, such as to approximately 250° C, although higher or lower temperatures may be employed based on the specific melting point of the waste plastic contained within a particular mixed material.
[0064] In various embodiments, the temperature controller may be configured to operate the heating element at a maintained temperature, while in alternative embodiments, the temperature controller may be configured to dynamically adjust operation of the heating element to raise or lower the temperature, as needed.
[0065] In various embodiments comprising an extrusion device, the extrusion device may comprise a compression zone and a melting zone arranged along a length of an extrusion barrel, wherein the mechanical shear of the extrusion device and the thermal energy provided by the heating element may combine to melt the plastic and bind or encapsulate the filler material within the molten plastic.
[0066] In various embodiments, the method 100 may further comprise homogenizing the mixed material within the plastic-melting and forming module (step 150). In an exemplary embodiment, step 150 may occur through mechanical shear generated by rotation of the extrusion screw and / or interaction between the mixed material and an internal surface of the extrusion device. In various embodiments, homogenization (step 150) promotes uniform dispersion of the filler material throughout the molten plastic of the melted mixed material, wherein the plastic feedstock functions as a binder to encapsulate or bond the solid constituents.
[0067] In various embodiments of the method 100, once homogenized, the mixed material is formed into at least one of a shaped article or a structural element (step 160). For example, in various embodiments, the mixed material may be extruded through an outlet of the extrusion device, such as through a nozzle, to form an extruded material. In various embodiments, the extruded material may be injected into a mold to form at least one of a block, brick, slab, or foundation pile. In alternative embodiments, the extruded material may be injected directly into a foundation application, such as directly into at least one of a borehole or an excavated space, to form an in-situ underground structural element.
[0068] In various embodiments, the mixed material of step 160 may be configured to produce one or more components or materials having various cross-sectional geometries, dimensions, or surface features depending on their intended application. For example, in various embodiments, the resultant material or component may comprise, for example, a surface with designed roughness pattern as opposed to smooth material, such that the material60980 15916may exhibit an enhanced degree of friction in comparison to conventional foundation materials comprising smooth surface, such as concrete. In this manner, the extruded material may be formed as a continuous or semi-continuous structural element suitable for use as a foundation component or portion thereof.
[0069] In various embodiments of step 160, forming the mixed material comprises injecting, displacing, or depositing the mixed material directly into soil or ground formations to form in-situ structural or functional elements. Such elements may include piles, anchors, reinforcement members, geosynthetic-like inclusions, or interconnected subsurface components having predefined or emergent geometries. In some embodiments, the mixed material is placed incrementally or continuously to form components in a manner analogous to three-dimensional printing within the ground.
[0070] In various embodiments, step 160 may further comprise cooling the mixed material to form a plastic foundation material. For example, cooling may be carried out by exposing the extruded material to ambient fluid conditions, such as ambient temperature air or water.
[0071] In various embodiments, the resultant plastic foundation material produced by method 100 may be particularly suitable for use as a foundation component due to its physical and chemical characteristics. For example, the plastic foundation material may be configured for use in load bearing or ground-contact applications, including subterranean or partially subterranean installations, in addition to above-ground applications. The plastic foundation material may be sized, shaped, formed, or assembled to support infrastructure such as utility pads, foundations for solar installations, wind turbines, equipment bases, retaining structures, or other civil or industrial applications; however, the present disclosure is not limited in this regard.
[0072] In various embodiments, the extrusion device may be moveable, allowing direct injection of the extruded material into an industrial setting, allowing for the formation of in-situ foundation systems. In said embodiments, the method 100 may be suitable for construction of customizable and intricate foundation systems difficult to manufacture or cast using traditional methods and materials.
