WO2020118175A1

WO2020118175A1 - Irradiated polymers in building materials for concrete forming

Info

Publication number: WO2020118175A1
Application number: PCT/US2019/064920
Authority: WO
Inventors: Oral Buyukozturk; Kunal Kupwade-Patil; Michael Philip SHORT; Michael Ortega
Original assignee: Massachusetts Institute Of Technology
Priority date: 2018-12-07
Filing date: 2019-12-06
Publication date: 2020-06-11

Abstract

Building materials include particles of a polymer in an irradiated form, cement, sand, and gravel. In concrete formed from these components, the polymer in the irradiated form may contribute to maintaining or improving structural characteristics, such as compressive strength, ductility, durability, or a combination thereof, as compared to concrete formed without the use of a polymer or as compared to concrete formed without the use of a polymer in an irradiated form. Further, or instead, the particles of the polymer that are irradiated may be from one or more of a variety of ubiquitous sources, such as recycled material. Thus, for example, the concrete formed using particles of the polymer in the irradiated form according to the present disclosure may facilitate achieving target structural performance while, additionally or alternatively, reducing emissions of greenhouse gases or other pollutants, as compared to concrete formed without a polymer.

Description

IRRADIATED POLYMERS IN BUILDING MATERIALS FOR CONCRETE FORMING

CROSS-REFERNECE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application No. 62/776,653, filed on December 7, 2018, the entire contents of which are hereby incorporated herein by reference.

BACKGROUND

[0002] Production of concrete contributes heavily to greenhouse gas emissions. To lower the carbon footprint associated with this source of emissions, cement used in the formation of concrete may be partially replaced with another material. Such partial replacement of cement with substitute material can reduce direct emissions associated with the calcination that takes place during the formation of concrete as well as indirect emissions associated with energy required to produce concrete. However, the effectiveness of such a substitution - both in terms of compressive strength and reduction of emissions - depends on the material used as a partial substitute for concrete. That is, substitute materials may offer improvements with respect to greenhouse emissions at a cost of decreased performance characteristics, such as structural performance.

[0003] There remains a need for substitute materials that may partially replace cement as a component of concrete to achieve adequate performance while reducing greenhouse emissions associated with formation of concrete.

SUMMARY

[0004] Building materials include particles of a polymer in an irradiated form, cement, sand, and gravel. In concrete formed from these components, the polymer in the irradiated form may contribute to maintaining or improving structural characteristics, such as compressive strength, ductility, durability, or a combination thereof, as compared to concrete formed without the use of a polymer or as compared to concrete formed without the use of a polymer in an irradiated form. Further, or instead, the particles of the polymer that are irradiated may be from one or more of a variety of ubiquitous sources, such as recycled material. Thus, for example, the concrete formed using particles of the polymer in the irradiated form according to the present disclosure may facilitate achieving target structural performance while, additionally or alternatively, reducing emissions of greenhouse gases or other pollutants, as compared to concrete formed without a polymer.

[0005] According to one aspect, a method may include receiving particles of a polymer in a non-irradiated form, irradiating the particles of the polymer with a dose of radiation to form particles of the polymer into an irradiated form, the particles of the polymer in the irradiated form having, in response to the dose of radiation, one or more properties modified relative to the particles of the polymer in the non-irradiated form, and forming a flowable mixture of a building material, the flowable mixture of the building material including the particles of the polymer in the irradiated form, cement, sand, and gravel, the gravel having a first average particle size, the sand having a second average particle size, and the particles of the polymer in the irradiated form having an average maximum dimension less than the first average particle size of the gravel and greater than the second average particle size of the sand.

[0006] In some implementations, the polymer in the non-irradiated form may has a first melting point, and the polymer in the irradiated form may have a second melting point less than the first melting point.

[0007] In certain implementations, the polymer in the non-irradiated form may have a semi-crystalline structure. In some instances, relative to the polymer in the non-irradiated form, the polymer in the irradiated form may have increased crystallinity and crosslinking.

Additionally, or alternatively, the polymer in the non-irradiated form may be any one or more of polyethylene terephthalate (PET), high -density polyethylene, low density polyethylene, or polypropylene.

[0008] In some implementations, the polymer in the non-irradiated form may have an amorphous structure. As an example, the polymer in the non-irradiated form may be one or more of polystyrene or polyvinyl chloride.

[0009] In certain implementations, the average maximum dimension of the particles of the polymer in the irradiated form may be at least twice as large as an average minimum dimension of particles of the polymer in the irradiated form. Additionally, or alternatively, the average maximum dimension of the particles of the polymer in the irradiated form may be greater than about 5 nm and less than about 5 mm. [0010] In some implementations, the first average particle size of the gravel is greater than about 3 mm and less than about 40 mm.

[0011] In certain implementations, irradiating the particles of the polymer in the non- irradiated form may include exposing the particles of the polymer in the non-irradiated form to gamma radiation.

[0012] In some implementations, the dose of radiation may be greater than about 1 kGy and less than about 1000 kGy (e.g., greater than about 10 kGy and less than about 100 kGy).

[0013] In certain implementations, the weight of the particles of the polymer in the irradiated form in the flowable mixture of the building material may be greater than 0 percent and less than about 25 percent of the weight of the cement in the flowable mixture of the building material. For example, the weight of the particles of the polymer in the irradiated form in the flowable mixture of the building material may be greater than about 0.5 percent and less than about 5 percent of the weight of the cement in the flowable mixture of the building material.

[0014] In some implementations, the method may further include hydrating the flowable mixture of the building material to form a slurry curable into concrete. As an example, hydrating the flowable mixture of the building material may include hydrating one or more components of the flowable mixture of the building material prior to forming the flowable mixture of the building material. Additionally, or alternatively, hydrating the flowable mixture of the building material may include hydrating an anhydrous form of the flowable mixture of the building material. In certain instances, the method may further include curing the slurry into a first concrete. The first concrete may have a first compressive strength, and a second concrete formed with the cement in place of the particles of the polymer, under otherwise identical conditions, has a second compressive strength less than the first compressive strength. For example, the first compressive strength may be between about 1 percent to about 25 percent greater than the second compressive strength. Additionally, or alternatively, the first concrete may have a first compressive strength, and a second concrete formed with particles of the polymer in the non-irradiated form in place of the particles of the polymer in the irradiated form, under otherwise identical conditions, has a second compressive strength less than the first compressive strength. For example, the first compressive strength may be between about 5 percent to about 30 percent greater than the second compressive strength. Further, or instead, the first concrete may have a first compressive strength greater than a second compressive strength of a second concrete formed, under otherwise identical conditions, with particles of the polymer irradiated at a different dose of the radiation in place of the particles of the polymer in the irradiated form in the first concrete. Still further or instead, the first concrete may have a first final strain value, and a second concrete formed with the cement in place of the particles of the polymer in the irradiated form, under otherwise identical conditions, has a second final strain value less than the first final strain value. Further or in the alternative, the first concrete may have a first porosity, and a second concrete formed with the cement in place of the particles of the polymer in the irradiated form, under otherwise identical conditions, has a second porosity greater than the first porosity. Still further, or instead, the first concrete may have a first Young’s modulus, and a second concrete formed with the cement in place of the particles of the polymer in the irradiated form, under otherwise identical conditions, has a second Young’s modulus less than the first Young’s modulus.

[0015] In certain implementations, the cement may include ordinary Portland cement.

[0016] In some implementations, the flowable mixture of the building material may further include one or more of silica fume, fly ash, ground granulated blastfurnace slag, limestone fines, microsilica, nanosilica, volcanic ash, clay, calcined clay, metakaolin, calcined shale, or bauxite.

[0017] According to another aspect, a building material may include gravel having a first average particle size, sand having a second average particle size, particles of a polymer in an irradiated form having one or more properties modified relative to the particles of the polymer in a non-irradiated form, the particles of the polymer in the irradiated form having an average maximum dimension less than the first average particle size of the gravel and greater than the second average particle size of the sand, and a cement including calcium oxide and belite, wherein the sand, the gravel, and the particles of the polymer are dispersed in the cement.

[0018] In certain implementations, the average maximum dimension of the particles of the polymer in the irradiated form may be at least twice as large as an average minimum dimension of particles of the polymer in the irradiated form.

[0019] In some implementations, the average maximum dimension of the particles of the polymer in the irradiated form may be greater than about 5 nm and less than about 5 mm.

[0020] In certain implementations, the first average particle size of the gravel may be greater than about 3 mm and less than about 40 mm. [0021] In some implementations, the weight of the polymer in the irradiated form may be greater than 0 percent and less than about 25 percent of the weight of the cement. For example, the weight of the polymer in the irradiated form may be greater than about 0.5 percent and less than about 5 percent of the weight of the cement.

[0022] In certain implementations, the cement may include ordinary Portland cement.

[0023] In some implementations, the building material may further include one or more of the following dispersed in the cement: silica fume, fly ash, ground granulated blastfurnace slag, limestone fines, microsilica, nanosilica, volcanic ash, clay, calcined clay, metakaolin, calcined shale, or bauxite.

[0024] In certain implementations, the sand, the gravel, and the polymer in the irradiated form dispersed in the cement may form at least a portion of a flowable mixture. The flowable mixture may be, for example, anhydrous. Alternatively, the flowable mixture may be hydrated.

[0025] In some implementations, the sand, the gravel, and the particles of the polymer in the irradiated form dispersed in the cement may form at least a portion of a concrete.

BRIEF DESCRIPTION OF THE FIGURES

[0026] The foregoing and other objects, features and advantages of the devices, systems, methods, and materials described herein will be apparent from the following description of particular embodiments thereof, as illustrated in the accompanying drawings. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the devices, systems, and methods described herein.

[0027] FIG. 1 A is a schematic representation of a system for forming a building material.

[0028] FIG. IB is an enlarged view of a flowable mixture of the building material, shown along the area of detail IB in FIG. 1 A.

[0029] FIG. 1C is an enlarged view of the building material in FIG. IB cured in the form of a first concrete.

[0030] FIG. 2 is a flow chart of an exemplary method of forming a building material.

[0031] FIG. 3 is a graphical representation of compressive strength measurements of samples of concrete, the samples of concrete including control samples without a polymer (C), samples of concrete including PET polymer in a non-irradiated form (RP), as well as samples of concrete formed according to the exemplary method of FIG. 2 using PET polymer exposed to a 10 kGy dose of radiation (LD), PET polymer exposed to 50 kGy dose of radiation (MD), and PET polymer exposed to 100 kGy dose of radiation (HD).

[0032] FIG. 4 is a graphical representation of stress as a function of strain for samples of concrete, the samples of concrete including a control sample without a polymer (C), a sample of concrete including PET polymer in a non-irradiated form (RP), as well as samples of concrete formed according to the exemplary method of FIG. 2 using PET polymer exposed to 10 kGy dose of radiation (LD), PET polymer exposed to 50 kGy dose of radiation (MD), and PET polymer exposed to 100 kGy dose of radiation (HD).

[0033] FIG. 5 is a graphical representation of Young’s modulus extracted from the stress-strain plots shown in FIG. 4.

[0034] FIG. 6 is a graphical representation of compressive strength as a function of gamma irradiation dosage in concrete samples, the samples of concrete including samples of concrete including PET polymer in a non-irradiated form (RP), as well as samples of concrete formed according to the exemplary method of FIG. 2 using PET polymer exposed to a 10 kGy dose of radiation (LD), PET polymer exposed to a 50 kGy dose of radiation (MD), and PET polymer exposed to a 100 kGy dose of radiation (HD).

[0035] FIG. 7 is a graphical representation of differential scanning calorimetry thermograms for a non-irradiated PET polymer sample and for PET polymer samples irradiated at 10 kGy, 50 kGy, and 100 kGy doses.

