Self-heating asphalt mixture filler and use method thereof

Abstract

The invention belongs to the technical field of road engineering pavement materials, and particularly relates to a self-heating type asphalt mixture filler and a use method thereof.According to the self-heating type asphalt mixture filler, under the condition that aluminum powder and magnesium powder are not used, CaO serves as an ignition agent, and on the basis of providing initial high-temperature softening RAP old asphalt, the self-heating type asphalt mixture filler is obtained; the reaction efficiency of the iron powder is improved through the composite effect of activated carbon and NaCl, the temperature range of 80-150 DEG C can be reached, the temperature of 130 DEG C or above is maintained for half an hour or above, and the workability of the mixture is improved. Moreover, the particle size is controlled, it is ensured that the filler can be well wrapped with asphalt, reaction uniformity and mass transfer efficiency can be guaranteed, filler function integration is achieved, the filler is a heat source and is also a permanent filler, and the reaction product Ca (OH) 2 is an excellent filler, has micro-expansibility, can be beneficial to gap filling and can be used for filling asphalt. The water stability is improved.

Description

Technical Field

[0001] This invention belongs to the field of road engineering pavement materials technology, specifically relating to a self-heating asphalt mixture filler and its application method. Background Technology

[0002] Self-heating materials are high-tech products that generate heat autonomously through internal chemical reactions or special material properties, requiring no external energy source. These products are widely used in medical care, warmth and health maintenance, food heating, and many other fields. Based on their heating principle, they are mainly divided into two categories: chemical heating technology (utilizing the oxidation reaction between substances such as iron powder, aluminum powder, and calcium oxide with water to release heat) and material heating technology (using tourmaline, special fibers, or thin-sheet heating elements to achieve continuous heating through water absorption and heat release or precise temperature control, widely used in medical patches, warmth products, and other fields).

[0003] Chinese patent document CN111892336A (202010741047.9) discloses a self-heating warm-mix asphalt repair material and its construction method. Although the self-heating material used in this technical solution achieves self-heating, it contains aluminum powder and magnesium powder, thus posing significant safety hazards. Furthermore, the self-heating material only has a heating function, its material function is singular, and it does not consider compatibility with filler gradation; moreover, the heating process of the self-heating material only involves adding water, lacking temperature control. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a self-heating asphalt mixture filler and its application method. This invention utilizes chemical heating technology, applying the self-heating filler to asphalt mixtures (especially recycled RAP). The process involves: aggregates (especially RAP) at room temperature + self-heating filler + dry premix + water (or emulsified asphalt) → heat release → improved workability of the mixture → molding / paving. The self-heating filler of this invention effectively releases heat, is compatible with asphalt mixture systems (especially fillers), and does not affect the final performance. The self-heating filler of this invention achieves a self-heating effect during production through the triggering agent water, assisting in (or aiding in) aggregate heating. It offers advantages such as reduced production energy consumption, environmental friendliness, non-toxicity, and no degradation of the asphalt mixture's material properties.

[0005] The technical problem to be solved by the present invention is achieved by the following technical solution: a self-heating asphalt mixture filler, comprising the following components by mass fraction: quicklime 50-65%, iron powder 18-22%, activated carbon 8-12%, NaCl 1-3%, and mineral powder 8-20%; The iron powder is reduced iron powder with a purity of ≥98.5%, and is coated with calcium stearate; In the filler, the component with a particle size ≤0.075mm accounts for 75-95%, and the component with a particle size of 0.075-0.30mm accounts for 5-25%. The total mass percentage of all components in the self-heating asphalt mixture filler is 100%.

[0006] This invention employs a quicklime system with the highest cost-effectiveness and thermal efficiency, using CaO as an "igniter" to provide initial high-temperature softening of old RAP asphalt, and supplemented by an iron powder system to maintain continuous temperature and improve the workability of the mixture.

[0007] Quicklime (CaO) reacts with water rapidly and at high temperatures (above 90°C), and the reaction product Ca(OH)₂ can itself serve as a mineral filler. The iron powder system exhibits a milder reaction, producing Fe(OH)₃ with minimal environmental impact, but its thermal efficiency is lower. The self-heating of iron powder is essentially an electrochemical corrosion process. This invention utilizes the synergistic effect of a composite catalyst of activated carbon and NaCl to improve both the reaction rate and thermal efficiency.

