Low-carbon, carbon-neutral, and carbon-negative asphalt composites using functionalized biochar

Abstract

Low-carbon, carbon-neutral, and carbon-negative asphalt composites are disclosed. The composites comprise an asphalt binder and a functionalized biochar incorporated as a partial replacement for the binder and / or mineral filler. The biochar is physically, chemically, or mineralogically modified to enhance dispersion, interfacial bonding, mechanical performance, and carbon sequestration. The invention further includes methods for producing such composites, biochar-based additive compositions, and kits for practical implementation. Applications include asphalt pavements, waterproofing membranes, crack sealants, conductive deicing systems, and VOC-reducing asphalt mixtures. The resulting materials demonstrate improved durability, thermal and electrical properties, and significant reductions in greenhouse gas emissions.

Description

LOW-CARBON, CARBON-NEUTRAL, AND CARBON-NEGATIVE ASPHALT COMPOSITES USING FUNCTIONALIZED BIOCHARCROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent Application 63 / 636,121 filed on April 19, 2024.TECHNICAL FIELD

[0002] The present disclosure provides asphalt-based materials comprising functionalized biochar, and methods of preparing such materials for various applications, including pavement, coatings, waterproofing membranes, sealants, and surface treatments. The functionalized biochar can improve mechanical strength, reduce greenhouse gas (GHG) emissions, suppress volatile organic compound (VOC) release, enhance thermal and ultraviolet (UV) stability, provide conductivity, enable self-healing, and impart fire resistance to the asphalt composites.BACKGROUND

[0003] Asphalt-based composites are widely employed in global infrastructure, particularly in pavement, waterproofing membranes, and sealing systems, owing to their favorable costperformance ratio, workability, and recyclability. Despite these advantages, conventional asphalt production and utilization contribute significantly to greenhouse gas (GHG) emissions and environmental degradation over their life cycle, from bitumen extraction and binder processing to mixing, paving, and end-of-life disposal. The volatile organic compound (VOC) emissions during and after paving of the asphalt mixture are also of environmental and health concerns.

[0004] In response to increasing sustainability demands, numerous additives and modifiers have been developed to enhance the mechanical and functional properties of asphalt mixtures. These include polymers, recycled rubber, synthetic fibers, and industrial byproducts. However, many ofthese materials are non-renewable, fossil-based, or offer limited carbon reduction benefits, thereby restricting their alignment with carbon-neutral or climate-positive objectives.

[0005] Biochar, a porous, carbon -rich material derived from thermochemical conversion (e.g., pyrolysis, hydrothermal carbonization, gasification, torrefaction, microwave assisted pyrolysis, plasma pyrolysis / arc discharge, and hydrothermal liquefaction) of biomass or non-biomass carbon-rich feedstock, has emerged as a promising candidate for carbon sequestration and functional enhancement in asphalt systems. When incorporated into asphalt composites, biochar has demonstrated potential to reduce material consumption, improve thermal and aging resistance, and contribute to carbon offset. Nonetheless, unmodified biochar often suffers from poor dispersion in hydrophobic asphalt matrices, low interfacial adhesion, and inconsistent performance under thermal and mechanical stress.

[0006] Therefore, there exists a continuing need for engineered approaches to functionalize biochar via chemical treatments, physical modifications, mineralization processes, or synergistic combinations thereof, in order to tailor its physicochemical properties for enhanced compatibility with asphalt binders and aggregates. Such functionalized biochar may enable the development of next-generation low-carbon, carbon-neutral, or carbon-negative asphalt composites with extended durability, multifunctionality (e.g., waterproofing, flame resistance, self-healing, conductivity), and broader applicability across pavement, construction, and protective barrier applications.SUMMARY OF THE INVENTION

[0007] The present invention relates to low-carbon, carbon-neutral, and carbon-negative asphalt composites that incorporate functionalized biochar as a partial replacement for asphalt binder and / or mineral filler. The biochar is derived from biomass through pyrolysis or gasification and subsequently modified through physical, chemical, or mineralization techniques — such as ball milling, steam activation, acid or base treatment, or CO2 carbonation — to enhance its dispersion, compatibility with asphalt, and carbon sequestration capacity.

[0008] This invention discloses compositions, methods, and additive systems that improve the mechanical performance, aging resistance, and environmental sustainability of asphalt products. The functionalized biochar can be used in a variety of asphalt technologies, including hot-mix asphalt (HMA), warm-mix asphalt (WMA), stone matrix asphalt (SMA), pervious asphalt concrete, cold in-place recycled asphalt (CIR), waterproofing membranes, crack sealants, flame-retardant coatings, and electrically conductive asphalt systems.

[0009] In some embodiments, nano-sized biochar particles with a diameter less than 100 nanometers are employed to suppress volatile organic compound (VOC) emissions via physical adsorption, pore entrapment, or catalytic surface reaction. These nano-biochars may be co-blended with other nanomaterials such as nanosilica, nanoclay, graphene oxide, or nanoalumina to further improve dispersion, thermal conductivity, and UV shielding properties.

[0010] The invention also provides methods for incorporating biochar into asphalt using conventional production equipment, including both wet and dry blending processes. Additional embodiments include asphalt composites containing rejuvenator-loaded biochar for delayed healing, or biochar-carbon fiber systems for resistive heating. Kits and additive formulations are also disclosed for practical implementation in commercial and municipal asphalt applications.

[0011] Overall, the disclosed materials and processes enable scalable deployment of biochar- enhanced asphalt systems that reduce greenhouse gas emissions, enhance pavement performance, and support the development of sustainable transportation and infrastructure technologies.DETAILED DESCRIPTION

[0012] In the description herein, a word appearing in the singular encompasses its plural counterpart, and a word appearing in the plural encompasses its singular counterpart, unless implicitly or explicitly understood or stated otherwise. Furthermore, it is understood that for any given component or embodiment, any of the possible candidates or alternatives listed for that component may generally be used individually or in combination with one another, unlessimplicitly or explicitly understood or stated otherwise. Additionally, any list of such candidates or alternatives is merely illustrative, not limiting, unless implicitly or explicitly understood or stated otherwise. In addition, unless otherwise indicated, numbers expressing quantities of ingredients, constituents, reaction conditions, and so forth used in the specification and claims are to be understood as being modified by the term “about.”

[0013] Accordingly, unless expressly stated otherwise, numerical parameters provided in the specification and claims are understood to be approximate values that may vary depending on the desired properties of the subject matter. Each value should be interpreted based on significant digits and standard rounding practices. While broad numerical ranges are intended to be approximate, specific example values are presented as precise measurements to the extent allowed by the measuring method. All numerical values inherently include some measurement uncertainty. The scope of the claims shall be construed in accordance with applicable law, including the doctrine of equivalents.

[0014] As used herein, the term “biochar” refers to a carbon-rich, porous solid product derived from the thermochemical decomposition (e.g., pyrolysis or gasification) of organic biomass and other carbon-rich feedstocks, including but not limited to carbohydrates, cellulose-containing materials, protein- or fat-containing organic matter, wood, agricultural residues, or municipal waste. The degree of decomposition depends on the equivalence ratio, defined as the molar ratio of oxygen to carbon during processing. An equivalence ratio of zero corresponds to pyrolysis, while values below approximately 0.15 may be classified as low-oxygen gasification. Biochar is distinct from ash or combustion residues in that it retains a partially graphitized carbon matrix and often exhibits internal porosity and residual surface functionality.

[0015] As used herein, the term “asphalt” (also referred to interchangeably as “bitumen”) refers to a viscous, black to dark-brown, semi-solid to solid hydrocarbon material derived from crude oil or natural sources. It is primarily composed of high-molecular- weight hydrocarbons and exhibits thermoplastic behavior — softening when heated and hardening upon cooling. Owing to itsadhesive and hydrophobic properties, asphalt is widely used in road construction, roofing, and waterproofing applications.

[0016] As utilized herein, "concrete" refers to any type of building material that contains aggregates embedded in a matrix (e.g., binder) that fills the spaces between the aggregates and binds them together

[0017] As used herein, the term “asphalt mixture” or “asphalt concrete” refers to a composite comprising asphalt as the binder phase combined with mineral aggregates such as sand, gravel, crushed stone, recycled particles, or mineral filler. The mixture may be produced using hot-mix, warm-mix, or cold-mix processes depending on the application.

[0018] For purposes of this disclosure, the terms “asphalt” and “bitumen” may be used interchangeably, and are intended to encompass the same material unless explicitly stated otherwise. Similarly, the terms “asphalt composite” and “bituminous composite” are used synonymously to refer to mixtures or structures comprising asphalt or bitumen as the binder phase combined with other components such as aggregates, additives, or modifiers.

[0019] As used herein, the term "low-carbon asphalt composite" refers to an asphalt-based mixture that incorporates additives, recycled materials, or processing methods designed to reduce GHG emissions relative to conventional asphalt. Such reductions may arise from using energyefficient production methods or replacing petroleum-based binders with sustainable alternatives.

[0020] As used herein, the term "carbon-neutral asphalt composite" refers to a system wherein net lifecycle GHG emissions are effectively zero, typically achieved through balancing emissions with equivalent carbon sequestration or offset mechanisms.

[0021] As used herein, the term "carbon-negative asphalt composite" denotes an asphalt system that results in a net reduction in atmospheric CO2 over its lifecycle. This may be accomplished via sequestration of carbon within the composite through materials such as functionalized biochar.

[0022] As used herein, the term "functionalized biochar" refers to biochar that has undergone physical, chemical, or physicochemical modifications to tailor its surface area, porosity, chemicalreactivity, electrical conductivity, or interfacial compatibility with asphalt systems. The biochar products can vary greatly in cost, size gradation, porosity, surface texture, chemical composition (e.g., lignin, cellulose, ash content), and potential for value-added applications, depending on their feedstock, and manufacturing and post-processing parameters. The biochar may be derived from various biomass feedstocks, including but not limited to: corn stover, corn husks, coconut shells and husks, rice husks, wheat straw, sugarcane bagasse, palm oil residues, hardwood residues, softwood bark, saw dust, pine needles and conifer residues, hemp biomass, microalgae, macroalgae / seaweed, bamboo, switchgrass, vegetable waste, and urban green waste (grass clippings, tree trimmings, etc.). The biochar may also be derived from non-biomass feedstocks, including but not limited to: poultry litter and manure, dairy or cattle manure, crumb rubber, waste plastics, spent coffee grounds, animal feces, food-producing waste, food waste, animal processing waste, and sewage sludge.

