JP2000263026A - Method for recycling concrete scrap - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method to obtain sand having a proper particle size distribution and powder which can be used as an extender for cement, asphalt, or pottery from concrete scraps simply, inexpensively, and efficiently. SOLUTION: After concrete scraps are crushed by a crusher into blocks of about 40 mm or below in size, the blocks are crushed into crushed sand about 10 mm or below in size by using a cage mill having ceramic percussion pins. Next, the crushed sand is separated by a wind selector into sand and powder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for recycling concrete waste generated when a concrete structure is dismantled.

[0002]

2. Description of the Related Art When a concrete structure such as a building is dismantled, a large amount of concrete scrap (concrete mass having a diameter of, for example, about 30 to 500 mm) as the dismantled article is generated. Such concrete waste is usually landfilled at a final disposal site as industrial waste or used as roadbed material as recycled crushed stone.

However, in recent years, it has become difficult to secure a disposal site for concrete waste as described above. Therefore, there is a strong demand for a method for efficiently recycling or recycling concrete waste. In addition, concrete gala contains sand as a constituent material, and it has become increasingly difficult in recent years to secure a collection site for this kind of sand from the viewpoint of environmental conservation.
Therefore, if materials such as sand can be efficiently obtained from concrete waste, which is industrial waste, it should contribute not only to environmental conservation but also to the effective use of resources.

When recycling concrete waste,
Conventionally, a method of reusing concrete waste as aggregate (specifically, a method of processing and reusing concrete coarse aggregate such as gravel) is generally employed.

[0005]

In general, concrete products are composed of coarse aggregate, fine aggregate and cement. However, it has been difficult to separate each component by a conventional method. For this reason, the recycled aggregate by the conventional method is JI
There was a problem that the conditions of specific gravity and water absorption specified in S could not be satisfied, and the grain shape was poor. Further, even if sand (recycled fine aggregate) or powder is obtained from concrete waste by the conventional method, there is a problem that the efficiency is low, a lot of labor is required, and the cost is high. Further, there is a problem that the particle size distribution of the sand and the powder is not appropriate and a large amount of unnecessary dust is generated.

[0006] When recycling concrete waste, it is necessary to grind the concrete waste. At this time, if a wet pulverizer such as a rod mill is used, (a) the disposal cost of industrial waste generated in the classification process is high,
(B) Since separate equipment such as a water treatment device is required, not only the initial cost is high but also it is necessary to secure a place, and (c) low frequency noise is generated when a rod mill is used. Occurs.

It is an object of the present invention to provide a method for recycling concrete waste, in which sand having a relatively small particle size and powder that can be reused as an extender for cement, asphalt, or pottery can be easily obtained from concrete waste. And inexpensively,
Moreover, it is an object of the present invention to provide a method which can be obtained efficiently. Another object of the present invention is to provide a method capable of efficiently obtaining sand or powder having an appropriate particle size distribution satisfying the JIS standard from concrete waste and suppressing the generation of unnecessary dust. is there.

[0008]

In order to recycle concrete waste, for example, if a dry classifier is used in the step of classifying pulverized materials, a water treatment step and equipment are not required. We paid attention to the points that the initial cost and running cost were relatively low, the drying cost of the classified product was unnecessary, and the sharp classification was possible. Then, in order to realize the commercialization of the recycled concrete waste material (artificial sand, powder), it was considered necessary to use at least a dry classification method, more specifically, a dry pulverization / dry classification method.

The method for recycling concrete waste according to the present invention has been completed based on the above findings.
It is characterized by including at least the following steps. A step of crushing the concrete crush to a predetermined size (crushing step), a step of crushing the obtained crushed material into finer sand (pulverizing step), and a wind separation device from the obtained sandy crushed material. The process of sorting sand and powder (sorting process).

In the crushing step, the solidified product is crushed so as to have a size of about 40 mm or less. In this case, as a crushing means, a roll crusher, a jaw crusher, an impeller breaker, or the like can be used.

In the pulverizing step, the obtained crushed material is pulverized into crushed sand having a size of about 10 mm or less (more preferably, about 5 mm or less). In this case, as a pulverizing means, a cage-type mill provided with a ceramic striking pin is used in order to efficiently pulverize the crushed material obtained in the above. The cage-type mill is a mill in which a plurality of cage members each having a striking pin sandwiched between a rotating disk and a band are arranged concentrically in a casing, and the object to be ground (the present invention) is rotated while rotating each cage member. In this example, the crushed material obtained in the above is charged and crushed by colliding with each cage member.

The reason why the cage type mill is used in the present invention is that the obtained pulverized material has a good particle size (for example, a particle size judgment rate of 57% or more is obtained) and the amount of unnecessary powder generated This is because there is no need for water treatment equipment and the like, which is expensive because dry grinding can be performed, and dry classification can be performed when the ground material is classified.

