Method for producing recycled aggregate and method for producing recycled asphalt mixture

Abstract

The present invention provides a method for producing recycled aggregate that allows as much of the waste material particles sieved before the primary crushing of asphalt waste material to be used as recycled aggregate for recycled asphalt mixtures. [Solution] The present invention provides a method for producing recycled aggregate, comprising: a primary classification step S1 in which asphalt waste is classified before primary crushing to obtain a first aggregate on the large particle size side and a second aggregate on the small particle size side; a primary crushing step C1 in which the first aggregate is crushed; a secondary classification step S2 in which the second aggregate is further classified to obtain a third aggregate on the large particle size side and a fourth aggregate on the small particle size side; and a secondary crushing step C2 in which the third aggregate is crushed to obtain a fifth aggregate, wherein 50% by mass or more of the fourth aggregate passes through a sieve with a nominal size of 9.5 mm.

Description

[Technical Field]

[0001] The present invention relates to a method for producing recycled aggregate and a method for producing a recycled asphalt mixture. [Background Art]

[0002] Waste asphalt materials generated from repair work on paved roads are collected and extracted as recycled aggregate. Recycled aggregate is mixed with virgin aggregate and reused as recycled asphalt mixture.

[0003] Conventionally, waste asphalt materials are crushed by mechanical crushing methods, thermal crushing methods, etc., and reused as recycled aggregate of 0 to 13 mm. For example, in the mechanical crushing method, after primary crushing using a jaw crusher or the like, secondary crushing is further performed using an impact crusher or the like, whereby the crushed product is recovered as a recycled road base material of 0 to 40 mm and also recovered as recycled aggregate of 0 to 13 mm.

[0004] When primary crushing is performed on waste asphalt materials, the waste material is generally supplied to a crusher while being sieved by a feeder that combines a vibrating feeder called a grizzly feeder and a vibrating screen. The waste material particles that are sieved out and not supplied to the crusher are also called grizzly under material, and are sometimes used by being mixed into recycled road base materials or the like.

[0005] Patent Documents 1 and 2 disclose that grizzly under material of 50 mm or less is sieved into particles of 30 mm or more and particles of less than 30 mm, the particles of 30 mm or more are crushed and finally reused as recycled aggregate with various particle sizes, and the particles of less than 30 mm are reused as crusher run, which is a type of recycled road base material. [Prior Art Documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 09-141243 [Patent Document 2] Japanese Patent Publication No. 2006-336290 [Overview of the project] [Problems that the invention aims to solve]

[0007] In recent years, the shipment volume of recycled asphalt mixtures has increased, while the shipment volume of recycled roadbed material has decreased in comparison. Therefore, if grizzlyander material is reused as described in Patent Documents 1 and 2, it is anticipated that the yard for recycled roadbed material within the factory will approach its storage limit.

[0008] On the other hand, even if recycled roadbed material obtained by the methods described in Patent Documents 1 and 2 is used as recycled aggregate in a recycled asphalt mixture, either as is or after being crushed once, the quality of the recycled asphalt mixture may not meet the standards, making it difficult to use as recycled aggregate.

[0009] Therefore, the present invention aims to provide a method for producing recycled aggregate that allows as much of the waste material particles sieved before the primary crushing of asphalt waste material to be used as recycled aggregate for recycled asphalt mixtures. [Means for solving the problem]

[0010] The present inventors have found that a method for producing recycled aggregate and a method for producing recycled asphalt mixture having the following embodiments can solve the above problems.

[0011] In other words, the present invention has the following aspects:

[0012] 《Aspect 1》 In the primary classification process, asphalt waste is classified before primary crushing to obtain a first aggregate for large particle size and a second aggregate for small particle size. A primary crushing step for crushing the first aggregate, A secondary classification process is performed, in which the second aggregate is further classified to obtain a third aggregate for the large particle size side and a fourth aggregate for the small particle size side, and The process includes a secondary crushing step in which the third aggregate is crushed to obtain a fifth aggregate, More than 50% by mass of the fourth aggregate passes through a sieve with a nominal size of 9.5 mm. A method for manufacturing recycled aggregate.

[0013] 《Aspect 2》 A method for manufacturing recycled aggregate according to Embodiment 1, wherein 50% or more by mass of the first aggregate does not pass through a sieve with a nominal dimension of 13.2 mm.