[0023] As used herein, "physical modification" of biochar refers to processes that alter the physical characteristics of the biochar without inducing substantial chemical transformation. Methods include but are not limited to: (i) Ball milling at 200-800 rpm for 1-12 hours to reduce particle size and increase surface area, with or without milling aid (e.g., stearic acid); (ii) Steam or CO2 activation at 600-950°C for 30-180 minutes to create microporous and mesoporous structures; (iii) Thermal annealing at >800°C for 30-240 minutes in argon or nitrogen atmosphere to increase graphitic carbon content and conductivity; (iv) Plasma treatment (e.g., Ar, O2, N2 plasma) to roughen surface texture at the nanoscale, typically at ambient to 150°C, 10-100 W power, for 1-30 minutes; (v) Vacuum impregnation for loading healing agents or modifiers into porous biochar; (vi) Laser treatment to modify surface physical characteristics without substantial chemical transformation, typically using a laser at 2-4 W power, nanosecond pulse duration, 10- 50 kHz frequency, and in an inert (e.g., N2) or ambient air atmosphere..

[0024] As used herein, "chemical modification" of biochar refers to processes involving chemical reactions that alter the surface chemistry, introduce new functional groups, or produce chemicallybonded species on or within the biochar matrix. These modifications involve transformation of the biochar’s chemical composition and typically enhance its interaction with other materials or improve specific functionalities. Preferred chemical modification methods include, but are not limited to, the following: (a) Acid treatment using HC1, HNO3, or H2SO4(0.1-5.0 M) to remove ash and introduce acidic groups; (b) Alkaline treatment using NaOH, KOH, or Ca(OH)2to increase polarity; (c) Oxidative functionalization with H2O2, KMnO4, or O3to introduce oxygencontaining functional groups; (d) Grafting of amine or silane agents (e.g., APTES, EDA) for reactivity enhancement; (e) In-situ mineralization with salts such as FeCl3or CaCl2; (f) Polymer grafting using PEI, PAA, or polyaniline; (g) Heteroatom doping with nitrogen, phosphorus, or sulfur. These chemical modifications can be employed individually or in combination, depending on the desired physicochemical properties and targeted end-use applications such as in asphaltbased composites, polymer matrices, water purification, or soil amendment.

[0025] As used herein, "physico-chemical modification" of biochar refers to treatment protocols wherein the biochar is subjected to both physical and chemical processes — either sequentially or simultaneously — to synergistically enhance its physicochemical properties. The goal of such combined modification is to simultaneously tailor the surface area, pore structure, and chemical functionality of the biochar to meet the performance demands of specific end-use environments. Preferred combined modification methods include, but are not limited to, the following: (a) Ball milling followed by acid oxidation to increase surface area and group density; (b) Plasma-assisted grafting with organosilanes or polymers; (c) Steam activation followed by salt impregnation and pH-controlled mineralization; (d) Ultrasonic-assisted oxidation to enhance dispersion and reactivity; (e) Thermal exfoliation followed by biopolymer coating for improved bonding; (f) Freeze-thaw pretreatment followed by alkaline activation for charge modification. Such synergistic modifications allow for multifunctional tuning of the biochar, making it suitable for applications including asphalt-based composites, electrically conductive coatings, andenvironmental remediation systems. In some embodiments, these treatments may also enhance the long-term carbon sequestration stability of the biochar in built environments.

[0026] The present disclosure provides compositions and methods for producing asphalt-based materials comprising biochar, wherein the biochar serves not only as a functional additive but also as a means to achieve carbon sequestration and enhanced material performance. In certain embodiments, the biochar may be structurally, chemically, or morphologically tailored to enhance its interaction with the binder and aggregate matrix.

[0027] In certain embodiments, biochar is used as a partial replacement for mineral filler, fine aggregates, or as a performance modifier in asphalt binders. The incorporation of biochar can result in reduced production temperatures, improved aging resistance, and enhanced rutting and cracking performance. Depending on the binder grade and aggregate gradation, the replacement level may range from approximately 1% to 50% by volume.

[0028] The biochar may optionally be surface-modified, activated, or combined with nanomaterials, including but not limited to nano-silica, nano-calcium silicate hydrate (C-S-H), graphene oxide, reduced graphene oxide (rGO), carbon nanotubes (CNTs), nanoclay, nanocellulose, nano-alumina, nano-titania, and nano-iron oxides. These nanomaterials can be embedded into biochar pores or coated onto its surface to form composite particles with improved mechanical interlocking, interfacial bonding, and durability to tailor its chemical compatibility with the bitumen matrix and to enhance dispersion, interfacial adhesion, or reactivity under asphalt processing conditions.

[0029] In some embodiments, the asphalt composite incorporating biochar exhibits improved sustainability metrics, such as reduced global warming potential (GWP), improved recyclability, or reduced reliance on virgin petrochemical-based additives.

[0030] The methods disclosed herein may be applied in the preparation of a wide range of asphalt technologies and products, including but not limited to hot mix asphalt (HMA), warm mix asphalt (WMA), stone mastic asphalt (SMA), cold in-place recycling (CIR), cold mix asphalt, emulsifiedasphalt, cutback asphalt, polymer-modified asphalt (e.g., styrene-butadiene- styrene (SBS), styrene-butadiene rubber (SBR), ethylene-vinyl acetate (EVA)), crumb rubber-modified asphalt, high-modulus asphalt (HiMA), foamed asphalt, rejuvenated asphalt, rubberized asphalt, stone matrix asphalt (SMA), pervious concrete asphalt, and open -graded friction course (OGFC) mixtures, and asphalt binders incorporating anti -stripping agents or warm mix additives. In certain embodiments, the suitability of biochar in these systems may depend on mix temperature, binder viscosity, or specific compatibility requirements.

[0031] In addition, the disclosed methods are applicable to the production of asphalt emulsions, waterproofing membranes, hot-pour crack sealants, asphalt primers, tack coats, fog seals, slurry seals, chip seals, crack fillers, joint sealants, pavement sealcoats, and other bituminous materials used in roadway construction, pavement rehabilitation, roofing, bridge deck protection, tunnel lining, airport runways, and industrial coatings. Such materials may further benefit from the hydrophobicity, thermal insulation, or flame-retardant properties of functionalized biochar. The biochar may be tailored in type, particle size, or surface functionality to meet the mechanical and environmental performance requirements of these specific applications.

[0032] In one embodiment, a biochar-modified asphalt binder is prepared by mixing biochar into base asphalt at elevated temperatures, typically ranging from about 60°C to 350°C. The mixing may optionally include compatibilizers, dispersants, or stabilizers to produce a homogeneous modified binder with improved durability, oxidative stability, and carbon sequestration potential.

[0033] In another embodiment, a dry process technique is employed in which biochar is preblended with aggregate components prior to binder addition. This method enables ease of field implementation without substantial alteration to existing asphalt plants or jobsite processes.

[0034] In certain embodiments, a method is provided for reacting biochar with an alkaline solution to capture and sequester carbon dioxide (e.g., CO2 from atmospheric or industrial sources). During this carbonation process, calcium carbonate or other carbonates may precipitate on the biochar surface or within its pore structure, forming what is referred to herein as CO2-weathered biochar. Incorporating such weathered biochar into asphalt binders or mixtures can enhance both mechanical properties and long-term carbon sequestration of the resulting composite material.

[0035] In some embodiments, fine-particle biochar (e.g., having a particle size of 150 microns or less) may be used to replace approximately 1% to 50% by mass of the asphalt binder, while coarse- particle biochar (e.g., greater than 150 microns) may be used to replace approximately 1% to 100% by mass of the mineral fines. The resulting composites may be used in various applications including, but not limited to, hot-mix asphalt (HMA), warm-mix asphalt (WMA), waterproofing coatings, and stone mastic asphalt (SMA). Biochar treatment methods may include physical grinding, surface functionalization, nano-modification, CO2 weathering, or synergistic combinations thereof, depending on the targeted performance criteria.

[0036] Exemplary biochar feedstocks include, but are not limited to, forestry residues (e.g., wood chips, bark, sawdust), agricultural byproducts (e.g., rice husks, coconut shells, corn stover, bagasse), biosolids (e.g., sewage sludge, animal manure), industrial byproducts (e.g., paper mill sludge, rubber powder), energy crops (e.g., switchgrass, miscanthus), and mixed organic solid waste streams. Feedstock selection may influence the chemical composition, mechanical properties, durability, and environmental sustainability of the resulting asphalt composites.

[0037] The physicochemical properties of biochar are influenced by both feedstock type and pyrolysis parameters, including but not limited to pyrolysis temperature, heating rate, residence time, and reaction atmosphere. For example, low-temperature pyrolysis (e.g., ~350°C) typically produces biochar with a lower (e.g., 50% to 60%) carbon content and a higher proportion of volatile matter, whereas high-temperature pyrolysis (e.g., ~800°C) generally yields biochar with a higher (e.g., 85% to 94%) carbon content and a more developed and thermally stable pore structure. These variations influence surface area, functional groups, porosity, and morphology, which in turn affect the compatibility, dispersion, and performance of biochar in asphalt composite systems.

[0038] In certain embodiments, the pyrolysis temperature used to produce biochar ranges from approximately 250°C to 1300°C, and preferably from 300°C to 800°C. The heating rate may range from 0.1°C / s to 1000°C / s, with a residence time between nanoseconds and 1000 seconds. Depending on these parameters, the resulting biochar may exhibit a specific surface area of about 100 to 600 m2 / g, a bulk density ranging from 0.01 to 0.90 Mg / m3, a pore size distribution between approximately 1 and 100 microns, and a particle size ranging from 10 nanometers to over 1000 microns.

[0039] Smaller biochar particles generally exhibit higher specific surface areas, which can improve their dispersion within asphalt binders and mixtures. This can lead to improved compactness, increased stiffness, and enhanced mechanical performance of the composite through a so-called “filler effect.” However, due to their increased surface energy, fine biochar particles may also exhibit a tendency toward agglomeration and high oil absorption, potentially impacting uniformity in asphalt. These effects may be mitigated through pre-dispersion techniques, high- shear mixing, or the use of compatibilizers.

[0040] Biochar particles with rough or angular surface textures may enhance mechanical interlocking with the surrounding asphalt matrix, thereby improving interfacial bonding strength, crack resistance, and overall durability of the composite material.

