Asphalt mixture

Abstract

To provide an asphalt composition which is excellent in filling properties, has no problem in workability, and can form asphalt pavement excellent in durability.SOLUTION: The asphalt composition contains a semi-carbonized material derived from nonwoven fabric products, the semi-carbonized material containing 50 to 90 mass% of asphalt and volatile components and 7 to 40 mass% of a fixed carbon content.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an asphalt mixture and a method for producing the same, an asphalt composition, and a road paving method. [Background technology]

[0002] Asphalt pavement, which uses asphalt mixture, is used for paving roads, parking lots, freight yards, sidewalks, etc., because it is relatively easy to lay and the time from the start of paving work to the start of traffic is short. Asphalt pavement has a road surface formed from an asphalt mixture in which aggregate is bound with asphalt, the paved road has good hardness and durability.

[0003] However, asphalt pavement surfaces deteriorate over time and require repair, which increases maintenance costs and has a significant impact on automobile traffic. For example, Patent Document 1 discloses an asphalt composition that is obtained by blending specific cellulose fibers with asphalt, as an asphalt composition that enables the production of asphalt pavement with excellent rutting resistance and fatigue crack resistance.

[0004] On the other hand, the amount of organic waste is increasing year by year. Technologies for carbonizing organic waste have been developed, and various applications of the resulting carbonized materials are being investigated. For example, Patent Document 2 discloses a method for producing a carbonized material, which comprises contacting waste material containing a superabsorbent resin that has absorbed moisture containing chloride with an aqueous solution containing at least one of water-soluble phosphates or sulfates to remove chloride ions from the waste material, and then heating the waste material for carbonization after removing the chloride ions. It also discloses that the carbonized material obtained can be effectively used as a soil conditioner, a water purification treatment agent, a building material such as a heat insulating material, an adsorbent, a detoxifier, a deodorant, a raw material for disposable hand warmers, a fuel, activated carbon as described below, and the like.

[0005] Furthermore, there is a technology for utilizing the carbonized material obtained by carbonizing organic waste in a carbonization device as road paving materials, including asphalt. For example, Patent Document 3 discloses an asphalt mixture obtained by mixing predetermined amounts of heated aggregate of various particle sizes, stone powder, and molten asphalt to obtain an asphalt mixture, and then mixing the mixture with a predetermined amount of carbonized material obtained by carbonizing organic waste. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2019-210384 A [Patent Document 2] Patent Publication No. 2022-21365 [Patent Document 3] JP 2003-184013 A Summary of the Invention [Problem to be solved by the invention]

[0007] The technology described in Patent Document 1 improves the dispersibility of cellulose fibers in the asphalt composition, and an asphalt composition can be obtained that enables the creation of asphalt pavements with excellent rutting resistance and fatigue crack resistance. However, since it is necessary to use specific cellulose fibers, further study is desirable from the viewpoint of ease of availability, etc. Regarding the use of organic waste, even if it is carbonized, the amount of consumption is limited for uses such as those described in Patent Document 2 above, and so new uses that can be expected to allow for mass consumption are desired. Patent Document 3 does not consider at all the durability of asphalt pavement, such as resistance to rutting.

[0008] In addition, asphalt mixtures for forming asphalt pavements are required to have a certain level of workability, such as packing ability. Packing ability can be improved, for example, by increasing the heating temperature during the manufacturing process and / or construction process, but this increases the fuel consumption. Therefore, other means for improving workability, such as packing ability, are desirable.

[0009] The present invention relates to an asphalt mixture that utilizes semi-carbonized material derived from a nonwoven fabric product and can form an asphalt pavement that is excellent in filling, has no problems with workability, and is excellent in durability, a method for producing the same, an asphalt composition, and a road paving method. [Means for solving the problem]

[0010] The present invention relates to the following <1> ~ <4> Regarding. <1> An asphalt mixture containing asphalt, aggregate, and semi-carbonized material derived from a nonwoven fabric product having a volatile matter content of 50% by mass or more and 90% by mass or less and a fixed carbon content of 7% by mass or more and 40% by mass or less. <2> A method for producing an asphalt mixture, comprising the steps of mixing asphalt, heated aggregate, and semi-carbonized material derived from a nonwoven fabric product having a volatile matter content of 50% by mass or more and 90% by mass or less and a fixed carbon content of 7% by mass or more and 40% by mass or less. <3> An asphalt composition comprising asphalt and semi-carbonized material derived from a nonwoven fabric product having a volatile matter content of 50% by mass or more and 90% by mass or less and a fixed carbon content of 7% by mass or more and 40% by mass or less. <4> the above <1> A road paving method comprising a step of applying the asphalt mixture according to claim 1 to a road to form an asphalt pavement layer. Effect of the Invention

[0011] According to the present invention, there is provided an asphalt composition which is excellent in filling properties, has no problems with workability, and is capable of providing an asphalt pavement which is excellent in durability. [Brief description of the drawings]

[0012] [Figure 1]FIG. 1 shows the configuration of a furnace used in the production of semi-carbide, which has a stirring blade for stirring, a heater, and a blower mechanism. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] [Asphalt mixture] The asphalt mixture of the present invention contains asphalt, aggregate, and semi-carbonized material derived from a nonwoven fabric product having a volatile matter content of 50% by mass or more and 90% by mass or less and a fixed carbon content of 7% by mass or more and 40% by mass or less. The inventors have discovered that an asphalt mixture containing semi-carbonized material derived from a nonwoven fabric product having a volatile content of 50% by mass or more and 90% by mass or less and a fixed carbon content of 7% by mass or more and 40% by mass or less can provide an asphalt pavement that has excellent filling properties, no problems with workability, and excellent durability.

[0014] An asphalt pavement having excellent durability also has excellent rutting resistance, for example. The rutting resistance of an asphalt pavement can be evaluated, for example, by a wheel tracking test shown in the examples described later.

[0015] The filling property of the asphalt mixture can be evaluated, for example, by measuring the void ratio shown in the examples described later. Filling ability is also called compaction degree, and an asphalt mixture with excellent filling ability (compaction degree) produces an asphalt pavement with excellent surface appearance and with less occurrence of hair cracks (microcracks).

