Method for producing asphalt mixture

Abstract

To provide a method for producing an asphalt mixture exhibiting superior resistance to stripping, and a medium-temperature agent for asphalt.SOLUTION: A method for producing an asphalt mixture including, in this order, the following steps (1) and (2): (1) mixing a heated asphalt with a mixed solution of compound A and water to obtain a foamed asphalt composition; and (2) mixing the foamed asphalt composition obtained in step (1) with heated aggregate to obtain an asphalt mixture, wherein the compound A is at least one selected from the group consisting of (i) a compound represented by the following general formula (I) and (ii) a quaternary ammonium salt having an aliphatic hydrocarbon group with 8 to 20 carbon atoms. [In the formula, R1, R2, EO, and n are as defined in the specification.]SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing an asphalt mixture and a warming agent for asphalt. [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. This asphalt pavement is made by forming a paved surface using an asphalt mixture in which aggregate is bound with asphalt, and has good hardness and durability.

[0003] Patent Document 1 discloses a method for producing an asphalt paving mixture, which includes a step of mixing heated asphalt with water in the presence of an antifoaming agent to prepare foamed asphalt through the evaporation and expansion of the water, and a step of mixing the foamed asphalt with aggregate, as an invention that aims to improve the properties of the air bubbles contained in foamed asphalt and extend the lifespan of the air bubbles, thereby giving the asphalt paving mixture obtained using such foamed asphalt excellent fluidity and making it possible to lower the mixing temperature during production and the compaction temperature during construction. Patent Document 2 discloses an invention for extending the foaming time of bubbles in an asphalt mixture containing foamed asphalt, and discloses a method for producing an asphalt mixture, which includes the steps of adding water and a foaming aid to heated asphalt to prepare foamed asphalt, and mixing the foamed asphalt with aggregate, wherein the foaming aid is one or more compounds selected from the group consisting of glycol ether compounds represented by formula (I), fatty acid compounds, surfactant compounds, and inorganic compounds. Patent Document 3 discloses a method for producing an asphalt mixture, which is an invention that reduces the mixing temperature and paving temperature of hot-mix asphalt used to prepare road surfaces and simultaneously improves moisture resistance without sacrificing the performance characteristics of the asphalt mixture, and which includes the steps of adding water and a foaming aid to heated asphalt to prepare foamed asphalt, and mixing the foamed asphalt with aggregate, wherein the foaming aid is one or more compounds selected from the group consisting of glycol ether compounds represented by formula (I), fatty acid compounds, surfactant compounds, and inorganic compounds. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2017-186842 [Patent Document 2] Japanese Patent Publication No. 2023-86095 [Patent Document 3] Special Publication No. 2011-503311 Summary of the Invention [Problem to be solved by the invention]

[0005] Heated asphalt requires that the asphalt binder and asphalt mixture be kept at high temperatures throughout the manufacturing, transportation, and construction processes to ensure workability. However, there are concerns that the carbon dioxide (CO2) emissions associated with heating could increase the environmental burden. Therefore, medium temperature technology is being considered, which can maintain the same workability even when the asphalt temperature drops.

[0006] One of the medium temperature technologies is a technology that lowers the mixing temperature and compaction temperature by using foamed asphalt, which is made by mixing heated asphalt with water and foaming it, as described in Patent Documents 1 to 3, for example. However, in the techniques described in Patent Documents 1 to 3, peel resistance was sometimes insufficient.

[0007] The present invention relates to a method for producing an asphalt mixture having excellent peeling resistance and a warming agent for asphalt.