[0073] With reference now to FIG. 2, also disclosed herein is a system 200 for upcycling plastic materials, in accordance with various embodiments. In various embodiments, the system 200 may generally comprise: a feedstock handling module 210 configured to receive aplastic feedstock 201; a mixing module 220 configured to combine the plastic feedstock 201 with one or more solid constituents 202 to form a mixed material 203; and a plastic-melting and forming module 230 configured to soften, partially melt, or fully melt at least a portion of60980 15916the plastic feedstock 201 and to form the resulting material into a shaped article or structural element 204 by molding, pressing, injection, extrusion, or a combination thereof. In various embodiments, the components of system 200 may be structurally and functionally similar to, or the same as, the components described herein with respect to method 100.
[0074] In various embodiments, the system 200 receives aplastic feedstock 201 (which may be shredded, pelletized, granulated, flaked, powdered, or otherwise provided) and, optionally, subjects the plastic feedstock 201 to size reduction. The plastic feedstock 201 is then combined with one or more solid constituents 202 and introduced into the mixing module 220 to produce a mixed material 203. The mixed material 203 is then introduced into the plastic-melting and forming module 230, where the mixed material 203 is heated to soften, partially melt, or fully melt at least a portion of the plastic feedstock 201 and is mixed or homogenized to disperse the solid constituents 202 within the plastic. The plastic-melting and forming module 230 then forms and discharges a formed material that may comprise a shaped article or structural element 204, which may be suitable for structural or foundation applications.
[0075] In various embodiments, the plastic-melting and forming module 230 comprises an extrusion device; however, the module 230 is not limited to extrusion devices and may alternatively comprise a heated press mold, a heated injection vessel configured to inject into a mold or defined space, a heated container with mechanical mixing, or other systems capable of melting plastics with or without solid constituents and forming the resulting material in situ in a mold, container, or defined void.
[0076] In various embodiments, the system 200 may operate in a continuous manner, while in other embodiments, one or more components may operate in a batch or semi-batch manner, without departing from the scope of the disclosed system 200.
[0077] In various embodiments of the systems and methods disclosed herein, the resultant foundation material may comprise one or more physical, chemical, or mechanical properties rendering it particularly suitable as a replacement or supplement to conventional materials used in foundation systems, such as concrete.
[0078] For example, the resultant plastic foundation material may comprise a material with a compressive strength of between about 27 MPa and about 35 MPa, measured by subjecting an exemplary cylindrical plastic foundation material — having a length-to-diameter ratio of 2: 1 — to a compressive load. In various embodiments, the resultant plastic foundation material may further comprise a splitting tensile strength of between 2.6 MPa and 6.7 MPa. In various embodiments, the plastic foundation material disclosed herein comprises a tensile strength of between 10% - 20% of the compressive strength. By virtue of these characteristics,60980 15916the plastic foundational materials disclosed herein may be configured with attributes similar to concrete.
[0079] Additionally, the plastic foundation material may comprise a material with a mass density ranging from between about 1.162 g / cm3to about 1.379 g / cm3, rendering it a lightweight solution in comparison to Portland cement concrete, which typically has a mass density of about 2.400 g / cm3, and even lightweight concrete, which typically has amass density of between about 1.680 g / cm3and about 1.920 g / cm3.
[0080] Moreover, the plastic foundation material may comprise a material with a water adsorption value of less than 1%, measured at ambient temperature and pressure, due to the hydrophobicity and dense molecular structure of the plastics within the plastic foundation material. In various embodiments, for example, the plastic foundation materials disclosed herein possess water absorption values of less than 0.7%, less than 0.6%, less than 0.5%, less than 0.4%, less than 0.3%, and less than 0.2%, providing a significant advantage over concrete, which comprises water absorption values ranging from between 3-20%, on average. As such, the plastic foundation materials disclosed herein may be particularly suitable for use in saturated environments, such as underground foundation systems, where moisture and environmental conditions pose a risk of degrading conventional foundation materials.
[0081] In various embodiments, the systems, methods, and resulting plastic foundation materials disclosed herein reduce the environmental impact of plastic recycling. For example, CO2 emissions are reduced, and water is not required as an input in the systems and methods disclosed herein, thereby minimizing environmental impact in comparison to existing techniques.
