Asphalt mixture

Abstract

The present invention relates to an asphalt mixture and a paving method that can produce a highly durable pavement in the compaction of asphalt mixtures for asphalt pavements such as roads, and that can suppress the occurrence of rutting. [Solution] An asphalt mixture containing asphalt, aggregate, polyester resin, and compound (A), wherein the aggregate contains a calcium-containing component and compound (A) is a cement setting retarder.

Description

[Technical Field]

[0001] This invention relates to asphalt mixtures and paving methods. [Background technology]

[0002] Asphalt paving is used for roads, parking lots, freight yards, and sidewalks because it is relatively easy to lay and the time from the start of paving work to the start of traffic is short. Asphalt paving is formed by an asphalt mixture in which aggregates are bound together with asphalt, so the pavement has good hardness and durability.

[0003] However, asphalt pavements develop ruts and cracks over time, necessitating repairs, which increases maintenance costs and significantly impacts automobile traffic.

[0004] Patent Document 1 discloses an additive package for a medium-temperature mixed asphalt formulation that reduces the mixing temperature and paving temperature of the heated mixed asphalt when producing a road surface without sacrificing the performance characteristics of the asphalt mixture, and at the same time improves moisture resistance. The additive package comprises a surfactant component and a rheology modifier component, wherein the surfactant component comprises at least one or more amines or modified amine surfactants, and the rheology modifier component comprises at least one or more of i) wax components and ii) resin components.

[0005] Patent Document 2 discloses an asphalt mixture for obtaining an asphalt pavement that is highly durable and can maintain its black color even after traffic is opened, which includes asphalt and aggregate containing recycled aggregate, and an asphalt modifier containing a polyester resin (A) and a compound (B) which is a compound having 8 or more carbon atoms and having a hydroxyl group or an amino group. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] International Publication No. 2009 / 062925 [Patent Document 2] Japanese Patent Publication No. 2023-36018 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] In the technology described in Patent Document 1, a novel combination of a surfactant and a rheology modifier reduces the viscosity of the mixture of asphalt binder and aggregate during the preparation of the mixture and during paving, thereby reducing the effort required for compaction to reach the optimal design density, and thus improving the ease of mixing, paving, and compacting the asphalt mixture.

[0008] In the technology described in Patent Document 2, an asphalt modifier that uses a polyester resin (A) in combination with a specific compound (B) that has high affinity with recycled asphalt aggregate improves the coating state of the aggregate by the binder composition, thereby maintaining the durability and blackness of the paint.

[0009] However, in the technologies described in Patent Documents 1 and 2, the calcium carbonate contained in the aggregate in the asphalt mixture at a concentration of about 5% by mass has the property of adsorbing onto polyester, which reduces the dispersibility of the aggregate in the asphalt mixture and prevents the maximum improvement of pavement performance.

[0010] The present invention relates to an asphalt mixture and a paving method that can produce a highly durable pavement in the compaction of asphalt mixtures for asphalt pavements such as roads, and that can suppress the occurrence of rutting. [Means for solving the problem]

[0011] The inventors of the present invention have discovered that the durability of the pavement, i.e., its resistance to rutting, can be improved by incorporating a cement setting retarder into the asphalt mixture, and have completed the present invention. The present invention relates to the following [1] to [3]. [1] An asphalt mixture comprising asphalt, aggregate, polyester resin, and compound (A), wherein the aggregate contains a calcium-containing component and compound (A) is a cement setting retarder. [2] A method for producing an asphalt mixture, comprising: step 1 of mixing asphalt and heated aggregate to obtain an asphalt and aggregate mixture; and step 2 of mixing the obtained asphalt and aggregate mixture with polyester resin and compound (A) to obtain an asphalt mixture, wherein the aggregate contains a calcium-containing component and compound (A) is a cement setting retarder. [3] A paving method comprising: step 1 of mixing asphalt and heated aggregate to obtain a mixture of asphalt and aggregate; step 2 of mixing the obtained mixture of asphalt and aggregate with polyester resin and compound (A) to obtain an asphalt mixture; and step 3 of compacting the obtained asphalt mixture, wherein the aggregate is formulated with a calcium-containing component and compound (A) is a cement setting retarder. [Effects of the Invention]

[0012] According to the present invention, in the compaction of asphalt mixtures for asphalt pavements such as roads, it is possible to create a pavement body with excellent durability, specifically an asphalt mixture and a paving method that can suppress the occurrence of rutting. [Modes for carrying out the invention]

[0013] [Asphalt mixture] The asphalt mixture of the present invention is an asphalt mixture containing asphalt, aggregate, polyester resin, and the following compound (A), wherein the aggregate contains a calcium-containing component, and the compound (A) is a cement setting retarder.

[0014] A cement setting retarder is an admixture that delays the setting or hardening of concrete. When this cement setting retarder is blended into a hot asphalt mixture, adsorption onto the surface of the aggregate etc. occurs due to the setting retarder, and the rutting resistance of the pavement improves.

[0015] The reason is not necessarily fully clear, but by adding a cement setting retarder to the asphalt mixture, the hydroxy group (-OH) and carboxy group (-CO2H) of the cement setting retarder are sacrificially adsorbed onto calcium carbonate, suppressing the adsorption of the polyester resin onto calcium carbonate, improving the dispersibility of the polyester resin in the asphalt mixture, and it is presumed that pavement performance such as durability and compactness is improved. That is, when a cement setting retarder is used in concrete containing cement, aggregate, and water, it is considered that the retarder adsorbs onto the particle surface of the unhydrated cement, temporarily hindering the hydration reaction of the cement and thus delaying the setting of the cement. In contrast, when a cement setting retarder is used in an asphalt mixture containing asphalt, aggregate, and polyester resin, it is considered that the retarder adsorbs onto calcium carbonate in the aggregate, the polyester resin is dispersed in the asphalt mixture, and the pavement performance such as the original durability and compactness of the polyester resin can fully exhibit the improvement effect.