[0008] The present invention relates to the following [1] and [2]. [1] A method for producing an asphalt mixture comprising the following steps (1) and (2) in this order: Step (1): A step of mixing heated asphalt with a mixture of the following compound A and water to obtain a foamed asphalt composition. Step (2): A step of mixing the foamed asphalt composition obtained in step (1) with heated aggregate to obtain an asphalt mixture. Compound A: (i) one or more compounds selected from the group consisting of compounds represented by the following general formula (I) and (ii) quaternary ammonium salts having an aliphatic hydrocarbon group having from 8 to 20 carbon atoms: [ka] [In the formula, R 1 represents an aliphatic hydrocarbon group or an acyl group having 8 to 20 carbon atoms, and R 2 represents a hydrocarbon group having 8 or less carbon atoms which may have a hydrogen atom or a heteroatom, EO represents an ethyleneoxy group, and n is 0 or more and 2 or less.] [2] A mixture of the following compound A and water, The warming agent for asphalt, wherein the content of compound A in the mixed liquid is 20% by mass or more and 50% by mass or less. Compound A: (i) one or more compounds selected from the group consisting of compounds represented by the following general formula (I) and (ii) quaternary ammonium salts having an aliphatic hydrocarbon group having from 8 to 20 carbon atoms: [ka] [In the formula, R 1 represents an aliphatic hydrocarbon group or an acyl group having 8 to 20 carbon atoms, and R 2represents a hydrocarbon group having 8 or less carbon atoms which may have a hydrogen atom or a heteroatom, EO represents an ethyleneoxy group, and n is 0 or more and 2 or less.] [Effects of the Invention]

[0009] According to the present invention, a method for producing an asphalt mixture having excellent peeling resistance is provided. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Asphalt mixture manufacturing method] The method for producing an asphalt mixture of the present invention includes the following steps (1) and (2) in this order. Step (1): A step of mixing asphalt with a mixture of the following compound A and water to obtain a foamed asphalt composition. Step (2): A step of mixing the foamed asphalt composition obtained in step (1) with heated aggregate to obtain an asphalt mixture. Compound A: (i) one or more compounds selected from the group consisting of compounds represented by the following general formula (I) and (ii) quaternary ammonium salts having an aliphatic hydrocarbon group having from 8 to 20 carbon atoms: [ka] [In the formula, R 1 represents an aliphatic hydrocarbon group or an acyl group having 8 to 20 carbon atoms, and R 2 represents a hydrocarbon group having 8 or less carbon atoms which may have a hydrogen atom or a heteroatom, EO represents an ethyleneoxy group, and n is 0 or more and 2 or less.]

[0011] The method for producing an asphalt mixture of the present invention is a method for producing an asphalt mixture that is excellent in peeling resistance. The peel resistance can be evaluated, for example, by the method shown in the examples below. Furthermore, according to the method for producing an asphalt mixture of the present invention, workability can be improved compared to a foamed asphalt composition that does not contain compound A. Workability refers to the degree of thermoplasticity of an asphalt mixture. For example, as shown in the examples below, it can be evaluated by the viscosity of a foamed asphalt composition at a specific temperature. As the viscosity decreases, the adhesive strength of the asphalt mixture to each other and to the asphalt application base decreases, improving workability.

[0012] Although the detailed mechanism by which the effects of the present invention are obtained is unknown, part of it is thought to be as follows. In a foamed asphalt composition, the apparent viscosity of the asphalt is reduced. On the other hand, compound A having a specific structure has a high affinity with asphalt and disperses uniformly in the asphalt. Furthermore, Compound A, which has a specific structure, has a high affinity with aggregate, and Compound A connects the asphalt and aggregate, improving adhesive strength. This, combined with the reduction in asphalt viscosity due to water, improves the mixability of the asphalt and aggregate and is thought to provide excellent asphalt separation prevention.

[0013] Furthermore, by using a mixture of Compound A and water at work sites where high-temperature asphalt is handled, it is possible to prevent ignition and the generation of volatile gases due to vaporized Compound A, thereby achieving high levels of safety and ease of handling.

[0014] <<Process (1)>> Step (1) is a step of mixing heated asphalt with a mixture of the following compound A and water to obtain a foamed asphalt composition.

[0015] <Asphalt> Various types of asphalt can be used. Examples include straight asphalt, which is petroleum asphalt for paving, as well as modified asphalt. Modified asphalts include blown asphalt and polymer-modified asphalt modified with polymeric materials such as thermoplastic elastomers and thermoplastic resins. Straight asphalt refers to the residual bituminous material obtained by subjecting crude oil to atmospheric distillation or vacuum distillation. Blown asphalt refers to asphalt obtained by heating a mixture of straight asphalt and heavy oil and then oxidizing it by blowing air into it. The asphalt is preferably selected from straight asphalt and polymer-modified asphalt. From the viewpoint of the durability of the resulting asphalt pavement, polymer-modified asphalt is more preferred, while straight asphalt is more preferred from the viewpoint of versatility. As polymer-modified asphalt, asphalt modified with a thermoplastic elastomer is more preferred. The modified asphalt is preferably a polymer-modified asphalt, more preferably a polymer-modified asphalt modified with a thermoplastic elastomer.

