Self-healing asphalt using carbon dioxide
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2025-11-17
- Publication Date
- 2026-08-13
Smart Images
Figure IB2025061709_13082026_PF_FP_ABST
Abstract
Description
DescriptionTitle of Invention : Self-healing asphalt using carbon dioxideTechnical Field
[0001] The present invention relates to an asphalt mixture used for pavement of a road and its production method.Background Art
[0002] Conventional asphalt pavements are widely used in road construction due to their cost efficiency and flexibility; however, they suffer from progressive aging, cracking, and loss of mechanical integrity under thermal and mechanical stresses. Existing rejuvenation techniques mainly focus on restoring the rheological properties of aged bitumen through the addition of softening agents or rejuvenators but fail to overcome long-term destruction and self-healing capabilities. Unlike cementitious materials, asphalt is an organic, hydrophobic system that prevents penetration of moisture and carbon dioxide, making carbonation-based self-healing reactions impossible in such media. In contrast, mineral-based systems such as concrete have long been known to undergo carbonation reactions that enhance strength and density through the conversion of calcium hydroxide into calcium carbonate in moist and alkaline environments. Despite extensive research, no practical method has been developed to enable similar mineral reactions or CO2utilization within bituminous matrices. Therefore, there remains a clear technological gap in creating an asphalt composition capable of both environmental CO2capture and intrinsic self-healing through controlled mineral reactions within an organic matrix.
[0003] Some patents address this issue, for example:
[0004] The Jap.Pat.No. JP2022170813 titled "ASPHALT MIXTURE" concerning an asphalt mixture that serves solely as a carbon dioxide absorber. The production method of this asphalt mixture involves the use of recycled materials (recycled asphalt aggregate), new materials (coarse or fine aggregate that has not previously been used as asphalt mix material), stone powder, new asphalt, and carbon dioxide, featuring a process that includes the mixing or blending of carbon-absorbing lime. This invention utilizes sodium ferrite or potassiumcarbonate in the asphalt mix to enable carbon dioxide absorption. The invention presented here is applicable to the self-healing of asphalt by the absorbed carbon dioxide and also absorbs carbon dioxide emitted from vehicle exhausts through a different formulation, which is completely distinct from the referenced registered invention. In fact, the application of the referenced registered invention remains limited to being an additive in current asphalt mixes, functioning only as a carbon dioxide absorber; whereas the invention presented in this document, with its unique formulation, not only absorbs carbon dioxide emitted from vehicle exhausts but also enables the asphalt to self-heal with the carbon dioxide captured from vehicle exhausts. Ultimately, the invention presented in this document is entirely different from the invention referenced above.
[0005] The Chinese Pat.No. CN117126548, titled "Anti-cracking self-healing modified asphalt and preparation method thereof," discloses an asphalt composition and its preparation method. This modified asphalt contains matrix asphalt, a self- healing microcapsule, SBS modifier (styrene-butadiene-styrene), UV-modified epoxy acrylate, an anti-aging agent, and a functional additive. The microcapsule wall is made from a modified urea-formaldehyde prepolymer, improving compatibility and dispersion in asphalt. When cracks occur, the UV-modified epoxy acrylate and broken microcapsules work together to heal the asphalt, enhancing crack resistance. The invention utilizes cross-linking between the modified wall materials, SBS modifier, and epoxy acrylate to address asphalt’s strength limitations. Ultimately, this registered invention differs from the invention presented in this document, including in its method of self-healing.
[0006] The Chinese Pat.No CN117228991 , titled "Self-healing asphalt concrete under microwave action and preparation method thereof," discloses a method to prepare asphalt concrete capable of rapid heating and self-healing under microwave irradiation. The asphalt concrete is made from steel slag aggregates (both coarse and fine), steel slag powder, and microwave-absorbing modified asphalt. Under microwave exposure, the material's dielectric and magnetic losses convert electromagnetic energy into heat, rapidly and uniformly heating the asphalt concrete to 45-85°C. This thermal effect enables quick self-healing of the asphalt concrete through asphalt's thermal repair properties.Technical Problem
[0007] In today’s era, when global sustainability policies have become a strategic necessity for governments, industries, and development institutions, transportation infrastructures stand at the center of climate and environmental agendas.
[0008] The road construction industry is currently at a critical crossroads between two opposing pressures: on one hand, the rapid pace of urbanization, population growth, and expansion of metropolitan areas have created an increasing need for resilient and efficient road networks; on the other hand, global imperatives to reduce greenhouse gas emissions and move toward low-carbon development have forced the industry to fundamentally rethink its materials, methods, and technologies.
[0009] Roads, as the lifelines of the economy and drivers of social development, now face simultaneous pressures from rapid urban expansion, population growth, and climate change. The growing need for durable, sustainable materials coincides with the global call to reduce the carbon footprint of infrastructure projects, compelling the road construction sector to redefine its identity.
[0010] Within this context, the asphalt industry occupies a paradoxical position: while it underpins modem civilization’s mobility, it is itself a major source of greenhouse gas emissions. The conventional asphalt life cycle — from raw material extraction to production, transportation, application, and maintenance — is energy-intensive, costly, and environmentally unsustainable. Bitumen, the main component of asphalt, is derived directly from crude oil, and its hydrocarbon nature leads to both direct and indirect carbon emissions at every stage.
[0011] In recent decades, rising awareness of the climate crisis and the need for a low-carbon economy have shifted global perspectives on the asphalt industry. Governments, regulatory bodies, and the scientific community increasingly agree that traditional approaches can no longer meet future environmental and economic demands. Concepts such as Life Cycle Sustainability, Advanced Recycling, and Low-Energy Pavement Technologies have emerged as key directions for research and policymaking.
[0012] Due to population growth, a significant amount of land is used for housing, leading to the creation of cities and villages. Roads are essential for connectingthese areas, and asphalt is commonly used to pave them because it is inexpensive. However, conventional asphalt has significant drawbacks, including a short lifespan due to factors like water, sunlight, heavy vehicles, and de-icing salts, as well as various forms of cracking and rutting.
[0013] Furthermore, vehicle emissions, particularly carbon dioxide (CO2), pose a serious threat to the environment and human health. CO2is a greenhouse gas that contributes to global warming and climate change.
[0014] To address these dual challenges of short asphalt lifespan and greenhouse gas emissions, this invention presents a novel formulation. The core aim of this invention is a self-healing asphalt that utilizes CO2from vehicle exhaust. The objectives of this invention are:
[0015] a) To absorb CO2from vehicle exhaust.
