Method for manufacturing asphalt mixture

Abstract

To provide a novel method for manufacturing an asphalt mixture that can be produced very simply without requiring modification or the like of existing plants.SOLUTION: A method for manufacturing an asphalt mixture comprises a step of mixing asphalt with aggregate pre-sprayed with a warm-mix additive. In particular, in this method, the warm-mix additive is sprayed onto the aggregate at an aggregate storage location. In particular, in this method, the step of mixing the asphalt with the aggregate pre-sprayed with the warm-mix additive is performed at or below 140°C.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Asphalt pavement is produced by thoroughly compacting an asphalt mixture containing asphalt and aggregate at the construction site. Asphalt is hard at room temperature and softens at high temperatures, so when producing the asphalt mixture, it is heated to around 150°C to 170°C and mixed to ensure good mixing and compaction properties.

[0003] Carbon dioxide is a greenhouse gas, and there is a need to reduce emissions. However, in order to heat the entire asphalt mixture, including the aggregate, to that temperature, large amounts of fossil fuels such as oil, natural gas, and coal must be burned, and the asphalt mixture manufacturing process emits large amounts of carbon dioxide.

[0004] In response to this, a technology called medium temperature mixing has been developed in recent years. This is a technology that reduces the mixing temperature of the asphalt mixture to, for example, around 120°C to 140°C or even lower, and by lowering the mixing temperature, it is possible to significantly reduce carbon dioxide emissions during the manufacturing process.

[0005] One known warm-mixing technology is foamed asphalt, which foams asphalt by adding water during mixing, making it easier to mix even at low temperatures.However, as described in Patent Documents 1 to 3, for example, there is also a known technology that uses an additive called a warm-mixing agent to soften asphalt, making it easier to mix at low temperatures. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-129020 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-129807 [Patent Document 3] Japanese Patent Application Laid-Open No. 2014-237754 Summary of the Invention [Problem to be solved by the invention]

[0007] In the asphalt mixture manufacturing method using a warm-air agent, asphalt and the warm-air agent that softens the asphalt are added to heated aggregate and mixed. However, with this method, if an existing plant does not have the equipment to measure and add the warm-air agent, it is difficult to manufacture warm-air asphalt mixture at that plant.

[0008] In contrast, the present invention provides a novel method for producing an asphalt mixture that does not require modifications to existing plants and allows for extremely simple production. [Means for solving the problem]

[0009] The present inventors have found that the above-mentioned problems can be solved by a method for producing an asphalt mixture having the following features.

[0010] That is, the present invention has the following aspects: <<Aspect 1>> A method for producing an asphalt mixture, comprising a step of mixing aggregate to which a warming agent has been previously spread with asphalt. <<Aspect 2>> The method for producing an asphalt mixture according to aspect 1, wherein the warming agent is applied to the aggregate at a storage location of the aggregate. Aspect 3 The method for producing an asphalt mixture according to aspect 1, wherein the step of mixing the aggregate to which the warming agent has been previously sprayed with the asphalt is carried out at 140°C or less. Aspect 4 The method for producing an asphalt mixture according to aspect 1, wherein the warming agent is a glycol ether compound represented by the following formula (I): R 1-O-(AO)nH····(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 and is an integer of 1 to 30. [Effects of the Invention]

[0011] According to the present invention, a novel method for producing an asphalt mixture can be provided that does not require modifications to an existing plant and allows for extremely simple production.

[0012] Asphalt mixtures whose temperature has dropped decrease in viscosity, which reduces their workability during construction. However, because the temperature of asphalt mixtures drops during transportation, there is a time limit for transporting the asphalt mixture; it must be transported to the construction site within approximately 1 to 2 hours after being shipped from the plant. For these reasons, asphalt mixture manufacturing plants are scattered throughout the country, and asphalt mixtures are manufactured at plants near construction sites and transported to the construction sites. Therefore, renovating many of the existing plants and installing new measuring equipment, dosing equipment, etc. for the warm-air agent would require a significant amount of cost. In contrast, the manufacturing method of the present invention is extremely advantageous because it eliminates the need to renovate plants scattered throughout the country. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 illustrates one embodiment of a method for producing an asphalt mixture. DETAILED DESCRIPTION OF THE INVENTION

[0014] <<Method for manufacturing asphalt mixture>> The method for producing an asphalt mixture of the present invention includes a step of mixing aggregate, onto which a warming agent has been sprayed in advance, with asphalt. The inventors have found that by simply spraying the aggregate with a warming agent in advance before mixing the asphalt and aggregate at a high temperature, an asphalt mixture can be produced without any major problems when the aggregate is subsequently mixed with asphalt.

[0015] <Process> The method for producing an asphalt mixture of the present invention can include a step of spraying a warm-up agent onto aggregate.

