Method for producing aggregate

Abstract

To provide a method for producing an aggregate capable of being used as a new aggregate by reducing an amount of deteriorated asphalt from the aggregate contained in an asphalt waste material without washing using a solvent.SOLUTION: A method for producing an aggregate regenerates a deteriorated asphalt adhered aggregate 1 which is an aggregate 5 contained in an asphalt waste material and having a degraded asphalt 3 adhered to a surface thereof, comprises: a deteriorated asphalt removing step S3 of reducing the deteriorated asphalt 3 of the deteriorated asphalt adhered aggregate 1 by grinding the deteriorated asphalt adhered aggregate 1 in a dry state; and a fine powder removing step S5 of removing a fine powder 15 from aggregates 13 obtained in the deteriorated asphalt removing step S3 and the fine powder 15 containing the deteriorated asphalt.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a method for producing aggregate, and more particularly to a method for producing aggregate from waste asphalt that was used to pave roads. [Background technology]

[0002] Asphalt pavement is made by heating and mixing aggregate, stone powder (filler) and asphalt to produce an asphalt mixture, which is then spread evenly on the roadbed and compacted. Asphalt pavement has a service life of about 10 to 20 years.

[0003] Therefore, asphalt mixture is peeled off from asphalt pavement that has reached the end of its useful life, and the resulting asphalt waste is recycled and used as a recycled resource (recycled aggregate). In other words, the asphalt waste is crushed and classified, and the resulting aggregate (aggregate with a lot of deteriorated asphalt attached to the surface) is used as part of the material to generate the asphalt mixture (asphalt mixture to be newly installed on the roadbed). This reduces the amount of new material (new aggregate) used.

[0004] To explain further, as shown in Figure 1, aggregates are reused in a cycle of paving, damage, removal, transportation, crushing, classification, recycled aggregate, and paving. The above pavement is a pavement using an asphalt mixture produced using new aggregate and recycled aggregate. The above damage is damage to the asphalt mixture due to many years of use. The above removal is the removal of the damaged asphalt mixture from the roadbed. The above transportation is the transportation of the removed asphalt mixture. The above crushing is the crushing of the removed asphalt mixture. The above classification is the classification of the crushed asphalt mixture. The above recycled aggregate is the recycled aggregate obtained by classification.

[0005] The recycling rate for all recycled aggregate is approximately 98%. However, the reuse rate of recycled aggregate in asphalt mixtures (asphalt mixtures newly installed on roadbeds) is only around 50%. The reason for this is that if a large amount of aggregate with deteriorated and hardened asphalt attached to it is used, there is a risk of some kind of problem occurring. In particular, if the cycle (number of times) of reuse is two or three or more times, the properties of the asphalt (deteriorated asphalt) attached to the aggregate will deteriorate further, so it is best to avoid increasing the reuse rate of recycled aggregate in asphalt mixtures.

[0006] As mentioned above, the reuse rate of recycled aggregate in asphalt mixtures is about 50%, but the remaining recycled aggregate is used as low-value roadbed material, etc. In addition, in waste material yards where waste asphalt is stored, the amount and number of days that it can be stored are limited, so it is necessary to promote the reuse of waste asphalt.

[0007] Also, a method for recycling aggregates as shown in Patent Document 1 is known. In this method for recycling aggregates, waste asphalt is crushed, heated, and an appropriate amount of seed powder is added thereto, so that the asphalt content in the generated asphalt mixture is adsorbed onto the seed powder. After this, the generated asphalt mixture is separated into aggregates and seed powder asphalt. The aggregates after this separation are washed with a petroleum-based solvent to remove the asphalt content and seed powder adhering to the surface of the aggregates, and then the aggregates are dried to produce recycled aggregates. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 9-111247 Summary of the Invention [Problem to be solved by the invention]

[0009] Incidentally, the aggregate recycling method shown in Patent Document 1 can remove deteriorated asphalt adhering to the recycled aggregate and sufficiently reduce the amount of deteriorated asphalt adhering to the aggregate. However, the recycling method shown in Patent Document 1 is not very preferable because it uses a petroleum-based solvent for cleaning.

