Manufacturing method of regenerated asphalt mixture and analysis method of waste material of asphalt mixture

Abstract

An asphalt mixture regeneration method including an analysis step of analyzing a rate of an amount of an effective asphalt component in a waste material of an asphalt mixture (102), a determination step of determining an amount of an additive required for regeneration of the waste material based on an effective asphalt amount rate obtained in the analysis step, a feeding step of feeding the waste material and the additive in the amount determined in the determination step into a container (3), and a stirring and heating step of reducing diameters of the waste material and the additive fed into the container to sizes of pebbles, maintaining a temperature inside the container in a temperature range of 170°C to 200°C by heating, and mixing the waste material and the additive to manufacture a regenerated asphalt material.

Description

Method for regenerating asphalt mixture

[0001] The present invention relates to a method for regenerating an asphalt mixture of an asphalt pavement that has been laid, for example, on a road.

[0002] Many roads, both in urban and suburban areas, are paved with asphalt. Asphalt pavements are made using an asphalt mixture, which is a mixture of aggregates such as crushed stone and sand and petroleum asphalt. Asphalt mixtures deteriorate over time. For example, the pavement layer (the surface layer of the asphalt mixture) can harden due to ultraviolet light, causing cracks on the surface of the pavement layer, ruts can form in the pavement layer due to contact with automobile tires, and depressions can occur in the pavement layer due to the weight of vehicles or objects falling onto the road. Therefore, for asphalt pavements that have been in operation for a certain period of time, the deteriorated pavement layer (the surface layer of the asphalt mixture) is stripped from the base layer, known as the roadbed, and a new pavement layer made of asphalt mixture is laid in its place. Even on roads that have been constructed recently, depressions may need to be repaired.

[0003] In recent years, unpaved roads have been replaced with asphalt-paved roads, even in island regions and developing countries. However, in such island regions and developing countries, the asphalt mixture manufacturing plants required for paving are not necessarily located nearby. This makes it difficult to prepare new asphalt mixture at the construction site when constructing new asphalt pavements, repaving, or repairing existing pavements. In consideration of such cases, it is desirable to heat the solidified asphalt mixture prepared in advance at the construction site or to recycle and reuse deteriorated asphalt mixture from existing asphalt pavements.

[0004] When new asphalt mixture is produced at a manufacturing plant, it must be transported from the manufacturing plant to the construction site by truck or other transportation means. Furthermore, the asphalt pavement layer (waste asphalt) removed at the construction site must be transported from the construction site to the manufacturing plant or disposal site. On the other hand, when waste asphalt is recycled at the construction site and used as new asphalt mixture, the time, cost, and effort required for the production and transportation of new asphalt mixture can be reduced. Furthermore, since waste asphalt, which would otherwise be considered industrial waste, can be reused, this method is in line with the Sustainable Development Goals (SDGs), and it offers significant benefits not only to island regions and developing countries, but to all countries and regions with asphalt-paved roads.

[0005] Regarding asphalt regeneration, Patent Document 1 listed below discloses an apparatus for regenerating asphalt waste by introducing asphalt waste into a rotating drum, rotating the rotating drum in an inclined state in the circumferential direction, and blowing hot air into the rotating drum. Patent Document 2 listed below also discloses a method in which a trailer equipped with an asphalt regeneration apparatus is coupled to a towing vehicle for transport to a construction site, the trailer is detached from the towing vehicle and coupled to the blade of a hydraulic excavator, and while the hydraulic excavator is excavating the site, the excavated asphalt mixture (waste asphalt) is fed into the asphalt regeneration apparatus to regenerate the asphalt mixture, and the regenerated asphalt mixture is successively laid on the excavated site to construct an asphalt pavement.