[0016] b) To enable self-healing of cracks using the absorbed CO2.
[0017] c) To increase the lifespan of asphaltAdvantageous Effects of Invention
[0018] The present invention provides several technical advantages over conventional asphalt materials and production methods:
[0019] Enhanced Durability and Self-Healing:
[0020] The integration of reactive zeolite and recycled rubber particles enables autonomous healing of microcracks through mineral carbonation and bitumenrubber rejuvenation mechanisms.
[0021] This self-healing behavior substantially extends the fatigue life and service period of pavements under repeated traffic loads.
[0022] Carbon Capture and Environmental Performance:
[0023] The asphalt matrix actively reacts with CO2from ambient air or vehicle exhaust, forming stable carbonates within the binder system.
[0024] This reaction reduces the net carbon footprint of the pavement and contributes to carbon sequestration at an infrastructural scale.
[0025] Compatibility with Existing Infrastructure:
[0026] The formulation is fully compatible with existing asphalt production equipment (batch and drum plants) and standard paving processes, eliminating the need for specialized machinery or high-cost retrofitting.
[0027] Temperature and mixing parameters remain within the conventional range, ensuring seamless industrial adoption.
[0028] Resource Efficiency and Recycling:
[0029] The use of reclaimed asphalt pavement (RAP) and recycled rubber powder allows for significant reductions in virgin bitumen consumption and aggregate demand.
[0030] This supports circular economy practices and decreases the environmental impact associated with asphalt manufacturing.
[0031] Improved Mechanical and Thermal Stability:
[0032] The modified binder composition enhances resistance to rutting, thermal cracking, and oxidative aging, maintaining stable performance across a wide temperature range.
[0033] The zeolite component also improves mix workability and moisture resistance, contributing to overall pavement quality.
[0034] Reduced Maintenance and Lifecycle Costs:
[0035] The self-healing and CO2-reactive characteristics lead to longer maintenance intervals, lower repair costs, and improved service continuity in road infrastructure.
[0036] These features collectively result in substantial economic and operational efficiency for municipalities and road authorities.Brief Description of Drawings
[0037] [Fig.1 shows the behavior of CO2-activated, self-healing asphalt mixtures developed through recycling and controlled chemical activation processes.
[0038] Fig. 2 shows the Marshall test results.
[0039] Fig.3 illustrates the steps of production of a compactable asphalt mixture designed to be paved into a road surface.]Description of Embodiments
[0040] Modified Asphalt Formulation for Enhanced Performance and Sustainability
[0041] Asphalt is a widely used material in the construction industry; however, it typically requires regular maintenance, which can be costly and time-consuming. Moreover, asphalt production can have a negative environmental impact, as it commonly relies on crude oil — a nonrenewable resource — as its raw material and contributes to greenhouse gas emissions through extraction, refining, and transportation processes, exacerbating climate change as per IPCC reports on fossil fuel dependency.
[0042] In one embodiment, ranges given herein are illustrative and non-limiting; alternative ranges and values achievable by routine optimization are encompassed.
[0043] To produce the proposed modified asphalt, the formulation should be enhanced with the following components, in accordance with embodiments of the invention, wherein percentages are by weight unless otherwise specified, and all components are integrated to achieve synergistic self-healing properties protected under patent law:
[0044] 1. Recycled Rubber Powder (2.2%)
[0045] Chemical Composition: Natural and synthetic polymers (such as polybutadiene and styrene-butadiene.
[0046] Function: Improves flexibility and resistance to cracking. Recycled rubber enhances the mechanical properties of asphalt through van der Waals and hydrogen bonding with other constituents, thereby preventing crack propagation.
[0047] 2. Clinoptilolite Zeolite (5%)
[0048] Chemical Composition: Hydrated aluminosilicates containing Na+, K+, and Ca2+cations, with a typical formula of (Na,K,Ca)4AI6Si30O72-24 H2O and a Si / AI ratio of approximately 4-5.5, contributing to its ion-exchange capacity of 1.5-2.5 meq / g.
[0049] Clinoptilolite is a tectosilicate mineral — meaning its crystal structure is made of a three-dimensional framework of SiO4and AIO4tetrahedra linked by sharedoxygen atoms.This framework contains channels and cages that can host exchangeable cations (Na+, K+, Ca2+, Mg2+) and water molecules.
[0050] Function: Captures carbon dioxide and creates active sites for reaction with calcium hydroxide. Clinoptilolite zeolite, due to its porous nanostructure, can adsorb approximately 20-40 grams of CO2per kilogram of zeolite. The nanometer-sized cavities facilitate gas adsorption on the surface.
[0051] 3. Calcium Hydroxide (2.3%)
[0052] Chemical Composition: Ca(OH)2, commonly known as slaked lime, with a molecular weight of 74.09 g / mol and solubility in water of about 1.73 g / L at 20°C.
[0053] Function: Reacts with carbon dioxide to form calcium carbonate. Calcium hydroxide absorbs CO2from the environment, initiating carbonation and forming CaCO3crystals that fill cracks. Its presence within the asphalt matrix enhances adhesion and mechanical stability.
[0054] 4. Recycled Asphalt Binder (5%) - RAP Binder
[0055] Functional Role: Serves as the base binder for reconstruction and matrix phase formation.
[0056] Scientific Behavior: Recycled binder, due to its higher content and partial oxidation, exhibits greater relative polarity than virgin bitumen. This property enables more stable dispersion of mineral phases, improving the structural stability of the composite.
[0057] The chemical inertness of asphalt provides environmental stability, while its interaction with other functionalized components — such as zeolite and Ca(OH)2— creates hybrid zones of controlled reactivity.
[0058] 5. Fresh Edible Oil
[0059] Functional Role: Acts as a rejuvenator and local polarity regulator.
[0060] Scientific Behavior: Triglyceride molecules in edible oil contain ester groups that induce moderate polarity and enhance compatibility between organic and mineral phases at the nanoscale. The oil reduces viscosity, increases selfleveling capability near cracks, and provides a temporary polar medium that facilitates the carbonation reaction.
[0061] 6. Limestone Powder (Filler)
[0062] Functional Role: Controls porosity and provides a solid-phase reaction medium.
[0063] Scientific Behavior: Limestone filler not only fills voids but also chemically overlaps with Ca(OH)2and can act as a nucleation site for CaCO3crystal growth. This effect promotes uniform formation of the self-healing phase. The final dosage is determined based on RAP mix design results, typically CaCO3content >95%, with particle sizes <75 pm, facilitating heterogeneous nucleation kinetics as per Gibbs free energy models for crystal formation.
