JP7511401B2 - How to supply asphalt mixture - Google Patents

Description

The present invention relates to a method for supplying asphalt mixture produced in an asphalt plant to a paving site.

Conventionally, in asphalt plants installed in asphalt mixture manufacturing factories, aggregates of various particle sizes are heated to a high temperature, for example, around 160°C, and then stirred and mixed in a mixer with filler (stone powder) and molten asphalt in predetermined amounts to produce asphalt mixtures. Asphalt mixtures that are in a moderately softened state at high temperatures immediately after production will gradually lose temperature and oxidize over time in the atmosphere, and depending on the extent of these progressions, they may become more viscous, reducing workability at the paving site, or harden and become unusable as a road paving material.

The manufactured asphalt mixture is stored in mixture silos (see, for example, Patent Documents 1 to 3) that are filled with inert gas and capable of keeping the mixture warm and are equipped at asphalt plants or satellite plants (plants specialized in storing and shipping asphalt mixtures, which are established in urban areas where noise regulations are strict and it is difficult to install asphalt plants) and when shipped, the asphalt mixture is transported and delivered to the paving site while taking measures to keep it warm, such as covering the asphalt mixture dispensed onto the loading platform of a transport vehicle with a protective sheet.

JP 2011-256615 A Japanese Patent Application Laid-Open No. 10-204816 Japanese Patent Application Laid-Open No. 4-169610

However, even when stored in the mixture silo, it is not possible to completely prevent the asphalt mixture from decreasing in temperature or deteriorating due to oxidation, and it is generally difficult to store it for long periods of time, such as more than one or two days. Furthermore, when transported by transport vehicle, the asphalt mixture is more likely to come into contact with the air, which makes it more likely that the temperature will decrease and the mixture will degrade due to oxidation. As a result, it is generally only possible to deliver to paving sites within about an hour and a half of shipment, and it is difficult to deliver to more remote locations.

In view of the above, the present invention aims to provide a method for supplying asphalt mixture that can be stored and transported without time constraints.

As a result of intensive research into solving the above problems, the inventors of the present invention have come to the conclusion that, although currently asphalt mixtures produced in asphalt plants are stored or transported to paving sites while maintained in a softened state at the temperature at which they were produced (for example, approximately 160°C) as much as possible, it would be better to cool the mixture to room temperature and store it in a solidified state, and then, at the time of paving work, transport the asphalt mixture in a solidified state at room temperature to the paving site or a nearby satellite plant, where it is reheated by appropriate heating means provided at the paving site or satellite plant to return it to its original softened state before being supplied to the paving site.

Conventionally, waste asphalt pavement materials (hereinafter referred to as "waste materials") dug up during road construction work, etc., have been crushed to a specified particle size or less, heated to soften and melt in a waste recycling dryer at an asphalt plant, etc., and mixed with separately heated new aggregate, etc. in any ratio to be used as an asphalt mixture without any problems. Therefore, even if the asphalt mixture immediately after being produced by mixing heated new aggregate, filler, and molten asphalt is cooled and solidified, and then reheated to soften and melt, it is expected that it can be used as a road pavement material without any problems, just like the waste materials. Furthermore, we thought that if the asphalt mixture is in a solidified state cooled to room temperature, there would be almost no risk of oxidation deterioration, and it would be possible to store and transport it without time constraints, which led to the creation of this invention.

That is, in the method of supplying asphalt mixture according to claim 1 of the present invention, the asphalt mixture produced by stirring and mixing aggregate, filler, and molten asphalt at 110 to 130°C in a mixer at an asphalt plant is molded into a block shape, cooled to room temperature, and stored in a solidified state, while at least one of the paving site, a satellite plant near the paving site, and an asphalt mixture transport vehicle is equipped with a dielectric heating device or microwave heating device as a means for reheating the block-shaped asphalt mixture, and during paving work, the stored block-shaped asphalt mixture is transported by the transport vehicle to the paving site or satellite plant, and reheated to 160°C by the dielectric heating device or microwave heating device to return it to a softened state before being supplied to the paving site.

The asphalt mixture supply method according to claim 2 of the present invention is characterized in that the block-shaped asphalt mixture is mixed with blast furnace slag and/or waste gypsum, which are materials that easily absorb high frequency waves or microwaves.

