Asphalt mixture and method for producing the same

Abstract

To provide an asphalt mixture which has sufficient quality and / or sufficient foamability and is easy to manufacture even when recycled aggregate is used, and a method for manufacturing the asphalt mixture.SOLUTION: An asphalt mixture of the present invention contains asphalt, an aggregate, a crystallization water-containing substance, and a workability improving agent, and the workability improving agent contains a fatty acid compound and / or a glycol ether compound. In addition, the method for manufacturing an asphalt mixture of the present invention includes heating a mixture of asphalt, an aggregate, a crystal water-containing substance, water, and a workability-improving agent, the workability-improving agent containing a fatty acid compound and / or a glycol ether compound.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Asphalt pavement uses an asphalt mixture made by mixing aggregates such as crushed stone and sand with asphalt as a binder.

[0003] Asphalt mixtures are produced by heating aggregate with a heater and then mixing it with asphalt at a high temperature, for example, 160°C to 170°C. However, in recent years, efforts to prevent global warming have required lowering the manufacturing temperature of asphalt mixtures and the construction temperature during paving, and this temperature reduction technology is called medium-temperature technology.

[0004] One known warm-air technology is foamed asphalt, which is made by mixing heated asphalt with water to foam the asphalt and then mixing the foamed asphalt with aggregate. For example, Patent Document 1 proposes a method of extending the foaming time by adding an antifoaming agent to the foamed asphalt to make the bubbles finer.

[0005] Furthermore, Patent Document 2 discloses an invention in which, instead of mixing water with asphalt, gypsum dihydrate is added to an asphalt mixture, and the gypsum dihydrate is caused to release its water of crystallization, thereby generating microbubble particles in the asphalt mixture. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2017-186842 [Patent Document 2] Japanese Patent Application Publication No. 11-36215 Summary of the Invention [Problem to be solved by the invention]

[0007] When conventional foamed asphalt was applied to recycled asphalt mixtures using recycled aggregate made by crushing, sorting, and classifying asphalt pavement waste, the deteriorated asphalt adhering to the recycled aggregate had a negative effect, making it impossible to maintain the quality of the asphalt mixture. Furthermore, with conventional foamed asphalt, the bubbles in the asphalt sometimes disappeared early or foaming was insufficient.

[0008] Furthermore, foamed asphalt needs to be foamed by injecting high-pressure water into the asphalt, and in order to produce foamed asphalt at existing hot asphalt mixture manufacturing plants, expensive equipment would have to be installed.

[0009] Therefore, an object of the present invention is to provide an asphalt mixture that can be easily produced and that has sufficient quality and / or foaming properties even when recycled aggregate is used, and a method for producing the same. [Means for solving the problem]

[0010] The present inventors have found that the above problems can be solved by the present invention having the following aspects. <<Aspect 1>> An asphalt mixture comprising asphalt, aggregate, a crystalline water-containing substance, and a workability improving agent, wherein the workability improving agent comprises a fatty acid compound and / or a glycol ether compound. <<Aspect 2>> 2. The asphalt mixture of claim 1, wherein the crystal water-containing material is gypsum dihydrate. Aspect 3 2. The asphalt mixture of claim 1, wherein the workability improver comprises a glycol ether compound. Aspect 4 The asphalt mixture of Aspect 3, wherein the glycol ether compound is a compound represented by the following formula (I): R 1 -O-(AO)nH····(I) (In the formula, R1 represents a linear, branched or cyclic hydrocarbon group having 1 to 24 carbon atoms which may have a substituent, AO represents a linear or branched oxyalkylene group having 2 to 4 carbon atoms, and n represents the number of moles of oxyalkylene groups added and is a number from 1 to 30. Aspect 5 2. The asphalt mixture of claim 1, wherein the workability improver comprises a fatty acid compound. Aspect 6 An asphalt mixture according to aspect 5, wherein the fatty acid compound is a compound of formula (II): R 11 -COO-(AO)mR 12 (II) (In the formula, R 11 is a linear, branched or cyclic hydrocarbon group having 1 to 24 carbon atoms which may have a substituent; R 12 represents a hydrogen atom or a methyl group, AO represents a linear or branched oxyalkylene group having 2 to 4 carbon atoms, and m represents the number of moles of oxyalkylene groups added, and is 0 or a number from 1 to 30). Aspect 7 2. The asphalt mixture of claim 1, wherein 30% by mass or more of the aggregate is recycled aggregate. Aspect 8 A method for producing an asphalt mixture, comprising heating a mixture of asphalt, aggregate, a substance containing crystal water, water, and a workability improving agent, wherein the workability improving agent comprises a fatty acid compound and / or a glycol ether compound. Aspect 9 A method for producing an asphalt mixture according to aspect 8, comprising: mixing a first mixture containing the crystalline water-containing substance, water, and the workability improving agent with the aggregate to obtain a second mixture; and mixing the second mixture with the asphalt to obtain an asphalt mixture. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide an asphalt mixture and a method for producing the same, which can obtain sufficient quality and / or have sufficient foaming properties even when recycled aggregate is used. DETAILED DESCRIPTION OF THE INVENTION

