JP4972242B2 - Method for producing roadbed materials from concrete waste - Google Patents

Description

  The present invention relates to a method for producing a roadbed material and an earthwork material from concrete waste generated as construction waste.

2. Description of the Related Art Conventionally, concrete waste generated as construction waste has been widely used as earthwork materials such as roadbed materials and backfill materials.
By the way, the cement may contain a small amount of hexavalent chromium derived from chromium mixed in the manufacturing process, but once the cement is solidified as concrete, there is a risk of elution of hexavalent chromium from the cement. Almost no. However, it has been pointed out that hexavalent chromium that exceeds soil environmental standards may be eluted when concrete that has been neutralized (deteriorated) is finely crushed. Recently, it has been demanded to further reduce the environmental burden caused by heavy metals such as chromium. In particular, roadbed materials and backfill materials are considered to come into contact with soil and permeate to the groundwater. It can be said that it is preferable to more reliably suppress elution of.

From such a viewpoint, Patent Document 1 discloses that ground concrete of blast furnace chilled slag is mixed with concrete waste material crushed for roadbed material to suppress elution of hexavalent chromium from the roadbed material (concrete waste material). A proposed method has been proposed.
This method focuses on the reducing ability of blast furnace chilled slag and aims to reduce hexavalent chromium in the waste concrete to trivalent chromium by mixing the pulverized product with the concrete waste.
JP 2005-240313 A

However, according to the study by the present inventors, in the above-mentioned conventional technology, although the effect by mixing the blast furnace slow cooling slag can be obtained, the effect is not necessarily sufficient as expected. However, there is a possibility that it will not be possible to sufficiently respond to environmental standards that are becoming increasingly severe in recent years.
Accordingly, an object of the present invention is to solve the above-described problems of the prior art and to manufacture roadbed materials and earthwork materials in which chromium elution from concrete waste is effectively suppressed.

  The present inventors have studied to find out a method for maximizing the reducing ability of the blast furnace slow cooling slag, and as a result, have obtained the following knowledge. First, many of the blast furnace slow-cooled slags used in the prior art have reduced surface reducing ability. As a result of re-crushing slag with reduced reducing ability and evaluating its reducing ability. , It was found that the internal capacity was sufficiently maintained. As a result, (i) in the prior art, blast furnace slow-cooled slag, which has passed for a while after being ground, is often mixed with concrete waste materials in a plant or the like. The surface is oxidized until it is mixed with the waste material, and the reduction ability is reduced. (Ii) The reduction ability deteriorates due to contact with the atmosphere, especially because the specific surface area of the blast furnace chilled slag is increased by grinding. (Iii) Therefore, in order to maximize the reduction ability of the blast furnace slow-cooled slag, it is particularly preferable to shorten the time from crushing the blast furnace slow-cooled slag to mixing it with the concrete waste as much as possible. Found that it was effective to bring the slag immediately after crushing into contact with the waste concrete. And as a result of examining the method to realize this, in the process of crushing concrete waste material into roadbed material and earthwork material, if blast furnace slow cooling slag is added to the concrete waste material and it is crushed as it is with blast furnace slow cooling slag, it will be crushed The blast furnace slow-cooled slag immediately after a new crushed surface is produced can be mixed and brought into contact with the concrete waste material, thereby making it possible to maximize the reduction capacity of the blast furnace slow-cooled slag, It was also found that the dispersion of the effect was reduced because the mixing property with concrete waste was increased.

  Furthermore, by pulverizing the blast furnace slow-cooled slag containing water, a part of the reducing sulfur of the slag dissolves in this moisture, and immediately acts to reduce hexavalent chromium simultaneously with mixing with the concrete waste. Therefore, it was also found that elution of hexavalent chromium in the initial stage can be more effectively suppressed.

The present invention has been made on the basis of such findings and has the following gist.
[1] In the process of crushing concrete waste material into roadbed material and / or earthwork material, adding blast furnace slow-cooled slag to the concrete waste material, and crushing the blast furnace slow-cooled slag together with the concrete waste material in a state of containing water A method for producing roadbed materials from concrete waste.
[2] In the manufacturing method of [1], the blast furnace slow-cooled slag is added to the concrete scrap at a ratio of 2 to 10 parts by mass with respect to 100 parts by mass of the concrete scrap. Etc. Manufacturing method.

[3] In the manufacturing method of [1] or [2], when producing a roadbed material having a particle size of 40 mm or less, a blast furnace slow-cooled slag having a particle size of more than 40 mm is added to the concrete waste material. , A method for producing roadbed materials from concrete waste .
[4] In the manufacturing method according to any one of [1] to [3] above, manufacturing roadbed material or the like from waste concrete, characterized in that water is contained in the blast furnace slow-cooled slag by watering or immersion in water Method.