[0006] JP 2001-90018 A Japanese Patent No. 4892711 A

[0007] In Japan, various quality standards have been established for the physical properties of paving asphalt. For example, the JIS standard (JIS K 2207) specifies the target physical properties for petroleum asphalt suitable for road paving. One of these standards is the penetration index. Penetration index is an index that represents the hardness of solidified petroleum asphalt. It is measured by pressing the tip of a specified needle (similar to a sewing needle) with a 100g weight against an asphalt sample at 25°C. The needle penetrates perpendicularly into the asphalt sample under its own weight for 5 seconds, and the length of penetration into the asphalt sample is measured. The penetration depth is then expressed in tenths of a millimeter to determine the hardness of the asphalt. For road paving asphalt, the penetration index must be within a specified range, e.g., greater than 40 and less than 60 for use in general regions excluding cold regions. If the penetration index falls within this range, the asphalt's softening point, elongation, strength, viscosity, and other properties tend to be suitable for paving.

[0008] Even when waste asphalt is recycled into asphalt mixtures at construction sites, the recycled asphalt must meet the specified penetration level. However, it is not easy to produce asphalt mixtures with penetration levels that meet the standards at construction sites with limited facilities.

[0009] The present invention has been made in consideration of the above circumstances, and aims to provide a method for recycling asphalt mixtures that can easily produce recycled asphalt material that complies with standards at asphalt pavement construction sites from asphalt waste material that was used in existing asphalt pavements.

[0010] The method for recycling asphalt mixtures according to the present invention comprises an analysis step of analyzing the content of effective asphalt components in waste asphalt mixtures; a determination step of determining the amount of additives required to recycle the waste based on the effective asphalt content obtained in the analysis step; an introduction step of putting the waste and the amount of additives determined in the determination step into a container; and a stirring and heating step of reducing the size of the waste and additives introduced into the container to the size of small pebbles, heating the container to maintain the temperature within the container at a temperature range of 170°C to 200°C, and mixing the waste and additives to produce recycled asphalt material.

[0011] In the method for recycling an asphalt mixture according to the present invention, the analysis process may include a crushing process in which a portion of the waste material to be recycled is collected and heated while being crushed into pebble-sized pieces, and a test specimen preparation process in which the crushed material obtained in the crushing process is placed in a container and a test specimen is prepared.

[0012] In the method for regenerating an asphalt mixture according to the present invention, the additive may be prepared by mixing the materials constituting the additive and solidifying them into a block.

[0013] In the method for recycling an asphalt mixture according to the present invention, the additive may be primarily composed of at least one polymer material selected from petroleum asphalt, rubber, thermoplastic elastomer, and thermoplastic resin, and an asphalt emulsion.

[0014] In the method for regenerating an asphalt mixture according to the present invention, in the determining step, the additive may be added at a rate of 1 kg to 4 kg per 1000 kg of the waste material.

[0015] In the method for regenerating an asphalt mixture according to the present invention, in the crushing step, a portion of the waste material may be stirred and heated in the container under the same operating conditions as in the stirring and heating step, and the waste material may be reduced in size to the size of pebbles.

[0016] In the method for regenerating an asphalt mixture according to the present invention, the analysis step may involve pressing a test paper against the test specimen, and then determining the amount of the additive to be added together with the waste material based on the adhesion rate of the effective asphalt component adhered to the test paper.

[0017] According to the present invention, recycled asphalt material that complies with standards can be easily produced at an asphalt pavement construction site from waste asphalt material that was used in an existing asphalt pavement.

[0018] Fig. 1 is a side view of a regeneration device used to carry out the regeneration method according to the present invention. Fig. 2 is a schematic vertical cross-sectional view of the drum in Fig. 1. Fig. 3 is a cross-sectional view of the drum taken along line III-III in Fig. 2. Fig. 4 is a schematic view showing the procedure for analyzing effective asphalt components. Fig. 5 is a schematic view showing the procedure for analyzing effective asphalt components. Fig. 6 is a schematic view showing the procedure for analyzing effective asphalt components. Fig. 7 is a schematic view showing the procedure for analyzing effective asphalt components. Fig. 8 is a view showing a list used to identify the amount of additives required for regenerating waste asphalt.