[0008] Reduced iron powder, rather than atomized iron powder, is selected to avoid premature oxidation and failure; the purity is ≥98.5%, otherwise sulfur and phosphorus impurities will corrode the asphalt; the surface treatment uses calcium stearate coating, which has an anti-oxidation effect; the activity testing method meets the quantitative index of a temperature rise ≥0.5℃ / s over 30 seconds. The use of calcium stearate coating is existing technology and will not be described further in this invention.

[0009] Preferably, the filler with a particle size ≤0.075mm comprises 100% quicklime, 100% iron powder, 100% NaCl, and 70% mineral powder. The 0.075-0.30mm composition includes 100% activated carbon and the remainder mineral powder.

[0010] Preferably, the quicklime particle size of this invention is 75-150 μm; The particle size distribution of iron powder meets the following requirements: D10≥5μm, D50=15±3μm, D90≤25μm. Powder that can pass through a 325-mesh standard sieve, i.e., with a particle size of less than 44μm, is generally referred to as sub-sieve powder.

[0011] Preferably, the mineral powder in this invention comprises limestone powder and silica. Silica is used to increase the adhesion of fillers, minerals, and asphalt. The mineral powder serves as a carrier in this invention, primarily comprising limestone powder; those skilled in the art can select suitable mineral powder materials as needed.

[0012] Preferably, the present invention also includes 0.6% boric acid to ensure that the H2 concentration is <0.1% LEL (one-tenth of the lower explosive limit), reflecting the ultimate safety considerations.

[0013] This invention also discloses a method for using the above-mentioned self-heating asphalt mixture filler, comprising the following steps: (1) Uniform premixing: The self-heating asphalt mixture filler is 5%~10% of the total weight of the asphalt mixture. The aggregate and the dry self-heating asphalt mixture filler are fully and uniformly dry-mixed using a mixing device. The mixing device is a mixing machine, and asphalt concrete mixing plants are used for large-scale production. (2) Gradient triggering technology: In the first stage, during the mixing process, 40% of the water is added by ultrasonic atomization to trigger CaO heating, and the temperature rises to 85℃ within 2 minutes; In the second stage, during the mixing process, 60% of the water is added in a columnar spray, and the mixed material is simultaneously assisted by air blowing to activate the Fe reaction and continuously raise the temperature to 130℃. (3) Onset time: The temperature starts to rise 30-60 seconds after adding water, with a peak temperature of 150±5℃, which can be maintained for 15 minutes; (4) The mixing is completed in the temperature range of 80-150℃, and the effective molding / rolling time at a temperature of ≥130℃ is ≥30min.

[0014] In the preferred embodiment of the present invention, in step (2), the droplet size of the ultrasonically atomized water is ≤50μm, the O2 concentration during blowing is ≥23%, and the blowing flow rate is 3m³ / min, so as to improve the reaction efficiency.

[0015] In the preferred embodiment of the present invention, in step (2), the amount of water added is 115-125% of the mass of the self-heating asphalt mixture filler, so as to ensure sufficient reaction while avoiding the presence of free water after the reaction.

[0016] Preferably, in step (1) of this invention, the aggregate includes recycled asphalt pavement milling material.

[0017] Preferably, in step (1) of this invention, the dry mixing time is more than 30 seconds.

[0018] The reaction principle of this invention: Quicklime (calcium oxide, CaO) is the main material. The reaction is: CaO + H₂O → Ca(OH)₂ + heat. The reaction is rapidly exothermic, with temperatures reaching over 90℃. Its advantages are low cost and high efficiency, but careful handling is required to avoid burns.

[0019] Iron powder (Fe). Iron powder reacts with water and oxygen (similar to the rusting process): 4Fe + 3O₂ + 6H₂O → 4Fe(OH)₃ + heat. The reaction is mild and long-lasting, suitable for prolonged heating at approximately 60-80°C. This invention utilizes a salt catalyst (such as sodium chloride) to accelerate the reaction.