[0012] The asphalt mixture of the present invention comprises asphalt, aggregate, a substance containing crystal water, and a workability improving agent.

[0013] This asphalt mixture can be produced at a relatively low temperature because water is released from the crystal water-containing substance during heating and mixing, causing the asphalt to foam. This eliminates the need to overheat aggregates and reduces the amount of carbon dioxide emitted by heating burners.

[0014] It is known that when constructing asphalt mixtures, workability improvers are used to reduce the viscosity of the asphalt mixture to facilitate on-site work. However, the inventors have discovered that the use of specific compounds as workability improvers can prolong the foaming process generated by the crystalline water-containing substance, further reducing the viscosity of the entire asphalt mixture. This allows for a reduction in the construction temperature during paving and an improvement in compaction. Furthermore, it has been found that the asphalt mixture of the present invention can produce paved roads that meet quality standards, even when a certain amount of recycled aggregate is used.

[0015] <asphalt> As the asphalt, various asphalts used in producing foamed asphalt can be used. For example, straight asphalt, which is petroleum asphalt for paving, and modified asphalt can be used. Modified asphalt includes blown asphalt and polymer-modified asphalt modified with polymeric materials such as thermoplastic elastomers and thermoplastic resins.

[0016] The content of new asphalt used in the production of an asphalt mixture other than the old asphalt attached to the recycled aggregate may be 1.0 parts by mass or more, 2.0 parts by mass or more, 3.0 parts by mass or more, or 4.0 parts by mass or more, and may be 6.0 parts by mass or less, 5.0 parts by mass or less, 4.0 parts by mass or less, or 3.0 parts by mass or less, per 100 parts by mass of the total mass of aggregate and filler. The total content of old asphalt and new asphalt may be 3.0 parts by mass or more, 3.5 parts by mass or more, 3.0 parts by mass or more, or 4.0 parts by mass or more, and may be 6.0 parts by mass or less, 5.5 parts by mass or less, 5.0 parts by mass or less, or 4.5 parts by mass or less, per 100 parts by mass of the total mass of aggregate and filler.

[0017] <aggregate> The aggregate is not particularly limited, and any aggregate commonly used in this field can be used.

[0018] Coarse aggregate and / or fine aggregate can be used as aggregate. Coarse aggregate with a particle size of 2.36 mm or more and fine aggregate with a particle size of less than 2.36 mm can be used with the particle size and blending ratio selected from the viewpoints of interlocking of the aggregates and fluidity. The particle sizes of the above coarse aggregate and fine aggregate refer to the values ​​specified in JIS A5001-2008.

[0019] Examples of coarse aggregate that can be used include No. 7 crushed stone, No. 6 crushed stone, No. 5 crushed stone, and No. 4 crushed stone. Examples of fine aggregate that can be used 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.

[0020] By selecting the type and mixing ratio of these aggregates, the resulting asphalt mixture can be a coarse-graded asphalt mixture, a dense-graded asphalt mixture, a dense-graded gap asphalt mixture, a fine-graded asphalt mixture, a fine-graded gap asphalt mixture, an open-graded asphalt mixture, or the like.