[0014] 《Aspect 3》 A method for producing recycled aggregate according to Embodiment 1, further comprising a tertiary classification step of classifying the crushed first aggregate to obtain a sixth aggregate as the large particle size side and a seventh aggregate as the small particle size side.

[0015] Appearance 4 A method for producing recycled aggregate according to embodiment 3, further comprising mixing the crushed first aggregate and the crushed sixth aggregate and performing a tertiary classification process.

[0016] Appearance 5 A method for producing recycled aggregate according to embodiment 3, further comprising a tertiary crushing step for crushing the sixth aggregate.

[0017] 《Aspect 6》 A method for producing recycled aggregate according to embodiment 3, further comprising a fourth classification step of further classifying the seventh aggregate to obtain an eighth aggregate as the large particle size side and a ninth aggregate as the small particle size side.

[0018] Appearance 7 A method for producing a recycled asphalt mixture comprising recycled aggregate, new aggregate, and new asphalt, wherein the recycled aggregate comprises one or more of the fourth aggregate and fifth aggregate obtained by the method of Embodiment 1, and one or more of the eighth aggregate and ninth aggregate obtained by the method of Embodiment 6. [Effects of the Invention]

[0019] According to the method for producing recycled aggregate of the present invention, as many waste particles screened before primary crushing of asphalt waste as possible can be used as recycled aggregate for recycled asphalt mixture. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] [Figure 1] Fig. 1 is a flow chart of one embodiment of the method for producing recycled aggregate according to the present invention. [Figure 2] Fig. 2 illustrates one embodiment of the method for producing recycled asphalt mixture. MODE FOR CARRYING OUT THE INVENTION

[0021] The present invention will be specifically described below by taking the following embodiments as examples, but the present invention is not limited thereby. Unless otherwise specifically detailed with respect to each mechanism, means, method, material, process and the like in the present specification, a person skilled in the art can use well-known configurations for these. Each embodiment can be combined by a person skilled in the art based on common general knowledge, and configurations not specifically described in each embodiment can adopt the same configurations as other embodiments or configurations suitable for that embodiment.

[0022] Method for Producing Recycled Aggregate Fig. 1 is a flow chart of one embodiment of the method for producing recycled aggregate according to the present invention.

[0023] The present invention provides a method for producing recycled aggregate, comprising: a primary classification step S1 in which asphalt waste is classified before primary crushing to obtain a first aggregate on the large particle size side and a second aggregate on the small particle size side; a primary crushing step C1 in which the first aggregate is crushed; a secondary classification step S2 in which the second aggregate is further classified to obtain a third aggregate on the large particle size side and a fourth aggregate on the small particle size side; and a secondary crushing step C2 in which the third aggregate is crushed to obtain a fifth aggregate, wherein 50% by mass or more of the fourth aggregate passes through a sieve with a nominal size of 9.5 mm.

[0024] Even if recycled roadbed material obtained by the methods described in Patent Documents 1 and 2 is used as recycled aggregate in a recycled asphalt mixture, either as is or after being crushed once, the quality of the recycled asphalt mixture may not meet the standards. Upon investigation, the inventors found that the cause of this is that the amount of attached asphalt is unstable, and that a large amount of elongated aggregate and flattened aggregate is mixed in.

[0025] Therefore, the inventor decided to first classify the second aggregate, such as grizzly sand material, obtained in the primary classification step S1, using a sieve with a relatively small mesh. This separated it into a third aggregate of a certain size and a fourth aggregate of very small size. By crushing the third aggregate and using it, it was found that the amount of attached asphalt in the fifth aggregate after crushing was relatively stable, and the amount of elongated and flat aggregate was significantly reduced. By using this as recycled aggregate, the inventor succeeded in obtaining a recycled asphalt mixture that met the standards.

[0026] <Primary classification process S1> In the primary classification process S1, the asphalt waste is classified before primary crushing to obtain a first aggregate for large particle size and a second aggregate for small particle size. "Before primary crushing of the asphalt waste" means before crushing by a crusher, specifically before being passed through a primary crusher such as a jaw crusher.

[0027] The primary classification process S1 can classify asphalt waste using screens such as a grizzly screen that classifies particles with a rake-shaped bar, a finger-shaped screen with a row of finger-shaped iron rods, or a mesh screen, while vibrating the screen as needed. These screens may also be incorporated into the feeder to the primary crusher.