[0020] Table 1 Chemical Reaction Equations

[0021] Table 2 Advantages and disadvantages of main materials

[0022] The self-heating material described in Chinese patent document CN111892336A (202010741047.9) uses aluminum powder (Al) and magnesium powder (Mg), as shown in Tables 1 and 2. Although aluminum powder and magnesium powder react violently and generate high heat, they are prone to producing hydrogen gas (which poses an explosion risk). Hydrogen inhibitors need to be added, which can easily affect the performance of asphalt and is not conducive to cost control. Therefore, this invention does not use magnesium / aluminum-based materials for heating.

[0023] While iron powder is safe, improving its reaction efficiency to ensure sufficient heat generation is a key challenge this invention addresses. Based on the fact that the iron powder reaction is an electrochemical reaction, this invention increases the oxidation efficiency of iron powder by adding NaCl, building upon activated carbon catalysis. Furthermore, iron powder oxidation requires a sufficient oxygen supply; therefore, during the mixing process, this invention utilizes a blower to ensure ample contact between oxygen and the iron powder, providing the necessary oxygen for the reaction and further improving reaction efficiency. This also enables effective control of the temperature rise process.

[0024] The present invention also incorporates water addition in stages based on the needs of different reaction stages, and fully controls the amount of water added to ensure the achievement of the target temperature.

[0025] This invention achieves temperature increase without utilizing aluminum and magnesium powder, ensuring safety. Furthermore, by limiting the particle size of the self-heating asphalt mixture filler, this invention ensures compatibility with the filler gradation.

[0026] Compared with the prior art, the beneficial effects of the present invention are: This invention relates to a self-heating asphalt mixture filler that, without using aluminum or magnesium powder, uses CaO as an "igniter" to provide initial high-temperature softening of old RAP asphalt. Furthermore, it utilizes the combined effect of activated carbon and NaCl to enhance the reaction efficiency of iron powder, achieving a temperature range of 80-150°C and maintaining a temperature above 130°C for more than half an hour, thus improving the workability of the mixture. In addition, this invention controls the particle size to ensure that the filler can effectively coat the asphalt while maintaining reaction uniformity and mass transfer efficiency. It also achieves integrated filler function, serving as both a heat source and a permanent filler. The reaction product, Ca(OH)₂, is itself an excellent filler with micro-expansion properties, potentially helping to fill voids and improve water stability.

[0027] The essence of this invention is the process of "the conversion of the enthalpy change of a chemical reaction into the internal energy of asphalt mixture". This invention takes a different approach and a fresh perspective, developing atypical road surface materials, breaking through the traditional asphalt mixture production and processing technology, and providing a disruptive (innovative) material and process with great practicality and promotional value.

[0028] The self-heating asphalt mixture filler of this invention is used at a rate of 5% to 10% of the total weight of the asphalt mixture. When all materials of the asphalt pavement are at room temperature, the self-heating asphalt mixture filler of this invention is prepared according to the mixing ratio. With the help of a triggering agent (water), the mixed asphalt mixture can be self-heated to 80°C to 150°C, achieving the effects of easy mixing and construction. This provides a more reliable method (process) for application scenarios such as cold patch construction and RAP precast component molding. Detailed Implementation

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below.

[0030] This embodiment discloses a self-heating asphalt mixture filler and its application method, which is used to prepare asphalt mixtures containing recycled asphalt pavement milling material (RAP) at room temperature, especially for the production of asphalt precast components or the paving of low traffic volume road surface layers.

[0031] This invention involves dry mixing aggregate (or RAP) with self-heating filler at room temperature; adding water in stages to the dry-mixed mixture to trigger heat release; utilizing the released heat to improve the workability of the mixture; and compacting the mixture into shape within the effective period of the heat.

[0032] In this invention, the formulation of the self-heating asphalt mixture filler is as follows: a self-heating filler mainly composed of quicklime (CaO) system and supplemented with iron powder (Fe) system to maintain a continuous temperature. The material proportions are as follows: quicklime (CaO) accounts for 50-65%, iron powder (Fe) accounts for 18-22%, activated carbon accounts for 8-12%, NaCl accounts for 1-3%, and mineral powder (carrier) accounts for 8-20%, as shown in Table 3. According to the proportions in Table 3, efficient heating can be achieved and a continuous high temperature can be maintained.

[0033] Table 3 Material Functions, Proportions, and Calorific Value Calculation

[0034] Note: The calorific value of the iron powder marked with "*" is the actual value after composite catalysis (theoretical value 7340kJ / kg × 85% efficiency).