[0016] (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 the durability of the resulting 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 at least one selected from styrene / butadiene block copolymers, styrene / butadiene / styrene block copolymers, styrene / butadiene random copolymers, styrene / isoprene block copolymers, and styrene / isoprene random copolymers, and even more preferably at least one selected from styrene / butadiene random copolymers and styrene / butadiene / styrene block copolymers. From the viewpoint of the durability and surface appearance of the resulting asphalt pavement, the content of thermoplastic elastomer in the polymer-modified asphalt is preferably 0.1% by mass or more and 30% by mass or less, more preferably 0.5% by mass or more, even more preferably 1% by mass or more, and more preferably 20% by mass or less, even more preferably 10% by mass or less.

[0017] In step (1), heated asphalt is used. The temperature of the heated asphalt is preferably 100°C or higher and 350°C or lower from the viewpoint of workability and performance stability, more preferably 120°C or higher, and even more preferably 140°C or higher from the viewpoint of workability, 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.

[0018] <Mixture of Compound A and Water> (Compound A) Compound A is at least one selected from the group consisting of (i) compounds represented by the following general formula (I) and (ii) quaternary ammonium salts having an aliphatic hydrocarbon group having from 8 to 20 carbon atoms. [ka] [In the formula, R 1 represents an aliphatic hydrocarbon group or an acyl group having 8 to 20 carbon atoms, and R 2 represents a hydrocarbon group having 8 or less carbon atoms which may have a hydrogen atom or a heteroatom, EO represents an ethyleneoxy group, and n is 0 or more and 2 or less.]

[0019] The compound (A) can be used alone or in combination of two or more.

[0020] (i) Compounds represented by general formula (I) In the compound represented by the above general formula (I) (hereinafter also referred to as compound (i)), R 1 represents an aliphatic hydrocarbon group or an acyl group having 8 to 20 carbon atoms. The aliphatic hydrocarbon group has 8 to 20 carbon atoms, and from the viewpoint of the effects of the present invention, preferably 10 or more, more preferably 12 or more, even more preferably 14 or more, and preferably 18 or less. The aliphatic hydrocarbon group may be either a saturated aliphatic hydrocarbon group or an unsaturated aliphatic hydrocarbon group. Furthermore, the aliphatic hydrocarbon group may be either a linear aliphatic hydrocarbon group or a branched aliphatic hydrocarbon group. Acyl groups with 8 to 20 carbon atoms are represented by R A -CO-(wherein, R A represents an aliphatic hydrocarbon group having 7 to 19 carbon atoms. A The number of carbon atoms in the aliphatic hydrocarbon group represented by is 7 or more and 19 or less, and from the viewpoint of the effects of the present invention, is preferably 9 or more, more preferably 11 or more, even more preferably 13 or more, and preferably 17 or less. In addition, the aliphatic hydrocarbon group may be either a linear aliphatic hydrocarbon group or a branched aliphatic hydrocarbon group.

[0021] In general formula (I), EO is an ethyleneoxy group (—C2H4O—), and n represents the average number of moles of ethyleneoxy groups added. n is 0 or more and 2 or less. When n=0, it represents a single bond.

[0022] In general formula (I), R 2 represents a hydrocarbon group having 8 or less carbon atoms which may contain a hydrogen atom or a heteroatom. The heteroatom means an oxygen atom, a nitrogen atom, a sulfur atom, a phosphorus atom, a halogen atom, or the like. The phrase "may contain a heteroatom" includes, for example, an embodiment in which the hydrocarbon group is interrupted by a group such as an oxygen atom (-O- group, i.e., an ether group), a nitrogen atom, an -NH- group, or a sulfur atom (-S- group), as well as an embodiment in which the hydrocarbon group has, at its terminal, a ═O group, a hydroxy group, a carboxy group, an amino group, a nitro group, a sulfo group, a halogen group, or the like, or, if capable of forming a salt, a salt thereof. In the case of a salt, any cation or anion can be appropriately selected as the counter ion. Examples of the anion include alkyl sulfate ions having 1 to 3 carbon atoms, sulfate ions, phosphate ions, carboxylate ions having 1 to 3 carbon atoms (formate ions, acetate ions, propionate ions), and halide ions such as chloride ions and bromide ions.