[0028] In the primary classification process S1, a large portion of the asphalt waste remains as primary aggregate on the larger particle size side, while not much is separated as secondary aggregate on the smaller particle size side. For example, 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, or 95% or more of the asphalt waste fed into the primary classification process S1 is crushed in the primary crushing process C1 as primary aggregate on the larger particle size side.

[0029] The particle size of the first aggregate may be relatively large, and 50% or more by mass of the particles may not pass through a sieve with a nominal size of 13.2 mm, and 50% or more by mass of the particles may not pass through a sieve with a nominal size of 19.0 mm, and 50% or more by mass of the particles may not pass through a sieve with a nominal size of 26.5 mm.

[0030] Furthermore, the classification in the primary classification process S1 is a coarse classification, and the second aggregate may also contain relatively large particle sizes. It is not necessary for 10% or more by mass of the particles of the second aggregate to pass through a sieve with a nominal size of 13.2 mm, nor for 10% or more by mass of the particles to pass through a sieve with a nominal size of 19.0 mm, nor for 10% or more by mass of the particles to pass through a sieve with a nominal size of 26.5 mm.

[0031] <Primary crushing process C1> The primary crushing step C1 is a step in which the first aggregate with larger particle sizes obtained in the primary classification step S1 is crushed, and the crushed first aggregate may be used as recycled aggregate as is. However, it is preferable to further process the first aggregate by further classifying and / or crushing it before using it as recycled aggregate.

[0032] The crusher used in the primary crushing process C1 is not particularly limited, but any crusher suitable for primary crushing, such as a jaw crusher, can be used. However, other crushers may also be used, such as an impact crusher (impeller crusher), cone crusher, roll crusher, or hammer crusher.

[0033] The primary crushed aggregate may be crushed to a relatively small size, and 50% or more by mass of the particles may pass through a sieve with a nominal size of 26.5 mm, or 50% or more by mass of the particles may pass through a sieve with a nominal size of 19.0 mm, or 50% or more by mass of the particles may pass through a sieve with a nominal size of 13.2 mm.

[0034] <Secondary classification process S2> The secondary classification step S2 is an essential step in this invention, and it is a step in which large and / or irregularly shaped aggregates contained in the second aggregate are extracted as a third aggregate on the larger particle size side. It has been found that if this third aggregate is to be used as recycled aggregate as is, it will adversely affect the quality of the recycled asphalt mixture.

[0035] The classification in the secondary classification process S2 can be performed using methods such as a trommel method, which rotates the sieve itself, or a vibrating sieve method, which combines a sieve with mechanical vibration, but the means are not particularly limited.

[0036] The third aggregate on the larger particle size side, classified by the secondary classification process S2, may be relatively large, and 10% or more by mass of the third aggregate particles, 20% or more by mass, 30% or more by mass, or 50% or more by mass do not need to pass through a sieve with a nominal size of 13.2 mm, and 10% or more by mass of the particles, 20% or more by mass, 30% or more by mass, or 50% or more by mass do not need to pass through a sieve with a nominal size of 19.0 mm, and 10% or more by mass of the particles, 20% or more by mass, 30% or more by mass, or 50% or more by mass do not need to pass through a sieve with a nominal size of 26.5 mm.

[0037] The fourth aggregate, which is classified by the secondary classification process S2 and has a small particle size, may have a relatively small particle size and can be used as is in place of stone powder or filler. The fourth aggregate may have 50% or more by mass, 70% or more by mass, 80% or more by mass, or 90% or more by mass of its particles pass through a sieve with a nominal size of 9.5 mm; 50% or more by mass, 70% or more by mass, 80% or more by mass, or 90% or more by mass of its particles pass through a sieve with a nominal size of 4.75 mm; or 50% or more by mass, 70% or more by mass, 80% or more by mass, or 90% or more by mass of its particles pass through a sieve with a nominal size of 2.36 mm.

[0038] <Secondary crushing process C2> The secondary crushing step C2 is a process in which the third aggregate, which has a larger particle size and was obtained in the secondary classification step S2, is crushed to obtain the fifth aggregate. The crushed fifth aggregate can be used as recycled aggregate as is. The third aggregate contains many irregularly shaped aggregates, but the secondary crushing step C2 can crush the irregularly shaped aggregates and reduce the amount of elongated or flattened aggregates.