[0016] <Asphalt> As the asphalt contained in the asphalt mixture of the present invention, various asphalts can be used. The asphalt is preferably asphalt that has never been used for asphalt pavement (also called virgin asphalt or unused asphalt). On the other hand, used asphalt derived from recycled asphalt aggregate can also be used in combination. Specific examples of asphalt include straight asphalt, which is petroleum asphalt for paving, as well as modified asphalt. Modified asphalt includes blown asphalt; polymer modified asphalt modified with polymeric materials such as thermoplastic elastomers and thermoplastic resins. Straight asphalt is a residual bituminous material obtained by subjecting crude oil to atmospheric distillation equipment, vacuum distillation equipment, etc. Blown asphalt means asphalt obtained by heating a mixture of straight asphalt and heavy oil, and then blowing air into the mixture to oxidize it. The asphalt is preferably selected from straight asphalt and polymer modified asphalt, and from the viewpoint of durability of asphalt pavement, polymer modified asphalt is more preferable, and from the viewpoint of versatility, straight asphalt is more preferable. Asphalt modified with thermoplastic elastomer is more preferable. The modified asphalt is preferably a polymer modified asphalt, more preferably a polymer modified asphalt modified with a thermoplastic elastomer.

[0017] (Thermoplastic elastomer) Examples of the thermoplastic elastomer in the polymer modified asphalt modified with a thermoplastic elastomer include styrene / butadiene block copolymers, styrene / butadiene / styrene block copolymers, styrene / butadiene random copolymers, styrene / isoprene block copolymers, styrene / isoprene / styrene block copolymers, styrene / isoprene random copolymers, ethylene / vinyl acetate copolymers, ethylene / acrylic acid ester copolymers, styrene / ethylene / butylene / styrene copolymers, styrene / ethylene / propylene / styrene copolymers, polyurethane-based thermoplastic elastomers, polyolefin-based thermoplastic elastomers, isobutylene / isoprene copolymers, polyisoprene, polychloroprene, synthetic rubbers other than those mentioned above, and at least one selected from natural rubber. The thermoplastic elastomer in the modified asphalt is preferably at least one selected from styrene / butadiene block copolymers, styrene / butadiene / styrene block copolymers, styrene / butadiene random copolymers, styrene / isoprene block copolymers, styrene / isoprene / styrene block copolymers, styrene / isoprene random copolymers, ethylene / vinyl acetate copolymers, and ethylene / acrylic acid ester copolymers. Among these, from the viewpoint of durability of asphalt pavement, the thermoplastic elastomer is preferably at least one selected from styrene / butadiene block copolymers, styrene / butadiene / styrene block copolymers, styrene / butadiene random copolymers, styrene / isoprene block copolymers, styrene / isoprene / styrene block copolymers, styrene / isoprene random copolymers, and ethylene / acrylic acid ester copolymers, more preferably styrene / butadiene block copolymers, styrene / butadiene / styrene block copolymers, styrene / butadiene random copolymers, styrene / isoprene block copolymers, and styrene / isoprene random copolymers. At least one selected from the group consisting of styrene / butadiene random copolymers and styrene / butadiene / styrene block copolymers is more preferred. From the viewpoint of durability and surface appearance of the asphalt pavement, the content of thermoplastic elastomer in the polymer modified asphalt is preferably 0.1 mass% or more, more preferably 0.5 mass% or more, even more preferably 1 mass% or more, and preferably 30 mass% or less, more preferably 20 mass% or less, even more preferably 10 mass% or less.

[0018] <Aggregate> The aggregate may be selected from any of the following: crushed stone, boulders, gravel, sand, ceramics, etc. In addition, the aggregate may be a coarse aggregate having a particle size of 2.36 mm or more, a fine aggregate having a particle size of 0.075 mm or more and less than 2.36 mm, or a filler having a particle size of less than 0.075 mm. Examples of coarse aggregate include crushed stone with a particle size range of 2.36 mm or more and less than 4.75 mm, crushed stone with a particle size range of 4.75 mm or more and less than 12.5 mm, crushed stone with a particle size range of 12.5 mm or more and less than 19 mm, and crushed stone with a particle size range of 19 mm or more and less than 31.5 mm. Examples of fine aggregates include river sand, dune sand, mountain sand, sea sand, crushed sand, fine sand, screenings, crushed stone dust, silica sand, artificial sand, glass cullet, and foundry sand. The particle size of coarse aggregate and fine aggregate is based on the sieve analysis test method specified in JIS A5001:2008.

[0019] Examples of the filler include sand, fly ash, calcium carbonate powder such as limestone powder, hydrated lime, etc. Among these, calcium carbonate powder is preferred from the viewpoint of durability of the asphalt pavement. From the viewpoint of durability of the asphalt pavement, the average particle size of the filler is preferably 0.001 mm or more, and preferably 0.05 mm or less, more preferably 0.03 mm or less, and even more preferably 0.02 mm or less. Here, the average particle size is the average particle size at 50% cumulative volume (D 50 ) and can be measured using a laser diffraction particle size distribution analyzer.

[0020] As the aggregate, it is preferable to use a combination of coarse aggregate and fine aggregate. In this case, from the viewpoint of the durability of the asphalt pavement, the mass ratio of the coarse aggregate to the fine aggregate is preferably 10 / 90 or more, more preferably 15 / 85 or more, even more preferably 20 / 80 or more, and is preferably 90 / 10 or less, more preferably 80 / 20 or less, even more preferably 70 / 30 or less.

[0021] The aggregate may include recycled asphalt aggregate. Recycled asphalt aggregate is made by collecting used asphalt pavement, crushing it, and classifying it. The used asphalt pavement from which the recycled asphalt aggregate is derived contains asphalt and aggregate, and may contain other additives as needed.

[0022] The physical and chemical properties of the asphalt contained in recycled asphalt aggregate are deteriorated compared to new asphalt due to the influence of environmental factors such as heat and light. The physical and chemical properties of asphalt can be evaluated by measuring the penetration, softening point, bending strength, strain at break, asphalt composition, etc. In general, asphalt in which the maltene fraction in asphalt has migrated to asphaltene and the penetration has decreased is often called deteriorated asphalt. However, even if the penetration of recycled asphalt is the same as that of new asphalt, it may not be able to perform the same as new asphalt due to changes in other properties.

[0023] The asphalt mixture from which the used asphalt pavement is derived contains aggregate. The asphalt mixture from which the used asphalt pavement is derived itself uses recycled asphalt aggregate as an aggregate. Examples of such aggregate include aggregates commonly used in asphalt mixtures for road paving, such as crushed stone, boulders, gravel, sand, and ceramics.