[0064] 7. Virgin Bitumen
[0065] Functional Role: Final binder for structural stabilization and viscoelastic recovery, ensuring compliance with performance-graded asphalt specifications like AASHTO M320.
[0066] Scientific Behavior: Stepwise addition of virgin bitumen after uniform dispersion of mineral-rubber components ensures a Theologically homogeneous and stable final matrix. This prevents localized clustering of Ca(OH)2and zeolite particles, ensuring uniform distribution of reactive microphases throughout the mix.
[0067] Role of Clinoptilolite Zeolite in CO2Capture
[0068] CO2Adsorption:
[0069] Clinoptilolite zeolite, due to its porous structure, adsorbs CO2molecules from the air through van der Waals interactions. Zeolites possess a well-ordered crystalline lattice and microporous cavities that enable the adsorption and storage of carbon dioxide. This process is facilitated by the difference in the partial pressure of CO2between the surrounding environment and the internal pores of the zeolite.
[0070] The mentioned percentages are expressed relative to the total mass of the asphalt mixture, and the remaining portion consists of aggregates and old and recycled mineral filler, which is used as the main solid phase.
[0071] Diffusion:
[0072] The adsorbed CO2diffuses through the asphalt matrix and reaches calcium hydroxide particles. This diffusion occurs due to concentration and pressure gradients of CO2between the environment, the zeolite structure, and the asphalt matrix.
[0073] Enhancing Asphalt Durability and Flexibility with Rubber Powder
[0074] Van der Waals and TT-TT Interactions:
[0075] Rubber powder particles form bonds with asphalt and zeolite molecules through van der Waals and TT-TT interactions. These interactions create a resilient and flexible three-dimensional network.
[0076] Flexibility and Crack Resistance:
[0077] These molecular bonds enhance flexibility and prevent crack propagation.The polymers in recycled rubber, due to their elastic nature, absorb mechanical stresses and prevent asphalt fracture and cracking, increasing fracture toughness K_IC by 20-40% as per ASTM E399, and reducing thermal cracking via low- temperature bending beam rheometer tests.
[0078] Formation and Function of Calcium Carbonate
[0079] Carbonation Reaction:
[0080] The absorbed CO2dissolves in moisture present in the environment to form carbonic acid (H2CO3).
[0081] Carbonic acid dissociates into hydrogen and bicarbonate ions.
[0082] Hydroxide ions from Ca(OH)2react with hydrogen ions to form water (H2O).
[0083] Calcium ions (Ca2+) react with carbonate ions (CO32-) to form calcium carbonate (CaCO3).
[0084] Overall reaction:
[0085] Ca(OH)2+ CO2CaCO3+ H2O
[0086] Formation of CaCO3Crystals:
[0087] Nucleation and crystal growth occur within cracks and voids, filling these spaces. CaCO3crystals, owing to their orderly crystalline structure, can readily penetrate the asphalt matrix and seal microcracks.
[0088] Van der Waals forces and mechanical interlocking form between the CaCO3crystals and the asphalt surface, strengthening the interface.
[0089] Improved Flexibility and Impact Resistance
[0090] Role of Rubber Powder:
[0091] Rubber powder particles act as elastic bridges between different regions of the asphalt. These bridges, due to their elasticity, absorb mechanical stresses and prevent crack propagation. As a result, they enhance the overall flexibility and durability of the composite system.
[0092] Beyond mechanical reinforcement, rubber powder contributes active interfacial interactions primarily through dispersive and TT-TT forces with asphaltenes and, when surface-oxidized or compatibilized, through limited hydrogen bonding and occasional chemical linkages with polar mineral surfaces (e.g., zeolite silanols) and alkaline sites (e.g., Ca(OH)2).
[0093] Reduction of Greenhouse Gases through CO2Capture
[0094] Role of Clinoptilolite Zeolite and Calcium Hydroxide:
[0095] CO2is captured by zeolite and subsequently reacts with calcium hydroxide within the asphalt structure. This process reduces atmospheric CO2concentration, thereby improving air quality and contributing to public health.The adsorption of CO2by zeolite and its conversion into CaCO3within asphalt leads to a net decrease in greenhouse gas emissions, supporting cleaner air and a more sustainable environment.
[0096] This component acts as a reactive nucleus for in-situ mineralization. Upon exposure to CO2supplied by zeolite, Ca(OH)2converts to CaCO3, which grows within micro-cracks, providing both self-healing and structural densification.
[0097] Fabrication Method
[0098] In the present invention, calcium hydroxide (Ca(OH)2) particles establish multiple physical and chemical interactions with the polar and nonpolar components of asphalt, enhancing its adhesion, stability, and structural cohesion.
[0099] Intermolecular Polar Interactions (Hydrogen Bonding):
[0100] The hydroxyl groups (-OH) in calcium hydroxide are capable of forming hydrogen bonds with polar functional groups such as carboxylic (-COOH) and hydroxyl (-OH) groups found in oxidized bitumen or asphaltic resins. These hydrogen bonds promote closer association between organic and inorganic chains, increase interfacial adhesion energy, and consequently improve the mechanical stability and structural coherence of the asphalt matrix.
[0101] Van der Waals Forces (Nonpolar Interactions):
[0102] In addition to hydrogen bonding, surface Ca2+ions and hydroxyl groups in Ca(OH)2form weak van der Waals interactions with nonpolar fractions in bitumen, such as heavy hydrocarbons and asphaltenes. Although these dispersion forces are relatively weak in energy, on a macroscopic scale they enhance interparticle adhesion and physical cohesion of the asphalt network.
[0103] Overall, the synergistic effect of hydrogen bonds and van der Waals forces strengthens the interfacial bonding between the inorganic phase (Ca(OH)2) and the organic phase (bitumen and asphaltenes) , leading to improved thermal and mechanical stability and enhanced adhesion within the self-healing asphalt matrix .
[0104] The combined polar and dispersive interactions ensure the uniform distribution of Ca(OH)2within the hydrophobic matrix, allowing stable coexistence of inorganic and organic domains
[0105] Role of Clinoptilolite Zeolite in CO2Capture
[0106] Clinoptilolite zeolite is a crystalline aluminosilicate with a three-dimensional porous framework containing microscopic channels and cavities. This ordered structure provides a very high specific surface area and exceptional gas adsorption capacity.
