Strength enhancer for asphalt mixture, asphalt mixture comprising same, and method for preparing same

Abstract

[Disclosure] [Technical Problem] The present invention has been made in an effort to provide a strength enhancer for an asphalt mixture having advantages of providing high strength and workability to the asphalt mixture.SOLUTION: The strength enhancer for asphalt mixture of the present invention comprises a first polyoxyalkylene-based surfactant represented by the following formula (1): R1 - O - (A1O) m - H (1) wherein R1 represents an aliphatic hydrocarbon group having 6 to 24 carbon atoms and having a branched chain, and A1O represents an oxyalkylene group having 2 to 4 carbon atoms. M represents the average number of moles of alkylene oxide added, and is a number of 2 to 30. ) Second polyoxyalkylene-based surfactants represented by the following formula (2): R2 - O - (A2O) n - H. (2) (In the formula (2), R2 represents an aliphatic hydrocarbyl group having 5 to 24 carbon atoms. A2O represents an oxyalkylene group having 2 to 4 carbon atoms, and the oxyalkylene group contains 5 to 40 mol% of an oxypropylene group. N represents an average number of moles of alkylene oxide added and is a number of 3 to 50. And polyhydric alcohols.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a strength improver for asphalt mixtures, an asphalt mixture containing the same, and a method for producing the same. [Background technology]

[0002] Bituminous materials such as asphalt are widely used for the surface layers of roads, parking lots, sidewalks, etc., and asphalt mixtures are used as pavement materials, in which asphalt is heated and mixed with aggregate, rubber and / or thermoplastic elastomer. In particular, rubber and / or thermoplastic elastomers are designed to be less susceptible to aggregate scattering and fluidization, and to have a long lifespan. Thus, the technical issues of improving the adhesion between asphalt and aggregate and preventing the fluidization of asphalt are extremely important for improving the performance of asphalt pavement, and various methods have been proposed.

[0003] For example, further improvements are required to improve the strength of asphalt mixtures, and Patent Document 1 proposes an asphalt mixture composed of an aliphatic carboxylic acid, an aliphatic carboxylic acid ester, an alkaline compound, a water-soluble solid material, and a hydrophilic solid material. Patent Document 2 also proposes a strength improver for asphalt recycling that is mainly composed of a specific petroleum-based mineral oil and a fatty acid ester.

[0004] While the use of these proposed materials can improve the strength of asphalt, there were concerns that they may have a negative impact on workability during construction at low temperatures and on the strength properties of the asphalt. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-161370 [Patent Document 2] Japanese Patent Application Publication No. 2018-53116 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention provides a strength improver for asphalt mixtures that can provide high strength and workability improvement performance to asphalt mixtures, an asphalt mixture containing the same, and a method for producing the same. [Means for solving the problem]

[0007] That is, the present invention has the following aspects: <<Aspect 1>> A first polyoxyalkylene surfactant represented by the following formula (1): R 1 -O-(A 1 O)mH···(1) (In formula (1), R 1 represents a branched aliphatic hydrocarbon group having 6 to 24 carbon atoms, and A 1 O represents an oxyalkylene group having 2 to 4 carbon atoms. m represents the average number of moles of alkylene oxide added and is a number from 2 to 30. A second polyoxyalkylene surfactant represented by the following formula (2): R 2 -O-(A 2 O)nH (2) (In formula (2), R 2 represents an aliphatic hydrocarbon group having 5 to 24 carbon atoms. 2 O represents an oxyalkylene group having 2 to 4 carbon atoms, and the oxyalkylene group contains 5 to 40 mol % of oxypropylene groups. n represents the average number of moles of alkylene oxide added and is a number from 3 to 50. Polyhydric alcohol A strength improver for asphalt mixtures comprising: <<Aspect 2>> The strength improver for asphalt mixtures according to aspect 1, comprising 10% by mass or more and 40% by mass or less of a first polyoxyalkylene surfactant, 10% by mass or more and 30% by mass or less of a second polyoxyalkylene surfactant, and 40% by mass or more and 60% by mass or less of a polyhydric alcohol. Aspect 3 3. An asphalt mixture comprising aggregate, the strength enhancer of embodiment 1 or 2, and asphalt. Aspect 4 4. The asphalt mixture of claim 3, comprising the strength enhancer in an amount of from 0.001% to 0.5% by weight. Aspect 5 A method for producing an asphalt mixture, comprising: spraying the strength improver according to aspect 1 onto aggregate; and heating and mixing the sprayed aggregate with asphalt. Aspect 6 A method for producing an asphalt mixture according to aspect 5, wherein the aggregate is recycled aggregate. Aspect 7 A method for constructing an asphalt mixture, comprising: spraying the strength improver according to aspect 1 onto aggregate; and heating and mixing the sprayed aggregate with asphalt. [Effects of the Invention]