[0016] Figure 1 illustrates one embodiment of a method for producing an asphalt mixture. As shown in Figure 1, aggregates can be stored in a stockyard, cold bin, or hot bin depending on their type. For example, the warming agent can be sprayed onto the aggregate manually or automatically in various storage locations such as the aggregate stockyard, the hopper of an aggregate storage device (cold bin or hot bin), or a silo. However, this step can be performed before the aggregate drying step, and it is preferable to spray the agent in the aggregate stockyard or cold bin.

[0017] The method for manufacturing an asphalt mixture may include a step of supplying various types of aggregate according to their blending ratios from an aggregate storage area such as a stockyard or cold bin using an aggregate supply device such as a cold feeder. The location from which the aggregate is supplied from the aggregate supply device may be a mixer, tank, hopper, silo, etc., or an accumulation conveyor. The various types of aggregate may be supplied directly from the aggregate supply device to an accumulation conveyor and then supplied to the dryer. For example, as shown in Figure 1, various types of aggregate may be supplied from the stockyard according to their blending ratios by a cold feeder. The aggregate supplied from the cold feeder may be sent to a cold elevator by an accumulation conveyor.

[0018] The method for producing an asphalt mixture may include a step of drying the aggregate in a dryer. As described above, this step may be performed after the various aggregates have been mixed according to their blending ratios, or after this step has been performed for the various aggregates, the various aggregates may be mixed according to their blending ratios. For example, as shown in Figure 1, the aggregates may be sent to the dryer using a cold elevator.

[0019] The dryer has a burner that uses fuel such as heavy oil, and the flame can drive off the moisture contained in the aggregate. A dust collector can be attached to the dryer to collect the combustion gases and dust generated during drying and detoxify them before discharging them. The dust collected by the dust collector can also be added directly to the asphalt mixture as a filler.

[0020] The method for producing an asphalt mixture may include a step of classifying the dried aggregate using a classifier and storing the aggregate in an aggregate storage device according to particle size. In this case, a hot elevator may be used to transport the aggregate from the dryer to the classifier so as not to lower the temperature of the dried aggregate.

[0021] Examples of classifying devices include a trommel type in which the sieve mesh itself is rotated, and a vibrating sieve type in which a sieve and mechanical vibration are combined.

[0022] The method for producing an asphalt mixture may include a dry mixing step in which various aggregates from a hot bin and, if necessary, fillers such as stone powder are weighed and mixed in a mixer. In the present invention, at least at this stage, the warming agent has already been sprayed onto the aggregates.

[0023] The method for producing an asphalt mixture can include a wet mixing step in which the mixture obtained in the dry mixing step is mixed with a weighed amount of asphalt. This mixing step can be carried out 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 170°C or lower, 160°C or lower, 150°C or lower, 140°C or lower, or 130°C or lower, but is particularly preferably carried out at a temperature of 140°C or lower.

[0024] The dry mixing step and the wet mixing step can be performed in the same mixer. The asphalt mixture does not need to be heated in these mixing steps as long as it is brought to the above temperature by the heat of the aggregate received from the dryer.

[0025] The asphalt mixture obtained in this manner can be loaded onto a dump truck or the like, kept warm, and transported to the construction site, as shown in Figure 1.

[0026] <Medium temperature agent> The temperature-regulating agent used in the present invention is not particularly limited, and may be any agent capable of reducing the viscosity of asphalt, such as one that foams asphalt or one that restores the properties of deteriorated asphalt adhering to recycled aggregate. Examples of temperature-regulating agents include those described in Patent Documents 1 to 3, mineral oil, fatty acid compounds, and glycol ether compounds. When the temperature-regulating agent is sprayed before the aggregate drying process, it is preferable to use a flame-retardant temperature-regulating agent. Here, flame retardancy refers to the property not changing even after the aggregate drying process, and in particular, the property not losing or deteriorating by 10% by mass or more when heated at 200°C for 10 seconds.

[0027] <Medium temperature agent - glycol ether compound> Glycol ether compounds are preferred because they are highly water-soluble among temperature-regulating agents, and therefore, even when sprayed in an aggregate stockyard, for example, they easily penetrate deep into the piled aggregate.

[0028] Examples of glycol ether compounds include compounds represented by the following formula (I):

[0029] R 1 -O-(AO)nH····(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 and is a number from 1 to 30.

[0030] 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.

[0031] Specific 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.

[0032] <Mid-temperature agent - fatty acid compound> The fatty acid compound may be, for example, a fatty acid compound having an iodine value of 50 to 110. The temperature reducing agent may be a combination of a plurality of fatty acid compounds, in which case the iodine value refers to the value of the fatty acid compound in which a plurality of compounds are combined. The iodine value of the fatty acid compound is the iodine value measured in accordance with JIS K0070-1992.

[0033] Examples of fatty acid compounds include fatty acids and fatty acid alkyl esters, fatty acid polyoxyalkylene alkyl esters, and polyoxyalkylene fatty acid esters, and these can be used alone or in combination of two or more selected from these.