[0107] The adsorption of carbon dioxide occurs mainly through van der Waals and electrostatic interactions between the partial charges of CO2molecules and the cations within the zeolite framework. The driving force for this process is the partial pressure difference of CO2between the external environment and the microcavities inside the zeolite. This pressure differential causes gradual diffusionof CO2into the porous network, where molecules are held by weak but stable intermolecular forces on the internal surfaces.
[0108] The zeolite’s cation-exchange capability enhances this adsorption by transiently binding CO2to cationic sites, enabling reversible gas storage essential for sustained carbonation. Clinoptilolite zeolite contains exchangeable cations (Na+, K+, Ca2+) that can interact with polar molecules like CO2, further increasing its adsorption capacity.
[0109] After adsorption, CO2molecules move within the zeolite through concentration and pressure-driven diffusion mechanisms and are subsequently transferred into the bituminous matrix. This process is facilitated by the CO2concentration gradient between the interior and exterior of the zeolite structure.
[0110] Within the asphalt environment, CO2molecules migrate from the zeolite phase to the bituminous phase and come into contact with calcium hydroxide (Ca(OH)2) particles — initiating the carbonation reaction described below.
[0111] Interactions of Recycled Rubber Powder
[0112] Recycled rubber powder particles are primarily composed of unsaturated polymers such as polyisoprene and polybutadiene, which contain hydroxyl, carboxylic, and TT-TT double bond functional groups. These properties enable diverse intermolecular interactions with bitumen and zeolite.
[0113] The polydiene chains in rubber interact with aromatic molecules and asphaltenes in bitumen through TT-TT stacking and van der Waals forces, forming a semi-elastic three-dimensional network. This network increases internal adhesion and enhances resistance to deformation and cracking.
[0114] The elastomeric nature of rubber allows it to absorb and dissipate mechanical energy arising from vehicle loads or temperature fluctuations. This behavior improves the viscoelastic performance of asphalt and prevents crack propagation.
[0115] Polar groups on the rubber surface also form hydrogen and ionic bonds with zeolite hydroxyl groups and Ca2+ions in Ca(OH)2, promoting uniform dispersion of rubber particles within the asphalt matrix. Furthermore, the ion-exchangeproperties of zeolite prevent local agglomeration of rubber, enhancing phase stability and structural homogeneity of the asphalt composite.
[0116] Carbonation Reaction and Formation of Calcium Carbonate
[0117] Within the bituminous matrix, after the adsorption and transfer of CO2by clinoptilolite zeolite, the absorbed gas reacts with structural water within the zeolite and trapped moisture in bitumen to form carbonic acid (H2CO3):
[0118] [CO2+ H2O H2CO3]
[0119] Carbonic acid is unstable and rapidly dissociates into hydrogen (H+) and bicarbonate (HCO3“) ions.
[0120] At this stage, hydroxide ions (OH-) from Ca(OH)2react with hydrogen ions to produce water, while calcium ions (Ca2+) from Ca(OH)2combine with carbonate ions (CO32-) generated from bicarbonate dissociation to precipitate solid calcium carbonate (CaCO3):
[0121] [Ca(OH)2+ CO2CaCO3+ H2O]
[0122] Nucleation and Growth of CaCO3Crystals
[0123] The formation of calcium carbonate crystals occurs within cracks and micropores of the asphalt matrix through heterogeneous nucleation , where active calcium surfaces and zeolite-bitumen interfacial boundaries act as nucleation sites .
[0124] Under suitable temperature and pressure conditions, CaCO3crystals grow gradually, filling pores and microcracks. These crystals bond with the asphalt surface through van der Waals and hydrogen interactions, forming a robust crystalline network that enhances compressive strength and prevents the penetration of moisture and harmful gases.
[0125] The presence of this mineral phase increases local hardness, structural density, and abrasion resistance of the asphalt.
[0126] The aforementioned percentages are expressed relative to the total mass of the asphalt mixture, and the remaining portion consists of aggregates and old and recycled mineral filler, which is used as the main solid phase.
[0127] Self-Healing Mechanism and Environmental Benefits
[0128] When surface cracks appear due to traffic loading or thermal stress, zeolite particles near the cracks reabsorb atmospheric CO2, locally reactivating the carbonation process.
[0129] Consequently, new CaCO3crystals grow within the cracks, filling the voids and restoring structural continuity, extending the asphalt’s lifespan without human intervention.
[0130] In parallel, the rubber powder functions as an elastic polymeric phase that absorbs mechanical stresses and prevents further crack propagation. These particles act as physical bridges between inorganic and organic components, enhancing mechanical stability and flexibility of the entire system, in synergy with the mineral phases for multi-scale healing.
[0131] The combined presence of clinoptilolite zeolite and calcium hydroxide enables direct CO2capture from the environment and its conversion into a stable solid phase (CaCO3).This process not only prevents the return of CO2to the atmosphere but also contributes to reducing greenhouse gas concentrations and improving air quality in urban and roadway environments.
[0132] Increase in Density
[0133] Before the Healing Process:
[0134] In conventional asphalt, the presence of cracks, voids, and discontinuities leads to reduced apparent density and weakened mechanical strength. In contrast, in the CO2self-healing asphalt, the presence of recycled rubber powder and clinoptilolite zeolite fills the voids and enhances the compaction of the matrix. Rubber particles, owing to their elasticity, fill the gaps and homogenize the structure, while zeolite — with its nanometric porosity — acts as a regulator between the bituminous and mineral phases, improving microstructural density.
[0135] After the Healing Process:
[0136] During self-healing, the carbonation reaction between Ca(OH)2and the CO2absorbed by zeolite results in the formation of dense CaCO3crystals within cracked regions:
[0137] [Ca(OH) 2+ CO2^CaCO3+H2O]
[0138] These crystals grow locally inside voids and cracks, and their high density significantly increases the overall density of the asphalt. As a result, bitumen permeability decreases, and the mechanical stability of the structure improves.
[0139] Relationship Between Density and Strength:
[0140] According to Hooke’s Law and solid mechanics principles, an increase in density leads to a higher Young’s modulus (E) and greater compressive and tensile strength. Thus, the more complete the carbonation process and the higher the structural density, the greater the asphalt’s resistance to traffic and thermal stresses.
[0141] Reinforcement of the Inter-Particle Matrix
[0142] Before Healing:
[0143] In CO2self-healing asphalt, the presence of active groups and cross-reactive components strengthens the matrix network.