[0082] EXAMPLE 1
[0083] To exemplify the physical and mechanical characteristics of the disclosed plastic foundation materials, Example 1 provides the results of compressive and tensile strength testing, and hydrophobicity testing of plastic foundation materials made using various combinations of plastic polymers and filler.
[0084] In particular, waste plastics and F60 silica sand (D50= 0.22 mm) were combined in various ratios to form plastic foundation materials. Four types of waste plastic, including PP, PET, HDPE, and PS, were collected, cleaned, dried, and shredded to approximately 5 mm to 10 mm. The four types of shredded plastics and sand were manually mixed in a container as per the nine mix proportions shown in Table 1.
[0085] Table 1Sample Mixed Plastics (wt. %) Sand (wt. Plastics: Sand PP PET HDPE PS %)60980 15916P1EM 12.5 12.5 12.5 12.5 50 1:1 P1LF 7.5 17.5 17.5 7.5 50P1HR 25 0 0 25 50P1.5EM 15 15 15 15 40 1.5:1 P1.5LF 9 21 21 9 40P1.5HR 30 0 0 30 40P2EM 16.75 16.75 16.75 16.75 33 2:1 P2LF 10 23.5 23.5 10 33P2HR 33.5 0 0 33.5 33
[0086] Solid samples were created by pouring each mixture into the hopper of a singlescrew plastic extrusion machine. The rotational speed of the screw was set to 150 rpm, and the processing temperature was maintained at 250° C, where the plastic was melted and extruded into a mold with a diameter of 25.4 mm and a length of 300 mm. The mold was then immersed in tap water to cool down. The specimens were pushed out of the mold using a hydraulic extruder and cut for mechanical testing into cylinders of 50.8 mm length using a concrete saw to ensure a consistent length-to-diameter ratio of 2: 1 for each sample.
[0087] The mass density of each sample was calculated by measuring its dimensions and weight. Water absorption of the specimens was determined following a 24-hour distilled water immersion of the samples. The results of these tests are shown in Table 2.
[0088] Table 2Plastics: Sand Sample Mass Density (g / cm3) Water Absorption (%) 1:1 P1EM 1.379±0.051 0.22P1LF 1.306±0.004 0.17 P1HR 1.317±0.114 0.671.5:1 P1.5EM 1.282±0.063 0.10P1.5LF 1.302±0.085 0.32 P1.5HR 1.198±0.088 0.332:1 P2EM 1.178±0.045 0.31P2LF 1.243±0.012 0.32 P2HR 1.162±0.042 0.20
[0089] As seen in Table 2, the mass density of each sample varies between 1.162 g / cm3and 1.379 g / cm3, depending primarily on the plastic-to-sand ratio. As expected, the density60980 15916decreased with increased plastic content in the mixture due to the lower mass density of plastic compared to sand. These results indicate that plastic-based materials created by the methods and systems disclosed herein can be significantly lighter than normal Portland cement concrete, which has a mass density of 2.400 g / cm3, and even lightweight concrete, which typically has a mass density of 1.680 – 1.920 g / cm3.
[0090] As further seen in Table 2, the water absorption values of all the samples were observed to be less than 1% at ambient temperature and pressure, primarily due to the hydrophobicity and dense molecular structure of plastics, making them nearly impermeable to water. It is noteworthy that water absorption in normal Portland cement concrete and lightweight Portland cement concrete typically ranges from 3 - 10% and 5 - 20%, respectively.
[0091] The samples were further subjected to testing to determine their respective compressive strength and splitting tensile strengths. In each instance, the samples were subjected to force delivered by a hydraulic-controlled uniaxial compression testing machine with a loading capacity of 500 kN, with each sample tested twice. The results of the compressive strength testing is provided in Table 3, and the results of the splitting tensile strength testing is provided in Table 4.