[0023] The heteroatom is preferably a nitrogen atom or an oxygen atom. R 2 Preferred embodiments of the hydrocarbon group having 8 or less carbon atoms which may have a heteroatom in the above formula include a hydrocarbon group having 8 or less carbon atoms interrupted by a nitrogen atom or an -NH- group, a hydrocarbon group having 8 or less carbon atoms interrupted by an oxygen atom (ether group), and a hydrocarbon group having 8 or less carbon atoms and an amino group at the terminal. Furthermore, a hydrocarbon group having 8 or less carbon atoms interrupted by a nitrogen atom or an -NH- group can form a tertiary ammonium group or a secondary ammonium group. R 2 is preferably -(EO) m H group [wherein m is 0 or more and 2 or less] or —(CH p -NR 3 R 4 The group [wherein, R 3 and R 4 are a hydrogen atom, a methyl group, and -(CH2) q N(R 5 )R 6 is one selected from the group R 5 and R 6 are each a hydrogen atom or a methyl group, p is 1 or more and 6 or less, and p+q is 2 or more and 6 or less. More preferably, -(EO) m H group (wherein m is 0 or more and 2 or less) or —(CH)—NR 3 R 4 The group [wherein, R 3 and R 4 are each a hydrogen atom or a methyl group. m represents the average number of moles of ethyleneoxy groups added.

[0024] Compound (i) is preferably a nonionic surfactant. When compound (i) is a nonionic surfactant, the HLB value calculated by the Davis method is, from the viewpoint of the effects of the present invention, preferably 1 or more, more preferably 3 or more, even more preferably 5 or more, and preferably 14 or less, more preferably 12 or less, even more preferably 10 or less. The HLB value is a value that indicates the affinity of a surfactant to water and oil as a hydrophilic-lipophilic balance. In this specification, the HLB value of compound (i) is determined by the Davis method and is calculated using the following formula: HLB value (Davis method) = 7 + Σ (number of hydrophilic groups) + Σ (number of lipophilic groups) Here, "Σ (number of hydrophilic groups)" indicates the total number of hydrophilic group groups contained in the compound, and "Σ (number of lipophilic groups)" indicates the total number of lipophilic group groups contained in the compound.

[0025] Specific examples of compound (i) include coconut amine acetate, polyoxyethylene (2) laurylamine, N-3-oleylamidopropyl dimethylamine lactate, and N-tallow alkyl trimethylene diamine lactate, among which one or more selected from coconut amine acetate, N-3-oleylamidopropyl dimethylamine lactate, and N-tallow alkyl trimethylene diamine lactate are preferred, and one or more selected from coconut amine acetate and N-tallow alkyl trimethylene diamine lactate are more preferred. Commercially available products of compound (i) include "Acetamine 24", "Amit 102", and "Diamine RRT" (all manufactured by Kao Corporation), and "FENTAMINE PKOO" (manufactured by Solvay Nicca Co., Ltd.).

[0026] (ii) Quaternary ammonium salts having an aliphatic hydrocarbon group having 8 to 20 carbon atoms The aliphatic hydrocarbon group in the quaternary ammonium salt having an aliphatic hydrocarbon group having from 8 to 20 carbon atoms (hereinafter also referred to as compound (ii)) may be either a saturated aliphatic hydrocarbon group or a branched aliphatic hydrocarbon group, and is preferably a saturated aliphatic hydrocarbon group, i.e., an alkyl group. The aliphatic hydrocarbon group may be either a straight-chain aliphatic hydrocarbon group or a branched aliphatic hydrocarbon group. The aliphatic hydrocarbon group has 8 or more and 20 or less carbon atoms, and from the viewpoint of the effects of the present invention, it preferably has 10 or more carbon atoms, more preferably 12 or more carbon atoms, even more preferably 14 or more carbon atoms, and preferably 18 or less carbon atoms.

[0027] An example of the quaternary ammonium group is a trimethylammonium group. Counter ions in quaternary ammonium salts include alkyl sulfate ions having 1 to 3 carbon atoms, sulfate ions, phosphate ions, carboxylate ions having 1 to 3 carbon atoms (formate ions, acetate ions, propionate ions), and halide ions such as chloride ions and bromide ions.