According to the method for supplying asphalt mixture according to claim 1 of the present invention, the asphalt mixture immediately after being produced by stirring and mixing aggregate, filler, and molten asphalt at 110 to 130°C in a mixer at an asphalt plant is molded into a block shape, cooled to room temperature, and stored in a solidified state. Meanwhile, at least one of the paving site, a satellite plant near the paving site, and an asphalt mixture transport vehicle is equipped with a dielectric heating device or a microwave heating device, and during paving work, the stored block-shaped asphalt mixture is transported by the transport vehicle to the paving site or satellite plant, reheated to 160°C by the dielectric heating device or microwave heating device to return it to a softened state, and then supplied to the paving site. This prevents temperature drop and oxidation deterioration of the asphalt mixture during storage and transportation, making it possible to store and transport it without time constraints, and also makes it possible to supply it to remote locations. In addition, by reheating using a dielectric heating device or microwave heating device, even asphalt mixtures that have low thermal conductivity and are molded into blocks can be efficiently heated all the way to the center, and can be returned to a softened state in a relatively short period of time, making them easy to use.

In addition, according to the asphalt mixture supply method described in claim 2 of the present invention, the block-shaped asphalt mixture is blended with blast furnace slag and/or waste gypsum, which are materials that easily absorb high frequency waves or microwaves, and this is advantageous in that it further increases the heating efficiency and allows the mixture to return to a softened state in a shorter time. In addition, since blast furnace slag and waste gypsum are normally to be disposed of, this makes it possible to make effective use of them, which is also beneficial from an environmental perspective.

FIG. 1 is a schematic diagram illustrating a method for supplying an asphalt mixture according to the present invention.

In the asphalt mixture supply method of the present invention, a portion of the asphalt mixture that is in a moderately softened state immediately after production in an asphalt plant installed in an asphalt mixture manufacturing factory is molded into a block shape, such as a roughly rectangular parallelepiped or flat plate shape, and then cooled to room temperature to solidify, and then placed and stored in an appropriate storage space (inside the asphalt mixture manufacturing factory, or in an appropriate free space prepared outside the factory, etc.).

By molding and solidifying the asphalt mixture into blocks, it can be stored and transported on its own, eliminating the need for containers, and the work of loading and unloading it onto transport vehicles can be done relatively easily with a forklift, making it easy to handle.

At least one of the paving site, the satellite plant near the paving site, and the asphalt mixture transport vehicle is equipped with a dielectric heating device or a microwave heating device as a means for reheating the asphalt mixture that has been molded and solidified into a block shape. By using a dielectric heating device or a microwave heating device as the reheating means, even if the asphalt mixture has been molded into a block shape with low thermal conductivity and a certain size, high frequency waves or microwaves can easily penetrate to the center, allowing it to be heated efficiently, and it can be returned to its original softened state in a relatively short time even at the paving site, making it easy to use.

It is also preferable to mix the block-shaped asphalt mixture with blast furnace slag containing a lot of metal powder and/or waste gypsum containing a lot of crystal water, which are materials that easily absorb high frequency waves or microwaves. This further improves the heating efficiency of the dielectric heating device or microwave heating device, making it possible to return the mixture to a softened state with less power and in a shorter time, making it easier to handle, for example, at paving sites where it is difficult to secure a large amount of power for a long period of time. Furthermore, since blast furnace slag and waste gypsum should originally be disposed of as industrial waste, making effective use of them is beneficial from an environmental perspective, and costs can also be reduced by mixing them in place of some of the aggregate and filler that are the materials used in the asphalt mixture.

When paving work is to be carried out using the block-shaped asphalt mixture, the stored block-shaped asphalt mixture at room temperature is loaded onto a transport vehicle and transported to the paving site or satellite plant, where it is reheated to a softened state using a dielectric heating device or microwave heating device provided at least in one of the paving site, satellite plant, or transport vehicle, and then supplied to the paving site. At the paving site, the supplied asphalt mixture is spread evenly in the same way as normal asphalt mixture (transported in a high-temperature softened state), and then compacted and paved.