[0013] As the ceramic constituting the striker, ceramics having a bending strength 30 Kg / mm ² or more and Vickers hardness 1200 Kg / mm ² or more, specifically, alumina ceramics, alumina-titanium carbide-based ceramics, zirconia Any of ceramics, silicon carbide ceramics, and silicon nitride ceramics is used. Since these ceramics have high abrasion resistance, using them makes maintenance work such as replacement of the striking pins due to wear relatively unnecessary for a relatively long period of time, so that predetermined crushed sand can be efficiently obtained. Conventional metal striking pins are intensely worn and require frequent replacement, which is costly.

In the sorting step, it is preferable to use a wind power sorting device that sorts the sorted material (crushed sand obtained in the present invention) according to the weight of the sorted material by using wind or air current while vibrating the sorted material. . In the wind separation device used in the present invention, a separation unit to which air is supplied from the outside so that air blows upward from below and a slit plate through which air can pass through the selection unit while forcibly vibrating ( Or punching metal), and when the material to be sorted placed on the conveyor passes through the sorting section, only the relatively small and light powder in the material to be sorted is lifted up by air. The powder in the object to be sorted is separated from sand by being blown up and collected by a filter provided separately. The selected sand can be used, for example, as a fine aggregate or a sand material for concrete, and the powder can be used, for example, as an expanding material such as cement, asphalt, or baked goods.

[0015] The water content of concrete waste varies depending on the condition after it is generated at the demolition site and before it is recycled by the method of the present invention. Concrete waste having a low moisture content (that is, concrete waste which is relatively dry or not wet) can be subjected to the above-mentioned treatment as it is, but concrete waste having a high moisture content can be directly subjected to, for example, a sorting step. , There is a possibility that the separation of the powder becomes difficult. Therefore, as for the concrete waste having a high water content (that is, wet), as a pre-process, the concrete waste is left in a predetermined place for a predetermined period to be naturally dried, and the moisture content is reduced to a certain extent.
Is performed.

[0016]

In the present invention, concrete crusher is first crushed to a predetermined size (specifically, about 40 mm or less) by a crusher such as a roll crusher or a jaw crusher. Next, the crushed material is turned into a sand-like crushed material (specifically, crushed sand having a size of about 10 mm or less, more preferably 5 mm or less) by a crusher such as a cage type mill equipped with a ceramic striking pin. Crushed. The pulverized material thus obtained, that is, the crushed sand in which the sand and the powder are mixed, is classified and sorted according to the particle size by the wind power sorting device. This allows
For example, sand having a predetermined particle size distribution as defined in JIS and powder having a smaller particle size can be obtained. The obtained sand can be used, for example, as a sand material for concrete, and the powder can be used, for example, as a cement raw material.

[0017]

Embodiments of the present invention will be described below. (1) Natural drying step and crushing step Concrete waste generated at the demolition site was transferred to a predetermined waste storage place, and left in this waste storage place for a certain period (here, seven days) to be naturally dried. Due to the natural drying, although the concrete still contains moisture, the water content was reduced to such an extent that the treatment in the sorting step described later can be performed without any trouble. Next, the naturally dried concrete waste was put into a crusher (here, a jaw crusher), and crushed so as to have a maximum diameter of 30 mm or less. The particle size distribution of the obtained crushed product was as shown in Table 1 described below. The particle size is measured according to JIS A50
According to the sieving test specified in No. 04 (the same applies to the following cases).

(2) Pulverization Step The crushed material obtained in (1) is crushed to a size of 10 mm (here, about 5 mm).
mm) and crushed with a cage type mill so as to obtain the following crushed sand.
The particle size distribution of the obtained crushed sand (crushed product) was as shown in Table 1 described below. The cage type mill used was “Sand Creator Mill (trade name)” manufactured by Cera Tech Co., Ltd.
It is. Here, a cage type mill called this sand creator mill will be briefly described.

As shown in FIG. 1, this cage type mill has:
It has a casing 30 provided with an inlet 31 and an outlet 32 for the material to be crushed and having a protective liner 33 laid on the inner wall surface. In the casing 30, two cage members A and B having different diameters are arranged concentrically. Each of the cage members A and B has a plurality of striking pins 14 and 24 sandwiched between the rotating disks 11 and 21 and the bands 12 and 22 at equal intervals.
The rotation shafts 11a and 21a of the cage members A and B are connected to a motor (not shown) via a drive shaft 34. And
In this cage type mill, the material constituting the protective liner 33 and the impact pins 14 and 24 has a bending strength of 30 kg / mm ² or more and a Vickers hardness of 1200 kg.
/ Mm ² or more is used.