[0041] Highly porous, low-density biochar derived from high-temperature pyrolysis may also impart advantageous properties such as reduced weight, thermal insulation, or energy absorption. These attributes can be beneficial in applications involving temperature-sensitive infrastructure (e.g., airport runways, bridge decks). Additionally, silica-rich biochar — such as that derived from rice husks — may offer filler or stabilizing functions similar to those of conventional mineral fillers used in asphalt.

[0042] In some embodiments, the inorganic mineral content of the biochar ranges from about 10 wt% to 80 wt%. When this content exceeds approximately 10 wt%, carbonation reactions duringC02weathering may lead to in-situ formation of calcium carbonate deposits, thereby increasing the carbon storage potential and structural reinforcement of the asphalt composite.

[0043] Advantages associated with incorporating biochar into asphalt materials include but are not limited to: (1) enhanced rutting and fatigue resistance; (2) improved oxidative aging resistance;(3) reduced thermal and ultraviolet degradation; (4) early-stage structural reinforcement; (5) decreased dependence on virgin petroleum-based materials; and (6) improved thermal stability and extended service life.

[0044] To further improve low-temperature flexibility and cracking resistance, biochar may be used in combination with softening or elasticizing agents such as waste cooking oil, recycled rubber powder, recycled plastics, or rejuvenating additives. These combinations may synergistically enhance both environmental performance and mechanical resilience.

[0045] The functionalized biochar described herein may be tailored to meet specific climate conditions and pavement performance requirements. For example, biochar with enhanced rutting resistance may be used in high-temperature or heavy-load environments; biochar with improved flexibility or energy absorption may benefit cold-climate applications by increasing low- temperature cracking resistance; hydrophobic or stabilized biochar may offer moisture damage resistance for use in humid or rainy regions; and antioxidant- or mineral-rich biochar may enhance durability in salt-spray or marine environments.

[0046] In some embodiments, functionalized biochar serves as an anti-aging agent in asphalt systems. Its porous structure and surface functionalities may stabilize free radicals, absorb oxidation byproducts, and slow oxidative chain reactions, thereby delaying binder degradation and prolonging service life.

[0047] To achieve uniform dispersion of biochar within asphalt matrices, high-shear mixing equipment may be utilized during blending operations. Alternatively, pretreatment methods such as ultrasonic dispersion, oil-phase surface coating, or pre-emulsification may be applied. Additivesincluding compatibilizers, dispersants, or adhesion promoters may be incorporated to further enhance interfacial bonding and dispersion stability.

[0048] In certain embodiments, biochar may be used in combination with nanomaterials to create synergistic enhancements in mechanical, rheological, and environmental performance. Suitable nanomaterials include, but are not limited to, nano-silica, nano calcium-silicate-hydrate (C-S-H), carbon nanotubes (CNTs), nanocellulose, graphene and its derivatives, nano-clays, nano-alumina, nano iron oxides, and nano-carbonates.

[0049] These nanomaterials may be embedded within the pore structure of biochar or coated onto its surface, forming composite biochar-nanomaterial particles. This composite architecture can improve compatibility with asphalt, strengthen interfacial bonding, and enhance resistance to thermal aging. In some embodiments, the nanomaterial dosage ranges from about 0.05% to 2.0% by weight of the biochar, and preferably from about 0.08% to 1.5%.

[0050] In other embodiments, biochar may be incorporated into asphalt systems containing rejuvenating agents, such as waste engine oil, waste vegetable oil, bio-based emulsifiers, or chemical activators. Such systems may be used for producing recycled asphalt pavement mixtures that exhibit improved mechanical performance, aging resistance, and sustainability metrics.

[0051] The methods described herein are compatible with existing asphalt production and construction processes, including but not limited to hot-mix asphalt (HMA), warm-mix asphalt (WMA), emulsified asphalt, foamed asphalt, and cold in-place recycling (CIR) techniques. Functionalized biochar may serve as an eco-friendly mineral filler, asphalt additive, or binder modifier without requiring substantial investment in new equipment or significant modification of standard production workflows.

[0052] The biochar-asphalt composite materials disclosed in this invention offer the combined benefits of carbon sequestration, resource recycling, and mechanical performance enhancement. These materials are suitable for use in various infrastructure applications, including but not limitedto roadways, airfields, industrial parks, bridge decks, port facilities, and other civil engineering projects, delivering both technical and environmental value.

[0053] In certain embodiments, the biochar may be produced from biomass and other carbon- rich feedstocks via thermal conversion methods such as conventional pyrolysis, microwave- assisted pyrolysis, flash carbonization, hydrothermal carbonization, or gasification. These processes yield both carbon-rich solid biochar and liquid byproducts (bio-oils), which may be used individually or synergistically in asphalt systems to enhance rheological performance, workability, and sustainability.

[0054] In one embodiment, a mixture of bio-oil and biochar — produced simultaneously through pyrolysis or microwave treatment — is directly blended with asphalt binder to prepare hot-mix or warm-mix asphalt. The bio-oil fraction can improve binder fluidity, reduce processing temperatures, and enhance flexibility or self-healing capacity, while the biochar contributes to mechanical reinforcement, interfacial compatibility, and carbon capture functionality.

[0055] In another embodiment, the bio-oil component is separated from the solid biochar and used independently as an asphalt rejuvenator. This bio-based rejuvenator may be particularly effective in recycled asphalt pavement (RAP) systems, where it serves to soften aged binder, improve ductility and cohesion, and promote interfacial reconstitution, thereby increasing the recyclability and serviceability of asphalt mixtures.

[0056] In some embodiments, bio-oil may be blended with other recycled or waste-derived oils — such as waste engine oil, waste cooking oil, plant residue oil, or emulsified oils — to form a composite asphalt modifier. This blended oil system may enhance the workability and rejuvenation efficiency of asphalt mixtures, while improving cost-effectiveness and environmental adaptability in diverse climatic and service conditions.

[0057] In certain embodiments, bio-oil-treated reclaimed asphalt pavement (RAP) is used in conjunction with functionalized biochar in the production of new asphalt mixtures. This integrated approach combines the benefits of asphalt recycling, biomass waste valorization, and carbonsequestration, resulting in improved pavement performance and reduced carbon footprint. Such systems may be applied in structural layers, including base courses, surface courses, or pedestrian pavement systems.

[0058] The combined use of functionalized biochar and bio-oil-treated RAP may lead to synergistic improvements in asphalt composite properties such as fatigue resistance, rutting resistance, weather durability, low-temperature crack resistance, and long-term aging resistance. These enhancements offer broad applicability and scalability across transportation and civil infrastructure sectors.

[0059] Pyrolysis processing conditions — including temperature, heating rate, reaction atmosphere, and residence time — may be adjusted to tailor the yield ratio and characteristics of bio-oil and biochar for specific asphalt-related functions. For example, high-temperature fast pyrolysis (e.g., ^ 500°C) tends to generate highly aromatic, low-viscosity bio-oils suitable as fluidizing and softening agents. In contrast, medium-to-low-temperature slow pyrolysis (e.g., 300- 500°C) produces biochar with higher fixed carbon content, larger specific surface area, and more reactive surface groups conducive to asphalt compatibility.

[0060] Residual semi-coke or high-ash biochar derived from thermal conversion processes may be further processed through carbonization, alkali activation, or CO2 weathering to improve its performance as a mineral filler substitute in asphalt mixtures. These treatments may enhance high- temperature stability, stiffness, or aging resistance, particularly in applications where conventional mineral fillers are used to improve mechanical integrity.

[0061] The technical framework described herein enables a modular and flexible processing strategy, allowing users to selectively apply bio-oil, biochar, or their combinations based on the availability of local biomass and other carbon-rich feedstocks, feedstock type, climatic conditions, and roadway classification. This adaptability facilitates both performance optimization and carbon footprint reduction in diverse geographical and engineering contexts.

[0062] The integrated utilization pathway of asphalt, biochar, and bio-oil proposed in this invention combines diversified feedstocks, energy -efficient processing techniques, and customizable product formulations. Together, these elements offer a practical material system and a sustainable engineering platform for the development of low-carbon transportation and infrastructure systems.

[0063] Asphalt is a thermoplastic hydrocarbon-based binder widely used in road pavement construction and roofing waterproofing systems. Its performance is governed by viscoelastic behavior, temperature susceptibility, and interfacial interaction with mineral and polymeric components. Conventional asphalt is derived from petroleum distillation and typically classified into penetration-grade asphalt, polymer-modified asphalt (e.g., styrene-butadiene-styrene (SBS), atactic polypropylene (APP)), or emulsified asphalt.

[0064] The methods disclosed herein are applicable to a broad range of asphalt products, including but not limited to hot-mix asphalt (HMA), warm-mix asphalt (WMA), stone mastic asphalt (SMA), open -graded friction courses (OGFC), cold in-place recycling (OR) asphalt, and emulsified waterproofing systems. Depending on the asphalt formulation and intended application, process parameters and additive dosages may be adjusted to optimize the compatibility and functional performance of biochar- and bio-oil-modified systems.

[0065] In some embodiments, CCh-weathered biochar with a particle size below approximately 150 microns may be used to replace about 1% to 60% by mass of mineral filler or fine aggregate or be incorporated directly into the binder as a functional additive at dosages up to 30% by binder mass. Coarse-particle CCh-weathered biochar (e.g., >150 microns) may also be used to partially replace fine or coarse aggregates, with a typical recommended range of 1% to 30% by mass.

[0066] In addition to biochar, the asphalt composite system may incorporate various recycled inorganic solid materials, including but not limited to recycled concrete aggregates (RCA), concrete demolition waste fines (CDW fines), crushed brick debris, cement paste residues, construction site dust, limestone, basalt, olivine, and inorganic industrial byproducts (fly ash,bottom ash, slags, cement kiln dust, coal gangue, calcined clay waste, fired ceramic waste, etc.). These materials may be pre-treated through carbonation methods such as natural weathering, aeration, pressurized CO2 exposure, carbonated mist spraying, or alkaline-liquid-assisted carbonation to enhance their reactivity and bonding performance within asphalt matrices while providing additional carbon sequestration benefits.

[0067] Suitable alkaline liquids for such carbonation processes may be sourced from industrial effluents such as food processing wastewater, concrete batching wash water, paper mill alkaline streams, or metal finishing and cleaning solutions. These liquids serve both as accelerants for carbonate formation and as means of valorizing waste liquids within a circular economy framework.