[0019] A preferred embodiment of the present invention will be described below. The asphalt regeneration device 1 used to carry out the method for regenerating waste asphalt mixture (hereinafter referred to as waste asphalt) according to the present invention may be fixedly installed in a factory or the like, but is preferably mounted on a cart equipped with a towing section or the bed of a self-propelled vehicle. In this case, by moving the cart or vehicle, the regeneration device 1 can be freely moved between asphalt pavement construction sites.

[0020] The regeneration device 1 of this embodiment has the following structure. That is, as shown in Figures 1 to 3, the asphalt regeneration device 1 has a base 2a, a tilt mechanism 2b, a frame 2, a drum 3 for regenerating waste asphalt mixture (hereinafter referred to as waste asphalt), drum rollers (support units) 4 and 5 that rotatably support the drum 3, a drive unit (drive unit) 6 that rotates the drum 3 around a rotation axis O that is a virtual center of rotation, and a burner 7 that heats the inside of the drum 3. The tilt mechanism 2b and the frame 2 are arranged on the base 2a. Furthermore, the drum 3, drum rollers 4 and 5, drive unit 6, and burner 7 are arranged on the frame 2. The drum 3 is supported by the drum rollers 4 and 5. The drum roller 5 is arranged on the back side of the drum 3 (the far side of the drum 3 in Figure 1), and is therefore not shown in Figure 1.

[0021] The frame 2 is composed of upper and lower frame members connected via hinges, with the lower frame member fixed to the base 2a. The base 2a is provided with a tilt mechanism 2b that tilts the frame 2 (upper frame member). When the tilt mechanism 2b is operated, the upper frame member is tilted so that the input port 11 of the drum 3 is higher than the output port 12. The tilt angle of the upper frame member can be selected as desired by changing the stroke length of the tilt mechanism. The tilt mechanism 2b is composed of, for example, a fluid cylinder.

[0022] The drum 3 is a hollow metal container for heating the waste asphalt and additives while stirring them therein. The waste asphalt is supplied to the drum 3 via a hopper 16. The drum 3 includes a cylindrical main body 9 and a truncated conical discharge section 10. The main body 9 is surrounded by a gate-shaped frame mounted on the base 2a. The main body 9 has an inlet 11 (see FIG. 2) at its front end, and the waste asphalt fed into the hopper 16 is introduced into the drum 3 through the inlet 11. The discharge section 10 forms the rear of the drum 3 and has a discharge outlet 12 for discharging the recycled asphalt mixture. The discharge outlet 12 can be closed with a lid member 24.

[0023] A male screw is provided on the outer periphery of the rod 25 fixed to the discharge portion 10, and a female screw hole is provided in the center of the handle 26. Furthermore, a hole slightly larger than the outer diameter of the rod 25 is provided in the center of the lid member 24, into which the rod 25 is inserted. The handle 26 is threadedly engaged with the rod 25 from the outside of the lid member 24, and by operating the handle 26, the lid member 24 is moved in the axial direction of the rod 25, thereby adjusting the gap between the discharge port 12 and the lid member 24. By adjusting this gap, the amount of recycled asphalt mixture discharged from the discharge port 12 can be adjusted.

[0024] The drum 3 is rotatably supported on the frame 2 via a plurality of drum rollers 4, 5. In the position shown in FIG. 1 (normal state), the rotation axis O of the drum 3 is oriented horizontally. The drum rollers 4, 5 include rollers 41, 51 that can rotate around a roller rotation axis that is arranged parallel to the rotation axis O, and the rollers 41, 51 abut against the outer circumferential surface of the main body 9, thereby rotatably supporting the drum 3. There are four drum rollers 4, 5: one at the front and rear of the drum 3 in the longitudinal direction as shown in FIG. 1, and one on each side of the drum 3 in the width direction as shown in FIG. 3. The rollers 41, 51 of each drum roller 4, 5 support the drum 3 from below.