[0092] Table 3Sample Average Peak Average Strain Average Modulus (MPa) Stress (MPa) at Peak (%) Initial Tangent Secant at Peak Stress P1EM 34.6±0.6 4.54±0.02 917±70 763±15 P1LF 30.3±2.0 4.57±0.25 871±204 662±9 P1HR 32.7±1.0 4.48±0.10 871±91 675±6 P1.5EM 29.8±2.6 4.79±0.31 809±49 623±16 P1.5LF 29.1±1.1 5.48±0.11 648±28 531±30 P1.5HR 32.2±2.5 4.76±0.14 789±59 679±74 P2EM 32.2±0.3 4.49±0.10 914±45 717±8 P2LF 30.9±0.2 5.09±0.28 798±40 609±37 P2HR 34.6±0.7 4.05±0.24 994±71 857±32
[0093] Table 3 summarizes the results of compressive strength tests. The stress-strain behaviors and failure patterns under compression loading are also shown in FIG. 3. It was found that the P1LF, P1.5LF, and P2LF have lower compressive strength and modulus compared to other samples in their respective groups. This might be attributed to the lower contents of PS, which has a higher rigidity compared to the other plastic types, in the mix design. Pl EM60980 15916samples had an initial modulus of 910 MPa and a peak modulus of 759 MPa, indicating a relatively high stiffness that gradually reduced under load. Comparatively, the P1LF samples had a higher initial modulus (853 MPa) but a lower peak modulus (691 MPa), suggesting they were initially stiff but became more ductile as deformation progressed. The P2HR samples showed the highest initial modulus (990 MPa) and peak modulus (840 MPa), indicating that higher plastic content can maintain stiffness even under substantial strain. The P1HR, P1.5HR and P2HR demonstrated less rounded peaks and more abrupt post-peak failure while P1LF, P1.5LF and P2LF showed wider peaks and smoother post-peak failure. For the 1:1 plastic-to-sand ratio, the P1EM samples displayed the highest average compressive strength at 35 MPa, followed by P1HR at 33 MPa, and P1LF at 30 MPa. As the plastic content increased to 1.5:1 and 2: 1 ratios, the average compressive strengths generally decreased, with P1.5EM and P2EM having strengths of 29 MPa and 32 MPa, respectively. However, P2HR at a 2:1 ratio still maintained a higher strength of 34 MPa. This suggests that while increasing plastic content can reduce strength, certain compositions (like P2HR) can still maintain or even enhance strength.
[0094] Table 4Sample Tensile Strength (MPa) Average T ensile / C ompressive Test 1 Test 2 Tensile Strength (%) Strength (MPa)P1EM 4.80 3.60 4.20±0.60 12 P1LF 3.05 3.85 3.45±0.40 11 P1HR 6.65 3.90 5.30±1.38 16 P1.5EM 3.95 2.60 3.30±0.67 11 P1.5LF 3.35 2.60 3.00±0.38 10 P1.5HR 4.65 4.20 4.45±0.23 14 P2EM 4.45 4.40 4.45±0.02 14 P2LF 3.55 3.20 3.40±0.18 11 P2HR 4.75 4.80 4.80±0.02 14
[0095] As presented in Table 4, P1HR, P1.5HR, and P2HR demonstrated the highest splitting tensile strength for each plastic-to-soil ratio, whereas P1LF, P1.5LF, and P2LF exhibited the lowest splitting tensile strength. The splitting tensile strength of the materials varies between 2.62 and 6.68 MPa, which is 10-16% of their compressive strength. This indicates that while the materials have moderate tensile strength, their tensile capacity is relatively low compared to their compressive strength. This ratio is comparable to concrete whose tensile strength is 10-15 % of its compressive strength.60980 15916
[0096] EXAMPLE 2
[0097] Example 2 illustrates non-limiting embodiments in which mixed-plastic compositions were evaluated to characterize mechanical and physical properties relevant to structural and geotechnical applications. The example is provided for illustrative purposes and does not limit the scope of the invention.