[0021] For example, recycled aggregate or recycled asphalt concrete aggregate may be used as the aggregate. Recycled aggregate is obtained by crushing waste asphalt mixtures used in the surface and base layers of asphalt pavement.

[0022] These recycled aggregates may account for 10% by mass or more, 20% by mass or more, 30% by mass or more, 40% by mass or more, 50% by mass or more, 60% by mass or more, or 70% by mass or more of the total mass of the aggregate and filler, and may also account for 90% by mass or less, 80% by mass or less, 70% by mass or less, 60% by mass or less, 50% by mass or less, or 40% by mass or less. For example, recycled aggregates may be used in an amount ranging from 40% by mass to 80% by mass of the total mass of the aggregate and filler. 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 not at all in the asphalt mixture.

[0023] Generally, in asphalt mixtures containing foamed asphalt, the degree of compaction tends to decrease when the proportion of recycled aggregate is high, but by applying the present invention, such a decrease in the degree of compaction can be suppressed.

[0024] The content of asphalt contained in recycled aggregate (hereinafter referred to as old asphalt) may be 1.0% by mass or more, 1.5% by mass or more, 2.0% by mass or more, 2.5% by mass or more, or 3.5% by mass or less, 3.0% by mass or less, 2.5% by mass or less, or 2.0% by mass or less, based on the total mass of the recycled aggregate. Here, the old asphalt content is the content measured in accordance with G028 "Asphalt Extraction Test Method" in the Pavement Survey and Testing Methods Handbook.

[0025] 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.

[0026] <Substances containing crystal water> The crystal water-containing substance releases crystal water at the temperature when the asphalt mixture is heated and mixed, causing bubbles in the asphalt mixture, thereby reducing the viscosity of the asphalt mixture like foamed asphalt. In the asphalt mixture, the crystal water-containing substance may or may not contain crystal water. However, when producing the asphalt mixture, the crystal water-containing substance may contain crystal water.

[0027] Examples of such crystal water-containing substances include, but are not limited to, inorganic hydrates such as gypsum dihydrate, gypsum hemihydrate, ammonium aluminum sulfate hydrate, cobalt chloride hydrate, cobalt acetate hydrate, chromium sulfate hydrate, copper sulfate hydrate, iron chloride hydrate, iron sulfate hydrate, magnesium carbonate hydrate, manganese chloride hydrate, manganese acetate hydrate, sodium sulfite hydrate (sodium sulfite), sodium phosphate, sodium tungstate hydrate, and nickel sulfate hydrate.

[0028] The crystal water-containing substance may contain, for example, 5% by mass or more, 10% by mass or more, or 15% by mass or more of water as crystal water, and may contain 40% by mass or less, 35% by mass or less, 30% by mass or less, or 25% by mass or less of water as crystal water.

[0029] The temperature at which the crystal water-containing substance releases water may be 50°C or higher, 80°C or higher, 100°C or higher, 120°C or higher, or 130°C or higher, or may be 160°C or lower, 150°C or lower, 130°C or lower, or 100°C or lower.

[0030] The crystal water-containing substance can be contained in the resulting asphalt mixture at 0.05% by mass or more, 0.1% by mass or more, 0.2% by mass or more, or 0.3% by mass or more,

[0031] <Workability improver> Workability improvers are usually used to facilitate the smooth spreading and leveling of the surface at the construction site, but they are not limited to this purpose. Glycol ether compounds also reduce the size of bubbles released from crystal water-containing substances, allowing the fine bubbles to persist in the asphalt mixture for a long time. Furthermore, fatty acid compounds can reduce viscosity by restoring the properties of deteriorated asphalt that adheres to recycled aggregate.

[0032] The workability improving agent may be used in an amount of, for example, 0.1 parts by mass or more, 0.3 parts by mass or more, 0.5 parts by mass or more, 1.0 parts by mass or more, or 1.5 parts by mass or more, relative to 100 parts by mass of asphalt, or 10 parts by mass or less, 7.0 parts by mass or less, 5.0 parts by mass or less, 3.0 parts by mass or less, 2.0 parts by mass or less, or 1.0 parts by mass or less. The workability improving agent may be, for example, 0.1 parts by mass or more and 10 parts by mass or less, 0.3 parts by mass or more and 7.0 parts by mass or less, or 0.5 parts by mass or more and 5.0 parts by mass or less, relative to 100 parts by mass of asphalt.