[0036] FIG. 8 is a graphical representation of differential scanning calorimetry thermograms for samples of concrete, the samples of concrete including control samples without a polymer (C), samples of concrete including PET polymer in a non-irradiated form (RP), as well as samples of concrete formed according to the exemplary method of FIG. 2 using PET polymer exposed to a 10 kGy dose of radiation (LD), PET polymer exposed to a 50 kGy dose of radiation (MD), and PET polymer exposed to a 100 kGy dose of radiation (HD).

[0037] FIG. 9 is a graphical representation of synchrotron X-ray diffraction for a non- irradiated PET polymer sample and for PET polymer samples irradiated at 10 kGy, 50 kGy, and 100 kGy doses. [0038] FIG. 10 is a graphical representation of synchrotron X-ray diffraction of the Portlandite phase in samples of concrete including PET polymer, the samples of concrete including PET polymer in a non-irradiated form (RP), as well as samples of concrete formed according to the exemplary method of FIG. 2 using PET polymer exposed to a 10 kGy dose of radiation (LD), PET polymer exposed to a 50 kGy dose of radiation (MD), and PET polymer exposed to a 100 kGy dose of radiation (HD).

[0039] FIG. 11 is a graphical representation of synchrotron X-ray diffraction of the C- S-H phase and the cal cite phase in the samples of concrete corresponding to FIG. 10.

[0040] FIG. 12 is a graphical representation of synchrotron X-ray diffraction of the ettringite phase in the samples of concrete corresponding to FIG. 10.

[0041] Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

[0042] The embodiments will now be described more fully hereinafter with reference to the accompanying figures, in which preferred embodiments are shown. The foregoing may, however, be embodied in many different forms and should not be construed as limited to the illustrated embodiments set forth herein.

[0043] All documents mentioned herein are hereby incorporated by reference in their entirety. References to items in the singular should be understood to include items in the plural, and vice versa, unless explicitly stated otherwise or clear from the text. Grammatical conjunctions are intended to express any and all disjunctive and conjunctive combinations of conjoined clauses, sentences, words, and the like, unless otherwise stated or clear from the context. Thus, the term“or” should generally be understood to mean“and/or” and, similarly, the term“and” should generally be understood to mean“and/or.”

[0044] Recitation of ranges of values herein are not intended to be limiting, referring instead individually to any and all values falling within the range, unless otherwise indicated herein, and each separate value within such a range is incorporated into the specification as if it were individually recited herein. The words“about,”“approximately,” or the like, when accompanying a numerical value, are to be construed as indicating a deviation as would be appreciated by one of ordinary skill in the art to operate satisfactorily for an intended purpose. Ranges of values and/or numeric values are provided herein as examples only, and do not constitute a limitation on the scope of the described embodiments. The use of any and all examples, or exemplary language (“e.g.,”“such as,” or the like) provided herein, is intended merely to better illuminate the embodiments and does not pose a limitation on the scope of the embodiments. No language in the specification should be construed as indicating any unclaimed element as essential to the practice of the embodiments.

[0045] In the following description, it is understood that terms such as“first”“second” “above,” and“below” and the like, are words of convenience and are not to be construed as limiting terms.

[0046] In the description that follows, the term“building material” shall be understood to refer to a material useful for construction purposes. Unless otherwise specified or made clear from the context, such construction purposes shall be understood to include structural applications, conduits, thermal applications, decorative applications, or a combination thereof. Thus, for example, the building materials described herein may be useful in the construction of buildings, bridges, roads, pipes, or any other application in which concrete may be used.

[0047] As used herein, the term“polymer” shall be understood to refer generally to the polymeric component of a building material or concrete formed from curing the building material, as the case may be. Accordingly, reference to a polymer is intended to be inclusive of a single polymeric material of a given composition as well as a plurality of polymeric materials of different compositions, unless otherwise specified or made clear from the content. For example, to the extent a polymer is described as having a particular property (e.g., crystallinity) this shall be properly understood as referring to the particular property of at least one polymeric material forming the polymeric component of the building material or concrete, as the case may be, and the polymer may include one or more other polymeric materials (e.g., in the form of impurities).

[0048] In the description that follows, building materials are described as being formed through co-located equipment in an integrated facility as one or more steps carried out to process and/or combine materials. It should be appreciated, however, that this is for the sake of clarity of description and, more generally, any one or more aspects of the following description may be carried out in separate locations, as may be useful for efficient construction techniques. As an example, one or more components of a building material may be mixed together at a central location and transported as necessary in an anhydrous form, which may be particularly useful for maintaining stability of the building material over long distances and periods of time. Continuing with this example, one or more components of the building material may be hydrated at or near a construction site to form concrete a short time before the concrete is poured or otherwise delivered into a form. Additionally, or alternatively, given the complexity and safety considerations associated with gamma irradiation, an irradiation facility may be located apart from (e.g., in a separate facility) other components of a system used to form the building materials of the present disclosure. Thus, continuing with this example, particles of a polymer may be irradiated at the irradiation facility and transported to another location, where the particles of the polymer in an irradiated form may be mixed with one or more other components of a building material.

[0049] Further, in the description that follows, the terms“non-irradiated” and “irradiated” are used distinguish relative changes in particles of a polymer resulting from exposure to radiation. That is, in general, the non-irradiated form of particles of a polymer should be understood to be the form of the particles of the polymer prior to a given dose of radiation, and the irradiated form of the particles of the polymer should be understood to be the form of the particles of the polymer following the given dose of radiation, provided that the given dose of radiation is sufficient to change one or more properties of the particles of the polymer. Accordingly, it shall be appreciated that particles of the polymer that have been exposed to a small dose of radiation may nevertheless be considered“non-irradiated” in the context of the present disclosure, to the extent such small doses do not change one or more properties of the particles of the polymer relative to the particles of the polymer prior to exposure to the small dose of radiation. By way of a non-limiting example, the polymer may include a semi-crystalline structure, and an irradiated form of the polymer may have crystallinity and crosslinking greater than respective crystallinity and crosslinking of the polymer in a non- irradiated form.

[0050] Referring now to FIGS. 1 A, IB, and 1C, a system 100 may include a processing unit 102, material sources 104a, 104b, 104c, 104d, a receptacle 106, a mixer 108, a hydration source 110, and a controller 112. In general, the controller 112 may be in communication with one or more of the processing unit 102, the material sources 104a, 104b, 104c, 104d, the mixer 108, and the hydration source 110 to form a building material 124 in the receptacle, with the building material 124 being a flowable mixture that may be delivered to a desired location and cured into concrete 126. In the description that follows components of the building material 124 are generally described as being mixed in the receptacle 106 separately from the material sources 104a, 104b, 104c, 104d, and the hydration source 110. It shall be appreciated, however, that such description is for the sake of clarity and efficiency of explanation and, unless otherwise specified or made clear from the context, any one or more of the components of a given instance of the building material 124 may be mixed together, prior to introduction into the receptacle 106. Thus, for example, while the hydration source 110 is generally described below as adding water to the receptacle to form the building material 124 in the form of a slurry, it should be appreciated that any one or more components of the building material 124 may be hydrated prior to introduction into the receptacle 106. Further or instead, through control of one or more of the material sources 104a, 104b, 104c, 104d, the system 100 may be used to form any one or more of the various different instances of the building material 124 described herein and curable into any one or more of the various different instances of the concrete 126 described herein, including the various different concrete formulations compared to one another in the experimental results below.

[0051] For example, as described in greater detail below, the controller 112 may be in communication with one or more of the processing unit 102, the material sources 104a, 104b, 104c, 104d, the mixer 108, and the hydration source 110 to form particles of a polymer 116 into an irradiated form and to mix the irradiated form of the particles of the polymer 116 into a flowable mixture including gravel 118, sand 120, and a cement 122 to form the building material 124 in the receptacle 106. As also described in greater detail below, the polymer 116 may be derived from one or more sources associated with low greenhouse gas emissions (e.g., one or more polymers recycled from any of various different waste streams). Further, the process of irradiating the particles of the polymer 116 is compatible with such responsible sourcing at least because irradiation generally does not contribute to greenhouse gas emissions. Thus, the particles of the polymer 116 in an irradiated form may be useful as an environmentally responsible additive in the building material 124 as a replacement for a least a portion of the volume of the cement 122 that would otherwise be used in the building material 124. In what amounts to a surprising and significant result, the experimental results described herein demonstrate that the building material 124 may be formed (e.g., through curing for a period of time) into a concrete 126 having greater compressive strength, greater ductility, and less porosity than a concrete formed, under otherwise identical conditions, without a polymer of any type (such concrete formed without a polymer of any type is generally referred to herein as a control concrete). Thus, as compared to other types construction materials, the building material 124 may be useful as an environmentally responsible material useful for forming concrete having comparable, or improved, structural characteristics relative to concrete formed without any polymer used to displace a volume of cement.

[0052] Referring now to FIGS. IB and 1C, the building material 124 may be a flowable mixture including the particles of the polymer 116, gravel 118, sand 120, and cement 122. As used herein, unless otherwise specified or made clear from the context, a flowable mixture of the building material 124 shall be understood to include an anhydrous mixture (e.g., as may be useful for transport) or a hydrated mixture (e.g., a mixture including water in a predetermine ratio useful for forming a slurry curable into concrete). For example, the gravel 118, the sand 120, and the particles of the polymer 116 may be dispersed in the cement 122 such that the flowable mixture of the building material 124 has a substantially uniform composition and, thus, may be curable to form the concrete 126 with consistent composition (e.g., to within a predetermined composition, such as defined by a standard). While the gravel 118, the sand 120, and the particles of the polymer 116 are described as being dispersed in the cement 122, this is not intended to indicate that the cement 122 necessarily forms the largest volume fraction of the flowable mixture of the building material 124. Rather, it shall be understood to refer to the gravel 118, the sand 120, and the particles of the polymer 116 as being well mixed at least with respect to the cement 122 such that these components are flowable with one another as the flowable mixture of the building material 124 is poured.

[0053] In general, the particles of the polymer 116 may have one or more properties modifiable to make the particles of the polymer 116 better suited for use in the building material 124. Examples of such improved suitability are described below. The one or more properties may be any one or more of various different physicochemical properties (e.g., surface properties, chemical structure, and combinations thereof). The one or more modifiable properties may, for example, increase compressive strength, increase ductility, reduce porosity, or a combination thereof, of the concrete 126 ultimately formed from the building material 124 including the particles of the polymer 116.

[0054] To form the building material 124 with a net carbon emissions benefit relative to conventional concrete, however, carbon emissions associated with techniques used to alter the one or more properties of a given polymer included in the particles of the polymer 116 must be considered. Further, or instead, to achieve a net carbon emissions benefit on an environmentally impactful scale, the techniques used to alter the one or more properties of a given polymer included in the particles of the polymer 116 must be suitable for large-scale commercial production. Thus, in addition to being alterable to improve suitability of the building material 124, the one or more properties of the particles of the polymer 116 may be any one or more properties modifiable using doses of radiation that can be safely and controllably delivered to the particles of the polymer 116 within periods (e.g., less than about 48 hours) suitable for commercial-scale production activity.

[0055] In certain instances, the particles of the polymer 116 may have a composition suitable for primary use as a formed article useful in other applications in which the formed article is ubiquitous and reuse of the formed article is limited. That is, the formed article may be abundant in commercial and/or residential waste streams such that the use of the particles of the polymer 116 in the building material 124 results in recycling of at least a portion of the material forming the particles of the polymer 116. Continuing with the example of sourcing the particles of the polymer 116 from recycled material, the formed article from which the particles of the polymer 116 may be sourced can be any of various different types of bottles or containers used in the packaging of food and/or beverages and, further or instead, amenable to separation from a mixed waste stream through high-volume separation techniques used in plastic recycling. By way of example, the formed article of the polymer 116 may be marked with a Resin

Identification Code defined in ASTM D7611/D7611M-I3el,“Standard Practice for Coding Plastic Manufactured Articles for Resin Identification, ASTM International, West

Conshohocken, PA (2013), the entire contents of which are incorporated herein by reference. Such marking may be useful, for example, for reliably identifying a particular composition of a polymer such that the particles of the polymer 116 used in the building material 124 may have a substantially known composition.