[0025] The drive unit 6 is a drive source that rotates the drum 3. The drive unit 6 includes a motor 20, a reducer 22, and a pinion gear (not shown). The output of the motor 20 is reduced in speed by the reducer 22 and rotates the pinion gear. An annular drive transmission unit 21 is provided on the outer circumferential surface of the main body 9. The drive transmission unit 21 is formed in an annular shape and has a number of teeth (racks) that mesh with the pinion gear. As the motor 20 rotates, the teeth of the pinion gear mesh with the teeth of the rack, causing the drum 3 to roll on each of the rollers 41, 51 around the rotation axis O.

[0026] The rotation speed of the drum 3 can be adjusted using an operation panel (not shown). The operation panel is provided with a switch for switching the rotation speed of the drum 3 between stop, low speed, medium speed, and high speed. By operating this switch, the worker can appropriately switch the rotation speed depending on the size of the asphalt waste material lumps and the progress of the heating and mixing processes.

[0027] The burner (heating unit) 7 heats the waste asphalt and its crushed recycled granules loaded inside the drum 3. In this embodiment, the burner 7 radiates (projects) a flame into the inside of the drum 3 through the inlet 11. This flame directly heats the waste asphalt inside the drum 3, so that the waste asphalt can be quickly and efficiently softened (the surface layer melted).

[0028] The temperature inside the drum 3 can be appropriately set by an operator using a temperature input means provided on the operation panel. The burner 7 controls the heating based on the temperature set by the operator and the measurement results of a temperature measuring means provided inside the drum 3.

[0029] The burner 7 applies pressure to liquid fuel to spray it in the form of a mist, which is then mixed with air and ignited to emit a flame. In the case of a single burner with one flame outlet, heating can be controlled by turning the burner 7 on and off. In the case of a dual burner with two flame outlets, one for high flame and one for low flame, heating can be controlled by adjusting the operation timing of each burner. The burner 7 may be a triple or more burner.

[0030] When recycling waste asphalt in the recycling device 1 configured as described above, waste asphalt and additives are fed into the hopper 16 as shown in Figure 1. This feeding is performed using a shovel, a hopper-hanging crane, or the like. The amount of waste asphalt fed is measured in real time by a measuring unit (not shown) provided in the recycling device 1, and feeding is stopped when the amount fed reaches the desired amount.

[0031] While the drive unit 6 is driven to rotate the drum 3, the burner 7 heats the waste asphalt inside the drum 3. The asphalt waste loaded into the drum 3 is crushed into chunks by the falling energy generated by the rotation of the drum 3. The crushed pieces are heated, melting their surface layers, and then granulated by rolling inside the drum 3. Furthermore, by maintaining the temperature inside the drum 3 at a predetermined temperature and continuing to heat the waste asphalt with the burner 7 for a predetermined time, the waste asphalt can be recycled into high-quality asphalt with a high yield, resulting in recycled granules. The recycled granules are discharged from the drum 3 and reused for asphalt paving of roads. During discharge, the tilt mechanism 2b is driven (extended) to rotate the frame 2 around the hinge portion and lift it up. This changes the drum 3 to an oblique position with the rear end (lid member 24) facing downward. During this position change, heating by the burner 7 and operation of the drive unit 6 may continue. When the cover member 24 is operated in the opening direction by operating the handle 26, a gap can be secured between the cover member 24 and the discharge section 10, and the recycled grains inside the drum 3 fall naturally through this gap due to their own weight.

[0032] Multiple guide members 19 are provided on the inner peripheral wall of the discharge section 10. The guide members 19 are plate-shaped members that are tilted relative to the radial lines extending from the center of the discharge port 12 along the inner peripheral wall. The guide members 19 are tilted so that their rear ends face the rotation direction of the drum 3, and their rear ends are curved in an arch shape facing away from the rotation direction. The guide members 19 guide the recycled particles granulated inside the main body 9 to the discharge port 12, enabling efficient discharge. Multiple guide members 18B are also provided circumferentially on the inner peripheral wall at the rear of the main body 9 to guide the recycled particles from the main body 9 to the discharge section 10.