[0016] <Asphalt mixture> The said asphalt mixture contains asphalt, aggregate, polyester resin, and compound (A). Hereinafter, each component of asphalt, aggregate, polyester resin, and compound (A) will be described.

[0017] (Asphalt) Various types of asphalt can be used. For example, in addition to straight asphalt, which is petroleum asphalt for paving, modified asphalt can be used. Modified asphalts include blown asphalt and polymer-modified asphalt, which is modified with polymer materials such as thermoplastic elastomers and thermoplastic resins. Straight asphalt refers to the residual bituminous substance obtained by subjecting crude oil to atmospheric distillation, vacuum distillation, etc. Blown asphalt refers to asphalt obtained by heating a mixture of straight asphalt and heavy oil, and then blowing air into it to oxidize it. It is preferable to select from straight asphalt and polymer-modified asphalt, with polymer-modified asphalt being more preferable from the viewpoint of pavement durability, and straight asphalt being more preferable from the viewpoint of versatility. Among polymer-modified asphalts, asphalt modified with thermoplastic elastomers is more preferable. The modified asphalt is preferably polymer-modified asphalt, and more preferably polymer-modified asphalt modified with a thermoplastic elastomer.

[0018] • Thermoplastic elastomer Examples of the thermoplastic elastomer in the polymer-modified asphalt modified with a thermoplastic elastomer include at least one selected from a styrene / butadiene block copolymer, a styrene / butadiene / styrene block copolymer, a styrene / butadiene random copolymer, a styrene / isoprene block copolymer, a styrene / isoprene / styrene block copolymer, a styrene / isoprene random copolymer, an ethylene / vinyl acetate copolymer, an ethylene / acrylic ester copolymer, a styrene / ethylene / butylene / styrene copolymer, a styrene / ethylene / propylene / styrene copolymer, a polyurethane-based thermoplastic elastomer, a polyolefin-based thermoplastic elastomer, an isobutylene / isoprene copolymer, polyisoprene, polychloroprene, a synthetic rubber other than those described above, and natural rubber. The thermoplastic elastomer in the modified asphalt is preferably at least one selected from a styrene / butadiene block copolymer, a styrene / butadiene / styrene block copolymer, a styrene / butadiene random copolymer, a styrene / isoprene block copolymer, a styrene / isoprene / styrene block copolymer, a styrene / isoprene random copolymer, an ethylene / vinyl acetate copolymer, and an ethylene / acrylic ester copolymer.

[0019] Among these, the thermoplastic elastomer is preferably at least one selected from styrene / butadiene block copolymer, styrene / butadiene / styrene block copolymer, styrene / butadiene random copolymer, styrene / isoprene block copolymer, styrene / isoprene / styrene block copolymer, styrene / isoprene random copolymer, and ethylene / acrylic acid ester copolymer, more preferably at least one selected from styrene / butadiene block copolymer, styrene / butadiene / styrene block copolymer, styrene / butadiene random copolymer, styrene / isoprene block copolymer, and styrene / isoprene random copolymer, and even more preferably at least one selected from styrene / butadiene random copolymer and styrene / butadiene / styrene block copolymer.

[0020] From the viewpoint of the durability of the pavement, the content of thermoplastic elastomer in the polymer-modified asphalt is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, even more preferably 1% by mass or more, and preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less.

[0021] (aggregate) The aggregate used in this invention contains a calcium-containing component in addition to the main component of the aggregate. The main component, aggregate, can be arbitrarily selected and used from crushed stone, pebbles, gravel, sand, ceramics, etc. The aggregate can be used as coarse aggregate with a particle size of 2.36 mm or more, fine aggregate with a particle size of 0.075 mm or more and less than 2.36 mm, or filler with 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. Fine aggregates include, for example, river sand, hill sand, mountain sand, sea sand, crushed sand, fine sand, screenings, crushed stone dust, silica sand, artificial sand, glass cullet, and foundry sand. The particle sizes of coarse and fine aggregates are based on the sieving test method specified in JIS A5001:2008.

[0022] Examples of calcium-containing components include fly ash, calcium silicate, limestone powder, slaked lime, and shells and corals found in sand such as sea sand. Among these, from the viewpoint of durability of the asphalt mixture, one or more selected from the group consisting of limestone powder, shells, and corals are preferred.

[0023] From the viewpoint of the strength of the pavement, the limestone powder content in the aggregate is preferably 3% by mass or more, more preferably 4% by mass or more, and even more preferably 5% by mass or more. Here, the limestone powder consists of calcium carbonate, and its purity is substantially 100% by mass. Calcium carbonate has the property of adsorbing polyester resin. For this reason, if the limestone powder content is excessive, the amount of calcium carbonate adsorbed to the polyester resin in the asphalt mixture will increase, which may reduce the dispersibility of the aggregate in the asphalt mixture and prevent sufficient modification of the asphalt mixture and pavement. From this viewpoint, the limestone powder content in the aggregate is preferably 10% by mass or less, more preferably 8% by mass or less, and even more preferably 7% by mass or less.

[0024] The average particle size of calcium carbonate is preferably 0.001 mm or larger, more preferably 0.05 mm or smaller, more preferably 0.03 mm or smaller, even more preferably 0.02 mm or smaller, and even more preferably 0.01 mm or smaller, from the viewpoint of functioning as a filler and improving the strength of the pavement. Here, the average particle size is the average particle size at 50% volume accumulation (D 50 This means that it can be measured with a laser diffraction particle size distribution analyzer.

[0025] It is preferable to use both coarse and fine aggregates as aggregate. Coarse and fine aggregates are usually distinguished by whether or not most of them can pass through a sieve with a mesh size of 4.76 mm (5 mm sieve). The mass ratio of coarse aggregate to fine aggregate (coarse aggregate / fine aggregate) is preferably 10 / 90 or more, more preferably 15 / 85 or more, even more preferably 20 / 80 or more, and preferably 90 / 10 or less, more preferably 80 / 20 or less, and even more preferably 70 / 30 or less, from the viewpoint of the durability of the pavement.