[0056] In some implementations, the polymer 116 may have a semi-crystalline structure, which is advantageously found in different types of commonly used polymers - and, more specifically, ubiquitous in polymers found in streams of waste materials - while also being amenable to beneficial alteration through exposure to radiation. For example, the semi crystalline structure of the polymer 116 may be irradiated such that an irradiated form of the polymer 116 has crystallinity and crosslinking greater than respective crystallinity and crosslinking of the particles of the polymer 116 in a non-irradiated form. For example, the polymer 116 may include one or more of polyethylene terephthalate (PET), high density polyethylene, low density polyethylene, or polypropylene, each widely used material in primary applications serving as potential sources of the polymer 116.

[0057] Additionally, or alternatively, the polymer 116 may have an amorphous structure. Such polymers may, for example, have primary uses requiring transparency (e.g., food packaging). More generally, amorphous polymers may also be prevalent in waste streams.

Some examples of amorphous polymers include, but are not limited to, polystyrene and polyvinyl chloride.

[0058] Whether the polymer 116 has a semi-crystalline structure or an amorphous structure, the polymer 116 may be thermoplastic. In addition to being in widespread use in primary applications serving as potential sources of the polymer 116, thermoplasticity of the polymer 116 may facilitate handling the polymer 116 as part of one or more processes for recycling the polymer 116 from a primary application to use in the building material 124. As an example, thermoplasticity of the polymer 116 may facilitate separating the polymer 116 from other types of material in a waste stream. Additionally, or alternatively, thermoplasticity of the polymer 116 may be useful for controlling physical characteristics (e.g., size, shape, or a combination thereof) of particles of the polymer 116 for use in the building material 124.

[0059] The particles of the polymer 116, prior to combination with one or more other components of the building material 124, may be in a form that is flowable, which may be useful for reliably metering or otherwise controlling an amount (e.g., mass or volume) of the particles of the polymer 116 introduced into the flowable mixture of the building material 124. For example, in instances in which the particles of the polymer 116 are sourced from recycled material, the particles of the polymer 116 may be formed (e.g., reduced or aggregated through one or more of various different mechanical techniques) from a primary object having a different form factor than the particles of the polymer 116. That is, the particles of the polymer 116 may have any one or more of various different aspect ratios corresponding to an increase in overall surface area of the particles of the polymer 116, as compared to the surface area of a primary object from which the particles of the polymer 116 may be formed. Without wishing to be bound by theory, it is believed that the increased surface area of the particles of the polymer 116 may facilitate increased interactions between the particles of the polymer 116 in the irradiated form and one or more other components of the building material 124 which, in turn, promotes improvements in the concrete 126, as observed in the experimental results described below.

[0060] In certain instances, the particles of the polymer 116 may be characterized by an average maximum dimension of the particles of the polymer 116 in the irradiated form. The average maximum dimension of the particles of the polymer 116 may be determined through any one or more of various different known techniques including, for example, optical techniques or sieving techniques. For example, the particles of the polymer 116 in the irradiated form may generally be thin and substantially elongate (e.g., in the form of flakes, fibers, or a combination thereof). As a more specific example, the average maximum dimension of the particles of the polymer 116 in the irradiated form may be at least twice as large as an average minimum dimension of the polymer 116 in the irradiated form. For these and other shapes that may be associated with the particles of the polymer 116, the average maximum dimension may be a useful proxy of the average surface area of the particles of the polymer 116 in the irradiated form. Thus, the average maximum dimension of the particles of the particles of the polymer 116 may be an adjustable parameter useful for controlling the likelihood of advantageous reactions on surfaces of the particles of the polymer 116 in the irradiated form.

[0061] In certain implementations, the particles of the polymer 116 in a non-irradiated form may have the same particle size distribution as the particles of the polymer 116 in the irradiated form. That is, by itself, irradiating the particles of the polymer 116 generally does not alter the physical size of the particles of the polymer 116. In some instances, however, the size distribution of the particles of the polymer 116 in the irradiated form may be adjusted (e.g., through the removal of fine particles, the removal of large particles, or a combination thereof) relative to the size distribution of the particles of the polymer 116 in the non-irradiated form, such as may be useful for facilitating metering the particles of the polymer 116 during formation of the flowable mixture of the building material 124.

[0062] In general, prior to combination with one or more other components of the building material 124, the gravel 118 may be a loose aggregation of rock fragments (e.g., rounded fragments) that is generally coarser than the sand 120. In particular, the gravel 118 may be characterized by a first average particle size. In this context, given that the fragments of the gravel 118 may be irregularly shaped, the size of the gravel 118 may be determined according to sieve analysis such that about 50 percent of the particles of the gravel 118 are larger than the first average particle size and about 50 percent of the particles of the gravel 118 are smaller than the first average particle size. As an example, the first average particle size of the gravel may be greater than about 3 mm and less than about 40 mm. Additionally, or alternatively, the gravel 118 may have a predetermined size distribution (e.g., as determined through sieve analysis), which may be useful for achieving substantially uniform properties in the concrete 126 ultimately formed from curing the building material 124. As an example, the gravel 118 may be P-gravel (also referred to as pea gravel), which includes semi-round particles having an average particle size of greater than about 8 mm and less than about 12 mm. More generally, the gravel 118 may include any of various different types of particle size distributions, provided that the first average particle size of the gravel 118 is appropriately sized relative to the sand 120 and the polymer 116, as described below.

[0063] In general, prior to combination with one or more other components of the building material 124, the sand 120 may be a loose granular material and, in certain instances may include silica. The loose granular material of the sand 120 may have a second average particle size, as determined according to sieve analysis. The second average particle size of the sand 120 may generally be less than the first average particle size of the gravel 118 such that particles of the sand 120 may move between the particles of the gravel 118, as may be useful for forming the concrete 126. Further, or instead, as described in greater detail below, the second average particle size of the sand 120 may generally be less than an average maximum dimension of the polymer 116, given challenges associated with forming the polymer 116 with particles of small size. A lower boundary of the second average particle size of the sand 120 may, for example, be dictated by considerations related to handling the sand 120 (e.g., flowability) prior combination of the sand 120 with one or more other components of the building material 124. In certain instances, the sand 120 may have a predetermined size distribution, as may be useful for achieving substantially consistent properties throughout the concrete 126 ultimately formed from curing the building material 124. As an example, the sand 120 may be fine grade (with particle sizes ranging from 0.063 mm to 0.2 mm), medium grade (with particle sizes ranging from 0.2 mm to 0.63 mm), or coarse grade (with particle sizes ranging from 0.63 mm to 2.0 mm).

[0064] The cement 122 may generally be any one or more of various different types of cement known for use in the formation of concrete. As an example, the cement 122 may be formed from naturally-occurring materials (e.g., limestone, shale, or a combination thereof) that are widely available and may be cost-effectively sourced. Thus, for example, the cement 122 may include calcium oxide and belite (C2S). As a more specific example, the cement 122 may include any of various different forms of Portland cement. As used herein,“Portland cement” may include a hydraulic material having a composition (by mass) including calcium silicates. Further, or instead, Portland cement may include any one or more cements as defined in ASTM C150/C150M - 18, entitled“Standard Specification for Portland Cement,” ASTM International, West Conshohocken, PA (2018), the entire contents of which are hereby incorporated herein by reference. As a specific example, ordinary Portland cement shall be understood to include any cement meeting the requirements of Type I Portland cement, as specified in ASTM

C150/C150M - 18. The cement 118 may have any of various different sizes useful in various different construction applications. For example, the cement 122 may have a mean particle size greater than about 10 microns and less than about 20 microns. This size range may be useful for facilitating handling the cement 122 using typical cement handling techniques and equipment and, further or instead, may be useful for facilitating mixing the cement 122 with other components of the building material 124 to achieve a substantially homogeneous mixture without the need for specialized equipment.

[0065] Referring again to FIG. 1 A, unless otherwise specified or made clear from the context, the building material 124 may be formed according to any one or more of the compositions described herein through operation of the system 100. In some implementations, the system 100 may have substantially fixed operating parameters useful for forming a predetermined composition of the building material 124, with such substantially fixed operating parameters being useful in large-scale manufacturing. In certain implementations, however, the system 100 may have one or more adjustable operating parameters useful for modifying composition of the building material 124, such as may be useful for varying formulation of the building material 124 to accommodate specific criteria.

[0066] In general, the processing unit 102 may include a radiation source

129positioned to direct a controlled dose of radiation to the particles of the polymer 116 in a volume 130 defined by the processing unit 102. The radiation source 129 may be, for example, a cobalt-60 irradiator facility, which has the advantage of being in common commercial use in other applications (e.g., food irradiation). That is, a cobalt-60 irradiator facility may be particularly useful as a well-understood radiation source that may be operated safely to handle a large throughput of material. As a more specific example, a cobalt-60 irradiator facility may deliver radiation at a rate (e.g., 58 Gy/min) suitable for radiating the particles of the polymer 116 within a timeframe (e.g. less than about 48 hours) compatible with high-volume production on a commercial scale. More generally, it should be appreciated that any of various different radiation rates may be used to irradiate the particles of the polymer 116, as may be suitable for a particular application.

[0067] In certain implementations, the processing unit 102 may include a grinder 132 in communication (e.g., through a gravity feed, a conveyor, or a combination thereof) with the volume 130 such that material processed in the grinder 132 is movable into the volume 130 for irradiation. The grinder 132 may receive a raw form of the particles of the polymer 116 in a non- irradiated form and, further or instead, may mechanically reduce the size of the raw form of the particles of the polymer 116 before or after irradiation. For example, the grinder 132 may process the raw form of the particles of the polymer 116 to achieve a size distribution having an average maximum dimension less than the first average particle size of the gravel and greater than the second average particle size of the sand, which has been found to be relative sizing that promotes efficient use of the particles of the polymer 116 to produce improvements in one or more properties of the concrete 126 formed from the building material 124. As an example, the particles of the polymer 116 in the irradiated form may have an average maximum dimension of greater than about 5 nm and less than about 5 mm. Below this range, the particles of the polymer 116 may require the use of specialized handling equipment and, above this range, the particles of the polymer 116 in the irradiated form may begin approaching the size of the coarse aggregate in certain instances and, in those instances, may be unlikely to confer benefits.

[0068] The grinder 132 may be any one or more of various different devices suitable for physically reducing the size of the particles of the polymer 116. For example, the grinder 132 may include a ball mill. As a more specific example, the grinder 132 may include a high energy ball mill. Additionally, or alternatively, the grinder 132 may include other hardware suitable for crushing the particles of the polymer 116. While the grinder 132 has been described as grinding the particles of the polymer 116 prior to irradiation, it should be appreciated that the grinder 132 may additionally or alternatively be positioned to grind the particles of the polymer 116 following irradiation. [0069] The volume 130 defined by the processing unit 102 may be in communication with one or more of the material sources 104a, 104b, 104c, 104d such that, following irradiation, the particles of the polymer 116 in an irradiated form may be movable into the respective one or more of the material sources 104a, 104b, 104c, 104d. Movement of the particles of the polymer 116 in the irradiated form from the volume 130 and into the one or more material sources 104a, 104b, 104c, 104d may be carried out according to any of various different techniques suitable for safely and efficiently moving the particles of the polymer 116. By way of example and not limitation, therefore, the particles of the polymer 116 in the irradiated form may be moved from the volume 130 and into one or more of the material sources 104a, 104b, 104c, 104d through movement of a conveyor extending from the volume 130 to the one or more material sources 104a, 104b, 104c, 104d.