[0033] <Workability improver - glycol ether compound> Examples of the glycol ether compound include glycol ether compounds represented by the following formula (I): R 1 -O-(AO)nH····(I)

[0034] In the formula, R 1 represents a linear, branched or cyclic hydrocarbon group having 1 to 24 carbon atoms which may have a substituent; AO represents a linear or branched oxyalkylene group having 2 to 4 carbon atoms; and n represents the number of moles of oxyalkylene groups added and is a number from 1 to 30.

[0035] In formula (I), R 1 is preferably an alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 2 to 6 carbon atoms. AO is preferably an oxyethylene group. n is preferably 2 to 20, more preferably 3 to 10.

[0036] Examples of glycol ether compounds represented by general formula (I) include (poly)ethylene glycol methyl ether, (poly)ethylene glycol ethyl ether, (poly)ethylene glycol propyl ether, (poly)ethylene glycol butyl ether, (poly)ethylene glycol hexyl ether, and (poly)ethylene glycol octyl ether.

[0037] <Workability improver - fatty acid compound> The fatty acid compound is preferably a compound represented by the following formula (II). R 11 -COO-(AO)mR 12 (II)

[0038] In the formula, R 11 is a linear, branched or cyclic hydrocarbon group having 1 to 24 carbon atoms which may have a substituent; R 12 represents a hydrogen atom or a methyl group, AO represents a linear or branched oxyalkylene group having 2 to 4 carbon atoms, and m represents the number of moles of oxyalkylene groups added and is a number of 0 or 1 to 30.

[0039] In formula (II), R 11 The number of carbon atoms in the formula (II) is preferably 6 to 24, more preferably 8 to 20, still more preferably 10 to 18, and particularly preferably 12 to 16. In formula (II), m is preferably 0 or 1 to 25, more preferably 0 or 1 to 20, and still more preferably 0 or 1 to 15. In formula (II), AO is preferably an oxyethylene group.

[0040] The fatty acid compound may have an iodine value of, for example, 50 to 110, 60 to 100, or 70 to 90. These may be a combination of multiple fatty acid compounds, in which case the iodine value refers to the value of the fatty acid compound in which multiple compounds are combined. The iodine value of the fatty acid compound is measured in accordance with JIS K0070-1992.

[0041] The fatty acid compound represented by formula (II) is preferably a fatty acid, a fatty acid alkyl ester, a fatty acid polyoxyalkylene alkyl ester, or a polyoxyalkylene fatty acid ester, and these can be used alone or in combination of two or more selected from these.

[0042] The molecular weight (g / mol) of the fatty acid compound may be, for example, 100 or more, 150 or more, 200 or more, 250 or more, 270 or more, or 280 or more, or 500 or less, 450 or less, 400 or less, 350 or less, 330 or less, or 320 or less. When a fatty acid compound is used in combination with multiple compounds, these molecular weights may be weight-average molecular weights.

[0043] The compound represented by formula (II) includes fatty acids: R 11 COOH, fatty acid methyl ester: R 11 COOCH3, fatty acid (poly)oxyethylene methyl ester: R 11 COO(CH2CH2O) m CH3, (poly)oxyethylene fatty acid ester: R 11 COO(CH2CH2O m Examples include H.

[0044] Specific examples include palmitic acid, palmitic acid methyl ester, palmitic acid (poly)oxyethylene methyl ester (average number of moles added: 1 to 15), (poly)oxyethylene palmitic acid ester (average number of moles added: 1 to 15), stearic acid, stearic acid methyl ester, stearic acid (poly)oxyethylene methyl ester (average number of moles added: 1 to 15), (poly)oxyethylene stearic acid ester (average number of moles added: 1 to 15), oleic acid, oleic acid methyl ester, oleic acid (poly)oxyethylene methyl ester ester (average number of moles added: 1 to 15), (poly)oxyethylene oleate ester (average number of moles added: 1 to 15), linoleic acid, linoleic acid methyl ester, linoleic acid (poly)oxyethylene methyl ester (average number of moles added: 1 to 15), (poly)oxyethylene linoleate ester (average number of moles added: 1 to 15), linolenic acid, linolenic acid methyl ester, linolenic acid (poly)oxyethylene methyl ester (average number of moles added: 1 to 15), (poly)oxyethylene linolenate ester (average number of moles added: 1 to 15).