[0144] Matrix Reinforcement Mechanisms:
[0145] Hydrocarbon Bonds: Intermolecular dispersive forces between hydrocarbon chains, complemented by TT-TT stacking with asphaltenes, provide the primary cohesion in the bituminous matrix.
[0146] Hydrogen Bonds: Polar groups such as carboxylic (-COOH) and hydroxyl (- OH) in asphalt form hydrogen bonds with similar groups in other phases (including zeolite and calcium hydroxide surfaces), enhancing interfacial adhesion energy.
[0147] Zeolite, as an active mineral phase, plays a crucial role in facilitating carbonation reactions and CO2transfer within the asphalt matrix. The micropores of zeolite adsorb CO2and deliver it at the nanoscale to reaction zones, where Ca(OH)2transforms into CaCO3. The resulting crystals behave like micro-cement particles, increasing adhesion, stability, and resistance to tensile and compressive stresses.
[0148] Rubber particles serve as elastic physical bridges between the organic and mineral components, forming semi-continuous networks in the bituminous matrixthat prevent crack propagation. The presence of polar groups (e.g., -OH) on the rubber surface promotes bonding with bitumen and zeolite surfaces, mechanically reinforcing the structure.
[0149] After Healing:
[0150] Following the chemical reactions and the formation of CaCO3crystals within the cracks, the self-healing asphalt matrix becomes significantly stronger than conventional recycled asphalt. The newly formed mineral bonds, combined with the rubber polymer network, produce a hybrid (mineral-polymeric) structure that simultaneously exhibits high strength, appropriate flexibility, and fracture resistance.
[0151] Final Fabrication Process of CO2Self-Healing Asphalt
[0152] Process conditions and proportions may be varied within ordinary skill to accommodate different RAP contents, aggregate gradations, and climatic conditions, without departing from the scope.
[0153] The fabrication process of CO2-based self-healing asphalt is designed around the controlled activation of recycled materials and chemical interactions.Optimization of temperature, mixing time, and the sequence of material addition plays a critical role in ensuring structural uniformity and phase stability.
[0154] Step 1 - Preparation of Reclaimed Asphalt Pavement (RAP)(10):
[0155] RAP samples are dried under controlled conditions at standard temperatures (typically 105-110 °C) to remove moisture without oxidizing or burning the aged bitumen. Careful temperature ramping prevents excessive hardening and preserves the original rheological properties as shown in Fig. 3.
[0156] Table 1 -Optimum Gradation Table for Reclaimed Asphalt Pavement (RAP)
[0157] The optimal particle size distribution to achieve maximum density, minimum moisture penetration, improved compressive strength, and increased durability in freeze-thaw cycles.
[0158] The gradation table defines the optimal particle size distribution in the asphalt mix, determined by the percentage passing through sieves of varying sizes. This optimal gradation ensures that coarse and fine aggregates pack efficiently, minimizing voids and maximizing mix density. High compaction enhances compressive and shear strength while reducing water permeability, thereby improving resistance to freeze-thaw cycles and extending pavement life.
[0159] Step 2 - Bitumen Rejuvenation (20):
[0160] Aged bitumen in RAP is rejuvenated using fresh edible oil as a bio-based softening agent, added at about 9.5 wt% of the aged bitumen. The mixture is heated for two hours at a controlled temperature in an oven. During this process, the chemical structure of the bitumen is restored, and its viscoelastic behavior becomes comparable to that of fresh bitumen.
[0161] Step 3 - Quality Evaluation of Rejuvenated Bitumen(30):
[0162] The extracted bitumen is tested following ASTM D36 (softening point) and ASTM D4402 (high-temperature viscosity). Changes in rheological parameters and softening point indicate the success of the rejuvenation process.
[0163] Step 4 - Addition of Fresh Bitumen and Mineral Filler(40):
[0164] Based on the mix design and residual bitumen content in RAP, a calculated amount of fresh bitumen and limestone powder (as filler) are added. Continuous mixing ensures uniform coating of aggregate and RAP particles and proper bonding between old and new phases.
[0165] Step 5 - Addition of Recycled Rubber Powder(50):
[0166] Rubber powder (0.5-1 mm particle size, 2.2 wt% of total mix) is added at 160-170 °C and mixed for 20-30 minutes. Partial dissolution of rubber in thebituminous phase promotes TT-TT interactions between rubber and asphaltenes. Rubber improves elasticity, absorbs thermal and mechanical stresses, and enhances crack resistance.
[0167] Step 6 - Addition of Clinoptilolite Zeolite(60):
[0168] Zeolite particles (0.1 -0.5 mm, %5 wt) are added and mixed at 160-170 °C for 10-15 minutes to ensure uniform distribution. With its porous structure, zeolite acts as a CO2and structural moisture adsorbent and provides a microenvironment for carbonation reactions in the bituminous matrix.
[0169] In one embodiment, zeolite serves as the main adsorbent material. However, its surface can be functionalized with amine groups to enhance CO2adsorption capacity. The presence of these amine functionalities allows for both physical and chemical adsorption (physicochemical adsorption) mechanisms.
[0170] Step 7 - Addition of Calcium Hydroxide(70):
[0171] Fine Ca(OH)2particles (0.05-0.1 mm, %2.3 wt) are added and mixed at MO- ISO °C for 5-10 minutes. Strict temperature control prevents premature reactions. Ca(OH)2acts both as a reactive mineral phase for carbonation and as an interfacial bonding enhancer between the bituminous and zeolitic phases.
[0172] Step 8 - Final Adjustment of Rheological Properties(80):
[0173] An additional %1.5 wt of fresh bitumen (as show in Step 2) is added to improve flowability and achieve a uniform distribution throughout the matrix.
[0174] Step 9 - Molding and Compaction (90):
[0175] Samples are prepared following the Marshall method. The mix is placed into Marshall molds and compacted with 75 blows per face to achieve standard air voids (Air Voids) and voids in mineral aggregate (VMA). After cooling, samples are tested for mechanical and rheological properties.
[0176] Final Industrial Implementation:
[0177] At the asphalt plant, precise control of temperature, humidity, and mixing time is critical. After preparation, the mix is transported to the construction site and compacted in two stages: first with a vibratory steel roller for initial compaction,and then with a pneumatic roller for final densification. The layer thickness, surface temperature, and final density must conform to the design specifications.