[0070] In certain implementations, the material sources 104a, 104b, 104c, 104d may each store one or more components of the building material 124 prior to forming the flowable mixture of the building material 124 in the receptacle 106. Thus, for example, the particles of the polymer 116 in the irradiated form may be stored in the material source 104a. Additionally, or alternatively, the gravel 118 may be stored in the material source 104b. Further, or instead, the sand 120 may be stored in the material source 104c. Still further, or instead, the cement 122 may be stored in the material source 104d. While such segregation of components in the respective material sources 104a, 104b, 104c, 104d may be useful for controlling the

compositional accuracy of the building material 124 in certain instances, it should be appreciated that other storage techniques are within the scope of the present disclosure. Thus, for example, multiple components of the building material 124 may be stored in a single one of the material sources 104a, 104b, 104c, 104d at the same time, as may be useful for premixing certain combinations of components and, in some cases, hydrating one or more components of the building material 124.

[0071] In some implementations, one or more of the material sources 104a, 104b, 104c, 104d may, additionally or alternatively, include supplementary cementitious material such that the supplementary cementitious material may be delivered to the receptacle 106 and ultimately be dispersed in the flowable mixture of the building material 124. Thus, returning to the example above, the cement 122 stored in the material source 104d may include supplementary

cementitious material. Examples of the supplementary cementitious material include, but are not limited to, silica fume, fly ash, ground granulated blastfurnace slag, limestone fines, microsilica, nanosilica, volcanic ash, clay, calcined clay, metakaolin, calcined shale, or bauxite.

[0072] The material sources 104a, 104b, 104c, 104d may be any of various different types of containers suitable for stably storing the components of the building material 124. As used in this context, stable storage of material may include reducing the likelihood of unintended aggregation or settling of each respective component. Further, or instead, stable storage of material may include controlling hydration of each respective component, with some

implementations including storing one or more components in a hydrated state. For example, the material sources 104a, 104b, 104c, 104d may be hoppers supported above the receptacle 106. Continuing with this example, the material sources 104a, 104b, 104c, 104d may each include respective valves 128a, 128b, 128c, 128d. Each of the valves 128a, 128b, 128c, 128d may be selectively actuatable to control delivery of the respective contents of the respective one of the material sources 104a, 104b, 104c, 104d. Further, or instead, the each of the valves 128a, 128b, 128c, 128d may include a metered orifice to facilitate accurately metering the flow of material from the respective one of the material sources 104a, 104b, 104c, 104d into the receptacle 106.

[0073] In general, the receptacle 106 may be of a size and shape suitable for supporting mixing of the contents of the building material 124 in quantities required for a particular manufacturing process. Further, or instead, the receptacle 106 may be formed of a material (e.g., steel) suitable for withstanding corrosion or other forms of degradation that may be associated with the building material 124.

[0074] The mixer 108 may be disposed in the receptacle 106 to facilitate mixing the constituent components of the flowable mixture of the building material 124 into a homogenous mixture. As used herein, a homogenous mixture shall be understood to include small variations in homogeneity such that the volumetric composition of the building material 124 varies by less than a predetermined percentage within the receptacle 106, with the predetermined percentage being associated with a design standard. For example, the predetermined percentage may be less than about ± 5 percent (e.g., less than about ± 1 percent) within the receptacle 106. The mixer 108 may be any one or more of various different types of mechanisms useful for combining the constituent components of the flowable mixture of the building material 124. Thus, for example, the mixer 108 may include a rotor or other similar component substantially submersible in the building material 124 and movable relative to the receptacle 106 to mix the components of the flowable mixture of the building material 124. Additionally, or alternatively, the receptacle 106 itself may move (e.g. through rotation, vibration, or a combination thereof) to mix the components of the flowable mixture of the building material 124. Thus, it should be more generally understood that the constituent components of the building material 124 may be formed into a flowable mixture of homogenous composition in any one or more of various different forms of mechanical agitation. Further, or instead, in instances in which a sufficient amount of hydration is introduced directly into the receptacle 106 via the hydration source 110, the constituent components of the building material 124 may further or instead be mixed through the flow of water in the receptacle 106.

[0075] In general, the hydration source 110 may control moisture content of the flowable mixture of the building material 124 in the receptacle 106. In certain instances, the hydration source 110 may provide a small amount of water relative to the volume of the flowable mixture of the building material 124 in the receptacle 106 such that the flowable mixture of the building material 124 remains anhydrous but the small amount of water is useful for reducing the formation of fine particulates as the flowable mixture of the building material 124 is mixed. As used herein, an anhydrous form of the building material 124 shall be understood to include a composition of the building material 124 having a low moisture content such that the building material 124 flows like a powder. Additionally, or alternatively, an anhydrous form of the building material 124 should be understood to have a moisture content less than about ± 2 percent by mass (e.g., less than about ± 1 percent by mass).

[0076] In certain implementations, the hydration source 110 may introduce larger quantities of water into the receptacle 106 to form a hydrated form of the flowable mixture of the building material 124. As used in this context, a hydrated form of the flowable mixture of the building material 124 shall be understood to be any form of the flowable mixture of the building material 124 that is not anhydrous. Thus, for example, a hydrated form of the flowable mixture of the building material 124 may include sufficient water content such that the flowable mixture of the building material 124 does not flow like a powder. As a more specific example, a hydrated form of the build material 124 shall be understood to include sufficient water content such that the flowable mixture of the building material 124 flows like a slurry. More specifically still, a hydrated form of the flowable mixture of the building material 124 shall be understood to include sufficient water content such that the building material 124 may cure into concrete without the addition of other material.

[0077] In general, the controller 112 may include one or more processors 134 and a non-transitory, computer-readable medium 136 having stored thereon computer executable instructions for causing the one or more processors 134 to communicate with one or more other components of the system 100 to carry out any one or more of the methods of forming building materials described herein. While the controller 112 may be single controller, it should be appreciated that the controller 112 may be implemented as a plurality of distributed controllers (e.g., operable individually), such as may be useful for controlling individual aspects of the system 100, particularly in instances in which the system 100 is itself distributed across multiple locations. Such distributed controllers may be, for example, in communication with one another (e.g., through a data network). Additionally, or alternatively, it should be appreciated that the controller 112 offers automation and control that may be useful for achieving consistency in large-scale production.

[0078] In certain implementations, the controller 112 may be in electrical

communication with the valves 128a, 128b, 128c, 128d to control dispensing of the particles of the polymer 116 in the irradiated form, the gravel 118, the sand 120, and the cement 122 into the receptacle 106 in controlled proportions relative to one another. Additionally, or alternatively, the controller 112 may be in electrical communication with the mixer 108 to control movement (e.g., a rotational speed, a rotational direction, or a combination thereof) of the mixer 108.

Further, or instead, the controller 112 may be in electrical communication with the hydration source 110 to control a rate or a total amount of water flow into the receptacle 106, into one or more of the material sources 104a, 104b, 104c, 104d, or a combination thereof, such that a target amount of moisture may be introduced into the flowable mixture of the building material 124 as desired for a particular application. Still further or instead, the controller 112 may be in electrical communication with the processing unit 102 to control one or more different aspects of preparation of the particles of the polymer 116. For example, the controller 112 may control actuation of the grinder 132 to form the particles of the polymer 116 into a target size distribution. As an additional or alternative example, the controller 112 may control movement of the particles of the polymer 116 into and out of the volume 130 defined by the processing unit 102 to control the amount of radiation delivered to form the particles of the polymer 116 in the irradiated form.

[0079] FIG. 2 is a flow chart of an exemplary method 200 of forming a building material. In general, the exemplary method 200 may be carried out using any manner and form of hardware described herein to form any one or more of the building materials described herein. Accordingly, unless otherwise specified or made clear from the context, the exemplary method 200 may be carried out using the system 100 (FIG. 1) to form the flowable mixture of the building material 124 (FIG. 1 A and IB), which may be curable to form the concrete 126 (FIG. 1C). Unless otherwise specified or made clear from the context, it should be generally appreciated that aspects of the exemplary method 200 may be carried out through manual processes (e.g., as carried out by one or more operators), automated processes (e.g., as carried out by the controller 112 of the system 100 in FIG. 1), or a combination thereof.

[0080] As shown in step 202, the exemplary method 200 may include receiving particles of a polymer in a non-irradiated form. In general, the polymer may be any one or more of the polymers described herein. Accordingly, the polymer may have a semi-crystalline structure, an amorphous structure, or a combination thereof.

[0081] In some implementations, receiving the particles of the polymer may include receiving a stock material (e.g., a stream of mixed material waste, such as may be associated with a single-stream recycling process). As should be generally understood, such a stream of stock material may be substantially non-uniform. Accordingly, receiving the particles of the polymer may further or instead include mechanically separating the polymer (in particle form or in another form) from other components in the stream of stock materials. Such separation techniques may include any of various different separation techniques used in plastic recycling and, thus, may include manual sorting, optical sorting, or a combination thereof.

[0082] In certain implementations, receiving the particles of the polymer may include reducing an average maximum dimension of the particles of the polymer. Particularly in implementations in which the particles of the polymer are sourced from a waste stream or other similarly non-uniform source, reducing the average maximum dimension of the particles may improve uniformity of the size distribution of the particles of the polymer. In turn, improved uniformity of the size distribution of the particles of the polymer may facilitate accurately metering the particles to achieve a target composition. Further, or instead, reducing the average maximum dimension of the particles of the polymer may facilitate handling the particles of the polymer.

[0083] The particles of the polymer may be reduced to a predetermined average maximum dimension suitable, for example, for end-use in a build material formable into concrete. In certain instances, the predetermined average maximum dimension of the particles of the polymer may serve as a useful proxy for the average surface area of the particles of the polymer and, thus, may be useful as an adjustable parameter for controlling the likelihood of advantageous reactions on surfaces of the particles of the polymer in the irradiated form as the build material is formed into concrete, as described in greater detail below. Thus, for example, the average maximum dimension of the polymer may be sized based on an average particle size of one or more components of the build material formable into concrete. For example, the average maximum dimension of the polymer may be less than the average particle size of gravel used to form a build material formable into concrete. Additionally, or alternatively, the average maximum dimension of the particles of the polymer may be greater than the average particle size of the sand used to form a build material formable into concrete.

[0084] Reducing the average maximum dimension of the particles of the polymer may include the use of any one or more of various different techniques useful for mechanically reducing the size of a polymeric material. As used in this context, mechanically reducing the size of a polymeric material should be understood to include reducing the size of the material without changing a chemical composition or state of matter of the particles of the polymer. As compared to certain thermochemical processes, mechanically reducing the size of the particles of the polymer may be more energy efficient and, further or instead, may reduce the need to store, handle, and dispose of additional materials that may be associated with such thermochemical processes. Grinding (e.g., through high energy ball milling) may be a particularly efficient and robust technique for reducing the average maximum dimension of the particles of the polymer.

[0085] As shown in step 204, the exemplary method 200 may include irradiating the particles of the polymer with a dose of radiation (e.g., gamma irradiation) sufficient to modify one or more properties of the particles of the polymer relative to the particles of the polymer in a non-irradiated form. As discussed above, the one or more properties may be any one or more of various different physicochemical properties (e.g., surface properties, chemical structure, and combinations thereof). The one or more properties modified through exposure to the dose of radiation may depend on the type of polymer. For example, through exposure to the dose of radiation, the one or more properties modified in the polymer may depend on the degree of crystallinity of the polymer (e.g., whether the polymer is semi-crystalline or amorphous).

Further, or instead, the one or more properties modified in the particles of the polymer may change bonding characteristics between the particles of the polymer with one or more other components initially in the building material or intermediate components formed in the building material as the building material cures into concrete. Still further or instead, while the dose of radiation may change one or more properties of the polymer, the rheological characteristics of the particles of the polymer may remain unchanged following exposure to the dose of radiation in some implementations.