[0028] Compound (ii) is preferably an alkyl quaternary ammonium salt in which a quaternary ammonium base is directly bonded to an aliphatic hydrocarbon group. Compound (ii) is preferably a cationic surfactant. When compound (ii) is a cationic surfactant, from the viewpoint of the effects of the present invention, the HLB value is preferably 1 or more, more preferably 3 or more, even more preferably 5 or more, and preferably 15 or less, more preferably 13 or less, even more preferably 11 or less. The HLB value of compound (ii) can be determined by the above-mentioned Davis method.

[0029] Specific examples of the compound (ii) include stearyltrimethylammonium chloride. Commercially available products of compound (ii) include "Cortamin 86W" (manufactured by Kao Corporation).

[0030] (mixed liquid) The mixed liquid is either an aqueous solution or a dispersion depending on the type of compound A and the content of compound A relative to water, and is not limited thereto. In step (1), the content of compound A in the mixed solution is preferably 10% by mass or more and 50% by mass or less, more preferably 20% by mass or more, even more preferably 30% by mass or more, and more preferably 45% by mass or less, even more preferably 40% by mass or less, relative to 100% by mass of the mixed solution.

[0031] The mixed solution of compound A and water can be prepared by a conventional stirring method or the like. The water is not particularly limited, and tap water, industrial water, supernatant water, sludge water, groundwater, lake water, river water, etc. can be used.

[0032] In one preferred embodiment of the present invention, the mixture of compound A and water acts as a warming agent for asphalt in the method for producing an asphalt mixture. An asphalt warming agent is a component that enables the production and / or application of an asphalt mixture at a lower temperature. More specifically, asphalt warming agents improve the mixing and compaction properties of an asphalt mixture based on their foaming, lubricating, and viscoelasticity adjusting effects, thereby enabling production and / or application at a lower temperature. "Low temperature" means a temperature that is preferably 10°C lower, more preferably 20°C lower, and even more preferably 30°C lower than the temperature at which a normal asphalt mixture is produced and / or applied. Therefore, the present invention also provides a warming agent for asphalt.

[0033] The warming agent for asphalt is composed of a mixed liquid of the compound A and water, and the content of compound A in the mixed liquid is 20% by mass or more and 50% by mass or less. In the warming agent for asphalt, the content of compound A in the mixed liquid is 20% by mass or more and 50% by mass or less, more preferably 30% by mass or more, more preferably 45% by mass or less, and even more preferably 40% by mass or less, relative to 100% by mass of the mixed liquid.

[0034] <Foamed asphalt composition> In step (1), heated asphalt is mixed with a mixture of the following compound A and water to obtain a foamed asphalt composition. A foamed asphalt composition is a foamed asphalt composition. Specifically, when heated asphalt comes into contact with water, the water expands and foams. It is known that foamed asphalt has a reduced apparent viscosity.

[0035] The mixing preferably includes a step of stirring and mixing the components until they are uniformly dispersed in a commonly used mixer, such as a homomixer, dissolver, paddle mixer, ribbon mixer, screw mixer, planetary mixer, vacuum countercurrent mixer, roll mill, or twin-screw extruder. The temperature during mixing is preferably 100°C or higher and 350°C or lower from the viewpoint of workability and performance stability, more preferably 120°C or higher, and even more preferably 140°C or higher from the viewpoint of workability, 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. The mixing may be carried out in a so-called medium temperature range, and the mixing conditions in the medium temperature range are preferably 160°C or lower.

[0036] In step (1), the content of the mixed liquid in the foamed asphalt composition is preferably 0.3 parts by mass or more and 30 parts by mass or less, more preferably 0.6 parts by mass or more, even more preferably 1 part by mass or more, and preferably more preferably 15 parts by mass or less, even more preferably 5 parts by mass or less, per 100 parts by mass of asphalt. In step (1), the content of compound A in the foamed asphalt composition is preferably 0.1 parts by mass or more and 10 parts by mass or less, more preferably 0.2 parts by mass or more, even more preferably 0.3 parts by mass or more, and preferably more preferably 5 parts by mass or less, even more preferably 2 parts by mass or less, per 100 parts by mass of asphalt.