[0178] Environmental and Functional Advantages
[0179] The above composition and process achieve the objectives of the invention — not only improving asphalt performance but also contributing to environmental protection by utilizing exhaust CO2as a useful resource for healing cracked asphalt. CO2capture and retention are core features of this advanced asphalt, reducing the negative impact of carbon emissions on the environment.
[0180] This process functions independently of mechanical self-healing and can be considered an inherent property of the asphalt. The proposed design allows the pavement to self-repair, reducing maintenance needs. The use of CO2as a healing agent represents a sustainable and eco-friendly approach that helps mitigate greenhouse gas emissions.
[0181] In conventional concrete and cement systems, the use of carbon dioxide (CO2) to enhance mechanical properties or achieve surface self-healing is a well- established phenomenon, based on the carbonation reaction occurring in mineral-based and hydrophilic environments. In such systems, hydrated phases such as Ca(OH)2and C-S-H react with dissolved CO2in water to form calcium carbonate (CaCO3), a process that increases density and reduces porosity in the concrete surface zone. As reported in classical carbonation studies of concrete, this reaction takes place only in moist and alkaline environments and is inherently dependent on CO2diffusion through water and the presence of a mineral phase.
[0182] In contrast, in asphalt systems, the matrix is entirely organic and hydrophobic, and there exists no thermodynamic or kinetic pathway for the natural occurrence of carbonation reactions. Bitumen, as a complex organic matrix, blocks the penetration of CO2and water, making replication of mineral carbonation reactions — such as those in concrete — scientifically impossible or highly improbable before the present invention.
[0183] The fundamental innovation of this invention lies in the design of a reactive mineral microenvironment embedded within the bituminous phase, which enables CO2reactivity in an organic medium for the first time. This three-phase system consists of:
[0184] Natural zeolite (as an adsorbent and carrier of CO2and moisture),
[0185] Calcium hydroxide (as a reactive calcium source), and
[0186] Recycled rubber powder (as a semi-permeable polymeric phase bridging between bitumen and the mineral phase).
[0187] Within this confined environment, zeolite can store and release CO2and moisture through its porous structure, thereby enabling the mineral reaction that converts Ca(OH)2into CaCO3inside an organic, nonpolar matrix. In this configuration, carbonation occurs not only at the surface but also throughout the material and within microcracks, where the resulting mineral products contribute in situ to both chemical and physical self-healing. Thus, the proposed system replaces a surface aqueous reaction with a controlled carbonation process in an organic medium, which is mechanistically and chemically distinct from prior art.
[0188] It is worth emphasizing that although zeolite has been used in some types of concrete as a natural mineral additive or pozzolanic material, its role there is entirely different. In concrete systems, zeolite mainly acts as an ion absorber and hydration accelerator — it plays no role in CO2transport or in activating carbonation in an organic medium, since carbonation in concrete depends on the presence of water and mineral Ca(OH)2. In the present invention, zeolite serves as an active carrier of CO2and moisture within a hydrophobic bitumen matrix, enabling a mineral reaction to occur in an organic environment. This function is entirely novel and unexpected, representing the transfer of a known mechanism into a previously incompatible environment.
[0189] This invention represents a fundamental transformation in the chemical behavior of bituminous systems by transferring the CO2reaction mechanism from a hydrophilic, mineral environment to a hydrophobic, organic one. Such a transformation is not achieved by a simple combination of known components but through the design of a reactive microenvironment with controlled phase distribution and surface energy interactions. Therefore, the system demonstrates not only functional innovation (self-healing in an organic medium) but also conceptual innovation (enabling a mineral reaction in an organic phase), constituting a fundamental inventive step in asphalt material science.
[0190] In this invention, two types of asphalt mixtures with different compositions and characteristics were prepared, labeled as M and N:
[0191] Sample M: A CO2-activated self-healing asphalt, containing a high percentage of reclaimed asphalt pavement (RAP) and mineral modifiers designed to enhance mechanical performance and durability. This type of asphalt can absorb CO2and activate self-healing reactions to resist cracking.
[0192] Sample N: A control asphalt consisting of purified reclaimed asphalt produced by the same method but without the modifiers. This represents a standard high - RAP asphalt mixture.
[0193] In this invention, the Resilient Modulus and Total Recoverable Horizontal Deformation of the RAP-based asphalt samples were evaluated. The specimens were prepared through a nine-step process, including controlled drying, rejuvenation of aged bitumen with vegetable oil, addition of fresh bitumen and mineral filler, mixing with rubber powder, addition of clinoptilolite zeolite and calcium hydroxide, rheological adjustment with new bitumen, and Marshallstandard molding. These steps ensured adequate compaction, strong adhesion between old and new phases, and high viscoelastic stability.
[0194] The resilient modulus test was conducted using five cycles of repeated load application, measuring the following parameters:
[0195] Total Resilient Modulus,
[0196] Total Recoverable Horizontal Deformation,
[0197] Applied Repeated Load, and
[0198] Separate Recoverable Horizontal Deformations (two measurements).
[0199] Results showed that the resilient modulus of the samples ranged between 7050 and 8545 MPa, with an average of 7885 MPa, a standard deviation of 609.62, and a coefficient of variation of 7.73%, indicating uniformity and stability of mechanical properties. The total recoverable horizontal deformation ranged from 0.38 to 0.47 pm, with an average of 0.42 pm and a coefficient of variation of 8.21%, reflecting the samples’ ability to recover after loading.
[0200] This behavior is attributed to the preserved viscoelastic response of rejuvenated bitumen and the effective bonding among asphalt particles, rubber,and zeolite. The individual recoverable horizontal deformations were in the range of 0.12-0.26 m, showing higher relative variation (12.56% and 21.19%), which reflects sensitivity to particle distribution and phase compatibility within the samples. The applied load during testing remained nearly constant at 378.6 N, with a standard deviation of 2.87 and a coefficient of variation of 0.76%, confirming the accuracy and repeatability of the test and the uniform mechanical performance of the asphalt specimens.
[0201] Table 2- Indirect Tensile Resilient Modulus (M) and Recoverable Horizontal Deformations per Pulse0202] The results show that the total resilient modulus of the samples ranges from 5263 to 5464 MPa , with an average value of 5384 MPa , a standard deviation of 76.23 , and a coefficient of variation (CV) of 1.42%. This value is lower than that of the previous samples with a higher modulus (7885 MPa), which may be due to differences in aggregate composition, the residual bitumen content in RAP, or the effect of additives. However, the low coefficient of variation indicates high uniformity of mechanical properties and good control over the preparation process.