[0033] A plurality of blade members 18A are also provided on the inner peripheral wall of the main body 9. The blade members 18A are arranged at intervals around the circumference of the drum 3. In the case of a drum without blade members 18A, even if the drum is rotated in the position shown in FIG. 1, the weight of the asphalt waste material will cause the asphalt waste material to remain accumulated at the bottom of the drum. On the other hand, in the case of a drum 3 having blade members 18A, the rotation of the drum 3 causes the plurality of blade members 18A to scrape up the asphalt waste material, forcibly lifting it without it remaining at the bottom of the drum 3, and then it naturally falls and is agitated within the drum 3.

[0034] Each blade member 18A is provided on the inner peripheral wall of the main body 9 along the direction of the rotation axis O and protrudes radially inward of the drum 3. In this embodiment, each blade member 18A extends continuously in parallel with the direction of the rotation axis O.

[0035] Next, we will explain how to regenerate waste asphalt using the asphalt regeneration device 1 having the above-mentioned structure. When the existing asphalt pavement layer is excavated at a site where an asphalt pavement layer is to be replaced, excavation debris consisting of chunks of various sizes is generated. This is the waste asphalt that will be used as material for the new asphalt pavement layer.

[0036] (Analysis of Effective Asphalt Components) Although the particle size of waste asphalt is consistent with that of aggregates in asphalt mixtures, the petroleum asphalt components are not necessarily of a quality suitable for use in actual asphalt pavements. This is due to the fact that pebbles and sand particles from the roadbed underlying the previous asphalt pavement layer are often incorporated during excavation. Because it is impossible to completely remove these pebbles and sand from the waste asphalt, the waste asphalt must be recycled while still containing the pebbles and sand. Furthermore, prolonged outdoor exposure to rainwater, ultraviolet light, and air can cause degradation over time, such as hardening and oxidation of the asphalt components. Due to the presence of impurities and degradation over time, using this waste asphalt directly to produce recycled asphalt results in a low-quality recycled asphalt with a low content of effective petroleum asphalt components, i.e., effective asphalt components, relative to the aggregate. In other words, recycled asphalt produced from this asphalt waste does not meet the quality standards required for road paving asphalt and cannot be used for repaving. Therefore, when producing recycled asphalt from asphalt waste, it is necessary to determine in advance the amount of effective asphalt components contained in the asphalt waste obtained from the construction site.

[0037] First, as shown in Figures 4A to 4D, a cylindrical test container 30 with a bottom and a predetermined diameter is prepared, along with two pieces of white filter paper 31 and 32 cut into circles approximately equal to the inner diameter of the container. The first filter paper 31 is placed on the bottom of the test container 30 (see Figure 4A). Next, a portion 102 of the asphalt mixture sample extracted from the waste asphalt is placed in the test container 30, covering the first filter paper 32 (see Figure 4B). Next, the asphalt mixture 102 loaded into the test container 30 is tamped down using a tool such as a tamping rod, and the surface is leveled. The asphalt mixture 102 loaded into the test container 30 is heated to 170-200°C and crushed to a predetermined particle size.

[0038] A second filter paper 32 is placed on top of the leveled asphalt mixture 102 (see Figure 4C), and then the asphalt mixture 102 is further compacted using a tamping rod 33 (see Figure 4D). This causes the effective asphalt components to seep out of the asphalt mixture 102 and adhere to the filter papers 31 and 32. The effective asphalt components adhering to the filter papers 31 and 32 appear as black stain-like patterns. The amount of asphalt mixture 102 loaded into the test container 30 is adjusted so that the layer thickness of the asphalt mixture 102 in the test container 30 is approximately equal to the construction thickness (80 to 120 mm) specified in the asphalt pavement specifications.