[0086] In certain implementations, the one or more modified properties of the polymer may be observable or detectable as a change in one or more bulk properties of the polymer in the irradiated form as compared to the comparable one or more bulk properties of the polymer in the non-irradiated form, which may be useful for facilitating inspection of the particles of the polymer prior to combination with one or more other components. As an example, the one or more modified properties of the particles of the polymer may be detectable as a visually observable change in color or opacity when comparing the polymer in the irradiated form to the polymer in the non-irradiated form. Further, or instead, the one or more modified properties of the particles of the polymer may be detectable as a reduction in melting point of the particles of the polymer. In implementations in which the size of the particles of the polymer remain unchanged through exposure to the dose of radiation, a reduction in melting point may be indicative of a reduction in molecular weight of the polymer which, in turn, may be indicative of an advantageous change in one or more properties of the polymer. For example, without wishing to be bound by theory, a reduction in melting point of certain semi-crystalline polymers is believed to be an indication of increased chain scission (and, thus, crystallinity) and crosslinking that contributes to improved interaction between the polymer and one or more other components of the building material. While the dose of radiation may modify one or more properties of the particles of the polymer, it shall be appreciated that the particles of the polymer do not become radioactive as a result of the dose of radiation and, therefore, do not present any special safety concern relative to the particles of the polymer in the non-irradiated form. [0087] As an example, the non-irradiated form, the polymer included in the particles may have a semi-crystalline structure. Without wishing to be bound by theory, it is believed that sufficient doses of radiation may increase chain scission (resulting in an increase in crystallinity), crosslinking, or a combination thereof of the polymer having such a semi-crystalline structure. Continuing with this example, such increases in chain scission, crosslinking, or a combination thereof, believed to contribute to observed increases in modulus, toughness, stiffness, and hardness of the particles of the polymer in the irradiated form.

[0088] In general, the dose of radiation may be a function of any one or more of various different factors. For example, the dose of radiation may be a function of the

composition of the polymer (e.g., whether the polymer is semi-crystalline or amorphous).

Further, or instead, the dose of radiation may be a function of a targeted property of concrete formed from a building material including the particles of the polymer in the irradiated form. As an example, the dose of radiation may be a function of one or more of targeted compressive strength, ductility, or porosity of the concrete formed from the building material including the particles of the polymer in the irradiated form. In general, low doses of radiation may be insufficient to produce a significant change in the one or more properties of the polymer, and high doses of radiation may change the one or more properties (or other properties) to a point at which diminishing performance is observed. For polymers that are ubiquitously found in waste streams, the dose of radiation may be greater than about 1 kGy and less than about 1000 kGy (e.g., between about 30 kGy and less than about 70 kGy), with doses on the order of 1000 kGy being achievable on a commercially useful timescale using dose rates on the order of 5.8 kGy/min to 58 kGy/min.

[0089] While the dose of radiation may be selected to achieve improvements in parameters of the concrete formed from curing the building material, it should be appreciated that certain applications may target maintaining parameters comparable to concrete formed without any polymer. In such instances, the benefit of forming concrete including particles of the polymer in the irradiated form shall be appreciated to be an environmental benefit (e.g., in displacing a portion of cement with the particles of the polymer from an environmentally responsible source, such as a waste stream) while achieving comparable performance in comparison to concrete formed without any polymer. [0090] The dosage of radiation delivered to the particles of the polymer may be delivered at a rate useful for safe operation in an industrial setting. Additionally, or alternatively, the dosage of radiation delivered to the particles of the polymer may be delivered at a rate sufficient to support high-volume throughput associated with commercial manufacturing. To accommodate these considerations in instances in which the radiation is gamma radiation, a dose gamma radiation to the particles may be delivered, for example, by a cobalt-60 irradiator facility producing 58 Gy/min.

[0091] As shown in step 206, the exemplary method 200 may include forming a flowable mixture of a building material, with the flowable mixture including the particles of the polymer in an irradiated form, cement, sand, and gravel. The flowable mixture of the building material may be any one or more of the flowable mixtures described herein. Further, or instead, the flowable mixture of the building material may be formed through any order of addition of the particles of the polymer, the cement, the sand, and the gravel, unless otherwise specified or made clear from the context. Further, or instead, the flowable mixture of the building material may be sufficiently homogeneous to produce concrete having variations of material properties on the order of such variations typically observed in concrete formed without the use of a polymer.

[0092] The cement may be any one or more of the cements described herein and, thus, in general may include calcium oxide and belite. As specific example, the cement may be any one or more of various different types of cement defined by a standard setting organization.

Thus, for example, the cement may be ordinary (Type I) Portland cement or any other type of Portland cement, as defined in ASTM C150/C150M - 18. As an additional, or alternative example, the cement may have an average particle size greater than about 10 microns and less than about 20 microns.

[0093] In general, the weight of the particles of the polymer in the irradiated form in the flowable mixture of the building material may be expressed as a percentage of the weight of the cement in the flowable mixture. As may be appreciated, expressing the weight of the particles of the polymer in the irradiated form relative to the weight of the cement may be useful for estimating an amount of cement displaced by the particles of the polymer in the irradiated form. While the addition of the particles of the polymer may be useful in advantageously changing one or more properties of the concrete formed from the building material, the addition of high weight fractions of the particles of the polymer may diminish one or more properties of the concrete and, in extreme cases, may prevent formation of the concrete. Accordingly, the weight of the polymer in the irradiated form in the flowable mixture may be greater than 0 percent and less than about 25 percent of the weight of the cement in the flowable mixture.

More specifically, the weight of the polymer in the irradiated form in the flowable mixture may be greater than about 0.5 percent and less than about 5 percent of the weight of the cement in the flowable mixture.

[0094] The gravel may be any one or more of the various different gravels described herein. Thus, for example, the gravel may be pea gravel. Further, or instead, the gravel may have an average particle size of greater than about 3 mm and less than about 40 mm.

Additionally, or alternatively, the sand may be any one or more of the various different sands described herein. Accordingly, the sand may be characterized by a second average particle size less than the first average particle size. More specifically, the particles of the polymer in the irradiated form may have an average maximum dimension less than the first average particle size of the gravel and greater than the second average particle size of the sand. Without wishing to be bound by theory, it is believed that the particles of the polymer in the irradiated form participate in formation of hydration products through surface reactions on the particles of the polymer in the irradiated form, and the average maximum dimension of the particles of the polymer in the irradiated form relative to the first average particle size of the gravel and the second average particle size of the sand advantageously facilitates such surface reactions that ultimately contribute to strength of the concrete.

[0095] In certain instances, the flowable mixture of the building material may include any one or more of various different additives useful in forming concrete. For example, the flowable mixture of the building material may, further or instead, include any one or more of the supplementary cementitious materials referred to herein.

[0096] As shown in step 208, the exemplary method 200 may include hydrating the flowable mixture of the building material to form a slurry curable into concrete. In general, unless otherwise specified or made clear from the context, such hydration of the flowable mixture of the building material may be at least partially carried out simultaneously with formation of the flowable mixture of the building material (e.g., through hydrating the one or more components of the flowable mixture prior to forming the flowable mixture). As an example, the cement may be hydrated in a material stream directed to a receptacle in which the flowable mixture of the building material is formed. In this way, the hydration of the cement in the material stream ultimately hydrates the flowable mixture of the building material as the hydrated cement is mixed with the other components forming the flowable mixture of the building material. Further, or instead, hydration may be at least partially carried out as hydration added to the flowable mixture of the building material following formation of the flowable mixture of the building material. For example, the flowable mixture of the building material may be anhydrous, and hydrating the flowable mixture may include hydrating the anhydrous form of the flowable mixture. Further, or instead, the flowable mixture of the building material may be partially hydrated through hydration of one or more components prior to forming the flowable mixture and, once the components are combined into the flowable mixture of the building material, additional hydration may be added to the flowable mixture of the building material as necessary to achieve a target hydration level.

[0097] As shown in step 210, the exemplary method 200 may include curing the slurry into a first concrete (e.g., the concrete 126 in FIG. 1C). As used herein, a first concrete shall be understood to be concrete cured from a slurry including at least the cement, the sand, the gravel, and the particles of the polymer in the irradiated form and, more specifically, with the sand, the gravel, and the particles of the polymer in the irradiated form sized relative to one another as described herein. Thus, in the context of this disclosure, a first concrete is generally used to distinguish from a second concrete formed according to a different formulation (as specified in each example) and used as a benchmark for comparing one or more properties of the first concrete.

[0098] For example, the first concrete may be compared to a second concrete formed with cement in place of the particles of the polymer (in any form), under otherwise identical conditions. That is, in this example, the second concrete does not include any polymer and, thus, shall be understood to correspond to the control sample used in the experimental results described below. Continuing with this example, the first concrete may have a first compressive strength, and the second concrete may have a second compressive strength less than the first compressive strength (e.g., the first compressive strength may be between about 1 percent to about 25 percent greater than the second compressive strength. Continuing further with this example, the first concrete may have a first final strain, and the second concrete may have a second final strain less than the first final strain. Still further, the first concrete may have a first porosity, and the second concrete may have a second porosity greater than the first porosity. Yet further, the first concrete may have a first Young’s modulus, and the second concrete may have a second Young’s modulus less than the first Young’s modulus. Stated differently, for an otherwise identical concrete formulation, the addition of the particles of the polymer in the irradiated form to displace an equivalent weight of cement may result in one or more of the following advantageous changes in the following properties of the concrete: increase the compressive strength of the concrete, increase the final strain of the concrete, reduce porosity of the concrete (contributing to improved durability), or increase the Young’s modulus of the concrete.

[0099] As another example, the first concrete may be compared to a second concrete formed, under otherwise identical conditions, with particles of the polymer in the non-irradiated form in place of the particles of the polymer in the irradiated form. That is, in this example, the particles of the polymer in the first concrete are in an irradiated form, and the particles of the polymer in the second concrete are in a non-irradiated form. Continuing with this example, the first concrete may have a first compressive strength, and the second concrete may have a second compressive strength less than the first compressive strength (e.g., the first compressive strength may be between about 5 percent to about 30 percent greater than the second compressive strength). Stated differently, for an otherwise identical formulation, the use of particles of the polymer in the irradiated form in placed of particles of the polymer in a non-irradiated form may increase the compressive strength of the concrete.

[00100] As still another example, the first concrete may be compared to a second concrete formed, under otherwise identical conditions, with particles of the polymer irradiated at a different dose. That is, in this example, the particles of the polymer in the first concrete and the particles of the polymer in the second concrete are irradiated at different doses. Continuing with this example, the first concrete may have a first compressive strength, and the second concrete may have a second compressive strength less than the first compressive strength. Stated differently, for an otherwise identical formulation, there may be a dose of radiation of the particles of the polymer that corresponds to a maximum compressive strength as compared to compressive strengths associated with concrete formulations including particles of the polymer radiated at different doses of radiation. Significantly and unexpectedly, as described in greater detail below, radiation doses may have diminished effectiveness beyond a given dosage, making it counterproductive (in terms of the benefit realized in exchange for additional dosing time) to use high radiation doses to modify one or more properties of the particles of the polymer.

[00101] In certain implementations, hydrating the mixture in step 208 may include maintaining substantially constant moisture content during a period in which the slurry cures to form concrete in step 210. The curing period may be, for example, a predetermined curing period, such as any one or more of various different curing periods (e.g., 7 days, 10 days, 14 days, 28 days) specified in various different standards. As an example, the curing period may be as defined in ASTM C150/C150M - 18.

[00102] Experiments

[00103] The following experiments describe one or more aspects of the build materials described herein. It is to be understood, however, that these experiments and corresponding results are set forth by way of example only, with the intention of describing certain aspects of the build material 124 (FIGS. 1A, IB, 1C) and/or the exemplary method 200 (FIG. 2). Nothing in these examples shall be construed as a limitation on the overall scope of the disclosure. Thus, for example, while these experiments are described with respect to build materials including polyethylene terephthalate (PET), this should not be understood to limit the techniques described herein. Further, while specific doses of 10 kGy, 50 kGy, and 100 kGy are described herein as low-dose, medium-dose, and high-dose, respectively, it shall be understood that these are labels of convenience to facilitate efficient discussion of the experiments below and should not be considered to be limiting. That is, it shall be understood that low-dose, medium-dose, and high- dose behavior described in the experiments below may be observed at different specific doses, depending on a variety of factors such as the type of polymer, the additives in the concrete, the relative weight percentages of components, etc. Accordingly, for any given formulation of building material formed according to the methods described herein, it shall be appreciated that it may be useful to analyze a variety of doses to identify a dose or range of doses that improve one or more properties for the given formulation of the building material.