In this way, the block-shaped asphalt mixture is stored and transported at room temperature, which prevents temperature drop and oxidation deterioration during storage and transport, and allows storage and transport without the time constraints of regular asphalt mixtures. For example, it makes it easier to supply to remote locations such as islands and isolated areas where it is difficult and cost-prohibitive to set up an asphalt plant. In addition, at room temperature there is no need to worry about odor generation, and the burden on the surrounding environment during storage and transport is also reduced.

In addition, since it is possible to store it for a long period of time, for example, when the asphalt plant is busy, the asphalt mixture can be delivered to the paving site immediately after production as usual, while when the plant is slow, the asphalt mixture can be produced in the same manner as above, molded into blocks, cooled to room temperature, and stored in a solidified state (prepared in advance), thereby increasing the plant's operating rate.

In addition, if some of the asphalt mixture scheduled to be shipped during peak times could be substituted with block-shaped asphalt mixture prepared during off-peak times, the peak energy (gas, electricity, etc.) usage during peak times at asphalt mixture manufacturing plants could be reduced and leveled out, which would reduce basic usage fees and is expected to lead to cost savings.

When producing the block-shaped asphalt mixture, it is not necessary to produce it at a high temperature of about 160°C, as with normal asphalt mixture. From the viewpoint of workability (construction) when constructing paved roads, heating to about 160°C is essential, but if the asphalt mixture is simply produced by stirring and mixing aggregate, filler, molten asphalt, etc. in a mixer (and not immediately after construction), it can be produced at a lower temperature than normal asphalt mixture. However, since it is necessary to remove moisture from the aggregate and make it completely dry, it is preferable to produce it at a temperature of, for example, about 110 to 130°C.

In general, when stirring and mixing in a mixer, the asphalt mixture repeatedly comes into close contact with air at high temperatures. It is therefore known that the higher the temperature of the asphalt mixture during mixing and the longer the mixing time, the more the asphalt mixture deteriorates. As mentioned above, it is believed that deterioration can be effectively suppressed if the temperature at that time can be lowered.

As mentioned above, even if the block-shaped asphalt mixture is manufactured at a lower temperature than normal asphalt mixtures, when it is reheated to return it to a softened state at the time of construction, i.e. at the paving site or a nearby satellite plant, it is necessary to raise the temperature to about 160°C, as with normal asphalt mixtures, from the viewpoint of workability. However, in the present invention, a dielectric heating device or microwave heating device that can heat statically without stirring or mixing processes such as a mixer is used as the reheating means. This effectively suppresses deterioration during reheating, especially oxidative deterioration, and as a result, it is possible to supply a high-quality asphalt mixture with relatively little deterioration to the paving site.

Furthermore, if the block-shaped asphalt mixture is manufactured and stored with a certain margin of safety during normal times, it is possible to quickly supply it to the site as emergency materials for road restoration, etc., in the unlikely event of a disaster such as an earthquake that makes it difficult to operate the asphalt plant.

An embodiment of the present invention will be described below with reference to the drawings.

In the figure, 1 is an asphalt mixture manufacturing plant that manufactures and ships asphalt mixture, a road paving material. On the premises, an asphalt plant 2 is installed where aggregates of various particle sizes are heated to a predetermined temperature, for example, a high temperature of about 160°C, and then stirred and mixed with filler, molten asphalt, etc. in predetermined amounts to manufacture asphalt mixture.

In the figure, 3 is a storage space where a portion of the asphalt mixture 4, which is in a high temperature and moderately softened state immediately after production in the asphalt plant 2, is temporarily placed and stored after being molded, for example, into a roughly rectangular or flat block shape using a formwork or the like, and then cooled to room temperature to solidify. Note that in this embodiment, the storage space 3 is provided within the premises of the asphalt mixture production plant 1, but this is not limiting, and any suitable vacant space prepared outside the premises of the asphalt mixture production plant 1, including a satellite plant described below, can be used as the storage space.

In addition, by molding and solidifying the asphalt mixture 4' into a block shape, it can be stored and transported by itself, eliminating the need for separate containers, and the work of loading and unloading onto a transport vehicle can be done relatively easily with a forklift, making it easy to handle. Furthermore, by molding the block-shaped asphalt mixture into a weight that can be carried manually, for example, about 20 kg or less, it becomes easy to use and is particularly suitable for supplying to small-scale paving sites, etc.