[0024] <Semi-carbonized materials derived from nonwoven fabric products> The asphalt composition of the present invention contains semi-carbonized material derived from a nonwoven fabric product having a volatile matter content of 50% by mass or more and 90% by mass or less and a fixed carbon content of 7% by mass or more and 40% by mass or less. Semi-carbonized materials derived from nonwoven fabric products refer to components that have been produced by subjecting raw nonwoven fabric products to relatively low-temperature heat treatment to reduce moisture content to almost zero, while still retaining as little combustible material (energy) as possible.

[0025] From the viewpoints of durability and workability, the volatile matter content of the semi-carbonized material is 50 mass% or more and 90 mass% or less, preferably 55 mass% or more, more preferably 60 mass% or more, and preferably 85 mass% or less, more preferably 80 mass% or less, relative to the total mass of the semi-carbonized material (100 mass%). Volatile matter is a combustible component in the semi-charred material, which generates combustible gases, mainly consisting of hydrocarbon gases, when heated. The volatile matter content can be measured in accordance with the method described in JIS M8812:2006 "Coals and cokes - proximate analysis method."

[0026] From the viewpoints of durability and workability, the fixed carbon content of the semi-carbide is, relative to the total mass of the semi-carbide (100 mass%), 7 mass% or more and 40 mass% or less, preferably 8 mass% or more, more preferably 10 mass% or more, and preferably 35 mass% or less, more preferably 30 mass% or less. The fixed carbon content can be measured in accordance with the method described in JIS M8812:2006 "Coals and cokes - proximate analysis method."

[0027] The semi-carbonized material contains almost no moisture due to the semi-carbonization process. For example, the moisture content is 0.01% by mass or less relative to the total mass of the semi-carbonized material (100% by mass). From the viewpoints of durability and workability, the fuel ratio of the semi-carbide [fixed carbon (mass%) / volatile matter (mass%)] is preferably 0.08 or more, more preferably 0.1 or more, and is preferably 0.8 or less, more preferably 0.6 or less. Semi-carbide is differentiated from carbide which has a high fuel ratio and is completely carbonized.

[0028] In the present invention, the semi-carbonized material is a semi-carbonized material derived from a nonwoven fabric product. The nonwoven fabric constituting the nonwoven fabric product is, as defined in JIS L 0222:2022, a planar fiber assembly in which a predetermined level of structural strength is imparted by physical and / or chemical methods. The fiber components constituting the nonwoven fabric are preferably fiber components made of a thermoplastic resin, more preferably fiber components made of a thermoplastic resin such as polyesters such as polyethylene terephthalate (PET) and polyolefins such as polyethylene (PE) and polypropylene (PP). The fiber components made of a thermoplastic resin are preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more, and 100% by mass or less of the fiber components constituting the nonwoven fabric. Examples of fiber components other than the thermoplastic resin include natural fibers such as pulp fibers and cotton fibers; and regenerated fibers such as rayon. Preferable specific examples of such nonwoven fabrics include air-through nonwoven fabrics, point-bonded nonwoven fabrics, spun-bonded nonwoven fabrics, spun-laced nonwoven fabrics, three-dimensionally shaped nonwoven fabrics, and composite materials of combinations of two or more of these.

[0029] Preferred examples of nonwoven fabric products include absorbent articles such as diapers for infants or adults, sanitary napkins, panty liners, and urine pads. Absorbent articles, which are nonwoven fabric products, typically have a surface material and an absorbent body made of a nonwoven fabric. The absorbent body typically has an aggregate of pulp fibers or an aggregate of pulp fibers and a highly water-absorbent polymer material.

[0030] When fiber components such as pulp and rayon are mixed in the asphalt pavement in hopes of improving its durability, the fiber components have a high polarity and tend to not disperse sufficiently in the asphalt, resulting in agglomeration of the fibers. As a result, the filling property is insufficient and workability is poor. As in the present invention, by using semi-carbonized material derived from nonwoven fabric products, particularly semi-carbonized material derived from absorbent articles, it is believed that the fiber components such as pulp and rayon contained in the nonwoven fabric products are uniformly dispersed in the asphalt, and an asphalt mixture can be obtained that can provide an asphalt pavement with excellent filling properties, no problems in workability, and excellent durability. More specifically, it is presumed that the fiber components of thermoplastic resins such as polyethylene and polypropylene that constitute the nonwoven fabric melt during the production of the semi-carbonized material and coat the fiber components such as pulp and rayon. It is believed that the fiber components of the thermoplastic resins that have a high affinity with asphalt are interposed, improving the compatibility of asphalt with fiber components such as pulp and rayon, enabling fine dispersion, and thus providing an asphalt pavement with excellent filling properties, no problems in workability, and excellent durability.

[0031] The method for producing semi-carbonized materials is not limited as long as it can produce semi-carbonized materials having a volatile matter content of 50% by mass or more and 90% by mass or less and a fixed carbon content of 7% by mass or more and 40% by mass or less, and the semi-carbonized materials can be produced by a process of heating the raw materials at a predetermined low temperature.

[0032] For example, the semi-carbonized material is produced by placing the non-woven fabric product, which is the raw material, in a furnace and carbonizing the raw material by heating. The heating is performed by increasing the temperature from room temperature to the heating temperature and then maintaining the temperature after the heating temperature is reached. The heating temperature is preferably 150° C. or higher, more preferably 200° C. or higher, and is 400° C. or lower, more preferably 300° C. or lower. The rate of temperature rise from room temperature to the heating temperature is preferably 0.1° C. / min or more, more preferably 0.3° C. / min or more, and is preferably 5° C. / min or less, more preferably 3° C. / min or less. The heating time can be appropriately set so as to obtain semi-carbonized material, and is preferably 1 hour or more, more preferably 2 hours or more, and preferably 6 hours or less, more preferably 5 hours or less. The heating time is the time for which the temperature is maintained after the heating temperature is reached. The heating is preferably carried out in the absence of contact with air. After the heating is completed, air or nitrogen can be circulated through the furnace to promote cooling of the resulting torrefied material. The temperature decreasing rate for cooling is preferably 0.05° C. / min or more, more preferably 0.1° C. / min or more, and is preferably 3° C. / min or less, more preferably 1° C. / min or less.

[0033] In the production of semi-carbide, it is preferable to carry out the production while stirring the raw materials. This is because semi-carbide that has lost moisture is generally brittle, and the semi-carbide obtained by stirring is crushed and obtained as granules.

[0034] The semi-carbide can be produced using a carbonization furnace. More specifically, a shaft furnace, a kiln, etc. can be mentioned.

[0035] <Additives> The asphalt mixture of the present invention can contain, in addition to the asphalt, aggregate, and semi-carbonized material described above, various additives that have been conventionally used in asphalt mixtures, such as film-forming agents, thickening stabilizers, emulsifiers, etc., as necessary.