[0026] The asphalt mixture of the present invention may contain recycled asphalt aggregate as aggregate. The aggregate may also consist only of recycled asphalt aggregate and not contain any new aggregate. Recycled asphalt aggregate is made by collecting used asphalt pavement, crushing it, and classifying it. Used asphalt pavements derived from recycled asphalt aggregate may contain asphalt and aggregate, and may contain other additives as needed.

[0027] Furthermore, the asphalt contained in recycled asphalt aggregate is physically and chemically degraded 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, flexural strength, fracture strain, and asphalt composition. Generally, asphalt in which the marten fraction has migrated to asphaltene and the penetration has decreased is often called degraded asphalt. However, even if the penetration of recycled asphalt is equivalent to that of new asphalt, changes in other properties may prevent it from exhibiting the same performance as new asphalt.

[0028] (Polyester resin) The asphalt mixture of the present invention contains a polyester resin. The polyester resin is an amorphous polyester resin and a crystalline polyester resin, preferably an amorphous polyester resin, and is a polycondensate of an alcohol component and a carboxylic acid component, comprising structural units derived from an alcohol component and structural units derived from a carboxylic acid component. The following describes the properties of the alcohol component, carboxylic acid component, and polyester resin.

[0029] • Alcohol content Examples of alcohol components include chain-type aliphatic diols, alicyclic diols, aromatic diols, and polyhydric alcohols with a hydride of three or more. These alcohol components can be used individually or in combination of two or more.

[0030] The chain-like aliphatic diol is preferably a straight-chain or branched chain-like aliphatic diol with 2 to 12 carbon atoms in the main chain, more preferably 2 to 8 carbon atoms. Furthermore, the chain-type aliphatic diol is preferably a saturated chain-type aliphatic diol. Specific examples of chain-type 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.

[0031] Examples of alicyclic diols include hydrogenated bisphenol A (2,2-bis(4-hydroxycyclohexyl)propane), alkylene oxide adducts of hydrogenated bisphenol A, cyclohexanediol, and cyclohexanedimethanol.

[0032] 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 those represented by the following formula (I).

[0033] [ka]

[0034] [In formula (I), OR 1 and R 1 O is an alkylene oxide, and R 1 x is an alkylene group having 2 or 3 carbon atoms, x and y are positive numbers representing the average number of added moles of alkylene oxide, and the sum of x and y is preferably 1 or more, more preferably 1.5 or more, and preferably 16 or less, more preferably 8 or less, and even more preferably 4 or less.

[0035] Examples of alkylene oxide adducts of bisphenol A represented by formula (I) include propylene oxide adducts of bisphenol A and ethylene oxide adducts of bisphenol A. These alkylene oxide adducts of bisphenol A can be used individually or in combination of two or more.

[0036] The polyhydric alcohol with a valency of three or higher is preferably a trihydric alcohol. Examples of polyhydric alcohols with a valency of three or higher include glycerin, pentaerythritol, trimethylolpropane, and sorbitol.

[0037] The alcohol component may further contain monohydric aliphatic alcohols from the viewpoint of adjusting physical properties. Examples of monohydric aliphatic alcohols include lauryl alcohol, myristyl alcohol, palmityl alcohol, and stearyl alcohol. These monohydric aliphatic alcohols can be used individually or in combination of two or more.

[0038] • Carboxylic acid components Examples of carboxylic acid components include aliphatic dicarboxylic acids, aromatic dicarboxylic acids, and polycarboxylic acids with a valency of 3 to 6. These carboxylic acid components can be used individually or in combination of two or more.

[0039] Examples of aliphatic dicarboxylic acids include those having a main chain with four or more carbon atoms, preferably 10 or fewer, more preferably 8 or fewer, and more preferably 6 or fewer carbon atoms. Specifically, examples include fumaric acid, maleic acid, oxalic acid, malonic acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, dodecanediic 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 their anhydrides, or their alkyl esters (for example, alkyl groups with 1 to 3 carbon atoms). Examples of substituted succinic acids include dodecyl succinic acid, dodecenyl succinic acid, and octenyl succinic acid.

[0040] Succinic acid substituted with an alkyl group having 1 to 20 carbon atoms or an alkenyl group having 2 to 20 carbon atoms, or their anhydrides, can be manufactured, for example, in accordance with the description in Japanese Patent Publication No. 2008-145712. Commercially available products can also be used.

[0041] Examples of aromatic dicarboxylic acids include phthalic acid, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, or their anhydrides, or their alkyl esters (for example, alkyl groups with 1 to 3 carbon atoms). Among these aromatic dicarboxylic acids, isophthalic acid and terephthalic acid are preferred from the viewpoint of durability, and terephthalic acid is more preferred.

[0042] The polycarboxylic acid with a valency of 3 to 6 is preferably a tricarboxylic acid. Examples of polycarboxylic acids with a valency of 3 to 6 include trimellitic acid, 2,5,7-naphthalentricarboxylic acid, pyromellitic acid, or their acid anhydrides.

[0043] From the viewpoint of adjusting physical properties, the carboxylic acid component may further contain monovalent aliphatic carboxylic acids. Examples of monovalent aliphatic carboxylic acids include lauric acid, myristic acid, palmitic acid, stearic acid, and monovalent aliphatic carboxylic acids with 12 to 20 carbon atoms, such as alkyl (1 to 3 carbon atoms) esters of these acids. These monovalent aliphatic carboxylic acids can be used alone or in combination of two or more.

[0044] • Constituent units derived from polyethylene terephthalate The polyester resin may be polyethylene terephthalate containing constituent units derived from ethylene glycol and terephthalic acid. In addition to the constituent units derived from ethylene glycol and terephthalic acid, polyethylene terephthalate may also contain small amounts of other components such as butanediol and isophthalic acid.