In the figure, 5a to 5c are paving sites, of which 5a is located within an area (e.g., within about an hour and a half by transport vehicle) where the asphalt mixture shipped from the asphalt plant 2 can be transported in a softened state at the temperature at which it was produced (e.g., about 160°C), while 5b and 5c are paving sites in remote locations outside that area.

In the figure, 6 is a satellite plant located in the vicinity of the remote paving site 5c. The satellite plant 6 is equipped on its premises with a mixture silo 7 for storing asphalt mixture 4 in its normal state (approximately 160°C, softened state) at an insulated temperature, and a storage space 3 for storing block-shaped asphalt mixture 4' at room temperature.

In the figure, 8 denotes a transport vehicle such as a dump truck that loads the asphalt mixture 4, 4' produced in the asphalt plant 2 and transports and supplies it to each of the paving sites 5a to 5c, and 9 denotes a rolling machine such as a road roller that rolls and processes the asphalt mixture 4, 4' supplied to each of the paving sites 5a to 5c by the transport vehicle 8.

At least one of the paving site 5b located in a remote location, the satellite plant 6 near the paving site 5c, and the asphalt mixture transport vehicle 8 is equipped with, for example, a dielectric heating device 10a or a microwave heating device 10b as a means for reheating the asphalt mixture 4' molded and solidified into a block shape. In this embodiment, the dielectric heating device 10a is provided at the paving site 5b and the transport vehicle 8, and the microwave heating device 10b is provided at the satellite plant 6, but the arrangement may be reversed, or both may be dielectric heating devices 10a or microwave heating devices 10b.

The dielectric heating device 10a is mainly composed of a high-frequency oscillator 11, a pair of electrodes 12, and a generator 13. When the block-shaped asphalt mixture 4' to be heated is sandwiched between the electrodes 12 and a high-frequency voltage is applied between the electrodes 12 from the high-frequency oscillator 11, the high-frequency F1 easily penetrates into the asphalt mixture 4'. As a result, even block-shaped asphalt mixture 4' with low thermal conductivity and a certain size can be efficiently heated and returned to its original softened state in a relatively short time.

In addition, instead of the generator 13 that supplies power to the high-frequency oscillator 11, power may be supplied from the transport vehicle 8. In addition, since the shorter the distance between the electrodes 12, the more efficiently the asphalt mixture 4' can be heated with less power, if heating efficiency is a priority, it is advisable to reduce the thickness of the asphalt mixture 4' and mold it into, for example, an approximately flat plate shape.

The microwave heating device 10b is mainly composed of a microwave oscillator 14, a waveguide 15, a generator 13, and a box-shaped metal shield 16. When the block-shaped asphalt mixture 4' to be heated is placed inside the metal shield 16 and microwaves F2 are emitted from the microwave oscillator 14, the microwaves are emitted into the metal shield 16 via the waveguide 15 and easily penetrate into the block-shaped asphalt mixture 4' placed inside the metal shield 16. As a result, it can be heated efficiently like the dielectric heating device 10a and can be returned to its original softened state in a relatively short time.

Preferably, the block-shaped asphalt mixture 4' is mixed with blast furnace slag containing a large amount of metal powder and/or waste gypsum containing a large amount of crystal water, which are materials that easily absorb high frequency waves or microwaves, to replace part of the aggregate and filler that are the raw materials of the asphalt mixture, thereby further improving the heating efficiency of the dielectric heating device 10a and the microwave heating device 10b.

Next, the case where the asphalt mixture 4, 4' manufactured in the asphalt plant 2 of the asphalt mixture manufacturing factory 1 is transported and supplied to the paving sites 5a to 5c will be described. First, during normal or busy times, as shown in (A) in the figure, the asphalt mixture 4 in a high temperature and softened state immediately after production is directly discharged onto the loading platform of the transport vehicle 8, and the transport vehicle 8 transports and supplies it to the paving site 5a after taking measures to keep it warm, such as covering the asphalt mixture 4 on the loading platform with a protective sheet. At the paving site 5a, the supplied asphalt mixture 4, which is still in a high temperature and softened state, is spread evenly to a specified layer thickness and then compacted with a rolling machine 9 for paving processing.