[0068] Carbonated recycled aggregates — such as RCA or CDW fines — may be used to partially or fully substitute natural fine or coarse aggregates in asphalt mixtures, typically at replacement levels ranging from 10% to 100% by mass. In some embodiments, such carbonated materials may be used in synergy with CCh-weathered biochar and / or bio-oil-treated RAP to form multifunctional asphalt composites that deliver both structural performance and long-term carbon sequestration.

[0069] This tri-component system may be customized according to pavement design requirements, local climate conditions, expected traffic loads, and target service life. Relevant design parameters include particle size distribution, surface alkalinity, interfacial reactivity, and blending ratio, all of which can be optimized to improve material performance during mixing, laying, compaction, and long-term use.

[0070] In certain embodiments, functionalized biochar may be pre-loaded with rejuvenating agents — such as vegetable oils, waxes, or thermoplastic elastomers — using vacuum impregnation, solvent-assisted absorption, or in-situ encapsulation techniques. These rejuvenators, embedded within the pore structure of the biochar, may be thermally or mechanically activated upon loading or cracking, providing autonomous self-healing functionality to asphalt composites.

[0071] The rejuvenator loading capacity typically ranges from 5% to 40% by weight of the biochar, with encapsulation efficiencies exceeding 80% when using shell-forming materials such as silica or polyurethane. The biochar-rejuvenator system may replace 0.5% to 15% of the virgin asphalt binder mass while simultaneously improving crack resistance and extending pavement service life by at least 30%, as demonstrated in laboratory-scale fatigue and aging tests.

[0072] For electrically conductive asphalt applications, functionalized biochar may be comodified with electrically conductive materials, including carbon fibers (0.1-5 mm in length) and carbon nanotubes (10-100 nm in diameter), to form a percolating conductive network. The resulting composite may exhibit volume resistivity values below 50 ohm cm, suitable for applications such as snow-melting pavements or embedded sensing systems.

[0073] These multifunctional asphalt systems remain compatible with conventional production equipment. Key process parameters may include a mixing temperature of 140-170°C to protect heat-sensitive rejuvenators, a shear rate of 500-2000 rpm to facilitate conductive network formation, and a compaction energy of 75-100 gyrations to preserve internal porosity and structural integrity.

[0074] This approach supports a closed-loop asphalt material system centered on resource recycling and carbon reduction, enhancing road performance and sustainability while providing high-value applications for construction waste and industrial byproducts, facilitating green infrastructure transition.

[0075] Although the invention has been described through specific embodiments and examples, it is not limited to the details provided. Various modifications, alternatives, and equivalents will be apparent to those skilled in the art in view of this disclosure. Accordingly, the scope of the invention encompasses the concepts and principles described herein and is not restricted to the particular implementations or illustrative examples provided.

[0076] It is further understood that terminology used in this disclosure is for descriptive purposes only and is not intended to be limiting. Variations and equivalents may be made without departing from the scope or spirit of the invention, unless explicitly stated otherwise.

[0077] Where numerical ranges are specified, all intermediate values within the stated range, to the precision of one decimal place, are intended to be included. Unless explicitly excluded, any sub-range defined between any two stated values is also encompassed within the invention.

[0078] Unless otherwise defined, all technical and scientific terms used herein carry the meanings that are commonly understood by those of ordinary skill in the art. Representative materials, methods, and formulations are described herein for illustrative purposes, and suitable alternatives may be used without departing from the intended function.

[0079] All publications, patents, and patent applications cited in this disclosure are hereby incorporated by reference in their entirety for all teachings relevant to the invention, including but not limited to materials, processes, and analytical methods.

[0080] The inclusion of references is intended for citation purposes only and should not be construed as an admission that such references constitute prior art. Publication dates may vary from actual disclosure dates and should be independently verified.

[0081] Unless the context indicates otherwise, terms expressed in the singular shall include the plural, and vice versa. Claims may expressly exclude optional elements using limiting language such as “only,” “solely,” or through the use of negative limitations (e.g., “wherein... is absent”).

[0082] As will be recognized by those skilled in the art, various features described in relation to particular embodiments may be used independently, in combination with one another, or substituted with equivalent components or processes. Unless explicitly required, method steps may be performed in the order described or in any functionally equivalent sequence.EXAMPLES

[0083] Examples 1.

[0084] A low-carbon hot mix asphalt (HMA) was formulated by replacing 10 wt.% of the asphalt binder and 20 wt.% of the mineral filler with functionalized biochar, targeting both enhanced mechanical performance and reduced greenhouse gas (GHG) emissions compared to a standard reference mix.

[0085] The asphalt binder used was PG 64-22 from a commercial supplier. Aggregates consisted of crushed granite, with a nominal maximum size of 19.0 mm and gradation conforming to a typical Superpave dense-graded mix: 100% passing 19.0 mm, 90-100% passing 12.5 mm, 50- 75% passing 9.5 mm, and 5-10% passing 4.75 mm sieves.

[0086] The reference mineral filler was Class F fly ash (ASTM C618 compliant). Functionalized biochar was produced from slow pyrolysis of hardwood residues at 600°C, yielding approximately 78 wt.% carbon and 15 wt.% inorganic minerals.

[0087] The biochar was oven-dried and subjected to ball milling at 400 rpm for 3 hours (ball-to- material ratio 2: 1), followed by alkaline activation using 1.0 M NaOH at 60°C for 2 hours. The treated biochar was washed to neutral pH and dried at 60°C. Final particle size was sieved to pass 125 pm (No. 120 sieve).

[0088] In the modified mix, 10 wt.% of asphalt binder and 20 wt.% of fly ash filler were replaced by the functionalized biochar, resulting in an effective binder content of 4.5 wt.% virgin asphalt and 0.5 wt.% biochar, and a filler content of 3.2 wt.% fly ash and 0.8 wt.% biochar.

[0089] Aggregates were preheated to 160°C, binder to 150°C. Biochar was pre-dispersed into the binder using high-shear mixing at 4000 rpm for 5 minutes. Mixing with aggregates was carried out at 145°C for a total of 7 minutes using a staged sequence (low / high / filler stages).

[0090] Specimens (100 mm diameter, 63.5 mm height) were compacted using a Superpave gyratory compactor at 600 kPa and 30 gyrations (internal angle 1.25°), targeting 4.0% air voids (±0.5%).

[0091] A reference mix was prepared with identical binder grade, aggregate gradation, 5.0 wt.% virgin asphalt, and 100% fly ash as filler.

[0092] The modified mix exhibited a density of 2.40-2.45 g / cm3(vs. 2.42-2.46 g / cm3control), air voids of 3.8%-4.2%, indirect tensile strength of 4.8 MPa (vs. 0.42 MPa control), and fracture toughness 580 J / m2(vs. 520 J / m2control), indicating improved cracking resistance.

[0093] Modified binder showed improved ductility (11-13 cm vs. 10-12 cm), increased rutting resistance (G* / sin8 = 2.5 vs. 2.1 kPa at 64°C), and a reduced aging index (P AV-aged G / original G = 0.9 vs. 1.3). Based on reasonable life-cycle assessment (LCA) assumptions, the estimated GWP of the asphalt mixture decreased from approximately 200 to -120 kg C Ch-eq per ton, representing a -40% reduction.

[0094] This example demonstrates a practical approach to incorporating functionalized biochar into asphalt mixtures without altering conventional production protocols, enabling improved mechanical properties and reduced environmental impact.

[0095] Example 2.

[0096] A chemically modified low-carbon asphalt composite was produced through partial substitution of asphalt binder and mineral filler with acid-functionalized biochar.

[0097] The base asphalt binder was PG 76-22, and the aggregates consisted of crushed granite conforming to a Superpave dense-graded mix with 100% passing the 19.0 mm sieve, 90-100% passing the 12.5 mm sieve, 50-75% passing the 9.5 mm sieve, and 0-10% passing the 4.75 mm sieve.

[0098] Biochar was produced via pyrolysis of mixed agricultural residues at approximately 550°C and sieved to pass a No. 120 sieve (<125 pm).