[0010] The present invention aims to provide a method for producing aggregate that can be used as new aggregate by reducing the amount of deteriorated asphalt adhering to aggregate contained in asphalt waste without washing with a solvent. [Means for solving the problem]

[0011] An aggregate production method according to one embodiment of the present invention is a method for producing aggregate from deteriorated asphalt-adhering aggregate, which is aggregate contained in asphalt waste and has deteriorated asphalt adhering to its surface, and includes a deteriorated asphalt removal step of reducing the deteriorated asphalt in the deteriorated asphalt-adhering aggregate by grinding the deteriorated asphalt-adhering aggregate in a dry state, and a fine powder removal step of removing the fine powder containing the deteriorated asphalt from the aggregate obtained in the deteriorated asphalt removal step.

[0012] In addition, in an aggregate production method according to an aspect of the present invention, recesses are present on the surface of the aggregate, and the deteriorated asphalt removal process is a process of reducing the deteriorated asphalt adhering to the aggregate while leaving the deteriorated asphalt in the recesses.

[0013] In the method for producing aggregate according to an embodiment of the present invention, the grinding in the deteriorated asphalt removal step is performed using a rotor mill.

[0014] The aggregate production method according to one embodiment of the present invention is an aggregate production method including an aggregate classification step in which the aggregate obtained through the deteriorated asphalt removal step and the fine powder removal step is sieved to classify it, thereby obtaining No. 6 crushed stone aggregate. Effect of the Invention

[0015] According to the present invention, there is provided an aggregate production method that produces aggregate that can be used as new aggregate by reducing the amount of deteriorated asphalt adhering to aggregate contained in asphalt waste without washing with a solvent. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a diagram showing the use cycle of aggregate used in an asphalt mixture. [Diagram 2] FIG. 2 is a diagram illustrating the peeling of deteriorated asphalt from deteriorated asphalt-adhering aggregate in the deteriorated asphalt removal process of the aggregate production method according to the embodiment of the present invention. [Diagram 3] FIG. 2 is a diagram showing aggregate (recycled aggregate) after a deteriorated asphalt removal step has been performed in the aggregate production method according to the embodiment of the present invention. [Figure 4] 1 is a schematic diagram of a rotor mill used in a deteriorated asphalt removing step of an aggregate producing method according to an embodiment of the present invention, in which (b) is a diagram showing a IVB-IVB cross section in (a), and (c) is a diagram showing an IVC-IVC cross section in (a). [Diagram 5] 2 is a flowchart showing an aggregate generating method according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The method for producing aggregate according to the embodiment of the present invention is a method for producing aggregate that can be used as new aggregate from deteriorated asphalt-adhering aggregate 1 (see FIG. 2(a)). In other words, it is a method for regenerating deteriorated asphalt-adhering aggregate 1 so that it can be reused in asphalt mixtures used for road paving, for example.

[0018] The deteriorated asphalt-adhering aggregate 1 is an aggregate 5 having deteriorated asphalt (deteriorated asphalt) 3 attached to its surface. FIG. 2(a) shows the deteriorated asphalt 3 attached to a portion of the surface of the aggregate 5. However, in reality, the deteriorated asphalt 3 is attached to almost the entire surface of the aggregate 5, and the deteriorated asphalt 3 covers almost the entire surface of the aggregate 5. The deteriorated asphalt-adhering aggregate 1 is contained in waste asphalt that was laid on a paved road. The waste asphalt is an asphalt mixture that was used on a paved road that has been used for many years and has reached the end of its useful life, and that has been peeled off from the roadbed (see step S1 in FIG. 5).

[0019] As shown in FIG. 5, the method for producing aggregate according to the embodiment of the present invention includes a deteriorated asphalt removing step S3 and a fine powder removing step S5.