[0034] The fatty acid compound can be a compound represented by formula (II):

[0035] R1-CO-(AO)m-OR2···(II) (In the formula, R1 represents a linear or branched hydrocarbon group having 15 to 19 carbon atoms; R2 represents either hydrogen or a linear or branched hydrocarbon group having 1 to 18 carbon atoms; AO represents a linear or branched alkylene oxide unit having 2 to 4 carbon atoms; and m represents the average number of moles added, which is a number from 0 to 30.)

[0036] 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, the molecular weights may be weight-average molecular weights.

[0037] Here, R1 can be a linear or branched alkyl group having 15 to 17 carbon atoms or a linear or branched alkenyl group having 15 to 17 carbon atoms. R2 can be hydrogen or a methyl group. AO can be an ethylene oxide unit. m can be 0 to 15. The iodine value of the fatty acid compound can be 60 to 100 (g / 100 mg) or 70 to 85 (g / 100 mg). In the present invention, the term "alkenyl group" refers to a hydrocarbon group containing 1 to 3 double bonds.

[0038] Fatty acid compounds include fatty acids: R1COOH, fatty acid methyl esters: R1COOCH3, and fatty acid (poly)oxyethylene methyl esters: R1COO(CH2CH2O).m CH3, (poly)oxyethylene fatty acid ester: R1COO(CH2CH2O) m Specific examples thereof 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 stearate ester (average number of moles added: 1 to 15), oleic acid, oleic acid methyl ester, oleic acid (poly)oxyethylene methyl ester ethyl 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).

[0039] The content of the warming agent in the asphalt mixture may be 5 parts by mass or more, 10 parts by mass or more, 15 parts by mass or more, 20 parts by mass or more, 25 parts by mass or more, or 30 parts by mass or more, or 70 parts by mass or less, 60 parts by mass or less, 50 parts by mass or less, 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 asphalt. For example, the content of the warming agent in the asphalt mixture may be 5 parts by mass or more and 50 parts by mass or more, or 10 parts by mass or more and 30 parts by mass or less, per 100 parts by mass of asphalt.

[0040] The content of the warming agent in the asphalt mixture may be 0.1% by mass or more, 0.3% by mass or more, 0.5% by mass or more, 1.0% by mass or more, or 1.5% by mass or more, and may be 5.0% by mass or less, 3.0% by mass or less, 2.0% by mass or less, 1.5% by mass or less, 1.0% by mass or less, or 0.8% by mass or less. For example, the content of the warming agent in the asphalt mixture may be 0.1% by mass or more and 5.0% by mass or less, or 0.5% by mass or more and 1.5% by mass or less.

[0041] The amount of warm-conditioning agent calculated from the above content and the aggregate content in the asphalt mixture can be measured and sprayed onto the aggregate. According to the studies of the present inventors, when an asphalt mixture is produced after spraying a warm-conditioning agent onto aggregate using the production method of the present invention, although the content of warm-conditioning agent varies between production batches of asphalt mixture, this is not enough to significantly affect the quality of the asphalt mixture.

[0042] <aggregate> The aggregate used in the present invention is not particularly limited, and any aggregate commonly used in this field can be used. Examples of aggregate include crushed stone, slag, sand, and other aggregates commonly used in paving. Aggregates of different particle sizes are usually used in combination.

[0043] 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.

[0044] 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.

[0045] <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.

[0046] 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.

[0047] <others> The asphalt mixture may contain other components than those mentioned above that are commonly used in the art. For example, the asphalt mixture may contain fillers such as stone powder.

[0048] The asphalt mixture may contain no other components other than aggregate, asphalt, and warming agent. For example, the asphalt mixture may contain no more than 50% by mass, no more than 40% by mass, no more than 30% by mass, no more than 20% by mass, no more than 10% by mass, no more than 5% by mass, no more than 1% by mass, or no more than 0.1% by mass of other components. [Industrial Applicability]

[0049] The novel method for producing an asphalt mixture of the present invention has high industrial applicability because it can be produced very simply without the need for modifications to existing plants, etc. Furthermore, the asphalt mixture obtained by this production method can be produced at a lower temperature, which allows for a significant reduction in carbon dioxide emissions, making it highly industrially applicable.

Claims

1. A method for producing an asphalt mixture, comprising a step of mixing aggregate to which a warming agent has been previously spread with asphalt.

2. The method for producing an asphalt mixture according to claim 1, wherein the warming agent is sprayed onto the aggregate at a storage location of the aggregate.

3. The method for producing an asphalt mixture according to claim 1, wherein the step of mixing the aggregate to which the warming agent has been previously sprayed with the asphalt is carried out at 140°C or less.

4. The method for producing an asphalt mixture according to claim 1, wherein the warming agent is a glycol ether 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 and is an integer of 1 to 30).

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