[0008] The strength improver for asphalt mixtures of the present invention can improve the strength and durability of asphalt mixtures. Furthermore, the asphalt mixtures of the present invention and the asphalt mixtures obtained by the manufacturing method thereof have excellent fluidity, making paving work easier than in conventional paving work. DETAILED DESCRIPTION OF THE INVENTION

[0009] <Strength improver for asphalt mixture and method of use> The strength improver for asphalt mixtures comprises a nonionic surfactant, particularly a polyoxyalkylene surfactant, and more specifically, a first polyoxyalkylene surfactant, a second polyoxyalkylene surfactant, and a polyhydric alcohol. The present invention also relates to a method for using such a strength improver.

[0010] <First polyoxyalkylene surfactant> Here, the first polyoxyalkylene surfactant is a specific polyoxyethylene-added nonionic surfactant having a branched aliphatic hydrocarbon group, and is represented by the following formula (1): R 1 -O-(A 1 O)mH···(1)

[0011] In formula (1), R 1 R is an aliphatic hydrocarbon group having a branched chain, and has 6 to 24 carbon atoms. In the present invention, those having 8 to 18 carbon atoms are preferred, and those having 10 to 14 carbon atoms are even more preferred. 1 When the number of carbon atoms in the aliphatic hydrocarbon group is within this range, it has excellent miscibility with the asphalt mixture and is likely to increase the strength, durability, and workability of the asphalt mixture.

[0012] Examples of the branched chain aliphatic hydrocarbon group include a 3,5,5-trimethylhexyl group, an isodecyl group, a 3-ethyldecyl group, a 2,2-dimethyloctyl group, an isotridecyl group, an isostearyl group, and a 2-decyltetradecyl group.

[0013] In formula (1), A 1 O represents an oxyalkylene group having 2 to 4 carbon atoms, preferably an oxyethylene group, and m, the average number of moles of alkylene oxide added, is 2 to 30, preferably 3 to 18, and more preferably 4 to 12. Within this range, the composition is excellent in storage stability when dissolved in water without causing layer separation, and also has good permeability into aggregate when sprayed onto the aggregate.

[0014] There is no particular limitation on the molar distribution of the added surfactants, and any of a narrow distribution of about 5 moles to a wide distribution of 15 moles or more can be used. The surfactants described above may be used alone or in combination of two or more types.

[0015] The first polyoxyalkylene surfactant can be produced by adding a predetermined amount of alkylene oxide to a branched aliphatic alkyl alcohol having 6 to 24 carbon atoms. Examples of the aliphatic alkyl alcohol include secondary alcohols obtained by oxidizing n-paraffins having 12 to 14 carbon atoms, Guerbet alcohols such as hexyldecyl alcohol and decyltetradecanol, and oxo alcohols obtained by oxidizing olefins or their oligomers by the oxo method. Among these, those derived from branched alcohols synthesized by the oxo method from short-chain olefin oligomers having 2 to 4 carbon atoms are preferred, and among these, those derived from oligomers of 3 to 10 monomers are particularly preferred.

[0016] The content of the first polyoxyalkylene surfactant in the strength improver for asphalt mixtures is 5% by mass or more, preferably 10% by mass or more, and more preferably 20% by mass or more, and is 60% by mass or less, preferably 50% by mass or less, and more preferably 40% by mass or less.