[0099] Surface functionalization was performed using a mixed-acid solution of 1 M nitric acid and 0.5 M sulfuric acid under reflux at 80°C for 2 hours. The treated biochar was rinsed to neutral pH, oven-dried at 60°C, and stored in sealed containers.[000100] The acid-functionalized biochar was used to replace 25 wt.% of the asphalt binder and 60 wt.% of the mineral filler, corresponding to 3.0 wt.% virgin binder and 1.0 wt.% biochar in the binder fraction, and 2.0 wt.% conventional filler with 3.0 wt.% biochar in the filler fraction.[000101] Aggregates were preheated to 160°C, and the binder to 150°C. Biochar was predispersed into the binder using a high-shear mixer at 4000 rpm for 7 minutes at 140°C. Final mixing with aggregates and fillers was conducted at 140°C for 4 minutes, with fillers added in the final minute.[000102] Gyratory compaction was conducted at 600 kPa and 40 gyrations using a 1.25° internal angle. Cylindrical specimens (100 mm x 63.5 mm) were conditioned for 24 hours. The control mix included 5.0 wt.% virgin binder and 100% conventional filler.[000103] The modified mix showed increased indirect tensile strength (0.48 MPa vs. 0.42 MPa), higher fracture toughness (610 J / m2vs. 520 J / m2), improved ductility (by 5-8%), lower flow value (3.2 mm vs. 3.7 mm), and enhanced rutting resistance (30-40% improvement in dynamic modulus and G* / sin8). The fatigue life of the asphalt mixture was improved by -20%, and its oxidative aging index was decreased by -38%.[000104] A life-cycle assessment indicated a GHG emission reduction exceeding 50% compared to the control mix, supporting the applicability of acid-functionalized biochar in low- carbon asphalt systems under conventional production and service conditions.[000105] Example 3.[000106] A carbon-negative asphalt composite was fabricated by partially replacing both the asphalt binder and mineral filler with biochar that had undergone CO2 weathering without any additional chemical surface treatment.[000107] The base asphalt binder was PG 58-22, and the aggregates were crushed granite with a nominal maximum size of 19.0 mm. The aggregate gradation followed a standard Superpave design, with 100% passing the 19.0 mm sieve, 90-100% passing the 12.5 mm sieve, 50-75% passing the 9.5 mm sieve, and 0-10% passing the 4.75 mm sieve.[000108] The biochar used in this study was derived from slow pyrolysis of mixed woody biomass (e.g., forest residues and sawdust) conducted at 600°C under limited oxygen conditions.[000109] The raw biochar was dried at 60°C, ball milled at 350 rpm for 4 hours to increase surface area, and sieved to pass a No. 120 sieve (<125 pm).[000110] CO2 weathering was performed by exposing the milled biochar to a humidified CO2- rich environment (40% CO2 by volume, 75% relative humidity, 50°C) in a sealed chamber for 12 hours. Through the use of a calcium-rich waste alkaline solution, this process induced mineral carbonation, leading to the precipitation of micron-sized calcium carbonate and related carbonates within and on the surface of the biochar, as evidenced by mass gain and increased alkalinity of the processed biochar[000111] The CCh-weathered biochar was used to replace 15 wt.% of the mineral filler and 10 wt.% of the asphalt binder. The final mix contained 4.5 wt.% virgin asphalt binder and 0.5 wt.% biochar as part of the binder fraction, and 3.4 wt.% fly ash and 0.6 wt.% carbonated biochar as the mineral filler fraction.[000112] Mixing was conducted by heating the binder to 150°C and the aggregates to 160°C. The biochar was added into the hot binder and blended using a high-shear mixer at 4000 rpm for 5 minutes. The modified binder was then mixed with the hot aggregates in a mechanical mixer at 145°C for 5 minutes, with filler added during the final minute.[000113] Compaction was performed using a Superpave gyratory compactor at 600 kPa vertical pressure and 30 gyrations. Cylindrical samples (100 mm diameter, 63.5 mm height) were prepared and conditioned at ambient temperature for 24 hours prior to testing. A control group was fabricated using 5.0 wt.% asphalt binder and 100% fly ash as filler, without any biochar.[000114] The biochar-modified asphalt composite demonstrated a 10% increase in indirect tensile strength (from 0.42 MPa to 0.46 MPa), a 7-10% increase in fracture toughness (from 520 J / m2), and a 10% reduction in flow value (from 3.7 mm). The binder ductility and viscosity remained within acceptable limits for PG 64-22, and the rutting resistance was improved by 15- 25%, depending on the test temperature and loading frequency.[000115] C O2- weathered biochar also improved the moisture resistance of the asphalt mixture, increasing its tensile strength ratio (TSR) from 0.80 to 0.85. A life-cycle assessment indicated that the carbonated biochar could offset 100-120% of the greenhouse gas emissions associated with virgin asphalt binder production, resulting in a net carbon-negative asphalt material, considering both the biogenic origin and in-situ CO2 sequestration of the biochar.[000116] This example illustrates that biochar treated solely through CO2 weathering can serve as a dual-function material in asphalt composites, offering performance benefits and enabling net- negative carbon outcomes without the need for additional chemical or physical modifications [000117] Example 4.[000118] A carbon-negative asphalt composite was prepared by incorporating underwater- carbonated biochar and fully replacing virgin aggregates with carbonated recycled concrete aggregates (RCA). This system was designed to enhance both mechanical performance and longterm carbon sequestration, while reducing binder absorption commonly associated with untreated RCA.[000119] The asphalt binder used in this study was PG 70-22, selected for its superior high- temperature performance. The aggregate component consisted entirely of crushed RCA obtained from a demolished urban pavement structure.[000120] The RCA was screened to remove fines smaller than 4.75 mm and then sieved to the following gradation: 100% passing 19.0 mm, 90-100% passing 12.5 mm, 50-75% passing 9.5 mm, and 5-10% passing 4.75 mm. Both the RCA and biochar were subjected to the same aqueous carbonation treatment.[000121] The carbonation process involved submerging biochar and RCA in a recycled alkaline water sourced from a concrete batching plant’s washout system. The solution was prefiltered to remove suspended solids and had a pH between 11.5 and 12.3, containing dissolved calcium, potassium, and sodium hydroxides.[000122] The biochar was produced from slow pyrolysis of softwood chips at 600°C and milled to a particle size smaller than 125 pm. Both the biochar and RCA were immersed in the alkaline solution within a sealed carbonation chamber. CO2 gas was slowly bubbled into the solution until the solution pH stabilized at ~7.0. Visual evidence of carbonate precipitation was observed on both RCA and biochar surfaces, indicating formation of calcium carbonate and related phases. After carbonation, the RCA was dried at 80°C and the biochar at 60°C. The biochar was used to replace 20 wt.% of the mineral filler (by total filler mass), and RCA was used to fully replace all virgin coarse and fine aggregates.[000123] The asphalt binder was heated to 160°C, and the carbonated biochar was dry-blended into the binder using mechanical stirring at 200 rpm for 10 minutes. Aggregates were preheated to 140°C and mixed with the binder in a planetary mixer: stirred for 2 minutes at 140°C, followed by an additional 4 minutes at 130°C with gradual filler addition.[000124] Compaction was conducted using a Marshall compactor, applying 75 blows per face on cylindrical specimens (101.6 mm diameter x 63.5 mm height). The specimens were conditioned for 48 hours at 25°C prior to testing.[000125] Compared to a control mix using PG 70-22 binder, virgin granite aggregate, and no biochar, the modified composite demonstrated significant performance improvements. Its indirect tensile strength increased from 0.44 MPa to 0.51 MPa, fracture toughness was improved by ~15%, and binder absorption (measured via ignition and solvent extraction) was reduced by over 30% due to the densified surface of carbonated RCA. The flow values remained stable (3.5-3.7 mm), the rutting resistance was improved by 25%, and the tensile strength ratio (TSR) increased from 0.80 to 0.88.[000126] A life-cycle assessment indicated that the CO2 captured during the carbonation process exceeded the total emissions generated across the production chain, resulting in a net carbon-negative asphalt composite.[000127] This example demonstrates the synergistic use of recycled industrial alkaline wastewater, biochar, and reclaimed concrete aggregates to engineer a high-performance, carbonnegative asphalt material that entirely eliminates the use of virgin aggregate resources.[000128] Example 5.[000129] A modified carbon-negative asphalt binder was prepared using a combined biocharbio-oil product derived from the fast pyrolysis of lignocellulosic biomass, without post-pyrolysis phase separation.[000130] The goal was to improve the compatibility and dispersion of biochar within the asphalt matrix, leveraging the natural miscibility of bio-oil with bitumen to act as a compatibilizer and plasticizer.[000131] The biomass feedstock consisted of hardwood sawdust and bark residues, dried to a moisture content below 10 wt.%. Rapid pyrolysis was conducted in a fluidized bed reactor at 600°C under inert nitrogen atmosphere. The biochar yield was approximately 51 wt.%, and the bio-oil yield was approximately 20 wt.%. Rather than separating the biochar from the bio-oil, the resulting mixture (a slurry-like product containing ~25 wt.% suspended solids) was homogenized by mechanical stirring at 60°C for 30 minutes and directly used as a binder modifier.[000132] The base asphalt binder was PG 58-28, heated to 150°C prior to modification. The biochar-bio-oil mixture was added to the binder at dosages of 5 wt.%, 10 wt.%, and 15 wt.% dosages (by total binder mass). Mixing was performed using a high-shear mixer at 3500 rpm for 15 minutes at 145°C to ensure uniform dispersion. The resulting modified binder was stored at 135°C for characterization.[000133] The binder performance was evaluated by standard rheological tests. At 10 wt.% dosage, the modified binder exhibited a 15-20% increase in complex modulus (G*) and a 10% increase in rutting resistance parameter (G* / sin8) at 64°C, compared to the unmodified PG 64-22 binder. The phase angle (8) decreased slightly, indicating improved elasticity. At low temperatures (-12°C and -18°C), the binder maintained a creep stiffness within Superpave specifications, andthe m-value remained above 0.3. In addition, the presence of bio-oil improved workability and reduced mixing viscosity by approximately 12% at 135°C, which translates to lowered energy demand during mixing and paving.[000134] Example 6.[000135] A recycled asphalt composite was fabricated using reclaimed asphalt pavement (RAP) pretreated with bio-oil derived from fast pyrolysis of biomass, in combination with a virgin binder partially modified by biochar obtained from the same pyrolysis process. The bio-oil and biochar were separated prior to use and applied to different phases of the asphalt system to improve compatibility, durability, and environmental performance.[000136] The RAP material was collected from surface milling operations and contained approximately 4.8 wt.% aged asphalt binder. The RAP was air-dried at 60°C for 24 hours and screened to pass a 19.0 mm sieve and retain particles larger than 4.75 mm. Bio-oil was produced through fast pyrolysis of softwood residues at 500°C in a nitrogen atmosphere, yielding a dark brown, low- viscosity oil phase with an oxygen content of approximately 35 wt.%.[000137] The bio-oil was separated from the char-rich bottom fraction via filtration and centrifugation. It was then applied to the RAP at 10 wt.% of the aged binder mass and thermally blended at 120°C for 2 hours to enable diffusion and softening of the oxidized binder. No biochar was introduced into the RAP at this stage.[000138] Separately, biochar from the same pyrolysis process was oven-dried at 60°C and sieved to <125 pm. It was chemically functionalized by immersion in a 1 M sodium hydroxide (NaOH) solution at 60°C for 2 hours, rinsed to neutral pH, and dried. This functionalized biochar was used to replace 10 wt.% of a PG 64-28 virgin binder, with high-shear mixing performed at 4000 rpm for 5 minutes at 145°C to ensure uniform dispersion.[000139] The final asphalt mixture consisted of 50 wt.% bio-oil-treated RAP and 50 wt.% virgin aggregates (crushed granite). The total binder content was 5.2 wt.%, with the biochar- modified PG 64-28 binder applied to the virgin portion only. Mixing occurred in two stages: thetreated RAP and virgin aggregates were combined first, followed by gradual addition of the modified binder, with total mixing at 145°C for 4 minutes.[000140] Compaction was carried out using a Superpave gyratory compactor at 600 kPa and 35 gyrations, forming cylindrical specimens (100 mm diameter x 63.5 mm height), which were conditioned at 25°C for 24 hours prior to testing.[000141] Compared to a control mix made entirely with virgin aggregates and PG 64-28 binder, the biochar-bio-oil-enhanced recycled composite exhibited improved mechanical performance. Indirect tensile strength increased from 0.43 MPa to 0.47 MPa, fracture toughness improved by -12%, and low-temperature creep stiffness (at -18°C) decreased by 10-15%. The m-value increased by 0.02-0.04, indicating enhanced relaxation behavior. The rutting resistance at 64°C was improved by 18-25%, and the tensile strength ratio (TSR) increased from 0.80 to 0.85.