[0203] The total recoverable horizontal deformation remained constant at 0.7 pm across all loading pulses, demonstrating stable and repeatable behavior of the samples under applied loads. This indicates that the specimens were able to fully recover their shape after loading and exhibited stable viscoelastic behavior.
[0204] The applied load during the test averaged 392.7 N , with a standard deviation of 5.56 and a coefficient of variation of 1.42%, confirming high accuracy and control of loading conditions during testing.
[0205] The individual recoverable horizontal deformations also provided interesting results. For #1 , the values ranged between 0.09 and 0.18 pm, with an average of 0.12 pm and a coefficient of variation of 27.39%, indicating that this parameter is more sensitive to local variations compared to previous samples. In contrast, #2 exhibited values between 0.53 and 0.62 pm, with a coefficient of variation of 5.48% , reflecting greater stability and representing a more consistent and reliable material behavior under loading.
[0206] Table 3- Indirect Tensile Resilient Modulus (N) and Recoverable Horizontal Deformations per Pulse
[0207] Interpretation of the Fatigue Behavior Graph
[0208] As shown in Fig. 1 , the presented graph evaluates the fatigue behavior of CO2-activated, self-healing asphalt mixtures developed through recycling and controlled chemical activation processes using modern additives.
[0209] The horizontal axis represents the number of load cycles (fatigue cycles) until specimen failure.
[0210] The vertical axis (logarithmic scale) typically shows the remaining strength or stiffness ratio (e.g., dynamic modulus or stress-to-strain ratio) during testing.
[0211] Four distinct datasets are displayed: before-m, after-m, before-n, and after-n, each corresponding to different modification or additive conditions.
[0212] Scientific Interpretation of the Curves
[0213] Before-m(empty square):
[0214] This curve lies mostly above the others, showing a gradual stiffness reduction in the asphalt samples before the addition of self-healing modifiers . The steady decline over high cycles reflects normal fatigue behavior and progressive stiffness loss.
[0215] After-m(full square):
[0216] After modification (e.g., CO2-activated formulation or addition of rejuvenating oil), the after-m curve shows a slower stiffness reduction, particularly in early cycles. This indicates activation of self-healing mechanisms and partial recovery of mechanical properties.
[0217] Before-n(full dot ) and after-n(empty triangle) :
[0218] These curves belong to samples under different modification or loading conditions (e.g., different oil content or varying rubber / mineral additive ratios). They appear generally lower on the vertical axis, reflecting initially lower stiffness. The significant difference between before-n and after-n highlights notable fatigue improvement and delayed crack initiation after chemical or structural modification.
[0219] Mechanistic and Chemical Analysis
[0220] The modified samples (after-m and after-n) exhibit improved fatigue life due to the formation of a physicochemical network among renewable additives (vegetable oil, rubber powder, zeolite, and calcium hydroxide) and the bitumen matrix.
[0221] This network enhances stress absorption and energy dissipation at crack tips, preventing the spread of secondary cracks.
[0222] The faster decline of the before-n curve relative to before-m is associated with weaker adhesion of aged bitumen and the absence of a structural support phase.
[0223] The key feature of the after-n samples is the reduced slope of the curve at higher cycles, indicating the occurrence of self-healing mechanisms — closure of microcracks through phase migration or gradual CO2and oil release to crack surfaces.
[0224] The addition of zeolite and calcium hydroxide supports dry carbonation reactions, resulting from CO2adsorption and stronger mineral-bitumen bonding, leading to delayed failure and improved durability.
[0225] Moisture Sensitivity Test (Latent Modified Lottman)
[0226] Results of the Latent Modified Lottman test indicate that Sample M (2) performs better than Sample N (1).
[0227] The dry strength of sample M is 12.58 kN, and its wet strength is 10.45 kN,
[0228] While sample N shows 11.54 kN(dry) and 8.82 kN(wet).
[0229] The Tensile Strength Ratio (TSR) is 76.43% for sample N and 83.07% for sample M, indicating lower moisture sensitivity and better performance of sample M in wet conditions.
[0230] These results demonstrate that the modifications in sample M increased the overall strength of the asphalt and reduced the negative effects of moisture, making it more stable and suitable for humid environments.
[0231] Table 4- Moisture Sensitivity (Modified Lottman Test)
[0232] Marshall Test Results
[0233] As shown in Fig.2, the Marshall test results show that sample M has higher stability and lower flow than sample N.
[0234] Stability (M): 24.12 kN
[0235] Stability (N): 21.43 kN
[0236] This indicates that asphalt mixture M exhibits greater load-bearing capacity .
[0237] Meanwhile,
[0238] Flow (M): 3.1 mm
[0239] Flow (N): 3.7 mm
[0240] This shows that sample M is stiffer and more stable, exhibiting less deformation under loading.
[0241] The combination of higher stability and lower flow confirms the improved mechanical properties and durability of sample M compared to sample N,demonstrating the positive effect of the proposed chemical and structural modifications in the asphalt formulation.
[0242] Based on the scientific analyses conducted, the self-healing asphalt behaves under various temperature and humidity conditions as follows:
[0243] At 70 °C and 5% humidity:Reactions occur faster, but the lack of moisture may impose limitations. The self- healing performance remains effective, though not optimal.
[0244] At 70 °C and 95% humidity:Reactions occur rapidly, and sufficient water is available to facilitate chemical interactions. The self-healing performance is optimal under these conditions.
[0245] At -40 °C and 5% humidity:Reactions proceed very slowly, and the materials may become brittle. However, the rubber powder in the formulation helps maintain flexibility.
[0246] At -40 °C and 95% humidity:Reactions are slow, and the available water freezes. The asphalt’s flexibility is preserved by the recycled rubber powder.
[0247] Overall, this asphalt performs well across different environmental conditions.Under high temperature and humidity, its self-healing ability is optimal. Under low temperature and low humidity, its performance decreases but remains acceptable due to the chosen formulation. To further improve performance in harsh conditions, additives such as humectants and temperature-regulating agents can be employed.
[0248] Tensile and Compressive Strength
[0249] Self-healing asphalt with CO2demonstrates significantly higher tensile and compressive strength compared to 100% recycled asphalt, due to its unique chemical and physical mechanisms.
[0250] 1. Increased Density
[0251] Before healing:
[0252] Conventional asphalt has lower density because of the presence of voids and cracks.
[0253] In contrast, CO2-based self-healing asphalt has higher density due to the inclusion of recycled rubber powder and clinoptilolite zeolite.