[0045] In a preferred embodiment of the polyester resin, from the viewpoint of ensuring compatibility with asphaltene in asphalt, the content of terephthalic acid in 100 mol% of the carboxylic acid component is preferably 20 mol% or more, more preferably 40 mol% or more, even more preferably 60 mol% or more, and preferably 100 mol% or less.

[0046] Furthermore, in a preferred embodiment of the polyester resin, from the viewpoint of further improving durability by interacting with asphaltene in asphalt, the content of the alkylene oxide adduct of bisphenol A in 100 mol% of the alcohol component is preferably 10 mol% or more, more preferably 20 mol% or more, even more preferably 30 mol% or more, and preferably 100 mol% or less.

[0047] • Physical properties of polyester resin From the viewpoint of the durability of the pavement, the softening point of the polyester resin is preferably 80°C or higher, more preferably 85°C or higher, even more preferably 90°C or higher, and preferably 140°C or lower, more preferably 130°C or lower, even more preferably 120°C or lower, and even more preferably 115°C or lower.

[0048] The glass transition temperature of the polyester resin is preferably 40°C or higher, more preferably 45°C or higher, even more preferably 50°C or higher, and preferably 80°C or lower, more preferably 75°C or lower, and even more preferably 70°C or lower, from the viewpoint of the durability of the pavement.

[0049] The acid value of the polyester resin is preferably 1 mg KOH / g or more, more preferably 3 mg KOH / g or more, even more preferably 5 mg KOH / g or more, from the viewpoint of durability of the pavement, and more preferably 60 mg KOH / g or less, more preferably 30 mg KOH / g or less, and even more preferably 10 mg KOH / g or less, from the viewpoint of improving the water resistance of the pavement surface.

[0050] The hydroxyl value of the polyester resin is preferably 1 mg KOH / g or more, more preferably 10 mg KOH / g or more, even more preferably 20 mg KOH / g or more, and preferably 50 mg KOH / g or less, more preferably 45 mg KOH / g or less, and even more preferably 35 mg KOH / g or less, from the viewpoint of the durability of the pavement.

[0051] The softening point, glass transition point, acid value, and hydroxyl value of polyester resin can be measured by the method described in the examples. Note that the softening point, glass transition point, acid value, and hydroxyl value can be adjusted by the raw material monomer composition, molecular weight, catalyst amount, or reaction conditions.

[0052] The polyester resin may be a modified polyester resin to the extent that its properties are not substantially impaired. Modified polyester resins include, for example, polyester resins grafted or blocked with phenol, urethane, epoxy, etc., by methods described in Japanese Patent Publication No. 11-133668, Japanese Patent Publication No. 10-239903, Japanese Patent Publication No. 8-20636, etc. Specifically, these include urethane-modified polyester resins obtained by urethane elongation of polyester resin with a polyisocyanate compound.

[0053] • Manufacturing method of polyester resin The polyester resin can be produced, for example, by polycondensation of the aforementioned alcohol component and carboxylic acid component. The temperature of the polycondensation reaction is preferably 160°C or higher, more preferably 190°C or higher, even more preferably 200°C or higher, and preferably 260°C or lower, more preferably 250°C or lower, and even more preferably 240°C or lower, from the viewpoint of adjusting the reactivity and the durability of the pavement.

[0054] When the polyester resin contains constituent units derived from ethylene glycol derived from polyethylene terephthalate and constituent units derived from terephthalic acid derived from polyethylene terephthalate, the amount of polyethylene terephthalate present in the raw material is preferably 5% by mass or more, more preferably 15% by mass or more, even more preferably 25% by mass or more, and preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 60% by mass or less, based on the total amount of polyethylene terephthalate, alcohol component and carboxylic acid component.

[0055] By adding polyethylene terephthalate during the polycondensation reaction between the alcohol component and the carboxylic acid component, a transesterification reaction occurs, resulting in a polyester resin in which the constituent units of polyethylene terephthalate are incorporated into the constituent units derived from the alcohol component and the constituent units derived from the carboxylic acid component.

[0056] Polyethylene terephthalate may be present from the start of the polycondensation reaction or added to the reaction system during the reaction. From the viewpoint of the durability of the pavement, the timing of adding polyethylene terephthalate is preferably when the reaction rate between the alcohol component and the carboxylic acid component is 10% or less, and more preferably when it is 5% or less. The reaction rate is defined as the value of (moles) of the amount of reaction water produced / (moles) of the theoretical amount of reaction water produced × 100.

[0057] From the viewpoint of reaction rate, an esterification catalyst can be used in the polycondensation reaction. Examples of esterification catalysts include tin(II) compounds that do not have a Sn-C bond, such as di(2-ethylhexanoic acid)tin(II). From the viewpoint of reaction rate, the amount of esterification catalyst used is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, even more preferably 0.2 parts by mass or more, and preferably 2.0 parts by mass or less, more preferably 1.5 parts by mass or less, and even more preferably 1.0 part by mass or less, per 100 parts by mass of the total amount of alcohol and carboxylic acid components. In addition to the esterification catalyst, a co-catalyst can be used in the polycondensation reaction. Examples of co-catalysts include pyrogallol compounds such as gallic acid. The amount of co-catalyst used is preferably 0.005 parts by mass or more, more preferably 0.01 parts by mass or more, even more preferably 0.03 parts by mass or more, even more preferably 0.05 parts by mass or more, and preferably 0.20 parts by mass or less, more preferably 0.15 parts by mass or less, and even more preferably 0.10 parts by mass or less, based on 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component.

[0058] (Compound (A)) Compound (A) is a cement setting retarder, specifically a Portland cement setting retarder. A cement setting retarder is an admixture that delays the initial hydration reaction by adsorbing onto the surface of cement particles and temporarily blocking contact between cement and water. In this invention, unlike cement that undergoes a hydration reaction, it has been found that by incorporating a cement setting retarder into a high-temperature asphalt mixture, adsorption of the setting retarder onto the aggregate surface, etc., occurs in a substantially water-free environment, improving the rutting resistance of the pavement.