[0039] The crusher used in the secondary crushing process C2 is not particularly limited, but it is preferable to use a crusher such as an impact crusher (impeller crusher) that can easily adjust the particle size to one suitable for use as aggregate.

[0040] The fifth aggregate is preferably graded so that it can be used as is as coarse aggregate with a maximum particle size of 13 mm or 20 mm. For example, 70% or more, 80% or more, 90% or more, or 95% or more of the particles of the fifth aggregate may pass through a sieve with a nominal size of 19.0 mm, and 70% or more, 80% or more, 90% or more, or 95% or more of the particles may pass through a sieve with a nominal size of 13.2 mm.

[0041] <Other processes> The first aggregate crushed in the primary crushing step C1 is preferably further processed by classification and / or crushing to be used as recycled aggregate. These steps can be carried out by conventional methods for obtaining recycled aggregate from asphalt waste.

[0042] For example, a tertiary classification process S3 can be performed, in which the crushed first aggregate is classified using a vibrating screen or the like. This allows for obtaining a sixth aggregate on the large particle size side and a seventh aggregate on the small particle size side. In the tertiary classification process S3, a classifier similar to that used in the secondary classification process S2 can be used.

[0043] The sixth aggregate, which has larger particle sizes, is crushed by a primary crusher such as a jaw crusher, and may contain relatively large particle sizes. Therefore, a tertiary crushing step C3 can be performed to further crush the sixth aggregate. The crusher used in the tertiary crushing step C3 is not particularly limited, but it is preferable to use a crusher such as an impact crusher (impeller crusher) that can easily adjust the particle size to one suitable for use as aggregate.

[0044] The crushed sixth aggregate is then mixed with the crushed first aggregate after the primary crushing process C1, and can be subjected to classification again in the tertiary classification process S3.

[0045] In this way, the seventh aggregate obtained may, for example, have 70% or more by mass, 80% or more by mass, 90% or more by mass, or 95% or more of its particles pass through a sieve with a nominal dimension of 19.0 mm, or 70% or more by mass, 80% or more by mass, 90% or more by mass, or 95% or more of its particles pass through a sieve with a nominal dimension of 13.2 mm.

[0046] The seventh aggregate can be used as is as recycled aggregate for recycled asphalt mixtures, but a fourth classification process S4 can be performed to further separate the aggregate by particle size. This makes it possible to obtain the eighth aggregate as the large particle size side and the ninth aggregate as the small particle size side, and for example, the eighth aggregate and the ninth aggregate can be made to have particle sizes equivalent to No. 6 crushed stone and No. 7 crushed stone, respectively.

[0047] Each recycled aggregate obtained as described above can be stored in its own stockyard, but it can also be mixed with new aggregate and used in that case, in which case it can be stored in the new aggregate's stockyard.

[0048] Method for manufacturing recycled asphalt mixture Each recycled aggregate obtained in this manner can be used as recycled aggregate contained in a recycled asphalt mixture. That is, the present invention provides a method for producing a recycled asphalt mixture comprising recycled aggregate, new aggregate, and new asphalt, wherein the recycled aggregate includes any of the above aggregates, and in particular includes one or more of the fourth and fifth aggregates and one or more of the eighth and ninth aggregates.

[0049] Figure 2 illustrates one embodiment of a method for producing recycled asphalt mixture. As shown in Figure 2, aggregates including new aggregates and recycled aggregates can be stored in a stockyard or cold bin depending on their type. Here, the fourth, fifth, eighth, and ninth aggregates obtained in the above production method can be stored in a stockyard or cold bin for recycled aggregates, but the fourth and fifth aggregates can also be supplied by the aggregate supply device for new aggregates.

[0050] A method for producing recycled asphalt mixtures may include a step of supplying various aggregates from aggregate storage areas such as stockyards and cold bins using aggregate supply equipment such as cold feeders, according to their mixing ratios.

[0051] The location from which aggregate is supplied from the aggregate supply device may be a mixer, tank, hopper, silo, etc., but it may also be a collection conveyor. Various aggregates may be supplied directly from the aggregate supply device to the collection conveyor and then supplied to the dryer. For example, as shown in Figure 2, various aggregates can be supplied from the stockyard by a cold feeder according to their mixing ratio. The aggregate supplied from the cold feeder can be sent to a cold elevator by a collection conveyor.