According to the present invention, since the blast furnace slow-cooled slag crushed together with the concrete waste material can maximize its reduction ability, hexavalent chromium in the concrete waste material is effectively reduced, and elution of hexavalent chromium from the concrete waste material. Can produce roadbed materials and earthwork materials that are highly suppressed.
Moreover, according to this invention , the hexavalent chromium elution from the concrete waste material in the initial stage can be suppressed more effectively.

In the present invention, in the step of crushing the concrete waste material into the roadbed material and / or earthwork material, the blast furnace slow cooling slag is added to the concrete waste material, and the concrete crushed together with the blast furnace slow cooling slag. In addition, the particle size of the concrete waste material and blast furnace slow cooling slag used in the present invention and the following description means a particle size defined using a sieve having the sieve mesh. As the size of the sieve, those represented by JIS Z 8801 and the like can be used.
The manufacturing object of the present invention is a roadbed material and / or earthwork material (hereinafter sometimes referred to as “roadbed material or the like” for convenience). Examples of the earthwork material include, but are not limited to, a backfill material, a hearth material, a laying material other than a roadbed material, and the like.

As the concrete waste material used in the present invention, construction waste material is most representative, but it is not limited thereto. Moreover, it does not prevent that waste materials other than concrete are mixed inevitably on the property of waste materials.
Blast furnace slow-cooled slag is a crystalline-based slag obtained by slowly cooling blast furnace slag (molten slag), and contains reducing sulfur in the produced state. Blast furnace slow-cooled slag is produced by granulating blast furnace slag in a fine granular form, whereas molten slag is produced by solidifying into a lump, and for this reason, the particle size is several tens mm or more or 100 mm or more. Even massive slag can be easily obtained.

  When such blast furnace slow-cooled slag is mixed with concrete waste, reducing sulfur in the slag reduces hexavalent chromium contained in the concrete waste to trivalent chromium, and as a result, elution of hexavalent chromium from the concrete waste Suppress. However, as mentioned earlier, when blast furnace chilled slag, which has been crushed for a while, is mixed with concrete waste, the blast furnace chilled slag surface is oxidized before mixing, reducing the reduction capacity. End up. Since the blast furnace slow-cooled slag that has been produced or pulverized may cause sulfur outflow from the permeated water, the conventional blast furnace slow-cooled slag is stabilized in the atmosphere for a considerable period (usually 6 months or more). Such a blast furnace slow cooling slag cannot provide a sufficient reducing action.

  On the other hand, in the present invention, the blast furnace chilled slag is added to the concrete waste material, and the blast furnace chilled slag is crushed as it is, so that the crushed surface (that is, the reducing sulfur is not oxidized) immediately after being crushed. The blast furnace slow-cooled slag having a crushing surface present in abundance can be mixed and brought into contact with the concrete waste material, whereby the hexavalent chromium reducing ability of the blast furnace slow-cooled slag can be maximized. Furthermore, in the present invention, the following specific effects can be obtained.

(I) In the prior art, crushed material of blast furnace chilled slag (usually the particle size is several mm or less) to concrete waste material (usually the particle size is several tens of mm or less) crushed to a particle size for roadbed materials or earthwork materials ), But it is difficult to mix evenly differing particles with different particle sizes, and this causes variations in the reduction effect of blast furnace chilled slag exerted on hexavalent chromium in concrete waste. Cheap. In order to suppress such a variation in the reducing action, special equipment for supplying a fixed amount of the ground blast furnace slag slag is necessary, which increases the equipment burden. In contrast, in the present invention, the blast furnace slow-cooled slag may contain slag particles having a small particle size, but since the blast furnace slow-cooled slag is crushed together with the concrete waste, the concrete waste and the blast furnace slow-cooled slag Therefore, compared with the prior art, waste concrete and blast furnace slag can be mixed uniformly. In addition, by simultaneously crushing the blast furnace slow-cooled slag and the concrete waste material, the mixing property between the two can be improved. As a result, the reducing action of the blast furnace slow-cooled slag exerted on the hexavalent chromium in the concrete waste can be made uniform.

(Ii) Since the ground granulated blast furnace slag used in the prior art has a large specific surface area, its reducing ability is likely to deteriorate due to contact with the atmosphere. For this reason, it can be initially mixed with concrete waste immediately after grinding. Even if the reduction action is ensured, it is difficult to maintain the reduction action over a long period of time. On the other hand, in the present invention, the blast furnace slow-cooled slag is crushed together with the concrete waste material, so that the blast furnace slow-cooled slag can be mixed with the concrete waste material in a state having a high reducing ability, and thus the initial reduction action can be sufficiently obtained. The blast furnace slow-cooled slag having a large particle size corresponding to the concrete waste material can maintain the reducing action for a long time because the reducing sulfur inside is maintained and the reducing ability is not easily deteriorated.