[0059] Cement setting retarders include organic types such as oxycarboxylic acids, polycarboxylic acids, sugars, cellulose, high molecular weight organic acids, and alcohols, and inorganic types such as silicic acid fluoride, boric acid, borax, phosphates, and zinc compounds. Of these, the present invention uses organic cement setting retarders. All of the aforementioned organic cement setting retarders have hydroxyl groups (-OH) and carboxyl groups (-CO2H) in common. It is believed that these hydroxyl groups (-OH) and carboxyl groups (-CO2H) adsorb to calcium carbonate in the aggregate, thereby suppressing the adsorption of polyester resin to calcium carbonate, and as a result, improving the dispersibility of polyester in the asphalt mixture and improving the performance of the asphalt mixture, such as durability and compaction.

[0060] In the present invention, it is preferable to use one or more compounds selected from the group consisting of (i) oxycarboxylic acids and their salts, (ii) polycarboxylic acids and their salts, (iii) sugars, and (iv) water-soluble cellulose ethers as compound (A).

[0061] (i) Oxycarboxylic acids and their salts The oxycarboxylic acid according to the present invention is an oxycarboxylic acid with a total number of carbon atoms, including the carbon atom of the carboxyl group, of 2 to 15. Specifically, examples include tartaric acid, glyceric acid, glycolic acid, citric acid, lactic acid, pyruvic acid, tropic acid, benzyl acid, malic acid, tartaric acid, etc. Of these, oxycarboxylic acids with a total number of carbon atoms, including the carbon atom of the carboxyl group, of 7 or less, specifically 3 or less, are preferred. Salts include alkali metal salts, alkaline earth metal salts, ammonium salts, amine salts, etc. Examples of alkali metal salts and alkaline earth metal salts include sodium salts, potassium salts, calcium salts, etc. The oxycarboxylic acid and its salts can be used individually or in combination of two or more types.

[0062] (ii) Polycarboxylic acids and their salts The polycarboxylic acid according to the present invention is a carboxylic acid having 2 to 6 valences, preferably a carboxylic acid having 3 to 6 valences, more preferably a trivalent carboxylic acid. Examples of the divalent carboxylic acid include HO2CR 1 CO2H (R 1 represents a direct bond between both carboxy groups or an alkylene group having 1 to 4 carbon atoms in the main chain), a saturated polycarboxylic acid represented by HO2CR 2 CO2H (R 2 represents an aliphatic hydrocarbon group having 2 to 4 carbon atoms in the main chain and having an unsaturated double bond), an unsaturated polycarboxylic acid represented by. R 1 The alkylene group of 2 The unsaturated hydrocarbon group of may be branched. Examples of the saturated polycarboxylic acid (HO2CR 1 CO2H) include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, etc., and examples of the unsaturated polycarboxylic acid (HO2CR 2 CO2H) include maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, etc. The saturated polycarboxylic acid and the unsaturated polycarboxylic acid may be anhydrides. Further, the saturated carboxylic acid and the unsaturated carboxylic acid may be used in combination. The polycarboxylic acid component may contain aliphatic polycarboxylic acids such as azelaic acid and sebacic acid, and aromatic polycarboxylic acids such as aromatic polycarboxylic acids such as aliphatic polycarboxylic acids. Examples of the polycarboxylic acid having 3 to 6 valences include trimellitic acid, 2,5,7-naphthalenetricarboxylic acid, pyromellitic acid, or acid anhydrides thereof. Among the polycarboxylic acids having 2 to 6 valences, trimellitic acid, 2,5,7-naphthalenetricarboxylic acid, or pyromellitic acid, which are trivalent carboxylic acids, are more preferable.

[0063] The salts of the polycarboxylic acid are alkali metal salts, alkaline earth metal salts, ammonium salts, amine salts, etc. of the above-mentioned carboxylic acids having 3 to 6 valences. Examples of the alkali metal salts and alkaline earth metal salts include sodium salts, potassium salts, calcium salts, etc. ​The aforementioned polycarboxylic acids can be used alone or in combination of two or more.

[0064] (iii) Sugars The sugars are one or more selected from the group consisting of monosaccharides, disaccharides, and polysaccharides. Examples of monosaccharides include glucose, fructose, and galactose; examples of disaccharides include maltose, sucrose, lactose, and trehalose; and examples of polysaccharides include cellulose, dextrin, maltodextrin, cyclodextrin, corn starch, tapioca starch, rice starch, wheat starch, potato starch, and xanthan gum. As for the sugars, sucrose fatty acid esters, in which a fatty acid is ester-bonded to the hydroxyl group of sucrose, may be used, or so-called refined sugar, which is mainly composed of sucrose and contains about 1% each of water and invert sugar (an equal mixture of glucose and fructose), may be used. In addition, sugar alcohols such as erythritol, xylitol, and mannitol may be used. The aforementioned sugars can be used individually or in combination of two or more types.

[0065] (iv) Water-soluble cellulose ether Water-soluble cellulose ethers include alkylcellulose such as methylcellulose (MC), hydroxyalkylcellulose such as hydroxyethylcellulose (HEC) and hydroxypropylcellulose (HPC), hydroxyalkylalkylcellulose such as hydroxyethylmethylcellulose (HEMC), hydroxypropylmethylcellulose (HPMC), and hydroxyethylethylcellulose (HEEC), and carboxymethylcellulose. The aforementioned water-soluble cellulose ether can be used alone or in combination of two or more types.

[0066] • Content of each component From the viewpoint of durability, the asphalt content in the asphalt mixture is preferably 1% by mass or more, more preferably 3% by mass or more, even more preferably 4% by mass or more, and preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less.

[0067] 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, and even more preferably 96% by mass or less.

[0068] Examples of suitable aggregate compositions in asphalt mixtures include the following (1) to (3): (1) Fine-graded asphalt comprising 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 comprising, for example, 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 comprising 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.