[000142] A life-cycle assessment showed that the use of biochar and bio-oil enabled a net reduction of 100-120% in greenhouse gas emissions compared to the control mix, due to partial binder replacement, RAP reuse, and carbon retention from the biochar.[000143] This example demonstrates the feasibility of separating bio-oil and biochar from a single pyrolysis process and applying them to distinct phases within an asphalt system, achieving both mechanical and environmental performance improvements in recycled asphalt mixtures.[000144] Example 7.[000145] An asphalt binder system with delayed self-healing functionality was developed by incorporating porous biochar preloaded with a liquid healing agent. The aim was to provide longterm durability enhancement by enabling in-situ repair of microcracks during service through controlled release of the encapsulated agent.[000146] The base asphalt binder was PG 64-22, and the healing agent used was sunflower oil, a bio-based, low-viscosity oil known for its compatibility with asphalt and oxidative resistance. The biochar was produced from pyrolysis of coconut shells at 650°C, which yielded high surfacearea material (BET -350 m2 / g) with a predominantly mesoporous structure. The biochar was sieved to <150 pm and oven-dried at 60°C for 12 hours to eliminate residual moisture.[000147] Sunflower oil was incorporated into the biochar through vacuum impregnation. Dried biochar was placed in a vacuum chamber and submerged in sunflower oil at room temperature. A vacuum of -90 kPa was maintained for 30 minutes to evacuate internal pores, after which the chamber was gradually returned to atmospheric pressure to enable capillary infiltration. Excess surface oil was removed by gentle centrifugation and blotting. The final oil loading was approximately 40 wt.% (i.e., 60% biochar and 40% oil by mass).[000148] The oil -loaded biochar was incorporated into PG 64-22 binder at a dosage of 5 wt.% relative to the binder mass, using low-shear mechanical mixing at 135°C for 10 minutes to avoid premature release. No visible phase separation or oil bleeding was observed after 72 hours of storage at 150° C.[000149] Short-term performance of the modified binder remained within the PG 64-22 specification. Rotational viscosity at 135°C was 440 ± 25 cP, compared to 420 ± 20 cP for the unmodified binder, indicating minimal impact on workability. Dynamic shear rheometer (DSR) tests showed a rutting parameter (G* / sinb) of 1.26 ± 0.05 kPa at 64°C for the modified binder, versus 1.21 ± 0.04 kPa for the control, both exceeding the 1.0 kPa Superpave minimum. Phase angle (5) ranged from 79.2° to 81.0°, indicating a primarily viscous behavior with minor elasticity enhancement due to the biochar.[000150] This example demonstrates that porous biochar can serve as a delivery platform for bio-based healing agents, enabling time-delayed or thermally triggered microcrack repair within asphalt binder systems, while preserving initial workability and rheological performance.[000151] Example 8[000152] An electrically conductive asphalt concrete was developed by physically enhancing the conductivity of biochar and combining it with short carbon fibers to enable Joule heating underlow-voltage electrical input, suitable for ice and snow melting in cold-climate pavement applications.[000153] The base binder used was PG 70-10, selected for its enhanced low-temperature cracking resistance. The aggregates were crushed basalt and graded according to a dense-graded mix design: 100% passing 19.0 mm, 90-100% passing 12.5 mm, 50-70% passing 9.5 mm, and 5- 10% passing 4.75 mm.[000154] The biochar was produced from rice husk pyrolysis at 700°C under nitrogen atmosphere and further subjected to thermal annealing in argon at 900°C for 2 hours. This physical treatment reduced oxygen-containing surface groups and increased the degree of graphitization, decreasing the electrical resistivity from ~50 Q cm (as-pyrolyzed) to 8.5 ± 1.2 Q cm. The biochar was sieved to pass a No. 100 mesh and oven-dried at 60°C.[000155] Short carbon fibers (6 mm length, 7 pm diameter) were added at 0.5 wt.% of the total mixture mass to enhance conductive continuity. The annealed biochar replaced 20 wt.% of the mineral filler. The modified binder was prepared by dry-blending the conductive biochar and carbon fibers with PG 70-10 at 155°C using high-shear mixing (4000 rpm, 8 minutes).[000156] The final asphalt mix contained 5.2 wt.% binder, 2.5 wt.% conductive biochar (by total mix mass), and 0.5 wt.% carbon fibers. Aggregates were preheated to 160°C and blended first with the biochar. The binder was then added, and mixing was completed at 150°C over 4 minutes using a two-stage blending approach.[000157] Compaction was performed using a Superpave gyratory compactor at 600 kPa and 40 gyrations, forming cylindrical specimens (100 mm diameter x 63.5 mm height). Air voids were controlled within the range of 3.5-4.0%. Prior to electrical testing, specimens were conditioned at -10°C for 24 hours.[000158] The surface resistivity of asphalt mixtures was measured by four-point probe and averaged 750 ± 60 Q cm, adequate for low-voltage heating. When powered by a 24V DC source, the surface temperature rose to 35-42°C within 6 minutes, maintaining a steady-state powerdensity of ~15 W / m2Electrical performance degradation after 20 freeze-thaw cycles was under 8%, indicating stable conductivity. The fracture energy under low-temperature semicircular bending was improved by 12%, and the tensile strength ratio (TSR) increased from 0,79 to 0.83.[000159] This example demonstrates the feasibility of using thermally annealed biochar combined with carbon fibers to produce conductive asphalt materials suitable for snow and ice melting without the use of chemical deicing agents, offering energy-efficient cold-climate pavement solutions.[000160] Example 9[000161] A modified asphalt binder was developed incorporating physicochemically treated biochar to reduce the release of volatile organic compounds (VOCs) during asphalt mixing and paving operations. The treatment strategy aimed to increase the porosity and surface functional group density of the biochar to promote adsorption and interaction with volatile hydrocarbon species.[000162] Biochar was produced from corn stover via pyrolysis at 600°C and sieved to <125 pm. The physical modification consisted of ball milling at 400 rpm for 6 hours followed by steam activation at 850°C for 1 hour, increasing the BET surface area from 95 m2 / g to 320 m2 / g. Subsequently, chemical oxidation was performed using 1 wt.% hydrogen peroxide (H2O2) at 60°C for 3 hours to introduce polar oxygen-containing groups, enhancing affinity for VOCs such as aldehydes and ketones.[000163] The base binder was PG 64-22, and the modified biochar was added at 7 wt.% relative to binder mass. Mixing was conducted at 150°C using a low-shear stirrer at 300 rpm for 10 minutes. The resulting modified binder was evaluated for both VOC emissions and standard rheological performance.[000164] VOC emissions were quantified using a sealed-headspace sampling system combined with gas chromatography-mass spectrometry (GC-MS). The unmodified binder emitted 168 mg / m2of VOCs after 30 minutes at 160°C, while the biochar-modified binder emitted 97 mg / m2,indicating a 42% overall reduction. Specific compound reductions included: aliphatic hydrocarbons (-39%), aromatic compounds (-48%), and aldehydes / ketones (-50%).[000165] Rheological testing confirmed that binder performance remained compliant with PG 64-22 specifications. Viscosity at 135°C was 420 cP, G* / sin§ at 64°C was 1.32 kPa, and phase angle was 80.5°. No phase separation was observed after 3-day storage at 150°C. Fourier transform infrared spectroscopy (FTIR) analysis indicated no detectable chemical degradation of asphalt components. Moreover, pressure aging vessel (PAV) testing showed a 20% decrease in oxidative aging index relative to control, suggesting additional aging resistance due to VOC capture and radical stabilization.[000166] This example demonstrates the feasibility of using high-surface-area, polar- functionalized biochar as a VOC-scavenging additive in asphalt binders, achieving significant emission reductions while maintaining or enhancing thermal and mechanical performance [000167] Example 10.[000168] An SB S-modified asphalt waterproofing membrane was formulated by incorporating fine-particle biochar as a multifunctional filler to enhance mechanical strength, ultraviolet (UV) resistance, and thermal stability. The base asphalt was oxidized bitumen with a softening point of 105°C and a penetration value of 20 dmm. Styrene-butadiene-styrene (SBS) polymer was incorporated at 10 wt.% relative to the asphalt to confer thermoplastic elastomer properties.[000169] The biochar was produced via pyrolysis of coconut shells at 600°C, followed by ball milling and sieving to <75 gm. The resulting fine powder exhibited a surface area of approximately 250 m2 / g and was incorporated at 10 wt.% of the total asphalt-polymer blend. The components were blended using a twin-screw compounder at 170°C for 1 hour to achieve homogeneous dispersion.[000170] The resulting biochar-enhanced SBS membrane exhibited improved performance metrics compared to the SBS-only membrane. Tensile strength reached 4.2 MPa, elongation at break was 560%, and softening point increased to 110°C. After 1000 hours of accelerated UVaging, elongation retention was above 95%, compared to 82% for the reference. Water absorption decreased by 22%, and dimensional stability under thermal cycling was improved, indicating enhanced resistance to physical deformation.[000171] This example demonstrates that fine-particle biochar can be effectively incorporated into polymer-modified asphalt membranes to enhance mechanical and environmental durability, offering a sustainable and high-performance alternative in waterproofing and protective coating applications[000172] Example 11.[000173] A hot-pour asphalt crack sealant was formulated using biochar as both a filler and anti-aging component. The base asphalt was a PG 64-28 binder, selected for its low-temperature flexibility, and a commercial naphthenic plasticizer was added at 8 wt.% to improve workability and long-term performance. Biochar derived from corn husk pyrolysis at 500°C was incorporated at 6 wt.% of the total sealant weight.[000174] The sealant was prepared by heating the asphalt binder to 150°C, followed by the sequential addition of plasticizer and biochar under continuous mechanical stirring. The mixing process lasted 30 minutes to ensure homogeneous dispersion. The porous biochar contributed to aging resistance by adsorbing reactive molecular species and stabilizing the colloidal structure of the bitumen matrix.[000175] Performance testing showed that the sealant had a penetration value of 55 dmm at 25°C, a softening point of 68°C, and ductility exceeding 100 cm at 15°C. After 7 days of pressure aging vessel (PAV) conditioning, the stiffness increase was 27% lower than that of a control sealant without biochar, indicating improved oxidative stability. Adhesion strength to concrete substrate improved from 0.48 MPa (control) to 0.62 MPa, and crack sealing retention after five freeze-thaw cycles at -10°C remained above 90%.[000176] This example illustrates the utility of biochar as a sustainable additive in hot-applied asphalt sealants, enhancing both adhesion and anti-aging properties while maintaining desirable rheological and thermal characteristics[000177] Example 12.[000178] A conductive asphalt-based surface coating was developed using high-temperature biochar for antistatic and electromagnetic shielding applications. The base asphalt was blended with 20 wt.% high-carbon biochar produced by pyrolysis of bamboo at 900°C under argon atmosphere. The resulting biochar exhibited an electrical conductivity of 2.5 S / cm and a specific surface area of 180 m2 / g.[000179] The asphalt was heated to 160°C, and the biochar was incorporated under mechanical stirring at 250 rpm for 20 minutes. The final paste was applied onto concrete slabs using a 3 mm notched trowel and cured at 25 °C.[000180] The dried coating formed a uniform film with an average thickness of 2.8 mm and surface resistivity of 8.7 x io2Q / sq, suitable for static charge dissipation in industrial flooring. Thermal stability testing at 85°C for 72 hours showed no bleeding or delamination. EMI shielding effectiveness at 1 GHz reached 18 dB. Abrasion resistance improved by 35% compared to a carbon black-modified control.[000181] Example 13.[000182] A fire-resistant asphalt coating was formulated by incorporating rice husk-derived biochar as a flame-retardant filler and thermal stabilizer. The goal was to improve fire resistance and smoke suppression for use in roofing, tunnels, and airport pavements.[000183] The base asphalt was oxidized bitumen with a softening point of 105°C and penetration of 18 dmm. The biochar, produced from pyrolysis of rice husk at 700°C, contained ~55 wt.% fixed carbon and >30 wt.% silica. It was ball-milled and sieved to <75 pm. TGA results showed thermal degradation onset at ~410°C and a 55% residue at 800°C in air.[000184] The formulation consisted of 88 wt.% oxidized asphalt, 4 wt % SBS polymer, and 8 wt.% biochar, blended at 160°C for 1 hour using a twin-screw compounder. Coating films (3 mm) were cast on aluminum foil.