(Iii) Based on the strength of the blast furnace slow-cooled slag and the original particle size distribution before crushing, when the blast furnace slow-cooled slag is crushed together with concrete waste, the particle size distribution becomes wider than the concrete waste and the initial reduction action and long-term Therefore, the particle size distribution is advantageous for appropriately ensuring both of the reduction effects of the above. This is because the blast furnace slow-cooled slag after being crushed together with the concrete waste material has a wide particle size in which small slag particles effective for the initial reduction action and large slag particles effective for the long-term reduction action are mixed. This is because it becomes a distribution. For this reason, the high reduction | restoration effect | action by blast furnace slow cooling slag can be maintained over a long period from immediately after manufacture of a roadbed material etc.

FIG. 1 shows a blast furnace slow-cooled slag (a) immediately after being crushed to a particle size of 19 mm or less after being produced in a blast furnace, and crushed to a particle size of 19 mm or less after being produced in a blast furnace, and then 4 months The result of having investigated the amount of reducing sulfur about the blast furnace slow cooling slag (b) which has passed is shown. In this test, 15 parts by mass of water was added to 1 part by mass of the blast furnace gradually cooled slag, and the amount of reducing sulfur eluted after shaking for 6 hours was evaluated.
According to FIG. 1, even if the crushed particle size is the same, the amount of elution S of the blast furnace annealed slag (a) immediately after crushing is nearly four times that of the blast furnace annealed slag (b) that has been crushed for 4 months. It is a value.

FIG. 2 shows a particle size of 40 mm or less produced by adding a predetermined amount (3 parts by mass, 5 parts by mass, 7 parts by mass) of a blast furnace slow-cooled slag having a particle size of 40 to 80 mm to 100 parts by mass of concrete waste, A certain amount (3 mass) of blast furnace slow-cooled slag having a particle diameter of 10 mm or less after 4 months of pulverization into 100 mass parts of the roadbed material (example of the present invention) and concrete waste material crushed to a particle diameter of 40 mm or less. 5 parts by mass, 7 parts by mass, and 7 parts by mass) of the roadbed material (comparative example) produced, the results of examining the Cr elution amount by the Environment Agency Notification No. 46 elution test are shown. Each Cr elution amount is an average value of N = 5.
According to FIG. 2, although a certain degree of effect is obtained even in the comparative example using the blast furnace slow cooling slag after 4 months from pulverization, the present invention example has a significantly superior effect (Cr Elution suppression effect).

In this invention, although the compounding quantity of the blast furnace slow cooling slag with respect to concrete waste material is not specifically limited, It is preferable to mix | blend in the ratio of about 2-10 mass parts with respect to 100 mass parts of concrete waste materials. If the ratio of the blast furnace slow-cooled slag to 100 parts by weight of the concrete waste is less than 2 parts by weight, the reducing action by the blast furnace slow-cooled slag may be insufficient, while if it exceeds 10 parts by weight, there is no problem in terms of the reducing action. However, when there is little Cr elution from a concrete waste material, there exists a possibility that elution water may show a little yellow with an excessive sulfur content.
There is no particular limitation on the crushing method when crushing the concrete waste with the blast furnace slow cooling slag, and for example, an impact crusher, a cone crusher, a jaw crusher, a mobile crusher, a roll crusher, or the like can be used.

  There is no special restriction on the particle size when crushing concrete waste with blast furnace slow cooling slag, but generally, concrete waste for roadbed etc. is crushed to a particle size of 40 mm or less. In order to manufacture roadbed materials, etc., concrete waste (of course, this concrete waste includes those having a particle size of more than 40 mm) and blast furnace chilled slag having a particle size of more than 40 mm (the blast furnace chilled slag has a particle size of 40 mm or less). (Which may contain slag particles) and is crushed together with the blast furnace slow-cooled slag. That is, according to the crushed particle size (upper limit) of the concrete waste material, blast furnace slow-cooled slag having a particle size in which part or all of the slag particles exceed the crushed particle size is added for crushing.

In the present invention, the blast furnace slow-cooled slag containing water is crushed together with the concrete waste material, so that a part of the reducing sulfur of the slag is dissolved in the water, and immediately mixed with the concrete waste material. Since it can exert a reducing action of valent chromium, elution of hexavalent chrome in the initial stage can be more effectively suppressed.
The form in which water is contained in the blast furnace slow-cooled slag may be any form in which at least a part of the reducing sulfur on the crushed surface is dissolved in water when the blast furnace slow-cooled slag is crushed. Either slag grains or slag lump water is absorbed, or water is attached to the surface of slag grains or slag lump (the surface is wet with water), but to prevent the outflow of sulfur It is desirable that the water is in a state where water is contained to such an extent that the water does not flow out.
In order to include water in the blast furnace slow cooling slag, an appropriate method such as watering or immersion in water can be employed. Also, there is no special restriction on the timing of adding water to the blast furnace slow-cooled slag, the stage before adding the blast furnace slow-cooled slag to the concrete waste, the stage after adding the blast furnace slow-cooled slag to the concrete waste, the concrete scrap + Water can be included at an appropriate timing such as during the crushing treatment of the blast furnace chilled slag.