[0052] A method for producing recycled asphalt mixtures may include a step of drying the aggregates in a dryer. As described above, this step may be performed after mixing the various aggregates according to their respective proportions, or after performing this step for each aggregate, the various aggregates may be mixed according to their respective proportions. For example, as shown in Figure 2, the aggregates can be transported to the dryer by a cold elevator.

[0053] A dryer has a burner that uses fuel such as heavy oil, and the flame can remove moisture contained in the aggregate. A dust collector can be attached to the dryer to collect combustion gases and dust generated during drying, detoxify them, and then exhaust them. The dust collected by the dust collector can also be directly incorporated into the asphalt mixture as a filler.

[0054] Here, recycled aggregate can be stored in a separate stockyard from new aggregate and supplied to the final mixer using a separate cold feeder and dryer system. However, the fourth and fifth aggregates can also be supplied to the final mixer using the cold feeder and dryer system of the new aggregate system.

[0055] A method for producing recycled asphalt mixtures may include a step of classifying dried aggregate in a classifier and storing the aggregate in an aggregate storage device (or hot bin) according to its particle size. In this case, a hot elevator can be used to transport the aggregate from the dryer to the classifier so as not to lower the temperature of the dried aggregate. A classifier such as the one used in the above-described method for producing recycled aggregate can be used as the classifier.

[0056] A method for producing recycled asphalt mixtures may include a dry mixing step in which various aggregates from a hot bin, recycled aggregate from a surge bin, and fillers such as stone powder as needed are weighed and mixed in a mixer. Furthermore, the method for producing the recycled asphalt mixture may include a wet mixing step in which the mixture obtained in the dry mixing step is mixed with the weighed new asphalt.

[0057] The dry mixing process and the wet mixing process can be carried out in the same mixer. A batch mixing type mixer with agitation blades, which is well known in this field, can be used as the mixer. The recycled asphalt mixture only needs to reach the above temperature due to the heat of the aggregate received from the dryer, and does not need to be heated in these mixing processes.

[0058] The recycled asphalt mixture obtained in this way can be loaded onto a dump truck or the like, as shown in Figure 2, and transported to the construction site while maintaining its temperature.

[0059] The amount of recycled asphalt mixture that can be mixed in a mixer, i.e., the amount of recycled asphalt mixture produced at one time, can be 0.5 tons or more, 1.0 tons or more, 1.5 tons or more, or 2.0 tons or more, and can also be 10 tons or less, 5.0 tons or less, or 3.0 tons or less. For example, the amount of recycled asphalt mixture produced at one time can be 0.5 tons or more and 10 tons or less, or 1.0 ton or more and 5.0 tons or less.

[0060] <aggregate> The recycled aggregate used in the method of the present invention may be one produced by the above-described method for producing recycled aggregate, and is obtained by crushing waste asphalt mixture. The recycled aggregate contains aggregate and old asphalt.

[0061] The recycled aggregate used in the method of the present invention may be deteriorated recycled aggregate that has been used repeatedly. Such deteriorated recycled aggregate usually degrades the properties of recycled asphalt mixtures, but in recycled asphalt mixtures produced by the method of the present invention, even when deteriorated recycled aggregate is used, excellent properties can be obtained by using recycled additives or foamed asphalt in combination.

[0062] As for the recycled aggregate for aging, it may be one with a penetration degree of 25 or less, 20 or less, or 18 or less. Here, the penetration degree is measured as described in "A041 Penetration degree test method" of the "Pavement Survey and Testing Methods Handbook (Japan Road Association)" (JIS K 2207:1996).

[0063] The novel aggregate used in the method of the present invention is not particularly limited, and any aggregate commonly used in the art may be used. Examples of aggregates include crushed stone, slag, and sand, which are commonly used in paving. It is common to use a mixture of multiple types of aggregates with different particle sizes.

[0064] The recycled aggregate may make up 30% or more, 50% or more, 60% or more, 70% or more, or 75% or more of the total aggregate by mass, and may also be 100% or less, 90% or less, 80% or less, or 70% or less by mass.