[0036] <Polyester resin> As an example of an additive that can be further contained, a polyester resin will be described. The polyester resin is a polycondensation product of an alcohol component and a carboxylic acid component, and contains a structural unit derived from an alcohol component and a structural unit derived from a carboxylic acid component. The polyester resin may be an amorphous polyester resin or a crystalline polyester resin, and is preferably an amorphous polyester resin. The alcohol component and the carboxylic acid component will be described below.

[0037] (Alcohol content) Examples of the alcohol component include an aliphatic diol, an alicyclic diol, an aromatic diol, a trihydric or higher polyhydric alcohol, etc. These alcohol components may be used alone or in combination of two or more kinds.

[0038] The aliphatic diol is preferably a linear or branched aliphatic diol having 2 to 12 carbon atoms in the main chain, and more preferably a linear or branched aliphatic diol having 2 to 8 carbon atoms in the main chain. Also, the aliphatic diol is preferably a saturated aliphatic diol. Specific examples of aliphatic diols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,4-butenediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 1,10-decanediol, and 1,12-dodecanediol.

[0039] Examples of alicyclic diols include hydrogenated bisphenol A (2,2-bis(4-hydroxycyclohexyl)propane), alkylene oxide adducts of hydrogenated bisphenol A, cyclohexanediol, and cyclohexanedimethanol.

[0040] Examples of aromatic diols include bisphenol A (2,2-bis(4-hydroxyphenyl)propane) and alkylene oxide adducts of bisphenol A. Examples of alkylene oxide adducts of bisphenol A include alkylene oxide adducts of bisphenol A represented by the following formula (I).

[0041] [ka]

[0042] [In the formula, OR 1 and R 1 O is an alkylene oxide, and R 1 is an alkylene group having 2 or 3 carbon atoms, x and y are positive numbers indicating the average number of moles of alkylene oxide added, and the sum of x and y is preferably 1 or more, more preferably 1.5 or more, and is preferably 16 or less, more preferably 8 or less, and even more preferably 4 or less.

[0043] Examples of the alkylene oxide adduct of bisphenol A represented by formula (I) include a propylene oxide adduct of bisphenol A and an ethylene oxide adduct of bisphenol A. These alkylene oxide adducts of bisphenol A can be used alone or in combination of two or more kinds.

[0044] The trihydric or higher polyhydric alcohol is preferably a trihydric alcohol, and examples of the trihydric or higher polyhydric alcohol include glycerin, pentaerythritol, trimethylolpropane, and sorbitol.

[0045] The alcohol component may further contain a monohydric aliphatic alcohol from the viewpoint of adjusting physical properties. Examples of the monohydric aliphatic alcohol include lauryl alcohol, myristyl alcohol, palmityl alcohol, and stearyl alcohol. These monohydric aliphatic alcohols may be used alone or in combination of two or more.

[0046] (Carboxylic acid component) Examples of the carboxylic acid component include aliphatic dicarboxylic acids, aromatic dicarboxylic acids, and polyvalent carboxylic acids having a valence of 3 to 6. These carboxylic acid components can be used alone or in combination of two or more.

[0047] Examples of the aliphatic dicarboxylic acid include aliphatic dicarboxylic acids having a main chain carbon number of preferably 4 or more and preferably 10 or less, more preferably 8 or less, and more preferably 6 or less, such as fumaric acid, maleic acid, oxalic acid, malonic acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, succinic acid substituted with an alkyl group having 1 to 20 carbon atoms or an alkenyl group having 2 to 20 carbon atoms, or anhydrides thereof, and alkyl esters thereof (e.g., alkyl groups having 1 to 3 carbon atoms). Examples of the substituted succinic acid include dodecylsuccinic acid, dodecenylsuccinic acid, and octenylsuccinic acid.

[0048] Examples of aromatic dicarboxylic acids include phthalic acid, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, anhydrides thereof, and alkyl esters thereof (for example, alkyl groups having 1 to 3 carbon atoms). Among the above aromatic dicarboxylic acids, isophthalic acid and terephthalic acid are preferred, and terephthalic acid is more preferred, from the viewpoints of suppressing aggregate scattering and water resistance.

[0049] The polyvalent carboxylic acid having a valence of 3 to 6 is preferably a trivalent carboxylic acid. Examples of the polyvalent carboxylic acid having a valence of 3 to 6 include trimellitic acid, 2,5,7-naphthalenetricarboxylic acid, pyromellitic acid, and acid anhydrides thereof.

[0050] The carboxylic acid component may further contain a monovalent aliphatic carboxylic acid from the viewpoint of adjusting physical properties. Examples of the monovalent aliphatic carboxylic acid include monovalent aliphatic carboxylic acids having 12 to 20 carbon atoms, such as lauric acid, myristic acid, palmitic acid, stearic acid, and alkyl (having 1 to 3 carbon atoms) esters of these acids. These monovalent aliphatic carboxylic acids may be used alone or in combination of two or more kinds.

[0051] (Structural unit derived from polyethylene terephthalate) The polyester resin may contain ethylene glycol-derived structural units and terephthalic acid-derived structural units derived from polyethylene terephthalate. The polyethylene terephthalate may contain small amounts of components such as butanediol and isophthalic acid in addition to the structural units derived from ethylene glycol and terephthalic acid. The polyethylene terephthalate is preferably recycled polyethylene terephthalate. When the polyester resin contains structural units consisting of ethylene glycol and terephthalic acid derived from polyethylene terephthalate, the "structural units derived from an alcohol component" contain structural units derived from ethylene glycol derived from polyethylene terephthalate, and the "structural units derived from a carboxylic acid component" contain structural units derived from terephthalic acid derived from polyethylene terephthalate.

[0052] The polyester resin may be modified to such an extent that its properties are not substantially impaired.Specific examples of the modified polyester resin include polyester resins grafted or blocked with phenol, urethane, epoxy, or the like by the methods described in JP-A-11-133668, JP-A-10-239903, JP-A-8-20636, etc.Preferred modified polyester resins include urethane-modified polyester resins obtained by urethane-extending polyester resins with a polyisocyanate compound.

[0053] <Content of each ingredient> From the viewpoint of durability, the content of asphalt in the asphalt mixture is preferably 1 mass% or more, more preferably 3 mass% or more, even more preferably 4 mass% or more, and preferably 20 mass% or less, more preferably 15 mass% or less, even more preferably 10 mass% or less.