[0039] After compacting the asphalt mixture 102, the filter paper 32 is removed from the asphalt mixture. The area of ​​the black pattern on the filter paper 32 is then analyzed as a percentage of the total area of ​​the filter paper 32, and the amount of effective asphalt components contained in the sample asphalt mixture 102 is determined based on this analysis value. The "area of ​​the pattern" here refers to the ratio of the white and black areas to the total area of ​​the filter paper. By determining the amount of effective asphalt components contained in the sample, it is possible to determine whether the waste asphalt from which the sample was derived: 1) meets the quality standards required for road paving asphalt, and 2) if it does not meet the quality standards, how much of the effective asphalt components are missing. Based on the results of determination 2), it is possible to determine the amount of additive to be added to the waste asphalt to make up for the missing effective asphalt components.

[0040] The additive contains as its main components at least one polymer material selected from petroleum asphalt, rubber, thermoplastic elastomer, and thermoplastic resin, and asphalt emulsion. The "additive" used in this embodiment refers to a mixture of the above components, to which a flammable binder is added, kneaded, and solidified into a block (hereinafter referred to as an additive block).

[0041] To determine the amount of additive to be added to the waste asphalt, first, a first table showing the relationship between the area percentage of the black pattern and the amount of effective asphalt component contained in the sample is created using multiple types of waste asphalt samples. Similarly, a second table showing the relationship between the amount of effective asphalt component contained in the sample and the amount of additive required to compensate for the deficiency is created. After these tables are prepared in advance, the amount of additive to be added to the waste asphalt is determined at the asphalt pavement construction site based on the area percentage of the black pattern in the sample obtained from the waste asphalt and the first and second tables.

[0042] The amount of additive to be added to the waste asphalt material increases as the area ratio (adhesion rate) of the black pattern of the effective asphalt component adhered to the filter paper 32 relative to the total area of ​​the filter paper decreases, and decreases as the area ratio of the black pattern increases. Specifically, a method for determining the amount of additive from stains on the filter paper 32 can be calculated using image analysis software running on a general-purpose computer. First, the filter paper 32 with the effective asphalt component adhered thereto is photographed, and the digital image is then run through the image analysis software. The image analysis software calculates the area ratio of the black pattern of the effective asphalt component relative to the total area of ​​the filter paper 32 (= (total area occupied by the pattern ÷ total area of ​​the filter paper) × 100) based on the black and white shading on the filter paper 32. The amount of effective asphalt component contained in the sample asphalt mixture 102 is then determined based on the relationship between the area ratio of the effective asphalt component pattern calculated from the image of the filter paper 32 and the first table. Regarding the filter paper, in this embodiment, the occupied area ratio of the pattern of the effective asphalt component was calculated using filter paper 32, but the occupied area ratio may also be calculated in a similar manner using filter paper 31, or the occupied area ratio may be calculated using two sheets of filter paper, 31 and 32, and the average value of the occupied area ratios of the two sheets may be used.

[0043] <Determination step> After identifying the amount of effective asphalt components contained in the sample, the amount of additive required to make up for the deficiency in the effective asphalt components is determined based on the relationship between this amount and the second table. Because the additive block is a block with a fixed weight per unit, the amount determined above can be added reliably without error.

[0044] When producing recycled asphalt from waste asphalt, considering the quality standards required for road paving asphalt, the weight of the additive block added to the waste asphalt is typically 1 to 4 kg per 1,000 kg of waste asphalt, preferably 2 to 3 kg. If the weight of the additive block added to 1,000 kg of waste asphalt is less than 2 kg, the penetration into the recycled asphalt pavement layer laid using the recycled asphalt may be low, potentially failing to meet quality standards. Furthermore, if the weight of the additive block added is less than 1 kg, the effective asphalt component is too low, resulting in a lower penetration into the recycled asphalt pavement layer. In addition, the viscosity (hardness) of the asphalt increases, resulting in poor flexibility, which makes the recycled asphalt pavement layer less able to conform to uneven roadbeds, making laying and construction difficult.

[0045] Furthermore, if the weight of the additive block added to 1,000 kg of waste asphalt is greater than 3 kg, the penetration into the recycled asphalt pavement layer may be too high, potentially failing to meet quality standards. Furthermore, if the weight of the additive block added is greater than 4 kg, the effective asphalt component will be too high, resulting in a higher penetration into the recycled asphalt pavement layer. Furthermore, the strength of the asphalt may be reduced, potentially reducing the durability of the recycled asphalt pavement layer and potentially causing cracks and ruts to form shortly after construction.