[0065] The aggregate content in the recycled asphalt mixture obtained by the method of the present invention, including recycled aggregate and new aggregate, 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, and may also 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.

[0066] <Recycling additives> The regeneration additive used in the method of the present invention is not particularly limited, and substances commonly used in the art can be used. The regeneration additive is not particularly limited as long as it is a substance that can restore the properties of the old asphalt, but examples include regeneration additives, asphalt-based additives, petroleum lubricant-based additives, mineral-based additives, animal oil-based additives, vegetable oil-based additives, asphalt emulsion-based additives, etc., as described in Patent Documents 1 and 2.

[0067] <asphalt> The new asphalt added in the method of the present invention is not particularly limited, and any asphalt commonly used in the art can be used. For example, various types of asphalt can be used. Examples include straight asphalt, which is petroleum asphalt for paving, as well as modified asphalt, formed asphalt, etc. Examples of modified asphalt include blown asphalt, asphalt modified with polymer materials such as thermoplastic elastomers and thermoplastic resins.

[0068] The total content of new asphalt and old asphalt adhering to recycled aggregate in the recycled asphalt mixture obtained by the method 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, and may be 8.0% by mass or less, 5.0% by mass or less, or 4.0% by mass or less.

[0069] <others> The recycled asphalt mixture obtained by the method of the present invention may contain other components not commonly used in the art. For example, the recycled asphalt mixture obtained by the method of the present invention may contain fillers such as stone powder.

[0070] The recycled asphalt mixture obtained by the method of the present invention does not need to contain any other components other than aggregate, asphalt, and a heat-reducing agent. For example, the asphalt mixture may contain other components in amounts of 50% by mass or less, 40% by mass or less, 30% by mass or less, 20% by mass or less, 10% by mass or less, 5% by mass or less, 1% by mass or less, or 0.1% by mass or less.

[0071] The present invention will be described in more detail by the following examples, but the present invention is not limited thereto. [Examples]

[0072] Asphalt waste was subjected to primary sieving using a grizzly feeder, and the remaining material after sieving was primary crushed using a jaw crusher. The material that passed through the primary sieve was then subjected to secondary sieving using a 7 mm sieve to separate it into particles of approximately 40-5 mm (third aggregate) and particles of approximately 5-0 mm (fourth aggregate). The content of elongated and flattened aggregates in the third aggregate was measured by aggregate shape testing, and the ratio of short side to long side of 1:3 was 19.2 mass%, while the ratio of 1:5 was 4.2 mass%.

[0073] The third aggregate was crushed using an impeller breaker to obtain a fifth aggregate, resulting in a particle size distribution of approximately 13-0 mm.

[0074] Property tests were conducted on the fourth and fifth aggregates. Specifically, asphalt (As) extraction tests and particle size distribution tests were performed on the fourth and fifth aggregates to confirm the asphalt (As) content. For the fifth aggregate, density tests and water absorption tests were also performed to calculate the theoretical density, Los Angeles abrasion tests and soft stone content tests were performed to evaluate the hardness of the aggregate, and shape tests were also conducted.

[0075] The results are shown in the table below:

[0076] [Table 1]

[0077] The fifth aggregate did not meet the target quality for coarse aggregate (No. 6 crushed stone) in terms of particle size (13-0 mm), but it met the target values ​​for other items. Furthermore, the fifth aggregate had a short-side:long-side ratio of 1:3 at 11.6 mass%, and a ratio of 1:5 at 0.3 mass%, indicating a significant improvement in shape compared to the third aggregate.

[0078] To confirm the properties of the recycled asphalt mixture containing the fourth and fifth aggregates, a test mix was conducted at a full-scale plant. In the test mix, the blend of the 13mm recycled dense-graded asphalt mixture (recycled aggregate = 70%) normally used at the full-scale plant was used as a baseline. The standard recycled aggregates (eighth and ninth aggregates) and recycled aggregates derived from grizzly ash (fourth and fifth aggregates) were mixed according to the blends shown in the table below. The fifth aggregate was used in place of the entire amount of new aggregate from 3 bins, and the fourth aggregate was used together with new aggregate from 1 bin, with the feed rate adjusted so that they were mixed at 20% by mass. The fourth and fifth aggregates were dried and heated using the same new material dryer as the new aggregates.