[0069] In addition, the mixing ratio of asphalt in conventional asphalt mixtures containing aggregate and asphalt is usually determined according to the optimal amount of asphalt found in the "Asphalt Composition Mix Design" described in the "Pavement Design and Construction Guidelines" published by the Japan Road Association.

[0070] In this invention, the above-mentioned optimal amount of asphalt corresponds to the total amount of asphalt and asphalt modifier. However, it is not necessary to limit the method to the method described in the "Guidelines for Pavement Design and Construction," and it may be determined by other methods.

[0071] Aggregates are hydrophilic and asphalt is hydrophobic, so they do not naturally mix well. In water, delamination can occur at the interface, which can significantly reduce the rutting resistance of asphalt-mixed molded bodies in a water-immersed state. However, by dispersing polyester in the asphalt mixture to adsorb the aggregate, rutting resistance can be greatly improved.

[0072] From the viewpoint of compaction properties, the content of compound (A) in the asphalt mixture is preferably 0.03 parts by mass or more, more preferably 0.05 parts by mass or more, even more preferably 0.1 parts by mass or more, even more preferably 0.3 parts by mass or more, and preferably 20 parts by mass or less, more preferably 16 parts by mass or less, even more preferably 11 parts by mass or less, and even more preferably 7 parts by mass or less.

[0073] From the viewpoint of compaction properties, the content of compound (A) in the asphalt mixture is preferably 0.5 parts by mass or more, more preferably 0.7 parts by mass or more, even more preferably 1 part by mass or more, and preferably 20 parts by mass or less, and more preferably 15 parts by mass or less, per 100 parts by mass of polyester resin.

[0074] From the viewpoint of durability of the pavement, the polyester resin content is preferably 1 part by mass or more, more preferably 7 parts by mass or more, even more preferably 10 parts by mass or more, and even more preferably 14 parts by mass or more, per 100 parts by mass of asphalt. From the viewpoint of maintaining flexibility, it is preferably 40 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 25 parts by mass or less.

[0075] [Method for producing asphalt mixture] The present invention provides a method for producing an asphalt mixture, comprising: step 1, mixing asphalt and heated aggregate to obtain an asphalt and aggregate mixture; and step 2, mixing the obtained asphalt and aggregate mixture with a polyester resin and compound (A) to obtain an asphalt mixture, wherein the aggregate contains a calcium-containing component, and compound (A) is a cement setting retarder.

[0076] In step 1, the temperature at which the asphalt and heated aggregate are mixed is preferably 130°C or higher, more preferably 140°C or higher, and preferably 200°C or lower, more preferably 190°C or lower, and even more preferably 180°C or lower, from the viewpoint of softening the asphalt. 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. There is no particular upper limit to the time, but for example it is about 30 minutes.

[0077] In step 2, the temperature at which the mixture of asphalt and aggregate obtained is mixed with the polyester resin and compound (A) is preferably 130°C or higher, more preferably 140°C or higher, and preferably 200°C or lower, more preferably 190°C or lower, and even more preferably 180°C or lower, from the viewpoint of softening the asphalt. 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 for example it is about 30 minutes.

[0078] The mixing process preferably includes a step of stirring and mixing the components in a commonly used mixer until each component is uniformly dispersed. Commonly used mixers include homomixers, dissolvers, paddle mixers, ribbon mixers, screw mixers, planetary mixers, vacuum backflow mixers, roll mills, and twin-screw extruders.

[0079] The asphalt mixture of the present invention may be used as a hot asphalt mixture that is substantially free of water, or water may be added to the above asphalt mixture to form an asphalt emulsion, and aggregates and the like may be added thereto to form a room-temperature asphalt mixture. The asphalt mixture of the present invention is preferably used as hot asphalt. From the viewpoint of exhibiting asphalt performance, the asphalt mixture is preferably substantially free of water.

[0080] [Paving Method] In the present invention, the pavement body is, for example, an asphalt pavement layer for roads, parking lots, etc. Therefore, the paving method is a method of compacting and applying the asphalt mixture to a pavement target such as a road or parking lot to form an asphalt pavement layer. The asphalt pavement layer may be either a base layer or a surface layer, but from the viewpoint of exhibiting durability, it is usually the surface layer.

[0081] The paving method of the present invention comprises the steps of: step 1, mixing asphalt and heated aggregate to obtain an asphalt and aggregate mixture; step 2, mixing the obtained asphalt and aggregate mixture with polyester resin and compound (A) to obtain an asphalt mixture; and step 3, compacting the obtained asphalt mixture, wherein the aggregate is formulated with a calcium-containing component, and compound (A) is a cement setting retarder.

[0082] The aforementioned paving method further includes step 3 in addition to steps 1 and 2 of the method for producing the asphalt mixture. Step 3 includes compacting the asphalt mixture at a temperature of 145°C or lower.

[0083] Compaction can be carried out, for example, using the same construction machinery setup as for regular asphalt paving. The compaction temperature of the asphalt mixture is 145°C or lower. Preferably, the compaction temperature is 100°C or higher, more preferably 120°C or higher, and preferably 140°C or lower. [Examples]

[0084] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited in any way by these. In the examples and comparative examples, unless otherwise specified, parts and percentages are based on mass. Various physical properties were measured and evaluated using the following methods.

[0085] (1) Softening point of polyester resin Using a CFT-500D flow tester (manufactured by Shimadzu Corporation), 1 g of the sample was heated at a heating rate of 6°C / min while a load of 1.96 MPa was applied by a plunger and extruded through a nozzle with a diameter of 1 mm and a length of 1 mm. The amount of plunger descent of the flow tester was plotted against temperature, and the temperature at which half of the sample flowed out was defined as the softening point.