[0035] Based on the heat contribution ratio, CaO dominates the temperature rise to 85℃ in the first 2 minutes → the iron powder maintains a plateau at 130℃ for ≥15 minutes thereafter.

[0036] 0-90 seconds: 25℃→92℃ (CaO dominant, heating rate 0.74℃ / s).

[0037] 90-300 seconds: 92℃→130℃ (Fe dominant, heating rate 0.16℃ / s).

[0038] 300-1200 seconds: Maintain at 130±3℃.

[0039] Self-heating fillers are designed to match the gradation requirements and mineral properties of asphalt fillers, as well as their heating function.

[0040] To ensure compatibility between the self-heating asphalt mixture filler and its gradation, this invention controls the particle size: in the self-heating composite filler, the component with a particle size ≤0.075mm accounts for 75-95%, and the component with a particle size of 0.075-0.30mm accounts for 5-25%. The fine component (≤0.075mm) includes 100% CaO, 100% Fe, 100% NaCl, and 70% mineral powder within this range; the coarse component (0.075-0.30mm) includes activated carbon, mineral powder, etc.

[0041] The particle size of quicklime should be 75-150μm.

[0042] The particle size distribution of iron powder meets the following requirements: D10≥5μm, D50=15±3μm, D90≤25μm (generally, powder that can pass through a 325-mesh standard sieve, i.e., with a particle size of less than 44μm, is called sub-sieve powder).

[0043] Safety measures: The statement excludes aluminum / magnesium powder systems (to avoid controversy over explosion risks) and adds 0.6% boric acid to inhibit hydrogen (H2 < 0.1% LEL).

[0044] The self-heating material system of this invention comprises two independent exothermic reactions (CaO hydration and Fe oxidation), the thermal effects of which need to be calculated separately and then superimposed. The goal is to raise the temperature of the mixture from room temperature (25°C) to 130°C.

[0045] In this embodiment, the self-heating asphalt mixture filler (hereinafter referred to as "self-heating filler") of the present invention is used to mix warm recycled AC-13 asphalt mixture. Under conditions without external heating, the room temperature material is heated to above 130°C, that is, the temperature change AT is 130-25=105K. The following calculations are based on the mixing of AC-13 asphalt mixture as an example (aggregate mass 1000kg, asphalt-aggregate ratio 5.0%): Based on mass composition, the ratio of warm-mix recycled AC-13, RAP (combined old asphalt content of 4.5%): new aggregate: self-heating filler is 90%: 2%: 8%, and the asphalt-aggregate ratio is 5.0% (modified emulsified asphalt), as shown in Table 4.

[0046] Table 4. Composition and Proportion of Mixture

[0047] 1. Calculate the total heat capacity Qreq of the mixture (i.e., the heat required to raise the temperature by 1°C). According to the thermodynamic calculation formula: Qreq=(m agg ×c agg +m bit ×c bit )×AT; Parameter description: m agg (Mineral quality); c agg =0.84 kJ / kg·K (specific heat capacity of mineral materials, including aggregates and fillers); m bit (Asphalt quality); c bit =1.76kJ / kg·K (specific heat capacity of asphalt); AT=105K (temperature change); specific heat capacity of water is 4.18kJ / kg·K (since the self-heating filler is solid before the reaction, its specific heat capacity is calculated based on the mineral material of 0.84).

[0048] 2. Calculate the total heat requirement (total heat capacity × AT) That is, the total heat required = [mass of mineral materials (including aggregates and fillers) + asphalt] × specific heat capacity × ΔT.

[0049] When the proportion of self-heating filler is 6.0%, that is, 60 kg.

[0050] Therefore, the total mass of the ore is 959.5 kg.

[0051] Total heat required = [959.5 × 0.84 + 50.42 × 1.76] × 105 = 93945.55 kJ.

[0052] 3. Calculate the actual heat release of the self-heating packing (based on the mixing ratio). The reaction formula for quicklime (CaO): CaO + H₂O → Ca(OH)₂; Enthalpy change of reaction: ΔH = -1125 kJ / kg (CaO); Water consumption ratio: 1 kg of CaO requires 0.32 kg of water; Therefore, the calorific value of the quicklime (CaO) system is 1125 kJ / kg.