[0079] [Table 2]

[0080] To investigate the influence of grizzlyander-derived asphalt on the properties of recycled asphalt mixtures, both standard and test samples produced through trial mixing, asphalt extraction tests and penetration tests using the extracted asphalt were conducted. The asphalt extraction tests were performed in accordance with G028 of the Asphalt Extraction Test: Pavement Survey and Test Method Handbook (published by the Japan Road Association). The penetration tests were performed in accordance with JIS K 2207:1996.

[0081] Similarly, the density and void ratio of the recycled asphalt mixture were determined in accordance with B008 of the above-mentioned Pavement Survey and Testing Methods Handbook.

[0082] Furthermore, to confirm workability, penetration tests and flow tests were conducted in the same manner as the penetration tests and flow tests described in the examples of International Publication WO2024 / 202337.

[0083] A Marshall stability test was conducted to confirm the compaction characteristics and strength. The Marshall stability test was performed in accordance with the above-mentioned Pavement Survey and Testing Methods Manual B001.

[0084] A Cantablo test was conducted to assess the resistance to scattering. The Cantablo test was performed in accordance with B010 of the above-mentioned Pavement Survey and Testing Methods Handbook.

[0085] Crush tests and other tests were conducted to assess the resistance to flow and cracking. The crush tests were performed in accordance with B006 of the above-mentioned Pavement Survey and Testing Methods Manual.

[0086] The results are shown in the table below:

[0087] [Table 3]

[0088] Regarding the amount of extracted asphalt (As), the difference between the standard product and the test product from the design asphalt amount (5.7 mass%) was approximately 0.05%, which is almost exactly as designed. There was also no significant difference in penetration, suggesting that even when the fourth and fifth aggregates were heated with a new material dryer, there was no particular problem with the thermal degradation of the old asphalt contained in them.

[0089] Furthermore, penetration and flow tests showed no significant difference between the standard product and the test product immediately after manufacturing, at 60 minutes, and at 120 minutes, suggesting that these tests did not affect workability. Density and porosity also showed no significant difference between the standard product and the test product, satisfying the standard values ​​for the standard product. Stability and Cantablo loss also showed no significant difference between the standard product and the test product, both exceeding the standard values ​​for the standard product. Fracture strength and fracture coefficient also showed no significant difference between the standard product and the test product.

[0090] These results show that a large amount of grizzlyander material can be reused as recycled aggregate for recycled asphalt mixtures. This not only solves the problem of storage limits in recycled roadbed materials yards, but also reduces the manufacturing cost of recycled asphalt mixtures.

Claims

1. In the primary classification process, asphalt waste is classified before primary crushing to obtain a first aggregate for large particle size and a second aggregate for small particle size. A primary crushing step for crushing the first aggregate, A secondary classification process is performed, in which the second aggregate is further classified to obtain a third aggregate for the large particle size side and a fourth aggregate for the small particle size side, and The process includes a secondary crushing step in which the third aggregate is crushed to obtain a fifth aggregate, More than 50% by mass of the fourth aggregate passes through a sieve with a nominal size of 9.5 mm. A method for manufacturing recycled aggregate.

2. A method for producing recycled aggregate according to claim 1, wherein 50% or more by mass of the first aggregate does not pass through a sieve with a nominal size of 13.2 mm.

3. A method for producing recycled aggregate according to claim 1, further comprising a tertiary classification step of classifying the crushed first aggregate to obtain a sixth aggregate as the large particle size side and a seventh aggregate as the small particle size side.

4. A method for producing recycled aggregate according to claim 3, further comprising mixing the crushed first aggregate and the crushed sixth aggregate and performing a tertiary classification step.

5. A method for producing recycled aggregate according to claim 3, further comprising a tertiary crushing step for crushing the sixth aggregate.

6. The method for producing recycled aggregate according to claim 3, further comprising a fourth classification step of further classifying the seventh aggregate to obtain an eighth aggregate as the large particle size side and a ninth aggregate as the small particle size side.

7. A method for producing a recycled asphalt mixture comprising recycled aggregate, new aggregate, and new asphalt, wherein the recycled aggregate comprises one or more of the fourth aggregate and fifth aggregate obtained by the method of claim 1, and one or more of the eighth aggregate and ninth aggregate obtained by the method of claim 6.

Images