[0054] When an asphalt mixture contains recycled asphalt aggregate, the asphalt content is the total content of new asphalt and the asphalt contained in the recycled asphalt aggregate. The asphalt contained in recycled asphalt aggregate is sometimes called asphalt derived from recycled aggregate or deteriorated asphalt to distinguish it from new asphalt. From the viewpoint of durability, the content of the new asphalt in the asphalt is preferably 50% by mass or more, more preferably 60% by mass or more, and preferably 80% by mass or less, and more preferably 70% by mass or less. From the viewpoint of durability, the content of the asphalt derived from recycled aggregate in the asphalt is preferably 20% by mass or more, more preferably 30% by mass or more, and preferably 50% by mass or less, and more preferably 40% by mass or less. The content of asphalt derived from recycled aggregate in recycled asphalt aggregate can be measured by solvent extraction method or ignition loss method. Usually, the content of asphalt contained in recycled asphalt aggregate derived from used asphalt pavement is about 5.5 mass%. In the present invention, the content of asphalt derived from recycled aggregate is measured according to the method specified in AASHTO (American Association of State Highway and Transportation Officials) T 308-10 (2015), which is a loss on ignition measurement. Since recycled asphalt aggregate is included as an aggregate, the amount of asphalt is calculated from the loss on ignition of the recycled asphalt aggregate and used in the mix calculation.

[0055] The content of the semi-carbide in the asphalt mixture of the present invention is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and even more preferably 10 parts by mass or more, per 100 parts by mass of asphalt from the viewpoint of durability of the asphalt pavement, and from the viewpoint of maintaining workability, it is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 20 parts by mass or less.

[0056] From the viewpoint of durability, the aggregate content in the asphalt mixture is preferably 50% by mass or more, more preferably 75% by mass or more, even more preferably 80% by mass or more, and preferably 99% by mass or less, more preferably 98% by mass or less, even more preferably 96% by mass or less. When the asphalt mixture contains recycled asphalt aggregate, the aggregate content is the total content of recycled asphalt aggregate and optionally new aggregate. From the viewpoint of reusing waste asphalt pavement, the content of recycled asphalt aggregate is preferably 15 parts by mass or more, more preferably 25 parts by mass or more, per 100 parts by mass of the total content of recycled asphalt aggregate and new aggregate, and from the viewpoint of achieving both the use of recycled asphalt aggregate and excellent pavement properties, it is preferably 60 parts by mass or less, more preferably 50 parts by mass or less. In addition, the content of asphalt derived from recycled aggregate is included in the aggregate content.

[0057] Examples of suitable aggregate blends for asphalt mixtures include the following (1) to (3): (1) Fine-graded asphalt containing 30% to less than 45% by volume of coarse aggregate, 30% to less than 50% by volume of fine aggregate, and 5% to less than 10% by volume of asphalt composition. (2) An example of an asphalt mixture is dense-graded asphalt containing 45% to less than 70% by volume of coarse aggregate, 20% to 45% by volume of fine aggregate, and 3% to 10% by volume of asphalt composition. (3) Porous asphalt containing 70% to 80% by volume of coarse aggregate, 10% to 20% by volume of fine aggregate, and 3% to 10% by volume of asphalt composition. The mixing ratio of asphalt in conventional asphalt mixtures containing aggregate and asphalt is usually determined according to the optimal amount of asphalt obtained from the "Mix Design of Asphalt Composition" described in the "Guidelines for Pavement Design and Construction" issued by the Japan Road Association, a public interest incorporated association. In the present invention, the above-mentioned optimum amount of asphalt corresponds to the total amount of asphalt and the above-mentioned semi-carbide. However, it is not necessary to be limited to the method described in the "Guidelines for Pavement Design and Construction" and it may be determined by other methods.

[0058] [Asphalt mixture manufacturing method] The method for producing an asphalt mixture of the present invention includes a step of mixing asphalt, aggregate, and the semi-carbonized material. The mixing is preferably performed under heated conditions, and more preferably the aggregate is a heated aggregate. In the mixing step, the asphalt, the aggregate, and the semi-carbide may be mixed simultaneously or in any order. From the viewpoint of durability of the asphalt pavement, the semi-carbide is preferably mixed with the aggregate after the asphalt. Specific methods for producing asphalt mixtures include conventional methods for producing asphalt mixtures called the premix method and the plant mix method. All of these methods involve adding asphalt and semi-carbide to heated aggregate. Examples of the addition method include the premix method in which asphalt and semi-carbide are dissolved in advance, and the plant mix method in which asphalt is added to heated aggregate and then the semi-carbide salt is added simultaneously or in random order. Among these, the plant mix method is preferred from the viewpoint of exerting asphalt performance. More specifically, in the method for producing an asphalt mixture, in the mixing step, preferably, (i) Adding and mixing asphalt to heated aggregate to obtain a mixture, and then adding and mixing the semi-carburized material; (ii) Adding and mixing asphalt and the above torrefied material simultaneously to the heated aggregate; or (iii) The mixture of asphalt and the semi-carbonized material, which has been previously heated and mixed, is added to the heated aggregate and mixed. Among these, the mixing step is preferably performed by the method (i).

[0059] In the method (iii), the mixing temperature at which the asphalt and the semi-carbide are pre-heated and mixed is, from the viewpoint of uniformly dispersing the semi-carbide in the asphalt, preferably 100°C or higher, more preferably 130°C or higher, even more preferably 160°C or higher, still more preferably 170°C or higher, and is preferably 230°C or lower, more preferably 210°C or lower, even more preferably 200°C or lower, and still more preferably 190°C or lower. In addition, the mixing time between the asphalt and the semi-carbide is preferably 30 seconds or more, more preferably 1 minute or more, and even more preferably 2 minutes or more, from the viewpoint of uniformly dispersing the semi-carbide in the asphalt, and is preferably 2 hours or less, more preferably 1 hour or less, and even more preferably 30 minutes or less. The asphalt and the semi-carbonized material can be mixed using, for example, a homomixer, a dissolver, a paddle mixer, a ribbon mixer, a screw mixer, a planetary mixer, a vacuum countercurrent mixer, a roll mill, a twin-screw extruder, or the like.