[0037] <<Process (2)>> Step (1) is a step of mixing the foamed asphalt composition obtained in step (2) with aggregate to obtain an asphalt mixture.

[0038] (aggregate) The asphalt mixture of the present invention may contain aggregate. Specific aggregates that can be used include, for example, crushed stone, boulders, gravel, sand, ceramics, etc. Also, as aggregates, coarse aggregates with a particle size of 2.36 mm or more, fine aggregates with a particle size of 0.075 mm or more but less than 2.36 mm, and fillers with a particle size of less than 0.075 mm can be used.

[0039] 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 the coarse aggregate and fine aggregate is based on the sieve analysis test method specified in JIS A5001:2008. Examples of the filler include sand, fly ash, calcium carbonate powder such as limestone powder, slaked lime, etc. Among these, calcium carbonate powder is preferred from the viewpoint of durability of the asphalt mixture molded body. From the viewpoint of the strength of the resulting 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.

[0040] 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 resulting asphalt pavement, the mass ratio of coarse aggregate to fine aggregate (coarse aggregate / fine aggregate) is preferably 10 / 90 or more and 90 / 10 or less, more preferably 15 / 85 or more, even more preferably 20 / 80 or more, and more preferably 80 / 20 or less, even more preferably 70 / 30 or less.

[0041] The asphalt mixture of the present invention may contain recycled asphalt aggregate as an aggregate. The aggregate may not contain new aggregate and may be composed solely of 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. For example, known warming agents may be used in combination as long as the effects of the present invention are not impaired.

[0042] The temperature of the heated aggregate is preferably 100°C or higher and 230°C or lower, more preferably 130°C or higher, even more preferably 140°C or higher, and more preferably 210°C or lower, even more preferably 190°C or lower, even more preferably 170°C or lower.

[0043] From the viewpoint of the durability of the resulting asphalt pavement, the content of aggregate in the asphalt mixture is preferably 500 parts by mass or more and 3000 parts by mass or less, more preferably 1000 parts by mass or more, even more preferably 1500 parts by mass or more, and more preferably 2500 parts by mass or less, even more preferably 2000 parts by mass or less, per 100 parts by mass of asphalt.

[0044] 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 50% by volume of fine aggregate, and 5% to 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 asphalt mixing ratio in conventional asphalt mixtures containing aggregate and asphalt is usually determined according to the optimal amount of asphalt determined from the "Mix Design of Asphalt Compositions" described in the "Guidelines for Pavement Design and Construction" published by the Japan Road Association, a public interest incorporated association.

[0045] (mixture) The mixing temperature when the foamed asphalt composition and aggregate are mixed to obtain an asphalt mixture in step (2) is preferably 100°C or higher and 230°C or lower, more preferably 210°C or lower, and even more preferably 200°C or lower, from the viewpoint of softening the asphalt. In the asphalt mixture manufacturing method of the present invention, asphalt pavement with excellent properties can be obtained even when the foamed asphalt composition and aggregate are mixed in the so-called medium temperature range. The mixing conditions in the medium temperature range are preferably 100°C or higher and 140°C or lower, more preferably 110°C or higher and more preferably 130°C or lower. The mixing time is preferably 30 seconds or more, more preferably 1 minute or more, even more preferably 2 minutes or more, and even more preferably 5 minutes or more. The upper limit of the time is not particularly limited, but is, for example, about 30 minutes.

[0046] The mixing preferably includes a step of stirring and mixing the components until they are uniformly dispersed in a commonly used mixer, such as a homomixer, dissolver, paddle mixer, ribbon mixer, screw mixer, planetary mixer, vacuum countercurrent mixer, roll mill, or twin-screw extruder.

[0047] In step (2), the content of compound A in the asphalt mixture is preferably 0.1 parts by mass or more and 10 parts by mass or less, more preferably 0.2 parts by mass or more, even more preferably 0.3 parts by mass or more, and preferably more preferably 5 parts by mass or less, even more preferably 2 parts by mass or less, per 100 parts by mass of asphalt.

[0048] Thus, an asphalt mixture is produced. The asphalt mixture produced according to the present invention is suitable for use in paving, and is particularly suitable for use in road paving.