[0020] The deteriorated asphalt removal step S3 is a step of rubbing the deteriorated asphalt-adhering aggregate 1 in a dry state to peel off, separate, and remove the deteriorated asphalt 3 of the deteriorated asphalt-adhering aggregate 1 from the aggregate 5, thereby reducing the amount of deteriorated asphalt. Fig. 2(a) shows the state of the deteriorated asphalt-adhering aggregate 1 before the deteriorated asphalt removal step S3 is performed, and Fig. 2(b) shows the state after the deteriorated asphalt removal step S3 is performed. As shown in Fig. 2(a), even before the deteriorated asphalt removal step S3 is performed, some of the deteriorated asphalt 3 is separated from the aggregate 5.

[0021] The rubbing in the deteriorated asphalt removal step S3 causes the deteriorated asphalt-adhering aggregate 1 to lightly collide and rub against each other. Furthermore, the rubbing causes the deteriorated asphalt-adhering aggregate 1 to lightly collide and rub against a member for moving the deteriorated asphalt-adhering aggregate (a member for stirring). The member for moving the deteriorated asphalt-adhering aggregate 1 is a member for imparting momentum to the deteriorated asphalt-adhering aggregate 1. For example, the blades 9, 11 of the rotor mill 7 shown in FIG. 4 can be cited as an example of this member.

[0022] Ideally, all of the deteriorated asphalt 3 adhering to the surface of the deteriorated asphalt-attached aggregate 1 should be removed in the deteriorated asphalt removal step S3. However, it is difficult to realize this ideal. Specifically, the amount of deteriorated asphalt 3 adhering to the aggregate (deteriorated asphalt-attached aggregate) 1 that had 2.5% deteriorated asphalt 3 adhering by mass is reduced to 1% or less by mass (for example, 0.01% to 1%) (see Fig. 2(b) and Fig. 3). A detailed explanation of Fig. 2(b) and Fig. 3 will be given later.

[0023] The fine powder removing step S5 is a step of removing the fine powder 15 from the aggregate (aggregate from which the deteriorated asphalt has been removed) 13 obtained in the deteriorated asphalt removing step S3 and the fine powder 15 containing the deteriorated asphalt 3. To explain further, the fine powder removing step S5 is a step of removing the fine powder (other than the aggregate 13) 15 from the aggregate 13 from which the deteriorated asphalt has been removed and the fine powder 15 using, for example, a dust collector (not shown).

[0024] The recycled aggregate 17 obtained by the aggregate production method according to the embodiment of the present invention can be reused in asphalt mixtures without problems, although a small amount of deteriorated asphalt 3 is attached to it as shown in Figures 2(b) and 3. Furthermore, the recycled aggregate 17 obtained by the aggregate production method according to the embodiment of the present invention can be reused in asphalt mixtures multiple times, not just once.

[0025] Incidentally, there is a recess (one or more recesses) 19 on the surface of the aggregate 5. In the deteriorated asphalt removal process S3, the deteriorated asphalt 3 adhering to the surface of the aggregate 5 other than the recesses 19 is almost entirely removed. However, in the deteriorated asphalt removal process S3, the deteriorated asphalt 3 adhering to the aggregate 5 is reduced, leaving the deteriorated asphalt 3 in the recesses 19.

[0026] In the deteriorated asphalt removal process S3, the aggregate 5 is ground so as to prevent the aggregate 5 from cracking and separating, and to prevent the generation of smaller-diameter aggregate as much as possible. As a result of this grinding, deteriorated asphalt 3 remains in the recesses 19 of the aggregate 5.

[0027] The grinding in the deteriorated asphalt removal step S3 is carried out using a rotor mill (for example, a crushing and grinding device shown in Japanese Patent Application Laid-Open No. 2007-50347).

[0028] 4, the rotor mill 7 is configured to include a drum 21, a rotor 23, a shell liner 12, and a rotor liner 10. The drum 21 is formed in a cylindrical shape and rotates around a central axis C1 of the cylinder.

[0029] The rotor 23 is formed in a cylindrical shape, and is provided eccentrically within the drum 21. The rotor 23 rotates in the opposite direction to the drum 21 about a central axis C2 of the cylinder.