[0017] <Second polyoxyalkylene surfactant> The second polyoxyalkylene surfactant can be a surfactant different from the first polyoxyalkylene surfactant and is represented by the following formula (2): R 2 -O-(A 2 O)nH (2)

[0018] In equation (2), R 2 R is an aliphatic hydrocarbon group having 5 to 24 carbon atoms, and in the present invention, those having 8 to 18 carbon atoms are preferred, and those having 10 to 16 carbon atoms are even more preferred. 2 When the branched chain aliphatic hydrocarbon group has 8 to 24 carbon atoms, it has excellent miscibility with the asphalt mixture, and the strength and workability of the asphalt mixture are improved.

[0019] R 2The aliphatic hydrocarbon group may be either linear or branched, but those having a branched chain and an unsaturated bond are preferred. Examples of linear aliphatic hydrocarbon groups include linear alkyl groups such as octyl, decyl, dodecyl, tetradecyl, octadecyl, and behenyl. Examples of branched aliphatic hydrocarbon groups include the same branched aliphatic hydrocarbon groups as those described in the first polyoxyalkylene surfactant, and also include branched alkyl groups such as 2-ethylhexyl and isooctyl. Furthermore, R 2 may contain an unsaturated bond in the molecule, and an example of such a structure is an oleyl group.

[0020] In equation (2), A 2 O represents an oxyalkylene group having 2 to 4 carbon atoms. This oxyalkylene group can contain 5 to 40 mol % of oxypropylene groups, and in the present invention, 5 to 35 mol % is preferred, and particularly 10 to 30 mol % is even more preferred. That is, A 2 O may be a combination of oxyethylene, oxypropylene, and / or oxybutylene groups, and in particular a combination of oxyethylene and oxypropylene groups. 2 In such a case, O is less likely to separate even at high temperatures, has high fluidity even at low temperatures, and exhibits sufficient storage stability.

[0021] In formula (2), n, the average number of moles of alkylene oxide added, is 3 to 50, but in the present invention, it is preferably 10 to 45, and more preferably 15 to 40. There are no particular restrictions on the distribution of moles added, and any distribution can be used, from a narrow distribution of about 5 moles to a wide distribution of 15 moles or more. Within this range, phase separation is unlikely to occur even at high temperatures, gelation is minimal, and storage stability is good. The above surfactants may be used alone or in combination of two or more.

[0022] The second polyoxyalkylene surfactant can be obtained, for example, by adding a predetermined amount of alkylene oxide to an aliphatic alkyl alcohol similar to those exemplified in the first polyoxyalkylene surfactant. This surfactant may be a block polymer or a random polymer, but is preferably a block polymer from the viewpoints of strength improvement effect, oxidation degradation prevention effect, etc. 2 When O is a block copolymer of a combination of an oxyethylene group and an oxypropylene group, either ethylene oxide or propylene oxide may be added first, but it is particularly preferred that propylene oxide be added first.

[0023] The content of the second polyoxyalkylene surfactant in the strength improver for asphalt mixtures is 5% by mass or more, preferably 10% by mass or more, and 50% by mass or less, preferably 40% by mass or less, and more preferably 30% by mass or less.

[0024] The mass ratio (a1 / a2) of the first surfactant (a1) to the second surfactant (a2) may be 9 or less, 6 or less, 4 or less, 2 or less, 1.5 or less, or 1.0 or less, or may be 0.25 or more, 0.3 or more, 0.4 or more, 0.5 or more, 1.0 or more, 1.5 or more, or 2 or more. Preferably, this mass ratio is 0.25 or more and 9 or less, or 0.4 or more and 4 or less.

[0025] <Polyhydric alcohol> The polyhydric alcohol is preferably a dihydric to hexahydric polyhydric alcohol. Specific examples of the polyhydric alcohol include water-soluble polyhydric alcohols such as ethylene glycol, propylene glycol, glycerin, diglycerin, diethylene glycol, polyethylene glycol, polypropylene glycol, hexanediol, pentaerythritol, sorbitan, and sorbitol. Among these, dihydric to trihydric polyhydric alcohols are particularly preferred from the viewpoints of strength and workability.

[0026] Among these, polyhydric alcohols having a molecular weight of 500 or less and being liquid at room temperature are preferred from the viewpoint of maintaining the fluidity of the composition, and dihydric to trihydric polyhydric alcohols having a molecular weight of 200 or less, such as glycerin, diethylene glycol, and polyethylene glycol having a molecular weight of 200, are particularly preferred.