[00104] 1. Materials and Methods

[00105] Concrete specimens were prepared with a combination of gamma irradiated plastic and Portland cement. Concrete samples were prepared using a water to cement ratio of 0.35 using Type I Portland cement. After a 28-day cure period, these specimens underwent compression testing to determine to determine strength variations according to ASTM-C09, “Standard Test Method for Compressive Strength of Hydraulic Cement Mortars (Using 2-in. or [50 mm] Cube Specimens), ASTM International, West Conshohocken, PA, 2016, the entire contents of which are hereby incorporated herein by reference. To examine the microstructure of 28 days cured concrete and to determine the aspects of the composition contributing to the observed strength differences, a microstructural analysis was performed using Differential Scanning Calorimetry (DSC) and Synchrotron X-Ray Diffraction.

[00106] 1.1 Materials

[00107] Commercial Type I Ordinary Portland Cement, sand and P-gravel were used along with polyethylene terephthalate (PET) polymer for preparing concrete specimens.

[00108] 1.2 Methods

[00109] In the description that follows, details are provided regarding gamma irradiation of the flakes of the PET polymer along with a description of experimental techniques used to characterize the concrete specimens with and without the flakes of the PET polymer.

[00110] 1.2.1 Irradiation of the Flakes of PET Polymer

[00111] Flakes of the PET polymer were obtained from a recycling facility and used as an additive for inclusion in certain concrete samples tested. The flakes of the PET polymer were between 1 mm to 2 mm in length, such that the average maximum dimension of the flakes of the PET polymer was between 1 mm to 2 mm. The flakes of the PET polymer were irradiated at a Cobalt-60 irradiation facility operating at 58 Gy/min. The flakes of the PET polymer were irradiated at three doses, designated in the description that follows as low (10 kGy), medium (50 kGy), and high (100 kGy). Flakes of the PET polymer that were not subjected to irradiation are referred to herein as regular polymer or“RP.”

[00112] 1.2.2 Mix Design for Concrete

[00113] The complete mix design for the concrete samples is shown in Table 1. Type I Portland cement was the primary binder. Using this binder, non-control samples were made with low-dose (10 kGy), medium-dose (50 kGy), high-dose (100 kGy), and regular polymer combinations of flakes of the PET polymer. To form control samples, the Type I Portland cement was formed into concrete without any polymer. Each individual combination was triplicated to determine average properties and an uncertainty associated with such properties.

For each non-control sample, the flakes of the PET polymer were 1.25% of the weight of the cement in the control sample. That is, 1.25% of the weight of the cement in the control sample was replaced with the flakes of the PET polymer to form the non-control samples.

[00114] Table 1. Summary of Mix design used for preparing concrete

Sample Notation Dosage of Portland Plastic (kg) Sand Gravel

Type Irradiation Cement (kg) (kg) (kg) of Plastic

(kGy)

Control C NA 1.397 0 2.15 3.57

Regular RP 0 1.3796 0.0175 2.15 3.57

Polymer

Concrete

Low Dose LD 10 1.3796 0.0175 2.15 3.57

Concrete

Medium MD 50 1.3796 0.0175 2.15 3.57

Dose

Concrete

High Dose HD 100 1.3796 0.0175 2.15 3.57

Concrete

[00115] The specimens were subjected to a compression test as per ASTM C39, “Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens,” ASTM International, West Conshohocken, PA, 2016, the entire contents of which are hereby incorporated herein by reference. A 0.20 MPa/s loading rate was selected and kept consistent throughout the testing procedure. The percentage of error for the loads within the proposed range of use of the testing machine did not exceed 1.0% of the indicated load. This procedure was performed for each of the three samples of the twelve concrete-polymer combinations.

[00116] 1.2.3 Differential Scanning Calorimetry (DSC)

[00117] DSC measures the difference in the quantity of heat between the sample and the reference as a function of temperature. Flakes of the PET polymer was subjected to power compensated DSC experiment using TA Instruments Discovery DSC, available from TA Instruments of New Castle, DE, USA, with a heating rate of 10 °C/min. A Pt/Rh crucible was used to place 10-30 mg of each sample. The specimen chamber was purged with nitrogen at a flow rate of 40 cc/min. The following profile was used: heating 50 °C to 300 °C for 10 °C min ¹, isotherm for 300 °C for 5 min, cooling for 300 °C to 50 °C at a heating rate of -5 °C min ¹ and reheating from 50 °C to 300 °C at a rate of 10 °C min ¹. [00118] The 28 days cured samples were powdered and subjected to heat compensated DSC experiment using NETZSCH Pegasus 404 F3 DSC, available from NETZSCH-Geratebau GmbH, Selb, Germany. A heating rate of 10 °C min ¹ was used for this experiment, with temperature from 50 °C to 1000 °C measured.

[00119] 1.2.4 Synchrotron X-ray Diffraction (XRD)

[00120] In these experiments, the 28-day cured samples were ground and analyzed using synchrotron radiation with a powder diffractometer on 1 IBM at the Advance Photon Source (APS), Argonne National Laboratory (ANL) in Lemont, IL, USA. For this instrument, a monochromatic beam was extracted from the white beam by a double Si(l 11) monochromator. These measurements were performed at ambient temperature. Each sample was ground to a fine powder (gran size = 1 - 10 mm) and introduced in a Lindeman tube (F=0.3 mm). Rotation of the sample around the capillary axis was applied to reduce the preferred orientation inherent in such layered compounds. The powder was sealed into kapton capillaries with a diameter of 0.3 mm. Wavelength of X-way was 0.4142 A and a fixed energy of 30 keV was used in these

measurements. Data was recorded at ambient temperature with a counting time of 1 h. The 20 range at wavelength of 0.4142 A was selected since the majority of the peaks were observed in this range. It is noted that the XRD data discussed herein was collected at a synchrotron facility at a fixed energy of 30 keV, whereas XRD data conventionally use Cu K-alpha x-ray source with an energy of 8.04 keV and a wavelength of 1.5406 A.

[00121] 2.0 Results and Discussion

[00122] 2.1 Compression Strength Testing

[00123] Referring now to FIG. 3, the results of the compression testing of the various test samples may be compared to one another to assess the impact of the use of irradiated flakes of PET polymer in concrete. The bar labeled“C” represents average the compressive strength of the control samples formed without any polymer. The bar labeled“RP” represents the average compressive strength of the samples formed with flakes of the polymer with no radiation. The bar labeled“LD” represents the average compressive strength of samples formed with flakes of the PET polymer irradiated with a dose of 10 kGy prior to introduction into a building material curable into the LD concrete samples. The bar labeled“MD” represents the average

compressive strength of samples formed with flakes of the PET polymer irradiated with a dose of 50 kGy prior to introduction into a building material curable into the MD concrete samples. The bar labeled“HD” represents the average compressive strength of samples formed with flakes of the PET polymer irradiated with a dose of 100 kGy prior to introduction into a building material curable into the HD concrete samples.

[00124] As may be appreciated from a comparison of the bar labeled“C” and the bar labeled“RP,” the inclusion of the flakes of the PET polymer in a non-irradiated form into concrete decreases the compressive strength from 41.1 MPa to 36 MPa. Stated differently, replacing 1.25 percent of the weight of concrete with flakes of the PET polymer in a non- irradiated form resulted in a 12 percent decrease in compressive strength of the concrete.

Accordingly, replacing concrete with flakes of the PET polymer in a non-irradiated form may not be well-suited to applications (e.g., structural applications) in which compressive strength of concrete is important or even critical.

[00125] Inclusion of irradiated forms of the flakes of the PET polymer into concrete, however, showed a significant and unexpected increase in compressive strength of the concrete. More specifically, inclusion of flakes of the PET polymer in irradiated form were observed to increase the compressive strength of concrete by 6.6 %, 29.4 %, and 11.54 % for low dose (LD), medium dose (MD), and high dose (HD) samples respectively as compared to the regular polymer (RP) samples. These results demonstrate that strength recovery is possible in concretes when particles of a polymer in a non-irradiated form are replaced with particles of a polymer in an irradiated form. Moreover, the medium dose (MD) samples had a higher compressive strength (51.0 MPa) as compared to the control (C) samples (41.1 MPa) formed without any polymer. Thus, collectively, these results demonstrate that flakes of PET polymer in an irradiated form may be included in Portland cement-based concretes with little or no strength loss and, under certain conditions, with some increase in compressive strength. Accordingly, at least based on these results, it shall be appreciated that appropriate doses of irradiation applied to particles of a polymer to form concrete according to the methods described herein may facilitate the formation of commercially useful concrete, while also providing an environmentally friendly solution for waste treatment of polymers.

[00126] Referring now to FIG. 4, stress-strain curves of the various test samples may be compared to one another to assess changes in ductility resulting from the use of irradiated flakes of PET polymer in concrete. In FIG. 4, a first stress-strain curve 402 corresponds to a control (C) sample, a second stress strain curve 404 corresponds to a regular polymer (RP) sample, a third stress-strain curve 406 corresponds to the low dose (LD) sample, a fourth stress-strain curve 408 corresponds to the medium dose (MD) sample, and fifth stress-strain curve 410 corresponds to the high dose (HD) sample. As may be appreciated from a comparison of the second stress strain curve 404 to the fourth stress-strain curve 408, an 11 percent increase in final strain value was observed when medium dose (MD) of irradiated PET polymer was added to concrete as compared to the addition of regular or non-irradiated (RP) PET polymer to concrete. This indicates that, under appropriate conditions, irradiating the PET polymer contributes to the ductile behavior of concrete. Further, comparison of the second stress strain curve 404 to the fourth stress-strain curve 408 indicates that the medium dose (MD) of irradiated PET polymer contributes to an increase in ductility at failure as well as to a high level of fracture toughness of concrete compared to concrete with the non-irradiated (RP) PET polymer. As may be appreciated from a comparison of the fifth stress-strain curve 410 to the fourth stress-strain curve 408, a lower level strength increase was found for high dose (HD) PET polymer in concrete. However, the use of high dose (HD) PET polymer in concrete was found to maximize ductility. Without wishing to be bound by theory, these results suggest that the plastic-concrete interface may itself be modified by the level of gamma irradiation dosage used to form the various samples.

[00127] Referring now to FIG. 5, Young’s modulus was extracted from the respective stress-strain plots shown in FIG. 4. As used herein, it shall be appreciated that the Young’s modulus for a given sample refers to the initial slope of the stress-strain curve obtained from the stress-strain curve of concrete under uniaxial loading. The effect of irradiation dose effect may be observed by comparing Young’s modulus for the various samples - the high dose (HD) of irradiated PET polymer in concrete had the highest Young’s modulus (17.49 GPa), whereas the low dose (LD) of irradiated PET polymer in concrete had the lowest Young’s modulus (14.47 GPa). More specifically, as the dosage of irradiation increased from 10 kGy (LD) to 50 kGy (MD), a 17 percent increase in Young’s modulus was observed. Further, as the dosage of irradiation was further increased from 50 kGy (MD) to 100 kGy (HD), a 14.35 percent decrease in Young’s modulus was observed. Thus, as demonstrated by these results, the maximum improvement in Young’s modulus is at the medium dose (MD) - away from the extremes in the range of radiation tested. Further, the Young’s modulus observed at the medium dose (MD) is also an improvement over the Young’s modulus observed in the regular polymer (RP) and control (C) samples. Collectively, these are unexpected results, suggesting that particularly advantageous changes in concrete chemistry are activated only at intermediate doses of radiation in the range of the medium dose (MD) sample.