[0098] In this example, plastic mixtures comprising different ratios of polyethylene terephthalate (PET), polypropylene (PP), low-density polyethylene (LDPE), and high-density polyethylene (HDPE) were prepared. The mixtures were processed using a plastic-melting and forming system to produce test specimens without requiring sorting of plastics by polymer type.
[0099] Mechanical properties of the mixed-plastic compositions were evaluated under different loading conditions. Specimens were tested to determine strength and elastic modulus under a standard loading rate, as well as under a slow loading rate representative of creep behavior. The results demonstrate that plastic composition and loading rate influence stiffness, strength, and time-dependent deformation characteristics.
[0100] In addition, density and water absorption were measured for the mixed-plastic compositions. The measured properties indicate that the resulting materials exhibit low water absorption and densities suitable for use in structural and non-structural applications, including subsurface and foundation systems.
[0101] Tables 5-8 summarize measured mechanical and physical properties for the mixed-plastic compositions, including strength, elastic modulus, density, and water absorption. FIGS. 4-11 illustrate representative test results for different plastic mixtures and loading rates, including stress-strain behavior and creep-related response.
[0102] Table 5. Unit weight and water absorption test resultsMixture Water Mixture Name Unit WeightNo. Absorption — — (g / cm3) (%) 1 PET (100%) 1.174 0.283 2 PP (100%) 0.898 0.205 3 HDPE (100%) 0.951 0.218 4 LDPE (100%) 0.936 0.384 5 PET (67%) & PP (33%) 1.048 0.290 6 PET (33%) & HDPE (67%) 1.033 0.259 7 PET (33%) & LDPE (67%) 1.028 0.392 8 PP (67%) & HDPE (33%) 0.889 0.276 9 PP (33%) & LDPE (67%) 0.864 0.342 10 HDPE (33%) & LDPE (67%) 0.894 0.303 11 PET (33%) & PP (67%) 1.017 0.288 12 PET (67%) & HDPE (33%) 1.078 0.24913 PET (67%) & LDPE (33%) 1.053 0.38160980 1591614 PP (33%) & HDPE (67%) 0.864 0.238 15 PP (67%) & LDPE (33%) 0.875 0.330 16 HDPE (67%) & LDPE (33%) 0.868 0.326 17 PET (33%), PP (33%), HDPE (33%) 0.945 0.282 18 PET (33%), PP (33%), LDPE (33%) 0.936 0.331 19 PET (33%), HDPE (33%), LDPE (33%) 0.972 0.310 20 PP (33%), HDPE (33%), LDPE (33%) 0.906 0.323 21 PET (25%), PP (25%), HDPE (25%), LDPE 0.950 0.312(25%)
[0103] Table 6. Compressive stress-strain test resultsStrainPeak Modulus Absorbed Mixture S at ofMixture Name trength Energy Number Peak Elasticity (MPa) (kJ / m’)(%) (MPa)1 PET (100%) 38.8 4.67 1013 1180 2 PP (100%) 32.0 8.38 799 2110 3 HDPE (100%) 24.8 27.90 441 5750 4 LDPE (100%) 19.8 17.58 377 2780 5 PET (67%) & PP (33%) 31.9 7.02 636 1490 6 PET (33%) & HDPE (67%) 18.5 4.88 503 590 7 PET (33%) & LDPE (67%) 16.6 5.89 458 710 8 PP (67%) & HDPE (33%) 20.1 13.69 427 2200 9 PP (33%) & LDPE (67%) 16.1 12.65 370 1520 10 HDPE (33%) & LDPE (67%) 17.9 22.55 335 3430 11 PET (33%) & PP (67%) 23.1 4.08 692 570 12 PET (67%) & HDPE (33%) 22.6 3.42 699 420 13 PET (67%) & LDPE (33%) 15.5 4.04 437 360 14 PP (33%) & HDPE (67%) 19.8 9.87 411 1420 15 PP (67%) & LDPE (33%) 20.3 8.68 463 1290 16 HDPE (67%) & LDPE (33%) 17.8 15.62 371 2250 17 PET (33%), PP (33%), HDPE (33%) 17.3 4.61 532 520 18 PET (33%), PP (33%), LDPE (33%) 17.3 3.56 545 350 19 PET (33%), HDPE (33%), LDPE (33%) 17.0 5.20 489 590 20 PP (33%), HDPE (33%), LDPE (33%) 17.1 13.82 379 1940 21 PET (25%), PP (25%), HDPE (25%), 17.4 5.99 499 780LDPE (25%)