[0046] (Regeneration of waste asphalt) <Addition process> First, waste asphalt and additive blocks are added to the hopper 16 of the asphalt regeneration device 1, which has been moved to the site, and the waste asphalt and additive blocks are loaded into the drum 3. The amount of additive blocks to be added is determined based on the analysis results described above. The tilt mechanism 2b is operated to tilt the frame 2 together with the drum 3 so that the inlet 11 of the drum 3 is slightly higher than the outlet 12. By making the inlet 11 higher than the outlet 12, the waste asphalt being processed in the drum 3 moves from the inlet 11 toward the outlet 12 under its own weight.

[0047] <Stirring and Heating Process> Next, the drive unit 6 is operated to rotate the drum 3, and a crushing process is carried out so that the waste asphalt and additive blocks have a predetermined particle size. In parallel with this crushing process, the burner 7 is ignited to heat the inside of the drum 3 to a temperature range of 170°C to 200°C.

[0048] The asphalt waste and additive blocks fed into the drum 3 are initially lumps of various sizes, but are gradually crushed (reduced in diameter) as they are repeatedly picked up and dropped by the blade members 18A as the drum 3 rotates. At the same time, the crushed asphalt waste and additive blocks are heated by the burner 7, which softens the petroleum asphalt contained in the asphalt waste and additive blocks and increases their viscosity.

[0049] The asphalt waste and additive blocks crushed in the drum 3 and having their viscosity increased by heating are stirred and heated until they reach a predetermined temperature range, i.e., a temperature range of 170°C to 200°C, and reach a predetermined particle size, i.e., a particle size of 4.75 to 19.00 mm (medium gravel), which is large enough to be used as aggregate for asphalt pavement. This heating process heats the asphalt waste and additive blocks while crushing them. As a result, the surface layers of both crushed bodies are melted and stirred, and the crushed bodies are mixed together to produce a homogeneous recycled asphalt material (recycled granules).

[0050] The recycled asphalt material produced in the drum 3 is discharged from the drum 3 at any time. At this time, by driving (extending) the tilt mechanism 2b, the frame 2 rotates around the hinge, lifting up the front end of the drum 3 (the left side in FIG. 1 ). This causes the drum 3 to change to an oblique position with its rear end (the side facing the lid member 24) facing downward. During this position change, heating by the burner 7 and rotation of the drum 3 by the drive unit 6 may continue. As the drum 3 changes position, the recycled granules inside the drum 3 are pulled toward the rear end of the drum 3 by their own weight and are collected toward the center of the drum 3 by the guide members 18B and 19. Then, by operating the handle 26 to open the lid member 24, a gap is created between the discharge port 12 and the lid member 24, through which the recycled granules inside the drum 3 fall naturally under their own weight. The discharged recycled granules are spread on the roadbed where the asphalt pavement layer has been removed, and are used for asphalt pavement as recycled asphalt material.

[0051] As explained above, the recycling method of this embodiment involves analyzing the waste asphalt used in existing asphalt pavements, determining the amount of additive to be added to the waste asphalt, and then heating and stirring the waste asphalt and additive together to easily produce recycled asphalt that meets the standards. As a result, high-quality recycled asphalt that meets quality standards can be easily produced at the construction site from the waste asphalt pavement layers that were used in existing asphalt pavements.

[0052] In the above explanation, a general-purpose computer was used to determine the amount of additive from the pattern of the effective asphalt components attached to the filter papers 31 and 32. However, it is conceivable that there may be an environment on-site where such electronic devices cannot be used. Therefore, a method for determining the amount of additive without using electronic devices will be described.