[0053] The reaction formula for iron powder is: 4Fe + 3O₂ + 6H₂O → 4Fe(OH)₃; Enthalpy change of reaction: ΔH = -1640kJ / (4×55.85)g = -1640kJ / 223.4g → -7340kJ / kg (Fe); The iron powder system requires a catalyst (NaCl + activated carbon) to achieve a complete reaction, which is affected by the catalytic efficiency. A correction factor of 0.85 is used. Effective calorific value = 7340 × 0.85 = 6239 kJ / kg (Fe); Water consumption ratio: 1 kg of Fe requires 0.48 kg of water; Oxygen consumption ratio: 1 kg of Fe requires 0.43 kg of oxygen; Therefore, the calorific value (including catalysis) of the iron powder (Fe) system is 6239 kJ / kg (under the catalysis of NaCl and activated carbon, the actual efficiency is 85%, so the actual heat release is 6239 kJ / kg).

[0054] Note: Iron powder releases heat and requires oxygen. Assume that air is blown in during the mixing process, and there is sufficient oxygen.

[0055] When the proportion of self-heating filler is 8.0%, that is, 80 kg.

[0056] Therefore, the heat released by the self-heating packing is 80 × (0.55 × 1125 + 0.18 × 6239) = 139341.6 kJ.

[0057] 4. Comparison of actual heat release and total heat demand The influence of other components in the filler: mineral powder (limestone powder), specific heat capacity 0.84 kJ / (kg·K), participates in heat absorption, and heat loss can be included; activated carbon does not directly release heat in the reaction, but its mass needs to be included; the heat capacity of trace amounts (<5%) of NaCl is negligible.

[0058] Heat loss correction: The heat loss rate during the mixing process is taken as 30% (due to the lack of insulation measures).

[0059] Actual heat release required (kJ) = Total heat required / (1-0.3) = 97539.12 kJ.

[0060] Based on the above calculations, the actual heat release of 97539.12 > the total heat demand of 93945.55, resulting in a heat surplus of 3.8%, which meets the heating demand.

[0061] Therefore, the solution is entirely feasible, and the key lies in the control of material particle size and the gradient water addition process.

[0062] 5. Water supply This example also demonstrates the need to add sufficient water to trigger the reaction. Based on the previous calculations, the amount of water to be added is 1.2 times the mass of the filler (i.e., 80 kg of filler requires 96 kg of water). However, RAP contains water (up to 27 kg), and emulsified asphalt also contains 6.6 kg of water, so the actual amount of additional water required should be reduced by this amount.

[0063] Actual added water volume = (1.2 × mass of self-heating filler) - (RAP water content + water in emulsified asphalt).

[0064] The RAP contains less than 27 kg (3%) of water, and the emulsified asphalt contains 6.6 kg of water. Therefore: When the self-heating filler is 80kg, the theoretical total water requirement is 96kg. The maximum existing water is 27 + 6.6 = 33.6kg. Therefore, the actual additional water is 96 - 33.6 = 62.4kg.

[0065] Based on the above thermodynamic calculations, the heat release value of the self-heating asphalt mixture filler and the actual heat release required to raise the ambient temperature mixture to the effective mixing temperature (e.g., 130°C) can be obtained. By applying the law of conservation of energy and the material ratio of this invention, the amount of self-heating asphalt mixture filler to be added can be determined comprehensively.

[0066] As shown in Table 5, after testing, the self-heating asphalt mixture filler used in this embodiment as an asphalt mixture filler meets the road technical specifications requirements for fillers.

[0067] Table 5. Test data of self-heating asphalt mixture filler

[0068] The test was conducted in accordance with the relevant test procedures for fillers in the "Test Procedures for Aggregates in Highway Engineering" (JTG 3432—2024). The test results are shown in the table above. This invention's self-heating filler composite road filler meets the test requirements.

[0069] Table 6. Quantitative Comparison of Energy Conservation, Emission Reduction, and Carbon Reduction Benefits

[0070] The core value of this invention is to use the exothermic chemical properties of materials to replace the heating of fossil fuels, thus propelling the field of asphalt recycling into the "zero external heat era" and achieving a quadruple breakthrough of "energy saving, emission reduction, carbon reduction, and cost reduction," which aligns with the national dual-carbon goals.