[0030] The shell liner 12 is attached to the inner circumferential surface of the drum 21 from the inlet 25 side of the deteriorated asphalt-adhered aggregate to the discharge outlet 27 side. The rotor liners 10 are attached in multiple rows along the axial direction (extension direction of the central axis C2) of the outer circumferential surface of the rotor 23. It can be said that the shell liners 12 are also attached in multiple rows along the axial direction (extension direction of the central axis C1) of the inner circumferential surface of the drum 21.

[0031] In the rotor mill 7, the aggregate 1 adhering to deteriorated asphalt is charged from the inlet 25 of the drum 21. In the rotor mill 7, the rotor 23 is rotated faster (at a higher rotational angular velocity) than the drum 21, so that the aggregate 1 adhering to deteriorated asphalt is crushed and milled in the gap 29 between the shell liner 12 and the rotor liner 10.

[0032] The blades 9 (9A) of the rotor liners 10 attached in multiple rows are formed higher than the other blades 9 (9B) in every other row or every few rows. The blades 11 (11A) of the shell liner 12 corresponding to the higher blades 9A of the rotor liner 10 are formed lower than the other blades 11 (11B). The gaps 29 between the rotor liner 10 and the shell liner 12 at the grinding and hulling area are formed in a zigzag shape (rectangular wave shape) from the inlet 25 side to the discharge outlet 28 side as shown in Figure 4(a).

[0033] The method for producing aggregate according to the embodiment of the present invention also includes an aggregate classification step S7. In the aggregate classification step S7, the aggregate 5 (aggregate 13 from which deteriorated asphalt has been removed) obtained through the deteriorated asphalt removal step S3 and the fine powder removal step S5 is sieved and classified to obtain aggregate 5 (recycled aggregate 17) of No. 6 crushed stone (crushed stone with a grain size of about 5 mm to 13 mm).

[0034] In addition to the recycled aggregate 17 of No. 6 crushed stone obtained in the aggregate classification step S7, aggregate 5 other than this recycled aggregate 17 (aggregate 13 from which deteriorated asphalt has been removed) may also be used as the recycled aggregate 17.

[0035] The recycled aggregate 17 thus obtained, new aggregate, asphalt and filler are used to produce an asphalt mixture (S9), and this asphalt mixture is used to pave roads. Note that the asphalt mixture may be produced from the recycled aggregate 17, asphalt and filler without using new aggregate.

[0036] In the aggregate production method according to the embodiment of the present invention, the deteriorated asphalt removing step S3 reduces the amount of deteriorated asphalt 3 in the deteriorated asphalt adhering aggregate 1 by rubbing the deteriorated asphalt adhering aggregate 1 in a dry state. This makes it possible to reduce the amount of deteriorated asphalt 3 adhering to the aggregate 5 without washing the aggregate with a solvent.

[0037] Furthermore, 50% or more (for example, about 60% to 80%) of the aggregate used when producing an asphalt mixture can be recycled aggregate 17 obtained by the aggregate production method according to an embodiment of the present invention.

[0038] Here, we will explain the aggregate recycling method according to the comparative example. In the first aggregate recycling method according to the comparative example, a vibro mill is used to remove cement paste from concrete waste to produce recycled concrete aggregate. In this method, the aggregate is crushed by the vibro mill, resulting in a small particle size of the aggregate.

[0039] Therefore, in the second aggregate recycling method according to the comparative example, the change in aggregate particle size is small, and the deteriorated asphalt covering the aggregate is efficiently peeled off using a wet rotor mill. However, with this method, the deteriorated asphalt covering the aggregate is once scraped off from the aggregate, but the scraped deteriorated asphalt sticks back to the aggregate due to moisture.

[0040] In the aggregate production method according to the embodiment of the present invention, in the deteriorated asphalt removal step S3, the deteriorated asphalt 3 is efficiently peeled off using a dry rotor mill 7. This alone leaves the fine powder 15 of the deteriorated asphalt 3 that has been finely scraped off mixed with the aggregate 5. Therefore, in the aggregate production method according to the embodiment of the present invention, in the fine powder removal step S5, a dust collector is used to remove the fine powder 15 from the aggregate 13 obtained by grinding in the deteriorated asphalt removal step S3 and the fine powder 15 containing the deteriorated asphalt.