On the other hand, during off-peak times, asphalt mixture is produced in the asphalt plant 2 in the same manner as above, then molded into a block shape using a formwork or the like, and the asphalt mixture 4' is cooled to room temperature and solidified, and stored (prepared) in the storage space 3 provided in the asphalt mixture manufacturing factory 1 or satellite plant 6. During this storage, there is almost no risk of oxidation deterioration of the asphalt mixture 4' at room temperature.

For example, when an order is placed from a paving site 5b located far from the asphalt mixture manufacturing plant 1, the stored block-shaped asphalt mixture 4' is loaded directly onto a transport vehicle 8 and transported to the paving site 5b, as shown in (B) in the figure. Next, the block-shaped asphalt mixture 4' is heated again by a dielectric heating device 10a (or a microwave heating device 10b) provided at the paving site 5b or the transport vehicle 8 to return it to its original (immediately after production) softened state, and then supplied to the paving site 5b. At the paving site 5b, the supplied asphalt mixture 4' is spread evenly to a predetermined layer thickness in the same way as normal asphalt mixture 4 (transported in a high-temperature softened state), and then compacted by a roller 9 for paving processing.

In addition, when an order is placed from the paving site 5c, as shown in (C) in the figure, the block-shaped asphalt mixture 4' stored in the satellite plant 6 near the paving site 5c is reheated in a microwave heating device 10b (or a dielectric heating device 10a) installed in the satellite plant 6 to return it to its original softened state asphalt mixture 4, and then loaded onto a transport vehicle 8 and delivered to the paving site 5c. Then, at the paving site 5c, the supplied asphalt mixture 4 is spread evenly and compacted with a compactor 9 to perform the paving process, as described above.

The block-shaped asphalt mixture 4' stored in the satellite plant 6 can be reheated in advance to return it to its original softened state, for example in accordance with the construction plan of the nearby paving site 5c, and then stored at an insulated state in the mixture silo 7 in the satellite plant 6, making it more suitable for smoother shipment to the paving site 5c.

In this way, in the present invention, the hot asphalt mixture 4 immediately after production is molded into a block shape, and then deliberately cooled to room temperature and solidified before storage and transportation. This prevents temperature drop and oxidation deterioration during the process, and allows storage and transportation without time constraints. This allows the asphalt mixture 4' to be supplied without hindrance to paving sites 5b, 5c located far from the asphalt mixture manufacturing plant 1, where supply would normally be difficult, and is also advantageous in that it can be prepared in advance during off-peak times at the asphalt mixture manufacturing plant 1, thereby increasing the plant's operating rate.

The present invention can be widely used when supplying asphalt mixtures produced in asphalt plants to paving sites.

REFERENCE SIGNS LIST 1...Asphalt mixture manufacturing plant 2...Asphalt plant 3...Storage space 4, 4'...Asphalt mixture 5a to 5c...Paving site 6...Satellite plant 7...Mixture silo 8...Transportation vehicle 9...Roller 10a...Dielectric heating device (reheating means)
10b...Microwave heating device (reheating means)

Claims (2)

A method for supplying an asphalt mixture, characterized in that an asphalt mixture immediately after production by stirring and mixing aggregate, filler, and molten asphalt at 110 to 130°C in a mixer at an asphalt plant is molded into a block shape, cooled to room temperature, and stored in a solidified state, while at least one of the paving site, a satellite plant near the paving site, and an asphalt mixture transport vehicle is equipped with a dielectric heating device or microwave heating device as a means for reheating the block-shaped asphalt mixture, and during paving work, the stored block-shaped asphalt mixture is transported by the transport vehicle to the paving site or satellite plant, and reheated to 160°C in the dielectric heating device or microwave heating device to return it to a softened state before being supplied to the paving site. The method for supplying asphalt mixture according to claim 1, characterized in that the block-shaped asphalt mixture is mixed with blast furnace slag and/or waste gypsum, which are materials that easily absorb high frequency waves or microwaves.

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