[0104] Table 7. Summary of strain rate effects on strength and stiffnessPeak Strength (MPa) Elastic Modulus (MPa) Mixture Mixture Number Mixture Name 2.56% / min. 0.0256% / min. Strength Reduction (%) 2.56% / min. 0.0256% / min. Modulus Reduction (%) PET1 38.8 28.1 27.6 1013 697 31.2 (100%)PP2 (100%) 32.0 24.8 22.5 799 380 52.4 HDPE3 (100%) 24.8 15.8 36.3 441 198 55.1 LDPE4 19.8 14.9 24.7 377 141 62.7(100%)60980 15916Peak Strength (MPa) Elastic Modulus (MPa) Mixture Mixture Strength Modulus Reduction Reduction Number 2.56% / 0.0256% / mi 2.56% / mi 0.0256% / mi Namemin. n. (%) n. n. (%) PET(67%)5 31.9 21.4 32.9 636 215 66.2 & PP(33%)PET(33%)6 & 18.5 12.9 30.3 503 136 73.1 HDPE(67%)PET(33%)7 & 16.6 11.1 33.1 458 118 74.3 LDPE(67%)PP(67%)8 & 20.1 14.9 25.9 427 189 55.8 HDPE(33%)PP(33%)9 & 16.1 11.7 27.3 370 183 50.4 LDPE(67%)HDPE(33%)10 & 17.9 13.5 24.6 335 171 48.9 LDPE(67%)PET(33%)11 23.1 16.8 27.3 692 188 72.9 & PP(67%)PET(67%)12 & 22.6 14.6 35.4 699 181 74.2 HDPE(33%)PET(67%)13 & 15.5 11.2 27.7 437 126 71.2 LDPE(33%)PP(33%)14 & 19.8 13.9 29.8 411 190 53.7 HDPE(67%)PP(67%)15 & 20.3 14.4 29.1 463 217 53.2 LDPE(33%)60980 15916Peak Strength (MPa) Elastic Modulus (MPa) Mixture Mixture Strength Modulus 2.5 Reduction Reduction Number 6% / 0.0256% / mi 2.56% / mi 0.0256% / mi Namemin. n. (%) n. n. (%) HDPE(67%)16 & 17.8 13.4 24.7 371 151 59.3 LDPE(33%)PET(33%),PP17 17.3 13.1 24.3 532 120 77.4 (33%),HDPE(33%)PET(33%),PP18 17.3 12.7 26.6 545 134 75.4 (33%),LDPE(33%)PET(33%),HDPE19 17.0 13.0 23.5 489 116 76.3 (33%),LDPE(33%)PP(33%),HDPE20 17.1 12.9 24.6 379 174 54.1 (33%),LDPE(33%)PET(25%),PP(25%),21 17.4 12.7 27.0 499 162 67.6 HDPE(25%),LDPE(25%)
[0105] Table 8. Summary of strain rate sensitivity of plastic specimens at different mixturesElastic Modulus (MPa) Modulus Rate Mixture Sensitivity Number Mixture Name Reduction 2.56% / min. 0.0256% / min. Exponent,(%) m 1 PET (100%) 1013 697 31.2 0.040 2 PP (100%) 799 380 52.4 0.081 3 HDPE (100%) 441 198 55.1 0.087 4 LDPE (100%) 377 141 62.7 0.1075 PET (67%) & PP (33%) 636 215 66.2 0.11860980 15916PET (33%) & HDPE6 (67%) 503 136 73.1 0.142 PET (33%) & LDPE7 458 118 74.3 0.147 (67%)8 PP (67%) & HDPE (33%) 427 189 55.8 0.089 9 PP (33%) & LDPE (67%) 370 183 50.4 0.076 HDPE (33%) & LDPE10 335 171 48.9 0.073 (67%)11 PET (33%) & PP (67%) 692 188 72.9 0.142 PET (67%) & HDPE12 699 181 74.2 0.147 (33%)PET (67%) & LDPE13 437 126 71.2 0.135 (33%)14 PP (33%) & HDPE (67%) 411 190 53.7 0.084 15 PP (67%) & LDPE (33%) 463 217 53.2 0.082 16 HDPE (67%) & LDPE 371 151 59.3 0.098 (33%)17 PET (33%). PP (33%), 532 120 77.4 0.161 HDPE (33%)18 PET (33%), PP (33%), 545 134 75.4 0.152 LDPE (33%)PET (33%), HDPE (33%),19 LDPE (33%) 489 116 76.3 0.156 PP (33%), HDPE (33%),20 LDPE (33%) 379 174 54.1 0.085 PET (25%). PP (25%),21 HDPE (25%), LDPE 499 162 67.6 0.122(25%)