[0049] Specifically, the method includes a step of compacting the asphalt mixture onto a pavement target such as a road, parking lot, etc. to form an asphalt pavement layer. The asphalt pavement layer is usually a base layer or a surface layer, and is preferably a surface layer from the viewpoint of exerting durability effects.

[0050] Compaction can be carried out using the same construction machinery and methods as for ordinary asphalt mixtures. The compaction temperature of the asphalt mixture when used as a hot asphalt mixture is 145°C or less, preferably 100°C or more, more preferably 120°C or more, and preferably 140°C or less. [Example]

[0051] The present invention will be described below with reference to examples, but the present invention is not limited to the scope of the examples.

[0052] Example 1 Compound A1 (stearyltrimethylammonium chloride) shown in Table 1 and tap water were mixed so that the content of compound A1 was 33 mass % to obtain mixed solution (1). Mixed solution (1) is an aqueous solution. Next, 50 g of straight asphalt (Straight Asphalt 60-80, manufactured by Mitsubishi Corporation Energy Co., Ltd.) heated to 150°C was weighed into a 200 mL stainless steel cup preheated to 150°C. While stirring on a hot plate at a rotation speed of 200 rpm, the heating temperature of the hot plate was adjusted so that the surface temperature of the asphalt became 120±5°C. The aqueous solution (1) was added to straight asphalt so that the amount of the mixed solution (1) added was 3 parts by mass per 100 parts by mass of asphalt, thereby obtaining a foamed asphalt composition (1).

[0053] (1) Viscosity measurement of foamed asphalt composition The actual viscosity (mPa·s) of the obtained foamed asphalt (1) at 120°C was measured under the following conditions. The results are shown in Table 1. Viscoelasticity is an index of the workability of a foamed asphalt composition, and the lower the viscoelasticity, the better the workability. <Equipment used> Rheometer "MCR301" (manufactured by Anton Paar) <Measurement conditions> Distortion: 0.1% Frequency: 5Hz Temperature: 180℃→0℃(4℃ / min) Measurement gap: 1.0 mm Measurement jig: 25mm parallel plate (disposable) Jig holder: 500 / 600 disposal dish

[0054] (2) Evaluation of asphalt peeling resistance 100 g of No. 6 crushed stone preheated to 150°C was weighed into a 200 mL stainless steel cup preheated to 150°C. 5 g of the foamed asphalt composition (1) obtained above was added and mixed for 30 seconds using a medicine spoon preheated to 150°C. Crushed stone whose surface was covered with asphalt was obtained as asphalt mixture 1. The amount of No. 6 crushed stone used as aggregate was 2000 parts by mass per 100 parts by mass of asphalt. Ten pieces of the prepared asphalt-coated crushed stone were placed on a wire mesh with 2 mm openings and cooled until the surface temperature reached 25°C. After cooling, the stones were immersed in a bath of 80°C water for 3 minutes. The asphalt-coated crushed stone was then removed and dried. After drying, the surface was photographed from above with a digital camera. The obtained images were analyzed using the image processing software ImageJ to measure the total surface area of ​​the crushed stone and the surface area of ​​the crushed stone not covered with asphalt. The peeling area (%) was calculated using the following formula. Peeling area (%) = surface area of ​​crushed stone not covered with asphalt × 100 / surface area of ​​crushed stone The results are shown in Table 1.

[0055] Examples 2 to 5 Foamed asphalt compositions (2) to (5) were obtained in the same manner as in Example 1, except that compounds A2 to A5 shown in Table 1 were used instead of compound A1. The viscosity of the foamed asphalt compositions was measured and the asphalt peeling resistance was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0056] Comparative Example 1 50 g of straight asphalt heated to 150°C was weighed into a 200 mL stainless steel cup preheated to 150°C. The viscosity of the weighed asphalt (C1) was measured and the asphalt peeling resistance was evaluated in the same manner as in Example 1.

[0057] Comparative Example 2 50 g of straight asphalt heated to 150°C was weighed into a 200 mL stainless steel cup preheated to 150°C. While stirring on a hot plate at a rotation speed of 200 rpm, the heating temperature of the hot plate was adjusted so that the surface temperature of the asphalt became 120±5°C. Tap water was added to the straight asphalt so that the amount of the mixed liquid (1) added was 2 parts by mass per 100 parts by mass of asphalt, to obtain a foamed asphalt composition (C2). In the same manner as in Example 1, the viscosity of the foamed asphalt composition was measured and the peeling resistance of the asphalt was evaluated. The results are shown in Table 1.