[0045] <water> This asphalt mixture may further contain water during production. In this case, unlike conventional foamed asphalt, it is not necessary to spray asphalt at high pressure. For example, the crystalline water-containing substance and the workability improving agent can be mixed or dispersed in water and then mixed with the aggregate and asphalt. This allows the added water, together with the water from the crystalline water-containing substance, to exist in the asphalt mixture as tiny bubbles of water vapor.

[0046] The amount of water that can be added together with the crystal water-containing substance during the production of an asphalt mixture may be 5 parts by mass or more, 10 parts by mass or more, or 15 parts by mass or more, or 40 parts by mass or less, 35 parts by mass or less, 30 parts by mass or less, or 25 parts by mass or less, per 100 parts by mass of the crystal water-containing substance.

[0047] <others> The asphalt mixture may contain other components than those mentioned above that are commonly used in the art.

[0048] For example, the asphalt mixture may contain fillers such as stone powder, hydrated lime, cement, reclaimed dust, and fly ash.

[0049] The amount of filler may be 0.1 parts by mass or more, 0.5 parts by mass or more, 1.0 parts by mass or more, or 2.0 parts by mass or more, and may be 10.0 parts by mass or less, 7.0 parts by mass or less, 5.0 parts by mass or less, or 3.0 parts by mass or less, relative to 100 parts by mass of the total of the aggregate and filler. The amount of filler may be, for example, 0.1 parts by mass or more and 10.0 parts by mass or more, or 1.0 parts by mass or more and 7.0 parts by mass or less.

[0050] For example, the asphalt mixture may contain a surfactant. However, since the asphalt mixture of the present invention contains the above-mentioned workability improving agent, it may be substantially free of surfactants.

[0051] When the aggregate contains recycled aggregate, a recycling additive can be used. Recycling additives are additives that have the effect of restoring properties such as flexibility of old asphalt. For example, petroleum lubricant-based recycling additives can be used. Examples of commercially available recycling additives include RDEX (product name of ENEOS Corporation), RJ-1 (product name of Santoku Aslead Co., Ltd.), and RJ-T (product name of Takenaka Sangyo Co., Ltd.).

[0052] The amount of the regeneration additive added may be 0.001% by mass or more, 0.005% by mass or more, 0.01% by mass or more, 0.03% by mass or more, 0.05% by mass or more, or 0.1% by mass or more, based on the total mass of the asphalt mixture, and may be 3% by mass or less, 1% by mass or less, 0.50% by mass or less, 0.30% by mass or less, 0.20% by mass or less, 0.15% by mass or less, or 0.10% by mass or less. For example, the content is 0.001% by mass or more and 3% by mass or less, or 0.01% by mass or more and 1.0% by mass or less.

[0053] <<Method for manufacturing asphalt mixture>> The method for producing an asphalt mixture includes heating an asphalt mixture of asphalt, aggregate, a crystalline water-containing substance, water, and a workability improving agent. Here, the asphalt mixture produced can be the asphalt mixture described above, and the respective components of this production method can be referenced to the respective components described above regarding the asphalt mixture.

[0054] The method for producing an asphalt mixture can include a step of obtaining a first mixture containing a crystal water-containing substance, water, and a workability improving agent. In this case, the amount of water to be contained in the first mixture can be determined by measuring the water content of the crystal water-containing substance.

[0055] The method for producing an asphalt mixture can include a step of heating the aggregate, and the heating can be performed by a method commonly used in this field using a burner or the like.

[0056] The method for producing an asphalt mixture can include a step of mixing aggregate and also mixing a filler such as stone powder with the aggregate, and in this step, the first mixture is mixed to obtain a second mixture containing the aggregate and the first mixture.