[00128] Referring now to FIG. 6, the improvement of compressive strength achievable through the use of intermediate doses of irradiation is observable in a graphical representation of compressive strength as a function of dose of irradiation. As shown, as gamma irradiation of PET polymer increase to a dosage of 50 kGy, an increase in compressive strength of concrete up to 51 MPa is observed. However, the compressive strength of concrete drops to 40.7 MPa as gamma irradiation of PET polymer is further increased to a dosage of 100 kGy. The graphical representation in FIG. 6 shows the existence of a value of irradiation dose, which lies around 50 kGy corresponding to a maximum compressive strength of 28 day cured concrete. It should be noted that the value of the irradiation dose corresponding to the maximum compressive strength is for gamma irradiated PET flakes ranging in sizes between 1-2 mm and with a polymer fraction of 1.25% of the weight of cement in concrete. The value of irradiation dose corresponding to a maximum compressive strength may be influenced, for example, by changing any one or more of the particle size of the flakes, by controlling the gamma irradiation rate of the PET polymer, the polymer fraction relative to the weight of concrete, the polymer composition, or a combination thereof. Note that due to the limitation of doses to three values in this experimentation, a linear relationship is shown between data points, while the dosage corresponding to the maximum compressive strength may shift through the inclusion of additional data. Thus, while a maximum compressive strength is shown at a dosage of 50 kGy, it should be appreciated that the maximum compressive strength may be within a range about 50 kGy (e.g., greater than about 40 kGy and less than about 70 kGy). To explore possible explanations for the increase in compressive strength attributable to inclusion of irradiated polymer, DSC and synchrotron X-ray diffraction was performed on the concrete samples for microstructure characterization.

[00129] 2.2 Differential Scanning Calorimetry (DSC)

[00130] Referring now to FIG. 7, a first thermogram 702 corresponds to heat flow as a function of temperature for non-irradiated PET polymer, a second thermogram 704 corresponds to heat flow as a function of temperature for PET polymer irradiated with a 10 kGy dose, a third thermogram 706 corresponds to heat flow as a function of temperature for PET polymer irradiated with a 50 kGy dose, and a fourth thermogram 708 corresponds to heat flow as a function of temperature for PET polymer irradiated with a 100 kGy dose. As shown in each of the first thermogram 702, the second thermogram 704, the third thermogram 706, and the fourth thermogram 708, all samples showed an endothermic peak near 250 °C, which represents the melting point of the PET polymer. However, subtle changes were observed in the heat flow at the temperature, particularly in the enthalpy of melting (integrated energy under the endothermic melting peak). As shown in the first thermogram 702 and the second thermogram 704, the PET polymer in the non-irradiated form and the PET polymer irradiated with 10 kGy each have a melting point of 245 °C. As shown in the third thermogram 706, the PET polymer irradiated with the 50 kGy dose had a melting point of 243 °, a slight decrease relative to the PET polymer in the non-irradiated form. As shown in the fourth thermogram 708, the PET polymer irradiated with the 100 kGy dose had a melting point of 246 °C, a slight increase relative the PET polymer in the non-irradiated form. Without wishing to be bound by theory, it is believed that the decrease in melting points is an indication of chain scission in the semi-crystalline structure of the PET polymer, which influences the growth and degree of crystallinity of the irradiated material. Further without wishing to be bound by theory, it is believed that the observed increase in melting points relates to a rise in cross-linking in the semi-crystalline structure of the PET polymer and, furthermore, an increase in melting point of the PET polymer suggests an increase in crystallization temperature leading to a more uniform thickness distribution of the crystals. It is also noted that the PET polymer used in these experiments was sourced from a recycling facility and may include impurities.

[00131] As may be appreciated through a comparison of the first thermogram 702, the second thermogram 704, the third thermogram 706, and the fourth thermogram 708 to one another, the non-irradiated PET polymer had a heat value of -2 W/g, whereas the PET polymer irradiated with the 50 kGy dose had a heat value of -1.25 W/g, the PET polymer irradiated with the 100 kGy dose had a heat value of -1.33 W/g, and the PET polymer irradiated with the 10 kGy dose had a heat value of -1.80 W/g. That is, the non-irradiated PET polymer had the highest endothermic peak and, irradiation of the PET polymer decreased the endothermic peak, with the PET polymer irradiated with the 50 kGy dose having the lowest value of -1.25 W/g. This suggests that the irradiation of the PET polymer may influence the melting point by reducing the endothermic value of the peak approximately at 250 °C. While these results are informative regarding the changes occurring in the irradiated PET polymer by itself, additional differential scanning calorimetry (DSC) on concrete formed with the irradiated PET polymer provides insight regarding the behavior of the irradiated PET polymer in the concrete formed according to the exemplary method 200 (FIG. 2).

[00132] Referring now to FIG. 8, a fifth thermogram 802 corresponds to heat flow as a function of temperature for the C concrete sample, a sixth thermogram 804 corresponds to heat flow as a function of temperature for the concrete sample, a seventh thermogram 806

corresponds to heat flow as a function of temperature for the LD concrete sample, an eighth thermogram 808 corresponds to heat flow as a function of temperature for the MD concrete sample, and a ninth thermogram 810 corresponds to heat flow as a function of temperature for the HD concrete sample. As shown in FIG. 8, phases related to C-S-H, calcium hydroxide, quartz and calcium carbonate were detected at 117 °C, 460 °C, 580 °C, and 765 °C, respectively. The endothermic peak at 117 °C relates to the C-S-H phase, which is commonly known as the primary binding agent in Portland cement-based concrete. The C concrete sample, which had no PET polymer, demonstrated the largest peak at 117 °C when compared to the other samples. The reduction in the size of the crystallization peak is believed to be a result of a reduction in the amorphous material as a consequence of the pozzolanic reaction by consuming calcium hydroxide to form additional C-S-H phase. For the C-S-H phase, the RP concrete sample had the highest crystallization melting point at 121 °C, whereas the irradiated PET polymer samples of concrete (LD, MD, and HD) had lower values of melting point as compared to the RP concrete sample. Based on these results, it is believed that regular PET polymer (RP) is present in the cement matrix as a remnant and, thus, an increase in crystallization melting point was detected as the regular PET polymer in the RP sample of concrete was exposed to the crystallization temperature. Without wishing to be bound by theory, the decrease in melting points for concrete samples including irradiated PET polymer is believed to be related to involvement of the irradiated PET polymer in the cement matrix indicating scission of the PET polymer as it may be intermingled with the cementitious matrix. Further without wishing to be bound by theory, it is believed that the irradiated PET polymer has surface modifications that enhance nucleation of C- S-H, possible leading to more disorder throughout the C-S-H phase and a consequently lower melting point.

[00133] The impact of irradiated PET polymer may also be observed via the calcium hydroxide (CH) peaks. The non-irradiated PET polymer (RP) concrete sample had the highest crystallization melting point (477 °C) compared to the other concrete samples. The RP concrete sample did not involve as much CH in the reaction to form C-S-H. Thus, at 477 °C, the CH was re-crystallized to a possible crystalline form of calcium hydroxide. The decrease in the crystallization melting points is believed to be indicative of consumption of calcium hydroxide in forming C-S-H phase.

[00134] Endothermal peaks that contributed to the decomposition of calcium carbonates (CaCCb) in the samples can be seen between 725 °C and 769 °C. The control (C) sample of concrete had the lowest decomposition temperature 725 °C of calcium carbonates, as compared to the other concrete samples. Inclusion of the PET polymer, in the non-irradiated form and in the various irradiated forms, increased the decomposition temperature of calcium carbonates to between 751 °C and 769 °C. The decomposition temperature of calcium carbonates for the MD and the HD concrete samples was greater than the decomposition temperature of calcium carbonates for the C concrete sample, the RP concrete sample, and the LD concrete sample. Based on these results, it is believed that irradiated PET polymer may influence the carbonation effect in concrete through heterogeneous distribution of calcium carbonates as a residual phase in concrete including ordinary Portland cement. Without wishing to be bound by theory, it is believed that formation of certain calcium carbonates is beneficial for carbon capture as well as contributing to increase in compressive strength.

[00135] 2.3 Synchrotron X-ray Diffraction (XRD)

[00136] Referring now to FIG. 9, synchrotron X-ray diffraction was used to analyze PET polymer by itself, prior to inclusion in concrete. A first XRD measurement 902

corresponds to a non-irradiated PET polymer, a second XRD measurement 904 corresponds to a PET polymer irradiated at 10 kGy, a third XRD measurement 906 corresponds to a PET polymer irradiated at 50 kGy, and a fourth XRD measurement 908 corresponds to a PET polymer irradiated at 100 kGy. The PET polymer showed a crystalline phase of (CioH804)n, ICDD# 00- 060-0989. These results shown in FIG. 9 demonstrate that the crystalline portion of the phases tends to increase with the increase in dose of irradiation, which may change the melting point of the PET polymer and, therefore, is consistent with the DSC data discussed above.

[00137] Referring now to FIG. 10, synchrotron X-ray diffraction was used to analyze the Portlandite phase in samples of the concrete including non-irradiated and irradiated forms of the PET polymer. In particular, a fifth XRD measurement 1002 corresponds to the Portlandite phase in RP concrete sample, a sixth XRD measurement 1004 corresponds to the Portlandite phase in LP concrete sample, a seventh XRD measurement 1006 corresponds to the Portlandite phase in the MD concrete sample, and an eighth XRD measurement 1008 corresponds to the Portlandite phase in the HD concrete sample. Portlandite is a crystalline form of calcium hydroxide, and a decrease in Portlandite is believed to be indicative of its utilization in the calcium silicate hydrate (C-S-H) phase. This is significant because C-S-H is the primary binding agent in Portland cement-based concretes. Thus, stated differently, the decrease in Portlandite is believed to form increased amounts of C-S-H that, in turn, result in better binding and less porosity in the resulting concrete.

[00138] As shown in FIG. 10, seventh XRD measurement 1006 corresponding to the Portlandite phase in the MD concrete sample had the smallest peak of Portlandite compared to the peaks of the other concrete samples. This suggests that, among the samples tested, the conversion of Portlandite to the C-S-H is greatest in the MD concrete sample. Accordingly, without wishing to be bound by theory, the increased compressive strength observed in the MD concrete samples (as discussed above with respect to FIG. 3) may be attributable to the additional C-S-H formed in the MD concrete sample relative to the formation of C-S-H formed in the other concrete samples. Further without wishing to be bound by theory, it is believed that the additional C-S-H formed in the MD concrete sample relative to the formation of C-S-H formed in the other concrete samples may result in reduced porosity which, in turn, may result in improved durability of the concrete.

[00139] While the synchrotron XRD analysis of the Portlandite phase demonstrated an increased consumption of Portlandite that is likely associated with formation of additional C-S-H in the MD sample, the synchrotron XRD analysis of the C-S-H phase further revealed different types of C-S-H are formed in the MD samples demonstrating improved properties relative to the control concrete. That is, in addition to having additional C-S-H, the MD samples appear to have different types of C-S-H, which may additionally or alternatively contribute to the observed improvements in the properties of the MD samples.

[00140] In particular, referring now to FIG. 11, synchrotron X-ray diffraction was used to analyze the C-S-H and calcite phases in samples of the concrete including non-irradiated and irradiated forms of the PET polymer. More specifically, a ninth XRD measurement 1102 corresponds to the C-S-H phase and the calcite phase in the RP concrete sample, a tenth XRD measurement 1104 corresponds to the C-S-H phase and the cal cite phase in the LD concrete sample, an eleventh XRD measurement 1106 corresponds to the C-S-H phase and the cal cite phase in the MD concrete sample, and a twelfth XRD measurement 1108 corresponds to the C-S- H phase and the calcite phase in the HD concrete sample. Significantly, the eleventh XRD measurement 1106 corresponding to the C-S-H phase in the MD concrete sample indicated the presence of C-S-H with ICDD # 00-012-0475, whereas the XRD measurements of the other concrete samples indicated the presence of C-S-H with ICDD # 00-015-642. Without wishing to be bound by theory, it is believed these differences in C-S-H phases are a result in a change in d- spacing at the nano/angstrom level, suggesting that the MD concrete sample has a different C-S- H chain length. That is, based on these results, it appears that irradiation of the PET polymer affected the interlayer spacing inside the C-S-H crystals in the MD concrete sample. This modification of the C-S-H crystal may be at least partially responsible for improved

plastic/cement bonding and associated reduction in porosity that accounts for the improvements in the macroscopic properties observed with respect to the MD concrete sample.