[0060] In the methods (i) to (iii), the temperature of the heated aggregate is preferably 140°C or higher, more preferably 145°C or higher, and even more preferably 150°C or higher, and from the viewpoint of the performance stability of the asphalt, is preferably 350°C or lower, more preferably 250°C or lower, and even more preferably 200°C or lower. The heating temperature is preferably 140° C. or higher, more preferably 145° C. or higher, and even more preferably 150° C. or higher, from the viewpoint of improving durability by sufficient mixing, and is preferably 350° C. or lower, more preferably 250° C. or lower, and even more preferably 200° C. or lower, from the viewpoint of performance stability. From the viewpoint of the durability of the asphalt pavement, the temperature during mixing is preferably 140°C or higher, more preferably 145°C or higher, and even more preferably 150°C or higher, and from the viewpoint of the performance stability of the asphalt, the temperature is preferably 350°C or lower, more preferably 250°C or lower, and even more preferably 200°C or lower. The mixing time is not particularly limited, and is preferably 30 seconds or more, more preferably 1 minute or more, and even more preferably 2 minutes or more, and is preferably 2 hours or less, more preferably 1 hour or less, and even more preferably 30 minutes or less.

[0061] The method for preparing the mixture is not particularly limited, but preferably includes a step of heating and melting asphalt, adding the semi-carbide and other additives as necessary, and stirring and mixing the components in a commonly used mixer until they are uniformly dispersed. Commonly used mixers include a twin-shaft pug mill type, a forced twin-shaft type, a horizontal single-shaft type, and a pan-type mixer.

[0062] The asphalt mixture of the present invention may be used as a heated asphalt mixture that is substantially free of water, or may be used as a cold asphalt mixture by blending an emulsifier and water with the asphalt mixture to form an asphalt emulsion and then blending aggregates and the like therewith. The mixture of asphalt and the semi-carbonized material preferably does not substantially contain water from the viewpoint of exerting asphalt performance.

[0063] When the asphalt mixture is used as a heated asphalt mixture, there are no particular limitations on the method for producing the asphalt mixture, and the asphalt mixture may be produced by any method. Generally, the method may be similar to the method for producing an asphalt mixture containing aggregate and an asphalt composition.

[0064] The method for producing an asphalt mixture of the present invention can include a step of producing a semi-carbide from a raw material. Such an embodiment includes a method for producing an asphalt mixture including the following steps 1a and 2a. Step 1a: A step of heating the raw material at 150°C or more and 400°C or less to produce a semi-carbide having a volatile matter content of 50% by mass or more and 90% by mass or less and a fixed carbon content of 7% by mass or more and 40% by mass or less. Step 2a: Mixing asphalt, heated aggregate, and semi-carbonized material obtained in step 1a

[0065] The heating temperature in the above step 1a is preferably 150° C. or higher, more preferably 200° C. or higher, and 400° C. or lower, more preferably 300° C. or lower. The heating time can be appropriately set so as to achieve semi-carbonization, and is preferably 1 hour or more, more preferably 2 hours or more, and is preferably 6 hours or less, more preferably 5 hours or less. The heating is preferably carried out in the absence of contact with air. The semi-carbide is preferably produced while stirring the raw materials. The semi-carbide can be produced using a carbonization furnace. More specifically, a shaft furnace, a kiln, etc. can be mentioned.

[0066] [Road pavement construction method] The asphalt mixture of the present invention is suitable for road pavement. The road pavement construction method of the present invention preferably includes a step of applying the asphalt mixture of the present invention to a road or the like to form an asphalt pavement layer. The asphalt pavement layer is usually the base layer or surface layer of a road, and is preferably the surface layer of a road from the viewpoint of exerting the effect of durability.

[0067] In the road paving method, the asphalt mixture may be compacted and constructed using the same construction machinery and method as for normal asphalt mixtures. The compaction temperature of the asphalt mixture when used as a heated asphalt mixture is preferably 100°C or higher, more preferably 120°C or higher, and even more preferably 130°C or higher, from the viewpoint of exerting asphalt performance, and is preferably 200°C or lower, more preferably 180°C or lower, and even more preferably 170°C or lower.

[0068] From the viewpoints of durability and workability, the asphalt pavement material formed by applying an asphalt mixture to roads etc. has a void ratio of preferably 2.5% or more, more preferably 3% or more, and preferably 20% or less, more preferably 10% or less, and even more preferably 6% or less. The void ratio can be determined in accordance with the measurement method specified in "B008-1 Density test method for dense-graded asphalt mixtures, etc." in the "Pavement Survey and Testing Method Handbook (2019 Edition)" (compiled by the Japan Road Association, a public interest incorporated association). The void ratio can be adjusted by the ratio of coarse aggregate, fine aggregate and filler in the aggregate.

[0069] [Asphalt composition] The present invention also provides an asphalt composition. The asphalt composition of the present invention contains asphalt and semi-carbide having a volatile matter content of 50% by mass or more and 90% by mass or less and a fixed carbon content of 7% by mass or more and 40% by mass or less. The description and preferred embodiments of the asphalt and toxigene are given above.

[0070] In the asphalt composition of the present invention, the content of the semi-carbide is, from the viewpoint of durability, preferably 3 parts by mass or more, more preferably 5 parts by mass or more, even more preferably 10 parts by mass or more, per 100 parts by mass of asphalt, and preferably 50 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 20 parts by mass or less.

[0071] The asphalt composition of the present invention is a binder composition, and can be used for paving after, for example, adding aggregate to the asphalt composition to form an asphalt mixture. That is, the asphalt composition of the present invention is suitable for paving, and particularly suitable for road paving.

[0072] [Method of producing asphalt composition] The method for producing the asphalt composition of the present invention preferably includes a step of mixing asphalt with the semi-carbide.

[0073] The asphalt composition is obtained by heating and melting the asphalt, adding the semi-carbonized material, and stirring and mixing the components in a commonly used mixer until they are uniformly dispersed. Commonly used mixers include homomixers, dissolvers, paddle mixers, ribbon mixers, screw mixers, planetary mixers, vacuum countercurrent mixers, roll mills, twin-screw extruders, etc.

[0074] From the viewpoint of uniformly dispersing the semi-carbide in the asphalt, the mixing temperature of the asphalt and the semi-carbide is preferably 100°C or higher, more preferably 130°C or higher, even more preferably 160°C or higher, still more preferably 170°C or higher, and preferably 230°C or lower, more preferably 210°C or lower, even more preferably 200°C or lower, and still more preferably 190°C or lower.

[0075] In addition, from the viewpoint of uniformly dispersing the semi-carbide in the asphalt, the mixing time of the asphalt and the semi-carbide is preferably 0.1 hour or more, more preferably 0.5 hour or more, even more preferably 1.0 hour or more, still more preferably 1.5 hour or more, and is preferably 10 hours or less, more preferably 7 hours or less, even more preferably 5 hours or less, and still more preferably 3 hours or less.