[0027] The polyhydric alcohol content in the strength improver for asphalt mixtures is 20% by mass or more, preferably 25% by mass or more, and more preferably 30% by mass or more, and 70% by mass or less, preferably 60% by mass or less, and more preferably 50% by mass or less.

[0028] The mass ratio (A / B) of the total mass (A) of the first and second polyoxyalkylene surfactants to the mass (B) of the polyhydric alcohol may be 9 or less, 6 or less, 4 or less, 3 or less, 2 or less, or 1.5 or less, or may be 0.25 or more, 0.3 or more, 0.4 or more, 0.5 or more, 1.0 or more, 1.5 or more, or 2 or more. Preferably, this mass ratio is 0.25 or more and 9 or less, or 0.4 or more and 4 or less.

[0029] <Other> The strength improver for asphalt mixtures may contain other components in addition to the first and second polyoxyalkylene surfactants and polyhydric alcohols, and when other components are contained, the content of the other components in the strength improver may be 0.1% by mass or more, 1% by mass or more, 5% by mass or more, or 10% by mass or more, and may be 40% by mass or less, 30% by mass or less, 20% by mass or less, or 10% by mass or less. For example, the content is 0.1% by mass or more and 40% by mass or less, or 1% by mass or more and 20% by mass or less.

[0030] If necessary, various surfactants such as cationic surfactants, anionic surfactants, amphoteric surfactants, and nonionic surfactants other than component (A), as well as colorants such as water-soluble dyes and antibacterial agents such as alkylparabens can be added to the strength improver for asphalt mixtures.

[0031] When a strength improver is used, it can be used as a strength improver solution, and the concentration of the strength improver in the strength improver solution can be, for example, 0.01 to 5 mass %, and preferably 0.1 to 2.5 mass %.

[0032] The strength improver can be diluted by mixing in a line blender or dilution tank. Water is usually used as the dilution solvent, but monohydric alcohols such as ethanol and methoxyethanol can also be used. In particular, aqueous solutions containing water are preferably used.

[0033] <<Asphalt mixture and its manufacturing method>> The asphalt mixture contains aggregate, the above-described strength improver for asphalt mixtures, and asphalt. The method for producing the asphalt mixture includes spraying the above-described strength improver for asphalt mixtures onto aggregate, and mixing the aggregate containing the strength improver with asphalt.

[0034] <Aggregate> The aggregate used in the present invention is not particularly limited, and any aggregate commonly used in this field can be used, including, for example, crushed stone, slag, sand, stone powder, filler, and other aggregates commonly used in paving.

[0035] For example, recycled aggregate or recycled asphalt concrete aggregate may be used as the aggregate. Recycled aggregate is obtained by crushing waste asphalt mixtures applied to the surface and base layers of asphalt pavement. These recycled aggregates may account for 5% by mass or more, 10% by mass or more, 20% by mass or more, 30% by mass or more, or 40% by mass or more of the total aggregate, and may be 100% by mass or less, 90% by mass or less, 80% by mass or less, 70% by mass or less, or 60% by mass or less. These recycled aggregates may not be used substantially, for example, less than 20% by mass, 10% by mass or less, 5% by mass or less, or none at all in the asphalt mixture.

[0036] It was found that the effect was even greater when recycled aggregate was used as the aggregate for the asphalt mixture. Without being bound by theory, it is thought that this is because the presence of asphalt (hereinafter referred to as "old asphalt") in the recycled aggregate makes it easier for the strength improver to penetrate the recycled aggregate.

[0037] The aggregate content in the asphalt mixture of the present invention may be 70% by mass or more, 75% by mass or more, 80% by mass or more, 85% by mass or more, or 90% by mass or more, or may be 97% by mass or less, 95% by mass or less, 93% by mass or less, 90% by mass or less, or 85% by mass or less.