[0071] As shown in Table 6, the present invention utilizes the self-heating of the packing (CaO hydration + Fe oxidation) to achieve a temperature rise of 130℃, which can significantly reduce energy consumption, avoid the high-temperature heating (160-180℃) required for traditional RAP thermal regeneration, save a lot of fuel or electricity consumption, and directly reduce CO2 emissions.

[0072] By using the filler of this invention to assist in the production (or mixing) of asphalt mixtures, the heating energy consumption in asphalt mixture production is reduced. Compared with traditional processes, energy consumption is reduced by 80.7%, and CO2 emissions are reduced by 40.5 kg / ton of mixture.

[0073] It also reduces the emission of harmful gases and avoids the asphalt fumes (containing harmful substances such as benzo[a]pyrene) produced by heating asphalt at high temperatures and the exhaust gas from fuel combustion.

[0074] This invention also improves the utilization rate of RAP: by improving workability, it can increase the application of high-proportion RAP (even 100% RAP) in low-grade roads or precast components, reducing the consumption of natural resources and waste landfill.

[0075] The reaction product, Ca(OH)₂, possesses slight expansibility and a certain degree of activity, which may help fill voids or slightly improve water stability. Fe(OH)₃ is an inert substance and does not affect the material properties of asphalt mixtures.

[0076] The target temperature rise of this invention should be sufficient to soften and make the old asphalt on the RAP surface viscous (typically in the range of 80-120°C), which is sufficient to ensure the coating and bonding between new material (if added) or RAP particles, facilitating compaction. Reaching the temperature of hot-mix asphalt (160-180°C) is not required.

Claims

1. A self-heating asphalt mixture filler, characterized in that, The composition includes the following components by mass fraction: quicklime 50-65%, iron powder 18-22%, activated carbon 8-12%, NaCl 1-3%, and mineral powder 8-20%. The iron powder is reduced iron powder with a purity of ≥98.5%, and is coated with calcium stearate; In the filler, the component with a particle size ≤0.075mm accounts for 75-95%, and the component with a particle size of 0.075-0.30mm accounts for 5-25%.

2. The self-heating asphalt mixture filler according to claim 1, characterized in that: The filler with a particle size ≤0.075mm includes 100% quicklime, 100% iron powder, 100% NaCl, and 70% mineral powder. The 0.075-0.30mm composition includes 100% activated carbon and the remainder mineral powder.

3. The self-heating asphalt mixture filler according to claim 1, characterized in that, Quicklime particle size must be 75-150μm; The iron powder particle size distribution satisfies: D10≥5μm, D50=15±3μm, D90≤25μm.

4. The self-heating asphalt mixture filler according to claim 1, characterized in that: The mineral powder includes limestone powder and silicon dioxide.

5. The self-heating asphalt mixture filler according to claim 1, characterized in that: It also includes 0.6% boric acid.

6. A method of using the self-heating asphalt mixture filler according to any one of claims 1 to 5, characterized in that, Includes the following steps: (1) Uniform premixing: The self-heating asphalt mixture filler is 5%~10% of the total weight of the asphalt mixture. The aggregate and the dry self-heating asphalt mixture filler are thoroughly and uniformly dry-mixed using a mixing device. (2) Gradient triggering: In the first stage, during the mixing process, 40% of the water is added by ultrasonic atomization to trigger the heating of CaO; In the second stage, during the mixing process, 60% of the water is added in a columnar spray, and the mixed materials are simultaneously assisted by air blowing to activate the Fe reaction. (3) Onset time: The temperature begins to rise 30-60 seconds after water is added; (4) Mixing is completed in the temperature range of 80-150℃.

7. The method of using the self-heating asphalt mixture filler according to claim 6, characterized in that: In step (2), the droplet size of the ultrasonically atomized water is ≤50μm, the O2 concentration is ≥23% during blowing, and the blowing flow rate is 3m³ / min.

8. The method of using the self-heating asphalt mixture filler according to claim 6, characterized in that: In step (2), the amount of water added is 115-125% of the mass of the self-heating asphalt mixture filler.

9. The method of using the self-heating asphalt mixture filler according to claim 6, characterized in that: In step (1), the aggregate includes recycled asphalt pavement milling material.

10. The method of using the self-heating asphalt mixture filler according to claim 6, characterized in that: In step (1), the dry mixing time is more than 30 seconds.

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