[0076] The method for producing the asphalt composition of the present invention can include a step of producing a semi-carbide from a raw material. Such an embodiment includes a method for producing an asphalt composition comprising the following steps 1b and 2b. Step 1b: A step of heating the raw material at 150°C or more and 400°C or less to produce a semi-carbide having a volatile matter content of 50% by mass or more and 90% by mass or less and a fixed carbon content of 7% by mass or more and 40% by mass or less. Step 2b: Mixing asphalt, heated aggregate, and semi-carbonized material obtained in step 1b

[0077] The heating temperature in the above step 1b is preferably 150° C. or higher, more preferably 200° C. or higher, and preferably 400° C. or lower, more preferably 300° C. or lower. The heating time can be appropriately set so as to achieve semi-carbonization, and is preferably 1 hour or more, more preferably 2 hours or more, and is preferably 6 hours or less, more preferably 5 hours or less. The heating is preferably carried out in the absence of contact with air. The semi-carbide is preferably produced while stirring the raw materials. The semi-carbide can be produced using a carbonization furnace. More specifically, a shaft furnace, a kiln, etc. can be mentioned.

[0078] [Asphalt modifier] The present invention also provides an asphalt modifier. The asphalt modifier of the present invention contains a semi-carbide having a volatile matter content of 50% by mass or more and 90% by mass or less and a fixed carbon content of 7% by mass or more and 40% by mass or less. The description and preferred embodiments of the torrefied material are given above.

[0079] The asphalt modifier of the present invention can be used, for example, by mixing with asphalt to obtain an asphalt composition. After adding heated aggregate to the obtained asphalt composition to prepare an asphalt mixture, the mixture can be used for paving. The asphalt modifier of the present invention can also be used as a modifier for incorporation into asphalt mixtures containing aggregates. EXAMPLES

[0080] Various physical properties were measured and evaluated by the following methods. In the following examples and comparative examples, parts and percentages are by weight unless otherwise specified.

[0081] [Measurement method] (1) Measurement of volatile matter content The volatile matter content was measured in accordance with the measurement method described in JIS M8812:2006 "Coals and cokes - Methods of proximate analysis." (2) Measurement of fixed carbon content The fixed carbon content was measured in accordance with the measurement method described in JIS M8812:2006 "Coals and cokes - proximate analysis method."

[0082] Sample 1 Sample 1 to be subjected to semi-carbonization and carbonization was prepared by absorbing 7.5 kg of tap water into 15 kg of unused disposable diapers for infants (product name "Meries Pants Smooth Airy Through L size", manufactured by Kao Corporation) and further adding 0.6 kg of ammonium dihydrogen phosphate.

[0083] The materials used in the "Merrys Pants Smooth Airy Through L Size" are as follows. The materials used are listed based on the guidelines set out by the Japan Sanitary Materials Industry Association. Surface material: Polyester / polyolefin nonwoven fabric Absorbent material: Absorbent paper / cotton pulp / acrylic polymer absorbent material Waterproofing material: Polyolefin film Adhesive material: Polyolefin film Elastic material: Polyurethane Binder: styrene-based elastomer synthetic resin, etc.

[0084] The polyester that constitutes the polyester / polyolefin nonwoven fabric is polyethylene terephthalate (PET) or the like, and the polyolefin is polyethylene (PE), polypropylene (PP) or the like.

[0085] The above conditions are those simulating those of used absorbent articles, and ammonium dihydrogen phosphate is a simulating component contained in urine.

[0086] Sample 2 As sample 2 to be semi-carbonized, 15 kg of used disposable diapers for babies used in sample 1 were used.

[0087] Production Example 1 (Production of Semicarbide 1) The above sample 1 was heated using a furnace having a stirring blade for stirring the raw material, a heater, and a blower mechanism, by increasing the temperature from 20°C to 250°C at a rate of 0.5°C / min and maintaining the temperature at 250°C for 180 minutes. Thereafter, the temperature was decreased from 250°C to 30°C at a rate of 0.2°C / min while blowing air, thereby cooling the sample. The sample was continuously stirred during heating and cooling. Semi-carbonized product 1, which is a semi-carbonized product of granular paper diapers, was obtained. The configuration of the furnace used, which had a stirring blade, a heater, and a blower mechanism, is shown in FIG. The content of volatile matter in the semi-carbonized product 1 was 70.4% by mass. The content of fixed carbon in the semi-carbonized product 1 was 17.2% by mass.

[0088] Manufacturing Example 2 (Manufacturing of Semi-Carbide 2) Semicarbonized material 2, which is a semicarbonized material of a disposable diaper, was obtained in the same manner as in Production Example 1, except that the heating temperature was changed to 200°C. The content of volatile matter in the semi-carbonized material 2 was 81.6% by mass. The content of fixed carbon in the semi-carbonized material 2 was 9.9% by mass.

[0089] Production Example 3 (Production of Semicarbide 3) Semicarbonized material 3, which is a semicarbonized material of a paper diaper, was obtained in the same manner as in Production Example 1, except that Sample 2 (used paper diaper) was used instead of Sample 1. The content of volatile matter in the semi-carbonized material 3 was 55.6% by mass. The content of fixed carbon in the semi-carbonized material 3 was 27.8% by mass.

[0090] Production Example 4 (Production of Semicarbide 4) Semicarbonized material 4, which is a semicarbonized paper diaper, was obtained in the same manner as in Production Example 1, except that the heating temperature was changed to 300°C. The content of volatile matter in the semi-carbonized material 4 was 59.0 mass %. The content of fixed carbon in the semi-carbonized material 3 was 11.7 mass %.

[0091] Production Example 5 (Production of Carbide 1) Sample 1 was placed in a crucible, and the temperature was increased from 20° C. to 800° C. at a rate of 10° C. / min in an electric furnace, and the temperature was maintained at 800° C. for 30 minutes to heat Sample 1. Thereafter, the temperature was decreased from 800° C. to 30° C. at a rate of 10° C. / min, and the sample was cooled to obtain carbide 1. The content of volatile matter in Carbonized Material 1 was 0 mass %. The content of fixed carbon in Carbonized Material 1 was 54.1 mass %.

[0092] Production Example 6 (Untreated Material 1) An unused disposable diaper for babies (product name "Merry's Pants Smooth Airy Through L size") was cut into pieces of approximately 1 cm square using scissors to obtain an untreated object 1. Using Untreated Material 1, a uniformly mixed asphalt mixture could not be obtained.