[0038] <Strength improver> The strength improver for asphalt mixtures is as described above, but the content of the strength improver in the asphalt mixture may be 0.001% by mass or more, 0.005% by mass or more, 0.01% by mass or more, 0.05% by mass or more, 0.1% by mass or more, or 0.5% by mass or more, or 5% by mass or less, 3% by mass or less, 1% by mass or less, 0.5% by mass or less, or 0.1% by mass or less. For example, this content is 0.001% by mass or more and 5% by mass or less, or 0.01% by mass or more and 1.0% by mass or less.

[0039] <Asphalt> The asphalt is not particularly limited, and those commonly used in this field can be used. For example, various asphalts can be used. Examples include straight asphalt, which is petroleum asphalt for paving, as well as modified asphalt and foamed asphalt. Examples of modified asphalt include blown asphalt and asphalt modified with polymer materials such as thermoplastic elastomers and thermoplastic resins.

[0040] The asphalt content in the asphalt mixture of the present invention may be 2.0% by mass or more, 3.0% by mass or more, 4.0% by mass or more, or 5.0% by mass or more, or may be 20% by mass or less, 15% by mass or less, 10% by mass or less, 8.0% by mass or less, 5.0% by mass or less, or 4.0% by mass or less.

[0041] <Other> The asphalt mixture may contain other components commonly used in the art, such as fillers, recycled aggregates, and foaming aids.

[0042] <Asphalt mixture manufacturing method and construction method> The method for producing and applying an asphalt mixture includes heating and mixing the above-described strength improver for asphalt mixtures, aggregate, and asphalt, and preferably includes spraying the above-described strength improver for asphalt mixtures onto aggregate, and heating and mixing the aggregate containing the strength improver with asphalt. Here, the asphalt mixture can be the asphalt mixture described above, and for each configuration of this production method, reference can be made to each configuration described above regarding the asphalt mixture.

[0043] The strength improver can be sprayed onto the aggregate in an aggregate mixer when mixing the aggregate into asphalt, but it can also be sprayed outdoors where the aggregate is stored. This prevents the aggregate from being blown away by strong winds. It was also found that the strength improver's effectiveness is not lost even if the aggregate is sprayed and stored outdoors for several months, even if snow accumulates during that time.

[0044] This method may also include spraying the strength improver onto the aggregate, and then curing the aggregate containing the strength improver outdoors. The spraying means is not particularly limited, but a means that can spray the strength improver evenly onto the aggregate is preferred. The curing period may be short, but may be, for example, from one day to ten days, preferably from two to eight days, or may be as long as two to three months.

[0045] The step of heating and mixing the aggregate and asphalt can be performed using a method commonly used in this field, and can include a step of drying the aggregate with a dryer before the mixing step.

[0046] The asphalt mixture obtained in this way exhibits a smaller temperature drop after heating and a lower penetration resistance value than the same asphalt mixture except that it contains a strength improver, resulting in very good workability at the construction site. Furthermore, even when heated under the same conditions, the asphalt mixture containing the strength improver tends to heat up more, and it was found that the energy required for heating can also be reduced. [Example]

[0047] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples. In the following, the unit of content, "%", is "% by mass" unless otherwise specified.

[0048] As a strength improver for asphalt mixtures containing a first polyoxyalkylene surfactant (a1), a second polyoxyalkylene surfactant (a2), and a polyhydric alcohol (B), the components (a1), (a2), and (B) shown in Tables 2 to 4 were blended in the proportions shown in Table 1, and this was diluted with water to prepare a strength improver for asphalt mixtures.

[0049] [Table 1]

[0050] [Table 2]

[0051] [Table 3]

[0052] [Table 4]

[0053] This strength improver for asphalt mixtures was diluted 50 times with water to prepare a 2.0 mass % aqueous solution of the strength improver.

[0054] 《Manufacturing》 <Example> New aggregate and recycled aggregate were used as the aggregate in an asphalt mixture manufacturing plant to produce the asphalt mixtures of Examples 1 to 3 and Comparative Examples 1 to 3. Table 5 shows the aggregate blending ratio of new aggregate and recycled aggregate, and the blending ratio of recycled aggregate to the total amount of aggregate.