[0053] First, from the past cases included in the first table, several representative cases are selected in stages according to the area coverage ratio of the effective asphalt component patterns formed on the filter paper. For example, case (1) obtained by performing the above analysis on an asphalt mixture suitable for paving, case (2) obtained by performing the above analysis on waste asphalt approximately three years after laying, case (3) obtained from waste asphalt approximately seven years after laying, and case (4) obtained from waste asphalt more than ten years after laying are selected. Then, for each case, the amount of additive required (kg / ton) is identified by referring to the second table. A table is then created, as shown in Figure 5, matching the digital image of the filter paper for each case with the amount of additive required for each case. The amount here refers to the amount of additive added per ton of waste asphalt.

[0054] When constructing an asphalt pavement, workers bring the above list to the construction site. This list may be printed on paper or saved as a digital image on a commercially available general-purpose computer, a mobile device with a display, or the like. Then, a sample of asphalt mixture 102 is obtained from the asphalt waste material removed from the construction site. The asphalt mixture 102 is then placed in a test container 30 and tamped to allow the effective asphalt components to soak into the filter paper 32. The filter paper 32 is then removed from the test container 30.

[0055] The worker compares the appearance of the filter paper 32 acquired at the site with the filter paper images of each case included in the list, and identifies the case that most closely resembles the proprietary pattern of the filter paper 32 acquired at the site. The worker then identifies the amount of additive required in that case as the amount of additive to be added to the waste asphalt material obtained at the site. If there is no case that most closely resembles the proprietary pattern of the filter paper 32 acquired at the site, and the image of the filter paper 32 appears to have less black background than the image of Case (2) and more black background than the image of Case (3), the worker identifies the average amount of additive (2.25 kg / ton) of the amount of additive in Case (2) (2.0 kg / ton) and the amount of additive in Case (3) (2.5 kg / ton) as the amount of additive to be added to the waste asphalt material obtained at the site.

[0056] In this way, even if the construction site is not in an environment where a general-purpose computer can be operated, the amount of additive can be easily determined without placing an undue burden on the workers. For example, this is especially advantageous in construction sites in severe environments such as extreme cold or heat, or in developing countries.

[0057] The present invention relates to a method for recycling asphalt mixtures, and is a method that can be applied at asphalt pavement construction sites when recycling recycled asphalt that complies with standards from asphalt waste material that was used in existing asphalt pavements.

Claims

1. A method for recycling asphalt mixtures, comprising: an analysis step of analyzing the content of effective asphalt components in waste asphalt mixtures; a determination step of determining the amount of additive required to recycle the waste based on the effective asphalt content obtained in the analysis step; an introduction step of putting the waste and the amount of additive determined in the determination step into a container; and a stirring and heating step of reducing the size of pebbles in the waste and additive introduced into the container, and maintaining the temperature within the container at 170°C to 200°C by heating, thereby mixing the waste and additive to produce recycled asphalt.

2. The method for recycling asphalt mixtures described in claim 1, wherein the analysis process comprises: a crushing process in which a portion of the waste material to be recycled is collected and heated while being crushed into pebble-sized pieces; and a test specimen preparation process in which the crushed material obtained in the crushing process is placed in a container and a test specimen is prepared.

3. The method for regenerating an asphalt mixture according to claim 1, wherein the additive is prepared by mixing the materials that make up the additive and solidifying them into a block.

4. The method for regenerating an asphalt mixture according to claim 1, wherein the additive is primarily composed of at least one polymeric material selected from petroleum asphalt, rubber, thermoplastic elastomers, and thermoplastic resins, and an asphalt emulsion.

5. The method for regenerating an asphalt mixture according to claim 1, wherein in the determination step, the additive is added at a rate of 1 kg to 4 kg per 1,000 kg of the weight of the waste material.

6. A method for regenerating an asphalt mixture as described in claim 2, wherein in the crushing step, a portion of the waste material is stirred and heated in the container under the same operating conditions as in the stirring and heating step, and the waste material is reduced in size to the size of pebbles.

7. The method for regenerating an asphalt mixture described in claim 2, wherein in the analysis step, after pressing a test paper against the test specimen, the amount of the additive to be added together with the waste material is determined based on the adhesion rate of the effective asphalt component adhered to the test paper.