[0058] The type and properties of Compound A used in Examples 1 to 5 are shown below. Compound A1: Stearyltrimethylammonium chloride; carbon number 18, quaternary ammonium salt Compound A2: Coconutamine acetate; a mixture of 8:7%, 10:7%, 12:51%, 14:19%, 16:8%, and 18:8% carbon atoms, acetate salt Compound A3: Polyoxyethylene(2) laurylamine; carbon number: 12, HLB value: 6.3 Compound A4: N-3-oleylamidopropyldimethylamine lactate; carbon number 18, lactate salt Compound A5: N-tallow alkyltrimethylenediamine lactate; carbon number 18, lactate salt

[0059] [Table 1]

[0060] In Table 1, the foamed asphalt composition containing Compound A exhibited superior anti-stripping properties compared to the asphalt composition without added water. Furthermore, the foamed asphalt composition containing Compound A exhibited a lower asphalt viscosity compared to the foamed asphalt composition without Compound A, reducing the adhesive strength of the asphalt mixture to each other and to the asphalt application base, improving workability. This is thought to be because Compound A of the present invention bonds the asphalt and aggregate, improving anti-stripping properties, and, combined with the reduction in the viscosity of the asphalt due to water, effectively reduces the viscoelasticity of the asphalt composition.

Claims

1. A method for producing an asphalt mixture comprising the following steps (1) and (2) in this order: Step (1): A step of mixing heated asphalt with a mixture of the following compound A and water to obtain a foamed asphalt composition. Step (2): A step of mixing the foamed asphalt composition obtained in step (1) with heated aggregate to obtain an asphalt mixture. Compound A: (i) one or more compounds selected from the group consisting of compounds represented by the following general formula (I) and (ii) quaternary ammonium salts having an aliphatic hydrocarbon group having from 8 to 20 carbon atoms: 【Chemical 1】 [In the formula, R １ represents an aliphatic hydrocarbon group or an acyl group having from 8 to 20 carbon atoms, and R ２ represents a hydrocarbon group having 8 or less carbon atoms which may have a hydrogen atom or a heteroatom, EO represents an ethyleneoxy group, and n is 0 or more and 2 or less.

2. The method for producing an asphalt mixture according to claim 1, wherein the mixing temperature in step (2) is 100°C or higher and 140°C or lower.

3. The method for producing an asphalt mixture according to claim 1 or 2, wherein in step (1), the content of compound A in the mixed liquid is 20% by mass or more and 50% by mass or less.

4. 3. The method for producing an asphalt mixture according to claim 1 or 2, wherein in step (2), the content of compound A in the asphalt mixture is 0.1 parts by mass or more and 10 parts by mass or less per 100 parts by mass of asphalt.

5. R in the general formula (I) ２ But -(EO) ｍ H group [wherein m is 0 or more and 2 or less] and —(CH ２ ) ３ -NR ３ R ４ The group [wherein, R ３ and R ４ and each represents a hydrogen atom or a methyl group.

6. The method for producing an asphalt composition according to claim 1 or 2, wherein in step (2), the content of the aggregate in the asphalt mixture is 500 parts by mass or more and 3,000 parts by mass or less per 100 parts by mass of asphalt.

7. The method for producing an asphalt composition according to claim 1 or 2, wherein in step (2), the temperature of the heated aggregate is 100°C or higher and 230°C or lower.

8. It consists of a mixed liquid of the following compound A and water, The warming agent for asphalt, wherein the content of compound A in the mixed liquid is 20% by mass or more and 50% by mass or less. Compound A: (i) one or more compounds selected from the group consisting of compounds represented by the following general formula (I) and (ii) quaternary ammonium salts having an aliphatic hydrocarbon group having from 8 to 20 carbon atoms: 【Chemistry 2】 [In the formula, R １ represents an aliphatic hydrocarbon group or an acyl group having from 8 to 20 carbon atoms, and R ２ represents a hydrocarbon group having 8 or less carbon atoms which may have a hydrogen atom or a heteroatom, EO represents an ethyleneoxy group, and n is 0 or more and 2 or less.

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