[0055] [Table 5]

[0056] Specifically, in Examples 1 to 3, the aqueous solution of the strength improver was sprayed onto aggregate and recycled aggregate stored outdoors. The aggregate and recycled aggregate containing the strength improver were then cured. The curing period for each Example is shown in Table 6. In Comparative Examples 1 to 3, the aqueous solution of the strength improver was not sprayed onto the aggregate and recycled aggregate, and aggregate and recycled aggregate stored outdoors for the same curing period as in each Example were used. [Table 6]

[0057] Thereafter, the dried aggregate, recycled aggregate, and straight asphalt were heated and mixed in a mixer using an indirect heating method to obtain an asphalt mixture.

[0058] "evaluation" <Method for measuring compaction degree> The degree of compaction was determined by preparing test specimens according to the method described in B001 (Marshall Stability Test Method) of the "Pavement Survey and Test Method Handbook, Volume 3 (published by the Japan Road Association)," and then measuring the density according to the method described in B008-1 ("Density Test Method for Dense Gradient Asphalt Mixtures, etc."). From the results, the density of each specimen was calculated as a percentage of the density immediately after production (standard density). Here, the compaction temperatures were 140°C and 110°C, and the number of compactions was 50. Three specimens were tested, and the average value was calculated.

[0059] <Low temperature cantabro test method> The low-temperature Cantablo loss rate was measured according to the method described in "B010 Cantablo Test Method" in the "Pavement Survey and Test Method Handbook (Japan Road Association)." The test conditions were a curing temperature and test temperature of the specimen of -30°C, and a drum rotation speed of 300 revolutions per minute.

[0060] <Penetration resistance test> For the penetration resistance test, the asphalt mixture is poured into the Marshall mold up to the top, leveled, and compacted three times. A push-pull gauge is then inserted into the mold at a speed of 1 inch per second to measure the resistance.

[0061] "result" These results are shown in Table 7 below.

[0062] It was confirmed that the degree of compaction improved with the addition of strength improvers in all cases. This confirmed that strength could be ensured. In particular, compaction at low temperatures was more effective than at high temperatures.

[0063] It was confirmed that the addition of the strength improver reduced the low-temperature cantabro loss rate, which confirmed that it had an effect of improving durability against aggregate scattering.

[0064] It was confirmed that the addition of the strength improver reduced the penetration resistance value, which confirmed that it had the effect of improving workability.

[0065] [Table 7]

Claims

1. A first polyoxyalkylene surfactant represented by the following formula (1): R １ -O-(A １ O)m-H・・・(1) (In formula (1), R １ represents a branched aliphatic hydrocarbon group having 6 to 24 carbon atoms, and A １ O represents an oxyalkylene group having 2 to 4 carbon atoms, and m represents the average number of moles of alkylene oxide added, which is a number from 2 to 30. A second polyoxyalkylene surfactant represented by the following formula (2): R ２ -O-(A ２ O)n-H・・・(2) (In formula (2), R ２ represents an aliphatic hydrocarbon group having 5 to 24 carbon atoms. ２ O represents an oxyalkylene group having 2 to 4 carbon atoms, and the oxyalkylene group contains 5 to 40 mol% of oxypropylene groups. n represents the average number of moles of alkylene oxide added and is a number from 3 to 50. Polyhydric alcohol A strength improver for asphalt mixtures comprising:

2. 2. The strength improver for asphalt mixtures according to claim 1, comprising 10% by mass or more and 40% by mass or less of a first polyoxyalkylene surfactant, 10% by mass or more and 30% by mass or less of a second polyoxyalkylene surfactant, and 40% by mass or more and 60% by mass or less of a polyhydric alcohol.

3. An asphalt mixture comprising aggregate, the strength improver according to claim 1 or 2, and asphalt.

4. The asphalt mixture according to claim 3, comprising the strength improver in an amount of 0.001% by mass or more and 0.5% by mass or less.

5. A method for producing an asphalt mixture, comprising: spraying the strength improver according to claim 1 onto aggregate; and heating and mixing the aggregate to which the strength improver has been sprayed with asphalt.

6. The method for producing an asphalt mixture according to claim 5, wherein the aggregate is recycled aggregate.

7. A method for applying an asphalt mixture, comprising: spraying the strength improver according to claim 1 onto aggregate; and heating and mixing the aggregate to which the strength improver has been sprayed with asphalt.

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