[0086] (2) Glass transition temperature of polyester resin Using a differential scanning calorimeter "Q-100" (manufactured by TA Instruments Japan Co., Ltd.), 0.01 to 0.02 g of the sample was sealed in an aluminum pan and heated to 200°C. From that temperature, it was cooled to 0°C at a rate of 10°C / min. Next, measurements were taken while heating to 150°C at a rate of 10°C / min. The temperature at the intersection of the extension of the baseline below the maximum endothermic peak temperature and the tangent line showing the maximum slope from the rise of the peak to the peak apex was defined as the glass transition point.

[0087] (3) Acid value and hydroxyl value of polyester resin The acid value and hydroxyl value of the polyester resin were measured according to the method of JIS K0070:1992. However, the measurement solvent was changed from the mixed solvent of ethanol and ether specified in JIS K0070:1992 to a mixed solvent of acetone and toluene (acetone:toluene = 1:1 (volume ratio)).

[0088] Manufacturing Example 1 BPA-PO, as shown in Table 1, was placed in a 5-liter four-necked flask equipped with a thermometer, stainless steel stirring rod, a fall-flow condenser, and a nitrogen inlet tube, and heated to 100°C. Terephthalic acid was added at 100°C, followed by the addition of 20 g of tin(II) di(2-ethylhexanoate) and 2 g of gallic acid under a nitrogen atmosphere at 100°C, and the temperature was increased to 235°C at a rate of 2.0°C / min. After reaching 235°C, the polymerization reaction was carried out for 3 hours, and after cooling to 180°C, PET was added. The temperature was then increased to 235°C at a rate of 0.5°C / min, and after reaching 235°C, the polymerization reaction was carried out for 8 hours, and after cooling to 180°C, alkenyl succinic anhydride was added. The temperature was increased from 180°C to 220°C at a rate of 0.3°C / min, and the reaction was carried out at 220°C and 20 kPa until the softening point shown in Table 1 was reached, yielding polyester resin P1. Table 1 shows the amount and molar ratio of each raw material, as well as the physical properties of polyester resin P1.

[0089] [Table 1]

[0090] Example 1 15 kg of aggregate with the following composition (1), heated to 180°C, was placed in an asphalt mixer and mixed at 180°C for 60 seconds. Then, 0.83 kg of modified type II asphalt (Epochphalt D (product name), manufactured by Nisshin Kasei Co., Ltd.), heated to 180°C, was added and mixed in the asphalt mixer for 1 minute. Subsequently, 161.2 g of the polyester resin P1 obtained in Production Example 1 and 4.8 g of citric acid, which is compound (A-1) in a content of 3 parts by mass per 100 parts by mass of polyester resin P1, were added simultaneously and mixed for a further 1 minute to obtain an asphalt mixture. The content of compound (A) in the asphalt mixture was 0.6 parts by mass per 100 parts by mass of asphalt. The obtained asphalt mixture was allowed to cool to approximately 170°C, and then 1180g was filled into a mold. The temperature of the asphalt mixture was then measured again, and when it reached 165°C, both sides were compacted 75 times each using an automatic asphalt compaction machine (model number: NA-507, manufactured by Nakajima Gihan Co., Ltd.) to form the structure. After that, it was allowed to cool to room temperature for 15 hours to obtain asphalt specimen M-1 as a pavement.

[0091] <Composition of aggregate (1)> Crushed stone No. 6, 40.0 parts by mass Crushed stone No. 7, 13.0 parts by mass 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 mass Passed mass%: Sieve mesh size 19.0 mm: 100% mass Sieve mesh size 9.50 mm: 80.1% by mass Sieve mesh size 4.75 mm: 59.4% by mass Sieve mesh size 2.36 mm: 43.4% by mass Sieve mesh size 1.18 mm: 29.1% by mass Sieve mesh size 600 μm: 18.9% by mass Sieve mesh size 300 μm: 11.7% by mass Sieve mesh size 150 μm: 7.6% by mass

[0092] [evaluation] The obtained asphalt specimens were subjected to the following evaluation tests. <Water immersion wheel tracking test> In a constant temperature chamber set to 60°C, asphalt specimens were immersed in 60°C hot water. Using a wheel tracking tester (manufactured by Iwata Industries Co., Ltd.), a 47mm wide steel wheel was driven back and forth over the specimen at a load of 686N and a linear pressure of 291.5N / cm at a frequency of 21 times per minute (21 round trips). The displacement after 2,000 passes was measured and defined as the rutting depth. Other measurement conditions followed the "B003 Wheel Tracking Test" described in the "Pavement Survey and Testing Methods Handbook" published by the Japan Road Association. The smaller the value of rutting, the more durable the asphalt pavement. The results are shown in Table 2.

[0093] Examples 2-9 Asphalt specimens M-2 to M-9 were obtained as pavement bodies in the same manner as in Example 1, except that compounds (A-2) to (A-9) shown in Table 2 were used instead of compound (A-1). The amount of rutting was measured in the same manner as in Example 1. The results are shown in Table 2.

[0094] Examples 10-13 Asphalt specimens M-10 to M-13 were obtained as pavement bodies in the same manner as in Example 1, except that compounds (A-10) to (A-13) shown in Table 2 were used instead of compound (A-1) so that the content of compound (A) was 11 parts by mass per 100 parts by mass of polyester resin P1 and the content of compound (A) was 2 parts by mass per 100 parts by mass of asphalt. The amount of rutting was measured in the same manner as in Example 1. The results are shown in Table 2.

[0095] Comparative Example 1 Asphalt specimen M-c1 was obtained as a pavement in the same manner as in Example 1, except that compound (A-1) was not used. The amount of rutting was measured in the same manner as in Example 1. The results are shown in Table 2.