[0093] Example 1 15 kg of aggregate heated to 180°C (see below for aggregate composition) was placed in an asphalt mixer and mixed for 60 seconds at 180°C. Next, 820 g of straight asphalt (manufactured by Mitsubishi Corporation Energy Co., Ltd.) was added and mixed in the asphalt mixer for 1 minute. Next, 41 g of the semi-carbonized material 1 obtained in Production Example 1 was added, and the mixture was mixed for 2 minutes in an asphalt mixer to obtain an asphalt mixture. The content of semi-carbide 1 was 10 parts by mass per 100 parts by mass of straight asphalt. (Aggregate composition:) No. 6 crushed stone 40.0 parts by weight No. 7 crushed stone 13.0 parts by weight Crushed sand 10.0 parts by mass River sand 22.0 parts by mass Mountain sand 10.0 parts by mass Stone powder (calcium carbonate) 5.0 parts by weight Passed mass%: Sieve size 15 mm: 100% by mass Sieve size 10 mm: 88.7% by mass Sieve size 5 mm: 60.5% by mass Sieve size 2.5 mm: 42.6% by mass Sieve size 1.2 mm: 29.9% by mass Sieve size 0.6 mm: 19.8% by mass Sieve size 0.3 mm: 11.5% by mass Sieve size 0.15mm: 6.2% by mass

[0094] The resulting asphalt mixture was quickly filled into a 300mm x 300mm x 50mm formwork, and a roller compactor (manufactured by Iwata Kogyosho Co., Ltd.) was used to perform a pressure treatment at 150°C and a load of 0.44kPa for 25 revolutions, followed by thermal curing at 180°C for 2 hours to prepare an asphalt specimen. In addition, 1.2kg of the asphalt mixture was weighed out and a cylindrical specimen was prepared using a Marshall test compaction machine (manufactured by Nakajima Gihan Co., Ltd., "Automatic Asphalt Compaction Device"). The specimen was gradually cooled to room temperature and demolded using a demolding machine.

[0095] [evaluation] <Wheel tracking test: Evaluation of rutting amount> The asphalt specimen was immersed in hot water set at 60°C in a 60°C thermostatic chamber, and a wheel tracking tester (Iwata Kogyosho Co., Ltd., load 1716N, iron wheel width 47mm, linear pressure 291.5N / cm) was used to move the wheel back and forth over the specimen at a speed of 15 round trips per minute, and the displacement was measured after 1,250 round trips. Other measurement conditions were in accordance with the measurement method specified in "B003 Wheel Tracking Test Method" in "Pavement Survey and Test Method Handbook (2019 Edition)" (compiled by Japan Road Association, a public interest incorporated association). The results are shown in Table 1.

[0096] <Porosity measurement> The void ratio of the asphalt specimens was determined in accordance with the measurement method specified in "B008-1 Density test method for dense-graded asphalt mixtures, etc." in the "Pavement Survey and Test Method Handbook (2019 Edition)" (compiled by the Japan Road Association, a public interest incorporated association). By measuring the void ratio under the same conditions, the workability of the asphalt mixture can be evaluated.

[0097] Examples 2 to 3 Except for changing the amount of semi-carbide 1 to the amount shown in Table 1, an asphalt specimen was prepared and a wheel tracking test was performed in the same manner as in Example 1. In addition, the void ratio of the asphalt specimen was measured. The results are shown in Table 1.

[0098] Examples 4 to 6 Except for changing the semi-carbide 1 to semi-carbide 2 to 4 shown in Table 1, asphalt specimens were prepared and wheel tracking tests were carried out in the same manner as in Example 1. In addition, the void ratio of the asphalt specimens was measured. The results are shown in Table 1.

[0099] Comparative Example 1 An asphalt specimen was prepared and a wheel tracking test was carried out in the same manner as in Example 1, except that the semi-carbide 1 was not mixed. In addition, the void ratio of the asphalt specimen was measured.

[0100] Comparative Example 2 An asphalt specimen was prepared and a wheel tracking test was carried out in the same manner as in Example 1, except that the semi-carbonized material 1 was changed to the carbonized material 1. In addition, the porosity of the asphalt specimen was measured.

[0101] [Table 1]

[0102] The results shown in Table 1 demonstrate that the present invention provides an asphalt mixture that can provide an asphalt pavement with excellent durability. In Examples 1 to 6, a filling rate of 3 to 6% was achieved, and it is understood that even if semi-carbonized materials 1 to 4 are mixed, there is no problem with the workability of the pavement. A comparison of Examples 1, 4, and 6 reveals that as the volatile content increases, the amount of rutting decreases, while the void ratio tends to increase. This is thought to be because the fiber components of the thermoplastic resin contained in the nonwoven fabric product, which is thought to contribute to the volatile content, melt during semi-carbonization, which contributes to improving durability, but also thickens the asphalt binder, reducing its fluidity. In addition, a comparison of Examples 5 and 6 shows that when the volatile content is approximately the same, the lower the fixed carbon content, the smaller the porosity tends to be. Although the reason is unclear, it is presumed that when the fixed carbon content is high, the semi-carbonized material tends to aggregate, which reduces the packing ability. [Explanation of symbols]

[0103] 100 Stirring device 101 Treatment tank 101b Storage section 102 Agitator shaft 102a Shaft 102b Wing 103 Heater 104 Blower mechanism C Rotational Axis

Claims

1. An asphalt mixture containing asphalt, aggregate, and semi-carbonized material derived from a nonwoven fabric product having a volatile matter content of 50% by mass or more and 90% by mass or less and a fixed carbon content of 7% by mass or more and 40% by mass or less.

2. 2. The asphalt mixture of claim 1, wherein the nonwoven product is a nonwoven product comprising a fiber component of a thermoplastic resin.

3. The asphalt mixture according to claim 1 or 2, wherein the content of the semi-carbide is 3 parts by mass or more and 20 parts by mass or less per 100 parts by mass of asphalt.

4. A method for producing an asphalt mixture, comprising the step of mixing asphalt, heated aggregate, and semi-carbonized material derived from a nonwoven fabric product having a volatile matter content of 50% by mass or more and 90% by mass or less and a fixed carbon content of 7% by mass or more and 40% by mass or less.

5. An asphalt composition comprising asphalt and semi-carbonized material derived from a nonwoven fabric product having a volatile matter content of 50% by mass or more and 90% by mass or less and a fixed carbon content of 7% by mass or more and 40% by mass or less.

6. A road paving method, comprising the step of applying the asphalt mixture according to claim 1 or 2 to a road to form an asphalt pavement layer.

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