[000185] Fire performance tests showed a limiting oxygen index (LOI) of 28.5% (vs. 22.3% control), and a cone calorimeter peak heat release rate (HRR) reduction from 480 to 330 kW / m2. Total heat release (THR) decreased by 31%, and the coating achieved a UL-94 V-0 rating. Smoke density was reduced by -25%.[000186] The coating retained suitable mechanical properties: tensile strength of 3.8 MPa, elongation at break of 430%, dimensional stability <1.2% under heat cycling, and adhesion >0.6 MPa to concrete / steel substrates.[000187] Example 14.[000188] A pervious asphalt concrete was prepared using functionalized biochar to partially replace mineral filler and asphalt binder, targeting water permeability and carbon sequestration.[000189] The mix used PG 58-28 binder and single-sized 9.5 mm granite aggregate, omitting sand. Target air voids were 18-22%. Functionalized biochar (from hardwood pyrolyzed at 600°C and NaOH-treated) replaced 20 wt.% of mineral filler and 10 wt.% of the binder.[000190] The binder and biochar were pre-mixed at 135°C. The final mixture had 5.5 wt.% total binder, compacted with 50 Marshall blows per side. Water permeability was 1.8 x 102cm / s, compressive strength >2.5 MPa, and net CO2 sequestration was 30-35 kg / ton.[000191] Example 15.[000192] A high-performance stone matrix asphalt (SMA) mix was formulated using CO2- weathered biochar to meet durability demands while achieving carbon-negative outcomes.[000193] The SMA included 70-80% coarse aggregate (>4.75 mm), 7.0 wt.% PG 70-22 binder, 0.3 wt.% cellulose fiber, and 2.0 wt.% filler. Biochar (from rice husk, <75 pm, CCh-weathered) replaced 30 wt.% of the filler and 10 wt.% of the binder.[000194] Mixing was done at 165°C, compacted via Superpave gyratory compactor. Hamburg rut depth <2.0 mm (20,000 passes), TSR >0.88, retained Marshall stability >90% after moisture conditioning. Carbon offset estimated at ~45 kg CChe / t of mix.[000195] Example 16.[000196] An open-graded friction course (OGFC) was developed using biochar to improve acoustic and environmental performance of surface layers in high-speed roads.[000197] The open-graded aggregate gradation had 100% passing 12.5 mm, 85-100% passing 9.5 mm, and 10-15% passing 4.75 mm. PG 76-22 polymer-modified binder was used at 6.0 wt.%, with 15 wt.% of the binder replaced by KMn Ch-treated, ball-milled biochar from switchgrass pyrolysis.[000198] Mixing was performed at 160°C with short duration. Steel-wheel compaction was used in two passes. Air voids >18%. Results: +2 dB sound absorption, 1.8 mm surface texture depth, tensile strength 0.42 MPa (wet), and 25-35 kg CO2 sequestration per ton of mix [000199] Example 17.[000200] A high-retention asphalt emulsion sealant was developed using plasma-treated biochar to enhance surface energy and binder-filler compatibility. The biochar was produced from pine sawdust at 600°C and sieved to <125 pm. The dried powder was subjected to oxygen plasma treatment for 15 minutes, creating a high surface oxygen content as confirmed by XPS analysis (O / C ratio increased from 0.18 to 0.32).[000201] The base asphalt was cationic emulsified asphalt (CSS-lh), and the plasma-treated biochar was added at 5 wt.% to the total emulsion mass. The mixture was prepared at 60°C using mechanical mixing. The final product was applied to aged asphalt concrete slabs with 3 mm film thickness.[000202] Adhesion and curing retention were evaluated. Film cohesion increased by 25%, and binder-filler interfacial pull-off strength improved from 0.39 MPa (control) to 0.53 MPa. Waterwash-off loss after 48 hours decreased from 18% to 9%, and aging resistance improved as shown by FTIR-based oxidation index reduction of 28%.[000203] Example 18.[000204] A VOC-scavenging asphalt-based coating was formulated using KMnO4-oxidized biochar. Biochar from rice husks was pyrolyzed at 650°C, then oxidized with 0.1 M KMnCh at 50°C for 1 hour. The oxidized surface showed increased carboxyl and hydroxyl content, as confirmed by FTIR and Boehm titration.[000205] The modified biochar was combined with nano-silica at a 4: 1 mass ratio and incorporated at 10 wt.% into a PG 64-22 asphalt binder to prepare a roller-applied surface coating. VOC emissions were tested via dynamic headspace GC-MS.[000206] Compared to the control binder, VOC release decreased by 46%, with major reductions in alkylbenzenes and aldehydes. The coating showed improved UV aging stability, and after 1000 hours of exposure, its color retention and surface modulus degradation were both better by >20%.[000207] Example 19.[000208] A carbon-negative asphalt mixture was prepared using alkali-carbonated recycled concrete aggregate (RCA) and CCL-weathered biochar. RCA was soaked in concrete washout water (pH —12) for 24 hours and then exposed to pressurized CO2 (1 atm) in a sealed chamber for 6 hours. Biochar from bamboo was similarly carbonated under the same condition.[000209] The asphalt mix used 60% RCA (by mass of total aggregate) and 2 wt.% carbonated biochar as mineral filler substitute. PG 70-22 binder was used at 5.8 wt.%. Mixing was conducted at 160°C and compacted with 75 gyrations in a Superpave compactor.[000210] The mixture achieved compressive strength of 3.5 MPa, TSR > 0.85, and rutting depth <2.2 mm after 20,000 wheel passes. Life-cycle carbon accounting showed a net sequestration of 55 kg CChe per ton of mix.[000211] Example 20.[000212] An asphalt fire-retardant coating was developed using a hybrid filler composed of silica-rich rice husk biochar and montmorillonite nanoclay. Biochar was pyrolyzed at 700°C and milled to <75 pm. It was combined with 3 wt.% nanoclay at a 7:3 ratio.[000213] The hybrid was incorporated at 12 wt.% into oxidized asphalt with 5 wt.% SBS polymer. Coatings were applied to 3 mm thickness and evaluated via cone calorimeter (35 kW / m2). [000214] Results showed HRR reduced from 480 kW / m2(control) to 310 kW / m2, LOI increased to 29.2%, and total smoke production dropped by 22%. The tensile strength and flexibility remained acceptable, and the UL-94 vertical burn test returned a V-0 classification.[000215] Example 21.[000216] A self-healing asphalt binder was formulated using porous biochar loaded with waste vegetable oil as a delayed-release rejuvenator. The objective was to provide crack-mitigation functionality through localized oil release under mechanical stress or thermal cycling.[000217] The biochar was derived from switchgrass pyrolyzed at 600°C and sieved to <150 pm. BET analysis showed a surface area of 220 m2 / g and dominant mesoporosity. Vacuum impregnation was performed by applying -90 kPa for 30 minutes in the presence of heated (40°C) waste cooking oil, followed by return to atmospheric pressure for 1 hour. The loading capacity reached 36 wt.% with >85% encapsulation efficiency.[000218] The oil-loaded biochar was blended into PG 64-22 binder at 5 wt.%, using low-shear mixing at 135°C to avoid premature oil release. The modified binder was then mixed with dense- graded granite aggregates and compacted into 100 mm diameter x 63.5 mm height cylinders using 30 gyrations.[000219] The fracture-healing experiments were performed using a semicircular bending test under three thermal cycles between -10°C and 40°C. The recovered fracture toughness increased by 23%, and micro-CT imaging confirmed oil migration into crack tips. Binder rheology remained within PG 64-22 limits, with creep stiffness at -12°C unchanged relative to the control.[000220] This example demonstrates that impregnated porous biochar can serve as a long-term self-healing additive in asphalt, improving resilience to microcracking while maintaining initial binder performance.[000221] Example 22.[000222] A flexible, low-slope asphalt roof coating was developed using biochar and plant- derived wax to enhance UV stability, elongation, and low-temperature flexibility.[000223] The base asphalt was oxidized bitumen (softening point 95°C, penetration 25 dmm). Biochar was obtained from pyrolysis of wheat straw at 550°C and sieved to <100 pm. Bio-based wax (soy-derived) was added at 3 wt.% and biochar at 7 wt.%, relative to asphalt mass. Blending was conducted at 160°C for 1 hour using a twin-blade mixer.[000224] The coating was applied to aluminum and concrete panels using a notched trowel at 2.5 mm thickness and cured for 48 hours at 25°C. Elongation at break reached 620%, tensile strength 3.5 MPa, and crack resistance at -20°C was verified through a static bend test.[000225] UV aging over 1000 hours showed only 7% loss in elongation. The surface reflectivity increased by 10% due to fine-particle char, and the water permeability through the film was <1.5 x 107cm / s. No cracking or blistering was observed after 25 thermal cycles between -20°C and +60°C.[000226] This example illustrates that functionalized biochar can synergize with renewable waxes in asphalt-based coatings to improve long-term performance for flexible, exposed, or semi- structural sealing applications such as roofing, decking, or below-grade waterproofing[000227] Example 23.[000228] A nano-engineered asphalt composite was developed by incorporating nano-calcium silicate hydrate (C-S-H) particles and functionalized biochar to improve interfacial adhesion and long-term moisture resistance.[000229] The base binder was PG 64-28, and the aggregate gradation followed a standard Superpave mix design with nominal maximum aggregate size of 12.5 mm. Biochar was derivedfrom coconut shell pyrolysis at 600°C, sieved to <125 pm, and pre-treated in 1 M NaOH at 60°C for 2 hours to improve surface reactivity.[000230] Nano-C-S-H particles (~80 nm average size, synthesized via Ca(NOs)2-Na2SiO3 coprecipitation) were blended with the biochar at a mass ratio of 1 :5 and added at 6 wt% of total binder mass. High-shear mixing was performed at 4000 rpm and 150°C for 10 minutes.[000231] The resulting binder was mixed with preheated aggregates at 155°C, and specimens were compacted using a Superpave gyratory compactor (600 kPa, 75 gyrations). Cylindrical samples (100 mm x 63.5 mm) were conditioned at 25°C for 24 hours prior to testing.[000232] Pull-off adhesion testing on asphalt-aggregate interfaces showed a 35% increase in interfacial tensile strength (from 0.46 MPa to 0.62 MPa). After five freeze-thaw cycles, the moisture-induced strength loss was 9% (i.e., a notable decrease from 22% of the control mix). SEM-EDS confirmed a denser interfacial zone with nano-C-S-H bridging phases between the biochar and the bitumen matrix.[000233] This example demonstrates that combining functionalized biochar with nano-C-S-H particles yields a synergistic interface reinforcement mechanism, offering improved adhesion, durability, and moisture resistance for asphalt composites under aggressive environmental exposure.[000234] Example 24.[000235] A nano-biochar modified asphalt binder was developed to suppress volatile organic compound (VOC) emissions during hot mixing and to enhance thermal stability and UV resistance. The biochar was prepared from softwood-derived lignocellulosic biomass via fast pyrolysis at 500°C under nitrogen atmosphere, followed by cryogenic ball milling and ultrasonic dispersion to achieve nanoscale particle sizes.[000236] The resulting nano-biochar was sieved and classified to obtain particles with an average size below 100 nanometers, and a BET surface area exceeding 550 m2 / g. Surface functionalization was conducted using a 1 wt.% aqueous solution of 3 -aminopropyltri ethoxy silane(APTES), resulting in the grafting of -NEE groups onto the biochar surface. The modified nanobiochar showed a VOC adsorption capacity of approximately 98-105 mg / g for mixed aliphatic and aromatic hydrocarbons.[000237] The asphalt binder used was PG 64-22, heated to 150°C, into which 1.0 wt.% of the surface-functionalized nano-biochar was introduced under high-shear mixing at 4000 rpm for 10 minutes. A control sample containing unmodified binder was also prepared. All mixing operations were conducted under controlled ventilation conditions.[000238] VOC emissions were quantified using sealed headspace GC-MS testing, in accordance with ASTM D7984. The nano-biochar modified binder showed a 55-62% reduction in total VOC release compared to the control. Reductions were particularly notable in aromatic hydrocarbons (e.g., toluene, xylene) and aldehydes, with up to 70% suppression observed. FTIR confirmed no structural degradation of the binder.[000239] Thermal conductivity of the binder increased from 0.21 W / m K (control) to 0.31 W / m K, as measured using a transient plane source method. The nano-biochar also increased the UV absorbance in the 250-400 nm range, leading to a 35% improvement in photo-aging resistance after 1000 hours of QUV exposure. Rheological testing (DSR) indicated a 20% increase in complex modulus (G*) at 64°C and a reduction in the oxidative aging index (G* / G*aged) by 0.3 points after PAV conditioning.[000240] In a separate variation, nano-biochar was co-blended with nanosilica (0.3 wt.%) and graphene oxide (0.2 wt.%) to further improve dispersion and synergistic emission suppression. The resulting ternary-modified binder exhibited a total VOC reduction of 67%, a viscosity reduction of 8% at 135°C after incorporating 4% bio-oil by total mass of asphalt binder, and no observable particle agglomeration under SEM analysis.[000241] This example demonstrates the effectiveness of surface-functionalized nano-biochar as a multifunctional modifier for asphalt binders, achieving VOC suppression, thermalconductivity enhancement, oxidative aging resistance, and UV shielding in a single additive system with high dispersion stability.