[0106] Examples
[0107] Example 1. In accordance with various exemplary embodiments, a system for upcycling plastic materials comprises: a feedstock handling module configured to receive a plastic feedstock; a mixing module configured to combine the plastic feedstock with one or more solid constituents to form a mixed material; and a plastic-melting and forming module configured to soften, partially melt, or fully melt at least a portion of the plastic feedstock, and to form the mixed material into a shaped article or structural element by at least one of molding, pressing, injecting, or extruding the mixed material.
[0108] Example 2. The system of Example 1, wherein the plastic feedstock comprises shredded plastic, pelletized plastic, granulated plastic, flaked plastic, powdered plastic, or combinations thereof.
[0109] Example 3. The system of Example 1, wherein the plastic feedstock comprises mixed plastics containing two or more polymer types.
[0110] Example 4. The system of example 1, wherein the plastic-melting and forming module is configured to displace the mixed material via a pressure generated by a screw, a60980 15916hydraulic ram, a piston, a mechanical press, a gear pump, gravity-assisted flow, or combinations thereof.
[0111] Example 5. The system of example 1, wherein the plastic-melting and forming module is configured to inject or deposit the mixed material into at least one of soil, a mold, formwork, a borehole, or an excavated space.
[0112] Example 6. The system of example 1, wherein the plastic feedstock comprises at least one of polypropylene, polyethylene terephthalate, high-density polyethylene, or polystyrene.
[0113] Example 7. The system of example 1, wherein the solid constituents comprise at least one of soil, sand, gravel, fly ash, coal ash, mine tailings, or glass.
[0114] Example 8. The system of example 1, wherein a ratio of plastic feedstock to solid constituents is between 1:1 and 2:1.
[0115] Example 9. The system of example 1, wherein a ratio of plastic feedstock to solid constituents is selected such that the plastic feedstock functions as a binder to encapsulate or bond the solid constituents.
[0116] Example 10. The system of example 1, wherein the shaped article or structural element comprises a material with a tensile strength of between 27 - 35 MPa and a splitting tensile strength of between 2.6 - 6.7 MPa.
[0117] Example 11. The system of example 1, wherein the shaped article or structural element comprises a material with a water absorption percentage of less than 1%.
[0118] While the principles of this disclosure have been shown in various embodiments, many modifications of structure, arrangements, proportions, the elements, materials and components, used in practice, which are particularly adapted for a specific environment and operating requirements may be used without departing from the principles and scope of this disclosure. These and other changes or modifications are intended to be included within the scope of the present disclosure.