[0096] <Aggregates of composition (2)> Crushed stone No. 6, 40.0 parts by mass Crushed stone No. 7, 13.0 parts by mass Sea sand 41.0 parts by mass Stone powder (calcium carbonate) 6.0 parts by mass Passed mass%: Sieve mesh size 19.0 mm: 100% mass Sieve mesh size 9.50 mm: 80.1% by mass Sieve mesh size 4.75 mm: 59.4% by mass Sieve mesh size 2.36 mm: 40.2% by mass Sieve mesh size 1.18 mm: 32.1% by mass Sieve mesh size 600 μm: 23.4% by mass Sieve mesh size 300 μm: 15.3% by mass Sieve mesh size 150 μm: 7.6% by mass

[0097] Example 14 Asphalt specimen M-14 was obtained as a pavement in the same manner as in Example 1, except that compound (A-2) shown in Table 2 was used instead of compound (A-1), and aggregate of composition (2) was used instead of aggregate of composition (1). The amount of rutting was measured in the same manner as in Example 1. The results are shown in Table 2.

[0098] Example 15 Asphalt specimen M-15 was obtained as a pavement in the same manner as in Example 1, except that compound (A-9) shown in Table 2 was used instead of compound (A-1), and aggregate of composition (2) was used instead of aggregate of composition (1). The amount of rutting was measured in the same manner as in Example 1. The results are shown in Table 2.

[0099] Comparative Example 2 Asphalt specimen M-c2 was obtained as a pavement in the same manner as in Example 14, except that compound (A-2) was not used. The amount of rutting was measured in the same manner as in Example 1. The results are shown in Table 2.

[0100] [Table 2]

[0101] The compounds (A-1) to (A-13) used in Examples 1 to 15 are shown below. Compound (A-1): Citric acid (Fujifilm Wako Pure Chemical Corporation) Compound (A-2): Sodium citrate (Fujifilm Wako Pure Chemical Corporation) Compound (A-3): Sodium gluconate (Fujifilm Wako Pure Chemical Corporation) Compound (A-4): DL-Malic acid (Fujifilm Wako Pure Chemical Corporation) Compound (A-5): Tartaric acid (Fujifilm Wako Pure Chemical Corporation) Compound (A-6): Succinic acid (Fujifilm Wako Pure Chemical Corporation) Compound (A-7): Adipic acid (Fujifilm Wako Pure Chemical Corporation) Compound (A-8): White sugar (Mitsui Sugar Co., Ltd.) Compound (A-9): Sucrose fatty acid ester (Daiichi Kogyo Seiyaku Co., Ltd.) Compound (A-10): Xanthan gum (Monart Gum 80N; MP Gokyo Food & Chemical Co., Ltd.) Compound (A-11): Methylcellulose (7000-10000 mPa·s, 2% aqueous solution; Tokyo Chemical Industry Co., Ltd.) Compound (A-12): Methylcellulose (13-18 mPa·s, 2% aqueous solution) (Tokyo Chemical Industries, Ltd.) Compound (A-13): Hydroxyethylcellulose (HEC) (4500-6500 mPa·s, 2% aqueous solution) (Tokyo Chemical Industries, Ltd.)

[0102] Table 2 shows that the rutting depth of asphalt specimens M-1 to M-13 from Examples 1 to 13, which were prepared from an asphalt mixture using an asphalt composition containing polyester resin and compound A, a cement setting retarder, at a compaction temperature of 165°C, was 1.5 to 4.0 mm, which was significantly smaller than the rutting depth of 8.0 mm for asphalt specimen M-c1 of Comparative Example 1, which was prepared from an asphalt mixture without compound A. This result indicates that the addition of compound A modifies the asphalt mixture, resulting in superior durability for asphalt specimens M-1 to M-13. In the asphalt specimens M-14 to M-15 of Examples 14 to 15, which use different types of aggregate, and in the asphalt specimen M-c2 of Comparative Example 2, the rutting depth was 3.5 to 4.5 mm for asphalt specimens M-14 to M-15, while it was 12.0 mm for asphalt specimen M-c2, showing a similar trend.

Claims

1. An asphalt mixture containing asphalt, aggregate, polyester resin, and compound (A), The aggregate contains a calcium-containing component, An asphalt mixture in which the compound (A) is a cement setting retarder.

2. The aforementioned compound (A) (i) Oxycarboxylic acids and their salts, (ii) Polycarboxylic acids and their salts, (iii) Sugars, and (iv) Water-soluble cellulose ether The asphalt mixture according to claim 1, which is one or more selected from the group consisting of the following.

3. The asphalt mixture according to claim 1, wherein the calcium-containing component contains one or more selected from the group consisting of limestone powder, shells, and coral.

4. The asphalt mixture according to claim 1, wherein the content of compound (A) is 0.03 parts by mass or more and 20 parts by mass or less per 100 parts by mass of asphalt.

5. The asphalt mixture according to claim 1, wherein the content of compound (A) is 0.5 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the polyester resin.

6. The asphalt mixture according to claim 1, wherein the content of the polyester resin is 1 part by mass or more and 40 parts by mass or less per 100 parts by mass of the asphalt.

7. The asphalt mixture according to claim 1, wherein the polyester resin has a softening point of 80°C to 140°C and a glass transition point of 40°C to 80°C.

8. The asphalt mixture according to claim 1, wherein the polyester resin comprises a structural unit derived from an alcohol component containing 10 mol% or more of an alkylene oxide adduct of bisphenol A, and a structural unit derived from a carboxylic acid component.

9. Step 1 involves mixing asphalt and heated aggregate to obtain a mixture of asphalt and aggregate, Step 2 involves mixing the obtained asphalt and aggregate mixture with polyester resin and compound (A) to obtain an asphalt mixture. A method for producing an asphalt mixture containing, The aggregate contains a calcium-containing component, A method for producing an asphalt mixture, wherein the compound (A) is a cement setting retarder.

10. Step 1 involves mixing asphalt and heated aggregate to obtain a mixture of asphalt and aggregate, Step 2 involves mixing the obtained asphalt and aggregate mixture with polyester resin and compound (A) to obtain an asphalt mixture. Step 3 involves compacting the obtained asphalt mixture. A paving method including, The aggregate contains a calcium-containing component, A paving method in which the compound (A) is a cement setting retarder.

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