Claims

AMENDED CLAIMS received by the International Bureau on 13 January 2026 (13.01.2026)Claim 1 (Independent)1. An asphalt composite comprising: an asphalt binder; and a functionalized biochar incorporated as a partial replacement for the asphalt binder and / or a mineral filler, wherein the functionalized biochar has been physically, chemically, mineralogically, or physicochemically modified and is configured to enhance dispersion, interfacial compatibility, mechanical performance, durability, and / or environmental performance of the asphalt composite.Claims 2-8 (Dependent - Material & Configuration Options)2. The asphalt composite of claim 1 , wherein the functionalized biochar is derived from biomass feedstocks selected from woody biomass, agricultural residues, or combinations thereof.

3. The asphalt composite of claim 1, wherein the functionalized biochar is produced through physical, chemical, mineralogical, or combined modification.

4. The asphalt composite of claim 1 , wherein the functionalized biochar is incorporated in an amount effective to partially replace the asphalt binder fraction.

5. The asphalt composite of claim 1, wherein the functionalized biochar is incorporated in an amount effective to partially replace the mineral filler fraction.

6. The asphalt composite of claim 1 , wherein the functionalized biochar comprises biochar particles having different particle size distributions.

7. The asphalt composite of claim 1 , wherein the functionalized biochar is configured to improve resistance to aging or moisture-induced damage.

8. The asphalt composite of claim 1, wherein the functionalized biochar is incorporated into reclaimed asphalt pavement (RAP) or recycled asphalt mixtures.47Claim 9 (Revised - Nano-Biochar Interaction)9. The asphalt composite of claim 1 , wherein the functionalized biochar comprises a fraction of nano-sized biochar particles having an average particle size of less than 100 nanometers, the nano-sized particles contributing to adsorption or entrapment of volatile organic compounds during asphalt processing or placement.Claims 10-12 (Binder / Additive Interactions)10. The asphalt composite of claim 1, further comprising a rejuvenating agent, softening agent, or compatibilizer.

11. The asphalt composite of claim 1 , wherein the functionalized biochar is incorporated into the asphalt binder prior to mixing with aggregates.

12. The asphalt composite of claim 1, wherein the functionalized biochar is incorporated during mixing of the asphalt binder and aggregates.Claim 13 (Revised - Environmental Performance)13. The asphalt composite of claim 1, wherein the functionalized biochar is carbon di oxideweathered and contributes to reduced greenhouse gas emissions relative to a conventional asphalt mixture.Claim 14 (Unchanged)14. The asphalt composite of claim 1, wherein the functionalized biochar contributes to enhanced thermal, electrical, or electromagnetic properties of the asphalt composite.

15. (Canceled)Claim 16 (Revised - Additive, System-Oriented)16. A functionalized biochar additive composition for use in asphalt, wherein the biochar is configured, through physical, chemical, mineralogical, or combined modification, to enhance dispersion, interfacial compatibility, and48environmental performance when incorporated into an asphalt binder or asphalt composite.Claims 17-19 (Kit and Use)17. A kit for preparing an asphalt composite, comprising: the functionalized biochar additive composition of claim 16; and instructions for incorporating the functionalized biochar into an asphalt binder or asphalt composite.

18. Use of the asphalt composite of claim 1 for reducing emissions or improving durability during asphalt production, placement, or service.

19. Use of the asphalt composite of claim 1 in pavement, roadway, or infrastructure applications.Claims 20-22 (Method Claims)20. A method for producing an asphalt composite, comprising: functionalizing biochar through physical, chemical, mineralogical, or combined modification; and incorporating the functionalized biochar into an asphalt binder and / or asphalt composite.

21. The method of claim 20, wherein the functionalized biochar is incorporated using conventional asphalt mixing equipment.

22. The method of claim 20, wherein the functionalized biochar is subjected to carbon dioxide exposure or mineral carbonation prior to incorporation into the asphalt composite.Claim 23 (Revised - Method Environmental Outcome)23. The method of claim 20, wherein the resulting asphalt composite exhibits a reduced greenhouse gas footprint compared to a conventional asphalt mixture.Claims 24—26 (Applications and Extensions)24. The asphalt composite of claim 1 , wherein the composite is applied as a surface layer, overlay, or coating.

25. The asphalt composite of claim 1, wherein the composite comprises recycled aggregates, recycled concrete aggregates, or reclaimed asphalt materials.

26. (Canceled)49[0001]STATEMENT UNDER ARTICLE 19 (1)[0002]Pursuant to PCT Article 19, Applicant hereby submits amended claims for the present international application.[0003]The amendments are made solely for the purpose of improving clarity, consistency, and internal coherence of the claims, particularly with respect to the relationship between different claim categories and the underlying inventive concept.[0004]In particular, the amendments:[0005]• clarify that the various claim categories (composition, additive, method, kit, and use) represent different implementations of a single system-level inventive concept, rather than distinct inventions;[0006]• align the claim language with the technical effects and embodiments already disclosed in the description as originally filed; and[0007]• remove or generalize claim language that could otherwise be misconstrued as introducing unsupported quantitative thresholds or speculative mechanisms.[0008]The amendments do not introduce any new technical features, do not rely on subject matter not disclosed in the international application as filed, and do not alter the core inventive concept of the application.[0009]No amendments to the description or drawings are submitted at this stage.