[0119] The present disclosure has been described with reference to various embodiments. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the present disclosure. Accordingly, the specification is to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of the present disclosure. Likewise, benefits, other advantages, and solutions to problems have been described above with regard to various embodiments. However, benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or60980 15916become more pronounced are not to be construed as a critical, required, or essential feature or element.
[0120] As used herein, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Also, as used herein, the terms "coupled," "coupling," or any other variation thereof, are intended to cover a physical connection, an electrical connection, a magnetic connection, an optical connection, a communicative connection, a functional connection, and / or any other connection. When language similar to "at least one of A, B, or C" or "at least one of A, B, and C" is used in the specification or claims, the phrase is intended to mean any of the following: (1) at least one of A; (2) at least one of B; (3) at least one of C; (4) at least one of A and at least one of B; (5) at least one of B and at least one of C; (6) at least one of A and at least one of C; or (7) at least one of A, at least one of B, and at least one of C.
Claims
60980 15916CLAIMSWhat is claimed is:
1. A method for upcycling plastic materials, the method comprising:providing a plastic feedstock;combining the plastic feedstock with solid constituents to form a mixed material; introducing the mixed material into a plastic-melting and forming module; heating the mixed material to soften, partially melt, or fully melt at least a portion of the plastic feedstock;homogenizing the mixed material; andforming the mixed material into at least one of a shaped article or a structural element.
2. The method of claim 1, wherein forming the mixed material comprises at least one of molding, pressing, injecting, or extruding the mixed material.
3. The method of claim 1, further comprising reducing a size of the plastic feedstock by shredding, grinding, milling, granulating, or combinations thereof prior to combining the plastic feedstock with the solid constituents.
4. The method of claim 1, wherein the plastic feedstock comprises shredded plastic, pelletized plastic, granulated plastic, flaked plastic, powdered plastic, or combinations thereof.
5. The method of claim 1, wherein the plastic-melting and forming module comprises an extrusion device configured to discharge the mixed material through a nozzle or die.
6. The method of claim 1, wherein forming the mixed material comprises heating and consolidating the mixed material within a mold or container using a press, a heated platen system, or a heat-press molding system.
7. The method of claim 1, wherein the plastic-melting and forming module is configured to displace the mixed material via a pressure generated by a screw, a hydraulic ram, a piston, a mechanical press, a gear pump, gravity-assisted flow, or combinations thereof.
8. The method of claim 1, wherein the plastic feedstock comprises mixed plastics containing two or more polymer types.60980 159169. The method of claim 1, wherein forming the mixed material comprises injecting or depositing the mixed material into soil, a borehole, or an excavated space to form a structural element.
10. The method of claim 1, wherein forming the mixed material comprises injecting the mixed material into a mold or formwork to form at least one of a block, brick, slab, or foundation pile.
11. The method of claim 1, wherein the solid constituents comprise at least one of soil, sand, gravel, fly ash, coal ash, mine tailings, or glass.
12. The method of claim 1, wherein a ratio of plastic feedstock to solid constituents is between 1:1 and 2:1.
13. The method of claim 1, wherein a ratio of plastic feedstock to solid constituents is selected such that the plastic feedstock functions as a binder to encapsulate or bond the solid constituents.
14. The method of claim 1, wherein the plastic feedstock comprises at least one of polypropylene, polyethylene terephthalate, high-density polyethylene, or polystyrene.
15. The method of claim 1, wherein heating the mixed material comprises heating the mixed material to about 250° C.
16. The method of claim 1, wherein forming the mixed material comprises cooling the mixed material via at least one of ambient temperature or water immersion.
17. The method of claim 1, wherein the shaped article or structural element is configured with a compressive strength of between 27 - 35 MPa.
18. The method of claim 17, wherein the shaped article or structural element is configured with a splitting tensile strength of between 2.6 - 6.7 MPa.
19. The method of claim 18, wherein the shaped article or structural element is configured with a tensile strength of between 10 - 20% of the compressive strength.