[00141] The XRD measurements in FIG. 11 further show the relative amounts of calcite in each of the concrete samples. As shown in FIG. 11, the eleventh XRD measurement 1106 corresponding to the calcite phase in the MD concrete sample has the least amount of calcite. Calcite is the main product resulting from carbonation of concrete. Thus, the results shown in FIG. 11 suggest that the irradiated PET polymer may impact the carbonation mechanism in the MD concrete sample, as compared to carbonation in the other concrete samples.

[00142] Referring now to FIG. 12, synchrotron X-ray diffraction was used to analyze the ettringite phase in samples of the concrete including non-irradiated and irradiated forms of the PET polymer. In particular, a thirteenth XRD measurement 1202 corresponds to the ettringite phase in RP concrete sample, a fourteenth XRD measurement 1204 corresponds to the ettringite phase in LP concrete sample, a fifteenth XRD measurement 1206 corresponds to the ettringite phase in the MD concrete sample, and a sixteenth XRD measurement 1208 corresponds to the ettringite phase in the HD concrete sample. As shown in these XRD measurements, the formation of ettringite is lowest in the MD concrete sample. More generally, as may be appreciated through a comparison of FIGS. 11 and 12, the impact of the irradiated form of the polymer on the formation of ettringite appears to follow a similar trend as the impact of the irradiated form of the polymer on the formation of calcite. [00143] The above systems, devices, methods, processes, and the like may be realized in hardware, software, or any combination of these suitable for a particular application. The hardware may include a general-purpose computer and/or dedicated computing device. This includes realization in one or more microprocessors, microcontrollers, embedded

microcontrollers, programmable digital signal processors or other programmable devices or processing circuitry, along with internal and/or external memory. This may also, or instead, include one or more application specific integrated circuits, programmable gate arrays, programmable array logic components, or any other device or devices that may be configured to process electronic signals. It will further be appreciated that a realization of the processes or devices described above may include computer-executable code created using a structured programming language such as C, an object oriented programming language such as C++, or any other high-level or low-level programming language (including assembly languages, hardware description languages, and database programming languages and technologies) that may be stored, compiled or interpreted to run on one of the above devices, as well as heterogeneous combinations of processors, processor architectures, or combinations of different hardware and software. In another aspect, the methods may be embodied in systems that perform the steps thereof and may be distributed across devices in a number of ways. At the same time, processing may be distributed across devices such as the various systems described above, or all of the functionality may be integrated into a dedicated, standalone device or other hardware. In another aspect, means for performing the steps associated with the processes described above may include any of the hardware and/or software described above. All such permutations and combinations are intended to fall within the scope of the present disclosure.

[00144] Embodiments disclosed herein may include computer program products comprising computer-executable code or computer-usable code that, when executing on one or more computing devices, performs any and/or all of the steps thereof. The code may be stored in a non-transitory fashion in a computer memory, which may be a memory from which the program executes (such as random access memory associated with a processor), or a storage device such as a disk drive, flash memory or any other optical, electromagnetic, magnetic, infrared or other device or combination of devices. In another aspect, any of the systems and methods described above may be embodied in any suitable transmission or propagation medium carrying computer-executable code and/or any inputs or outputs from same. [00145] The method steps of the implementations described herein are intended to include any suitable method of causing such method steps to be performed, consistent with the patentability of the following claims, unless a different meaning is expressly provided or otherwise clear from the context. So, for example, performing the step of X includes any suitable method for causing another party such as a remote user, a remote processing resource (e.g., a server or cloud computer) or a machine to perform the step of X. Similarly, performing steps X, Y and Z may include any method of directing or controlling any combination of such other individuals or resources to perform steps X, Y and Z to obtain the benefit of such steps. Thus, method steps of the implementations described herein are intended to include any suitable method of causing one or more other parties or entities to perform the steps, consistent with the patentability of the following claims, unless a different meaning is expressly provided or otherwise clear from the context. Such parties or entities need not be under the direction or control of any other party or entity, and need not be located within a particular jurisdiction.

[00146] It will be appreciated that the methods and systems described above are set forth by way of example and not of limitation. Absent an explicit indication to the contrary, the disclosed steps may be modified, supplemented, omitted, and/or re-ordered without departing from the scope of this disclosure. Numerous variations, additions, omissions, and other modifications will be apparent to one of ordinary skill in the art. In addition, the order or presentation of method steps in the description and drawings above is not intended to require this order of performing the recited steps unless a particular order is expressly required or otherwise clear from the context. Thus, while particular embodiments have been shown and described, it will be apparent to those skilled in the art that various changes and modifications in form and details may be made therein without departing from the spirit and scope of this disclosure and are intended to form a part of the invention as defined by the following claims, which are to be interpreted in the broadest sense allowable by law.

Claims

CLAIMS What is claimed is:

1. A method comprising:

receiving particles of a polymer in a non-irradiated form;

irradiating the particles of the polymer with a dose of radiation to form particles of the polymer into an irradiated form, the particles of the polymer in the irradiated form having, in response to the dose of radiation, one or more properties modified relative to the particles of the polymer in the non-irradiated form; and

forming a flowable mixture of a building material, the flowable mixture of the building material including the particles of the polymer in the irradiated form, cement, sand, and gravel, the gravel having a first average particle size, the sand having a second average particle size, and the particles of the polymer in the irradiated form having an average maximum dimension less than the first average particle size of the gravel and greater than the second average particle size of the sand.

2. The method of claim 1, wherein the polymer in the non-irradiated form has a first melting point, and the polymer in the irradiated form has a second melting point less than the first melting point.

3. The method of claim 1, wherein the polymer in the non-irradiated form has a semi-crystalline structure.

4. The method of claim 3, wherein, relative to the polymer in the non-irradiated form, the polymer in the irradiated form has increased crystallinity and crosslinking.

5. The method of claim 3, wherein the polymer in the non-irradiated form is polyethylene terephthalate (PET).

6. The method of claim 3, wherein the polymer in the non-irradiated form is one or more of high -density polyethylene, low density polyethylene, or polypropylene.

7. The method of claim 1, wherein the polymer in the non-irradiated form has an amorphous structure.

8. The method of claim 7, wherein the polymer in the non-irradiated form is one or more of polystyrene or polyvinyl chloride.

9. The method of claim 1, wherein the average maximum dimension of the particles of the polymer in the irradiated form is at least twice as large as an average minimum dimension of particles of the polymer in the irradiated form.

10. The method of claim 1, wherein the average maximum dimension of the particles of the polymer in the irradiated form is greater than about 5 nm and less than about 5 mm.

11. The method of claim 1, wherein the first average particle size of the gravel is greater than about 3 mm and less than about 40 mm.

12. The method of claim 1, wherein irradiating the particles of the polymer in the non-irradiated form includes exposing the particles of the polymer in the non-irradiated form to gamma radiation.

13. The method of claim 1, wherein the dose of radiation is greater than about 1 kGy and less than about 1000 kGy.

14. The method of claim 13, wherein the dose of radiation is greater than about 10 kGy and less than about 100 kGy.

15. The method of claim 1, wherein the weight of the particles of the polymer in the irradiated form in the flowable mixture of the building material is greater than 0 percent and less than about 25 percent of the weight of the cement in the flowable mixture of the building material.

16. The method of claim 15, wherein the weight of the particles of the polymer in the irradiated form in the flowable mixture of the building material is greater than about 0.5 percent and less than about 5 percent of the weight of the cement in the flowable mixture of the building material.

17. The method of claim 1, further comprising hydrating the flowable mixture of the building material to form a slurry curable into concrete.

18. The method of claim 17, wherein hydrating the flowable mixture of the building material includes hydrating one or more components of the flowable mixture of the building material prior to forming the flowable mixture of the building material.

19. The method of claim 17, wherein hydrating the flowable mixture of the building material includes hydrating an anhydrous form of the flowable mixture of the building material.

20. The method of claim 17, further comprising curing the slurry into a first concrete.

21. The method of claim 20, wherein the first concrete has a first compressive strength, and a second concrete formed with the cement in place of the particles of the polymer, under otherwise identical conditions, has a second compressive strength less than the first compressive strength.

22. The method of claim 21, wherein the first compressive strength is between about 1 percent to about 25 percent greater than the second compressive strength.

23. The method of claim 20, wherein the first concrete has a first compressive strength, and a second concrete formed with particles of the polymer in the non-irradiated form in place of the particles of the polymer in the irradiated form, under otherwise identical conditions, has a second compressive strength less than the first compressive strength.

24. The method of claim 23, wherein the first compressive strength is between about 5 percent to about 30 percent greater than the second compressive strength.

25. The method of claim 20, wherein the first concrete has a first compressive strength greater than a second compressive strength of a second concrete formed, under otherwise identical conditions, with particles of the polymer irradiated at a different dose of the radiation in place of the particles of the polymer in the irradiated form in the first concrete.

26. The method of claim 20, wherein the first concrete has a first final strain value, and a second concrete formed with the cement in place of the particles of the polymer in the irradiated form, under otherwise identical conditions, has a second final strain value less than the first final strain value.

27. The method of claim 20, wherein the first concrete has a first porosity, and a second concrete formed with the cement in place of the particles of the polymer in the irradiated form, under otherwise identical conditions, has a second porosity greater than the first porosity.

28. The method of claim 20, wherein the first concrete has a first Young’s modulus, and a second concrete formed with the cement in place of the particles of the polymer in the irradiated form, under otherwise identical conditions, has a second Young’s modulus less than the first Young’s modulus.

29. The method of claim 1, wherein the cement includes ordinary Portland cement.

30. The method of claim 1, wherein the flowable mixture of the building material further includes one or more of silica fume, fly ash, ground granulated blastfurnace slag, limestone fines, microsilica, nanosilica, volcanic ash, clay, calcined clay, metakaolin, calcined shale, or bauxite.

31. A building material comprising:

gravel having a first average particle size;

sand having a second average particle size;

particles of a polymer in an irradiated form having one or more properties modified relative to the particles of the polymer in a non-irradiated form, the particles of the polymer in the irradiated form having an average maximum dimension less than the first average particle size of the gravel and greater than the second average particle size of the sand; and

a cement including calcium oxide and belite, wherein the sand, the gravel, and the particles of the polymer are dispersed in the cement.

32. The building material of claim 31, wherein the average maximum dimension of the particles of the polymer in the irradiated form is at least twice as large as an average minimum dimension of particles of the polymer in the irradiated form.

33. The building material of claim 31, wherein the average maximum dimension of the particles of the polymer in the irradiated form is greater than about 5 nm and less than about 5 mm.

34. The building material of claim 31, wherein the first average particle size of the gravel is greater than about 3 mm and less than about 40 mm.

35. The building material of claim 31, wherein the weight of the polymer in the irradiated form is greater than 0 percent and less than about 25 percent of the weight of the cement.

36. The building material of claim 35, wherein the weight of the polymer in the irradiated form is greater than about 0.5 percent and less than about 5 percent of the weight of the cement.

37. The building material of claim 31, wherein the cement includes ordinary Portland cement.

38. The building material of claim 31, further comprising one or more of the following dispersed in the cement: silica fume, fly ash, ground granulated blastfurnace slag, limestone fines, microsilica, nanosilica, volcanic ash, clay, calcined clays, metakaolin, calcined shale, or bauxite.

39. The building material of claim 31, wherein the sand, the gravel, and the polymer in the irradiated form dispersed in the cement form at least a portion of a flowable mixture.

40. The building material of claim 39, wherein the flowable mixture is anhydrous.

41. The building material of claim 39, wherein the flowable mixture is hydrated.

42. The building material of claim 31, wherein the sand, the gravel, and the particles of the polymer in the irradiated form dispersed in the cement form at least a portion of a concrete.