[0041] In the aggregate generating method according to the embodiment of the present invention, the fine powder is removed using a dust collector after the grinding in the rotor mill 7. Here, a dust collector may be provided in the rotor mill 7, and the fine powder 15 may be removed using the dust collector during grinding.

[0042] Furthermore, in the aggregate production method according to the embodiment of the present invention, the deteriorated asphalt removal step S3 is configured to leave the deteriorated asphalt 3 in the recesses 19 of the aggregate 5 and reduce the deteriorated asphalt 3 adhering to the aggregate 5. This makes it possible to remove the deteriorated asphalt 3 adhering to the aggregate surface excluding the recesses 19 without substantially reducing the particle size of the aggregate 5. Even if the deteriorated asphalt 3 remains in the recesses 19 of the aggregate 5, no problems will occur.

[0043] Furthermore, in the aggregate production method according to an embodiment of the present invention, the grinding in the deteriorated asphalt removal step S3 is performed using a rotor mill 7, so that the grinding in the deteriorated asphalt removal step S3 can be performed efficiently using commercially available equipment.

[0044] In the aggregate production method according to the embodiment of the present invention, the aggregate 5 (recycled aggregate 17) obtained through the fine powder removal step S5 is sieved and classified in the aggregate classification step S7 to obtain No. 6 crushed stone aggregate 5 (recycled aggregate 17). As a result, even if the particle size of some of the aggregate 5 becomes small by processing in the deteriorated asphalt removal step S3, it is possible to obtain aggregate 5 (recycled aggregate 17) of an appropriate particle size by performing the aggregate classification step S7.

[0045] Incidentally, in the aggregate production method according to an embodiment of the present invention, prior to the deteriorated asphalt removal process S3, a waste asphalt drying process may be carried out in which waste asphalt removed from a paved road that has reached the end of its useful life is crushed and the crushed waste asphalt is dried.

[0046] That is, in the asphalt waste drying process, the asphalt waste removed from the paved road that has reached the end of its useful life before the execution of the deteriorated asphalt removal process S3 may be crushed and the crushed asphalt waste dried. This makes it possible to further reduce the moisture contained in the asphalt waste before the deteriorated asphalt removal process S3, and to more accurately execute the deteriorated asphalt removal process S3.

[0047] Although the present embodiment has been described above, the present embodiment is not limited to this, and various modifications are possible within the scope of the gist of the present embodiment. [Explanation of symbols]

[0048] 1. Aggregate adhering to deteriorated asphalt 3. Deteriorated asphalt 5. Aggregates 7. Rotor Mill 13 Aggregate (aggregate with deteriorated asphalt removed) 15 Fine powder 17 Aggregate (recycled aggregate) 19 Recess S3 Deteriorated asphalt removal process S5 Fine powder removal process S7 Aggregate classification process

Claims

1. A method for producing aggregate from deteriorated asphalt-attached aggregate, which is an aggregate that is contained in asphalt waste and has deteriorated asphalt attached to its surface, comprising the steps of: A deteriorated asphalt removal process for reducing the deteriorated asphalt of the deteriorated asphalt-adhering aggregate by rubbing the deteriorated asphalt-adhering aggregate in a dry state; A fine powder removing step of removing the fine powder from the aggregate and the fine powder containing the deteriorated asphalt obtained in the deteriorated asphalt removing step; A method for producing an aggregate having the following structure:

2. The aggregate has a surface having recesses thereon, The method for producing aggregate according to claim 1 , wherein the deteriorated asphalt removing step is a step of reducing the deteriorated asphalt adhering to the aggregate while leaving the deteriorated asphalt in the recessed portion.

3. The method for producing aggregate according to claim 1 or 2, wherein the grinding in the deteriorated asphalt removal step is performed using a rotor mill.

4. 3. The method for producing aggregate as described in claim 1 or claim 2, further comprising an aggregate classification step of sifting the aggregate obtained through the deteriorated asphalt removal step and the fine powder removal step to obtain No. 6 crushed stone aggregate.

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