  In the present invention, the concrete waste material and the blast furnace annealing slag may be simultaneously crushed by only one crushing process, and a roadbed material or the like may be manufactured, or a roadbed material or the like may be manufactured through a plurality of crushing processes. . In the latter case, for example, concrete waste and blast furnace chilled slag may be simultaneously crushed in multiple crushing processes. In the primary crushing process, only the concrete waste material is crushed and the secondary crushing process (final crushing process) is performed. Then, you may make it crush a concrete waste material and blast furnace slow cooling slag simultaneously. In short, it is sufficient that at least one of the crushing steps can crush the concrete waste material and the blast furnace slow-cooled slag at the same time.

FIGS. 3A and 3B illustrate an embodiment (processing flow) of the present invention, and show a case where a roadbed material having a particle size of 40 mm or less is obtained.
In the embodiment of FIG. 3 (a), concrete waste material and blast furnace slow cooling slag are respectively charged into the hopper 1, and the concrete waste material and blast furnace slow cooling slag are simultaneously fed from the hopper 1 to the crusher 2 for crushing treatment. Is called. This crushed material (concrete waste material + blast furnace slow cooling slag) is sieved by the sieving device 3, the particle size of 40 mm or less is made into a product, and the particle size of more than 40 mm is retransmitted to the crusher 2 and crushed. Thereby, a roadbed material with a particle size of 40 mm or less is obtained.

  In the embodiment of FIG. 3 (b), the concrete waste material is charged into the hopper 4, and the concrete waste material is input from the hopper 4 to the primary crusher 5 to perform the primary crushing process. The primary crushed concrete waste material is inserted into the sieving device 6 together with the blast furnace slow cooling slag and sieved. Then, the particle size of 40 mm or less is regarded as a product, and the concrete waste having a particle size of more than 40 mm and the blast furnace chilled slag are sent to the secondary crusher 7, crushed here, and then sent to the sieving device 6. Thereby, a roadbed material with a particle size of 40 mm or less is obtained. In the embodiment of FIG. 3B, the slag particles having a particle size of 40 mm or less contained in the blast furnace slow cooling slag become a part of the product without being crushed.

  The roadbed material and the like produced by the production method of the present invention described above is a roadbed material or the like mainly containing concrete waste material and including blast furnace slow cooling slag, and is subjected to a step of crushing the concrete waste material together with the blast furnace slow cooling slag. It is the obtained roadbed material. As described above, in this roadbed material and the like, hexavalent chromium in the concrete waste material is effectively reduced, and elution of hexavalent chromium from the concrete waste material is highly suppressed.

After 4 months have passed since it was produced in the blast furnace, the blast furnace gradually cooled slag (a) immediately after being crushed to a particle size of 19 mm or less, and after being produced in the blast furnace, it was crushed to a particle size of 19 mm or less and then 4 months later. The graph which shows the result of having investigated the amount of reducing sulfur about cold slag (b) The graph which shows the result of having investigated the amount of Cr elution by the environmental agency notification 46 elution test about the roadbed material obtained by this invention method, and the roadbed material obtained by the conventional method Explanatory drawing which shows embodiment (processing flow) of this invention

Explanation of symbols

1,4 Hopper 2 Crusher 3,6 Sieve device 5 Primary crusher 7 Secondary crusher

Claims (4)

In the process of crushing concrete waste material into roadbed material and / or earthwork material, adding blast furnace slow cooling slag to concrete waste material, and crushing the blast furnace slow cooling slag together with concrete waste material in a state of containing water To manufacture roadbed materials from concrete waste.   The method for producing a roadbed material or the like from concrete waste according to claim 1, wherein the blast furnace slow cooling slag is added to the concrete waste at a ratio of 2 to 10 parts by weight with respect to 100 parts by weight of the concrete waste.   The roadbed material from the concrete waste material according to claim 1 or 2, characterized in that, when producing a roadbed material having a particle size of 40 mm or less, a blast furnace slow cooling slag having a particle size of more than 40 mm is added to the concrete waste material. Manufacturing method. The method for producing a roadbed material or the like from waste concrete material according to any one of claims 1 to 3, wherein water is contained in the blast furnace chilled slag by watering or immersion in water.

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