[0254] The recycled rubber powder fills the voids and cracks, while the zeolite compacts the asphalt structure.
[0255] After healing:
[0256] The density of CO2-based self-healing asphalt increases significantly compared to conventional asphalt.
[0257] This improvement results from the formation of CaCO3crystals through carbonation between Ca(OH)2and CO2absorbed by the zeolite.
[0258] The high-density CaCO3crystals further increase the overall density of the asphalt.
[0259] Relationship between density and strength:According to Hooke’s Law, tensile and compressive strength are directly proportional to material density. This means that the denser the material, the greater its resistance to compressive and tensile stresses.
[0260] 2. Matrix Reinforcement
[0261] Before healing:
[0262] The matrix of recycled asphalt is weaker due to the lack of strong bonding between asphalt particles.
[0263] In contrast, CO2-based self-healing asphalt forms stronger matrices through hydrocarbon and hydrogen bonds between asphalt particles.
[0264] Matrix reinforcement mechanisms:
[0265] Hydrocarbon bonds: Hydrocarbon molecules in the recycled asphalt interconnect through hydrocarbon linkages, strengthening the matrix.
[0266] Hydrogen bonds: Carboxylic (-COOH) and hydroxyl (-OH) groups in the asphalt molecules form hydrogen bonds, further reinforcing the matrix.
[0267] Role of clinoptilolite zeolite:Zeolite facilitates the carbonation reaction by absorbing CO2and releasing it gradually within the asphalt matrix, promoting CaCO3crystal formation at cracksites. These crystals act like cement, enhancing structural cohesion and increasing compressive and tensile strength.
[0268] Role of recycled rubber powder:Rubber particles create physical bonds with the asphalt matrix, further improving mechanical strength and flexibility.
[0269] After healing:The matrix of CO2-based self-healing asphalt becomes significantly stronger than that of recycled asphalt.
[0270] This improvement results from CaCO3crystal formation due to the carbonation reaction between Ca(OH)2and CO2absorbed by zeolite.
[0271] The crystals act like cement, enhancing structural integrity.
[0272] Additionally, the chemical reactions among Ca(OH)2, CO2, and clinoptilolite zeolite create stronger bonds between asphalt particles.
[0273] Environmental and Functional Benefits
[0274] The combination of the above mechanisms achieves the invention’s goals — not only preserving the environment but also utilizing exhaust CO2emissions for the rejuvenation of cracked asphalt.CO2absorption and retention are key features of this advanced asphalt, helping mitigate the negative environmental effects of greenhouse gas emissions.
[0275] This process functions independently of the self-healing mechanism and can be considered a core feature of the asphalt. The proposed design allows asphalt pavements to repair themselves, reducing the need for frequent maintenance.
[0276] Using CO2as a resource for self-healing represents a sustainable and eco- friendly approach, contributing to lower greenhouse gas emissions and longer pavement life.Industrial Applicability
[0277] The invention is industrially applicable in the field of road construction and pavement materials, where it can be readily integrated into existing asphalt production and paving processes without the need for specialized equipment. The incorporation of clinoptilolite zeolite and recycled rubber powder enablescontinuous absorption of atmospheric CO2and in-situ formation of calcium carbonate, providing self-healing and strengthening effects within the asphalt matrix. This multifunctional material enhances pavement durability, flexibility, and resistance to cracking while simultaneously contributing to carbon capture and emission reduction. The process is compatible with conventional asphalt plants and can utilize reclaimed asphalt and industrial by-products, ensuring economic efficiency, environmental sustainability, and large-scale feasibility in commercial and municipal infrastructure applications, i
Claims
Claims
1. Self-healing asphalt using carbon dioxide, comprising:Recycled rubber powder comprising natural and synthetic polymers, configured to form van der Waals and hydrogen bonds with asphaltic components;Clinoptilolite zeolite, comprising hydrated aluminosilicates, having a porous crystalline framework, configured to adsorb carbon dioxide from ambient air; Calcium hydroxide, configured to react with the adsorbed CO2to form calcium carbonate crystals that fill cracks and enhance matrix cohesion;Recycled asphalt binder, serving as the base binder for matrix formation;Fresh edible oil functioning as a rejuvenator;Limestone filler acting as a nucleation site for calcium carbonate crystal growth; andVirgin bitumen to provide final rheological stabilization and viscoelastic recovery; wherein the clinoptilolite zeolite and calcium hydroxide synergistically enable in- situ carbonation under ambient conditions.
2. The self-healing asphalt composite of claim 1 , wherein the edible oil contains triglycerides with oleic and linoleic acid chains.
3. A method for producing a carbon dioxide-responsive self-healing asphalt composite, comprising the steps of:drying reclaimed asphalt pavement at 105-110 °C under controlled conditions to remove moisture without oxidizing the aged bitumen;rejuvenating the aged bitumen in the RAP by adding approximately 9.5 wt % of edible oil relative to the aged bitumen mass and heating the mixture for about two hours;adding fresh bitumen and limestone filler to the rejuvenated RAP mixture and mixing until uniform coating of aggregates is achieved;incorporating recycled rubber powder, maintaining the mixture at 160-170 °C for 20-30 minutes to promote TT-TT and van der Waals interactions between the rubber and bitumen phases;introducing clinoptilolite zeolite mixing at 160-170 °C for 10-15 minutes to achieve uniform dispersion, wherein the zeolite functions as a CO2and moisture adsorbent;adding fine calcium hydroxide (Ca(OH)2) particles and mixing at 140-150 °C for 5-10 minutes to create a reactive mineral phase;adjusting rheological properties by incorporating an additional 1.5 wt % of fresh bitumen to ensure flowability and uniformity;molding and compacting the prepared mixture using the Marshall method; and allowing carbonation to occur in the compacted asphalt under ambient environmental exposure, wherein CO2captured by the zeolite reacts with Ca(OH)2to form CaCO3, thereby filling cracks and enhancing matrix cohesion.
4. The method of claim 3, wherein the zeolite is clinoptilolite functionalized with amine groups to enhance CO2adsorption capacity by combining physical and chemical adsorption mechanisms.
5. The method of claim 3, wherein carbonation occurs both on the surface and within microcracks of the asphalt matrix, forming CaCO3crystals that act as microstructural bridges and restore mechanical integrity.
6. The method of claim 3, wherein recycled rubber powder provides an elastic polymeric network that bridges inorganic (Ca(OH)2and zeolite) and organic (bitumen) phases, improving fatigue life and crack resistance under cyclic loading by 20—40%.