[0057] Thereafter, asphalt is mixed with the second mixture to obtain an asphalt mixture. These mixing steps can be performed at a temperature of the asphalt mixture of, for example, 80°C or higher, 100°C or higher, 120°C or higher, 130°C or higher, or 140°C or higher, or at a temperature of 170°C or lower, 160°C or lower, 150°C or lower, 140°C or lower, or 130°C or lower. [Example]

[0058] Example 1 As the asphalt, straight asphalt 80 / 100 was used. In addition, dihydrate gypsum (Yamada Sangyo Co., Ltd.) was used as the crystal water-containing substance. As the glycol ether compound of the workability improving agent, Work Fine W (manufactured by Nippon Nyukazai Co., Ltd.), which corresponds to the compound of formula (I), was used.

[0059] The crystal water-containing substance, water, and workability improving agent were mixed to obtain a first mixture having a water content including the crystal water of gypsum dihydrate of about 23% by mass, a gypsum dihydrate content excluding the crystal water of gypsum of about 67% by mass, and a workability improving agent content of about 10% by mass. An aggregate mixture containing equal amounts of recycled aggregate and new aggregate was heated with a burner, and the first mixture was poured into the heated aggregate mixture and mixed for 20 seconds.

[0060] Thereafter, new asphalt was mixed and mixed for about 40 seconds to obtain the asphalt mixture of Example 1. Here, the mixing temperature was 140°C.

[0061] Example 2 The asphalt mixture of Example 2 was obtained in the same manner as in Example 1, except that a composition containing 11.2 mass% of methyl stearate, 76.0 mass% of methyl oleate, and 10.9 mass% of methyl linolenate, which corresponds to the compound of formula (II), was used as the workability improver instead of the compound of formula (I), and having an iodine value of 84.1.

[0062] An asphalt mixture of Comparative Example 1 was obtained in the same manner as in Example 1, except that a cationic surfactant was used instead of the workability improving agent.

[0063] When these were used to prepare a small-scale asphalt pavement in a laboratory, it was found that Examples 1 and 2 could improve the degree of compaction compared to Comparative Example 1.

Claims

1. An asphalt mixture comprising asphalt, aggregate, a crystalline water-containing substance, and a workability improving agent, wherein the workability improving agent comprises a fatty acid compound and / or a glycol ether compound.

2. 2. The asphalt mixture according to claim 1, wherein the crystal water-containing substance is gypsum dihydrate.

3. 2. The asphalt mixture of claim 1, wherein the workability improver comprises a glycol ether compound.

4. The asphalt mixture according to claim 3, wherein the glycol ether compound is a compound represented by the following formula (I): R １ -O-(AO).-H・・・・(I) (In the formula, R １ represents a linear, branched or cyclic hydrocarbon group having 1 to 24 carbon atoms which may have a substituent, AO represents a linear or branched oxyalkylene group having 2 to 4 carbon atoms, and n represents the number of moles of oxyalkylene groups added which is a number from 1 to 30.

5. 10. The asphalt mixture of claim 1, wherein the workability improver comprises a fatty acid compound.

6. 6. The asphalt mixture of claim 5, wherein the fatty acid compound is a compound of formula (II): R １１ -COO-(AO)m-R １２ ・・・・(II) (In the formula, R １１ is a linear, branched or cyclic hydrocarbon group having 1 to 24 carbon atoms which may have a substituent; R １２ represents a hydrogen atom or a methyl group, AO represents a linear or branched oxyalkylene group having 2 to 4 carbon atoms, and m represents the number of moles of oxyalkylene groups added, and is 0 or a number from 1 to 30).

7. The asphalt mixture according to claim 1, wherein 30% by mass or more of the aggregate is recycled aggregate.

8. A method for producing an asphalt mixture, comprising heating an asphalt mixture of asphalt, aggregate, a substance containing crystal water, water, and a workability improving agent, wherein the workability improving agent comprises a fatty acid compound and / or a glycol ether compound.

9. 9. The method for producing an asphalt mixture according to claim 8, comprising: mixing a first mixture containing the crystalline water-containing substance, water, and the workability improving agent with the aggregate to obtain a second mixture; and mixing the second mixture with the asphalt to obtain an asphalt mixture.