The pulverization of the object to be pulverized by such a cage type mill is performed as follows. When the objects to be ground are thrown into the casing 30 from the inlet 31 with the cage members A and B relatively rotated by the motor, the objects to be ground come into collision with the striking pins 24 constituting the cage member B having a small diameter. Collides with the striking pin 14 constituting the large-diameter cage member A rotating in the reverse direction, and finally collides with the protective liner 33. Thereby, the material to be crushed is crushed into crushed sand having a size of 5 mm or less. The crushed sand obtained by the pulverization is discharged from the discharge port 32 to the outside of the casing 30. In addition,
In this embodiment, the rotation speed of the cage members A and B at the time of crushing the material to be crushed was set to 33 m per second at the peripheral speed.

(3) Sorting step The crushed sand (crushed material) obtained in (2) is classified according to the particle size by an air-flow sorting device to obtain sand (crushed sand after classification) and dust collection powder (powder after classification). Sorted out. The powder in this case was collected by a dust collector provided in the wind separation device. The particle size distribution of the obtained powder (after classification) was as shown in Table 1 described later. The wind separation device used was “Sand Creator Separator (trade name)” manufactured by Cera Tech Co., Ltd.
This apparatus is of the above-described type in which powder is separated from a sorting object by air while vibrating the sorting object. Unwanted dust contained in the crushed sand or having a size of 0.075 mm or less generated during sorting (so-called -0.0.
075 mm) was collected by a filter provided in the wind separator.

(4) Evaluation Table 1 shows the crushed material, crushed sand after mill (crushed material), crushed sand after classification (sand), and powder (powder after classification) obtained in each of the above steps (1) to (3). 2 shows the respective particle size distributions. FIG. 2 shows them graphically. For comparison, FIG.
The particle size distribution of the crushed sand for concrete specified in IS A5004 is also shown. Among the lines in the figure, (A) is the crushed material after the crushing process, (A) is the crushed material after the crushing process (crushed sand after the mill), (C) and (D) are the sand after the sorting process (after classification). (Crushed sand) and powder (dust collection powder). Also,
Both lines (f) and (g) indicate the limit value of the particle size of the crushed sand for concrete specified in JIS A5004. In FIG. 2, if the particle size distribution of the sand is between the two lines (f) and (g), it satisfies the particle size distribution condition of the crushed sand for concrete specified by JIS. Table 1
The “screen size” in the table means the nominal size (size of sieve) of the sieve, and its unit is mm. "FM"
Is a so-called coarseness modulus (Finess Modulus).

[0023]

[Table 1]

From Table 1 and FIG. 2, according to the present invention, J
It is possible to obtain sand that satisfies the particle size distribution conditions for crushed sand for concrete specified in IS, that is, sand with an appropriate particle size distribution and powder with a size (particle size) of 0.075 to 0.15. I understand. Unnecessary dust of 0.075 mm or less (−0.0
(075 mm) is only 1.7% in the case of crushed sand, that is, sand after classification, and there is no unnecessary dust in dust collected powder, that is, powder after classification. The obtained sand can be used, for example, as a sand material for concrete, and the powder can be used, for example, as a raw material (extending material) for cement, asphalt, and baked goods.

[0025]

As described above, according to the present invention, concrete galley is mechanically crushed and crushed sequentially by using a crusher and a crusher, and then a predetermined sorter ( By simply performing a process of separating sand and powder using a classifier, for example, sand that can be used as a sand material for concrete and powder that can be used as a cement raw material can be obtained. Moreover, according to the present invention,
In addition to obtaining sand having an appropriate particle size distribution from concrete waste, it is possible to suppress generation of unnecessary dust in recycling concrete waste.

In the pulverizing step, the bending strength is 30 kg.
/ Mm ² or more, and using a cage type mill having a striking pin made of silicon carbide ceramics having a Vickers hardness of 1200 kg / mm ² or more, maintenance work such as replacement of the striking pin due to wear is required. Since it becomes unnecessary for a relatively long time, predetermined crushed sand can be obtained more efficiently.

[Brief description of the drawings]

FIG. 1 is a crusher (cage type mill) used in an embodiment of the present invention.
FIG. 2 is a longitudinal sectional view schematically showing the structure of FIG.

FIG. 2 shows the particle size distribution of the crushed sand obtained in the example of the present invention.
It is a table | surface shown with the particle size range of the crushed sand for concrete prescribed | regulated by A5004 of JIS.

[Explanation of symbols]

14 ... hitting pin (a) crushed material (crushed sand before mill) obtained in the example of the present invention
Line showing the particle size distribution of (a) The pulverized product obtained in the examples of the present invention (crushed sand after milling)
Line showing particle size distribution of (c) Line showing particle size distribution of sand (crushed sand after classification) obtained in Examples of the present invention (d) Particle size of powder (powder after classification) obtained in Examples of the present invention Line indicating distribution (f) / (g) Line indicating particle size range of crushed sand for concrete specified in JIS (A5004)

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Tsukasa Matsuda 6-11-7 Ebie, Fukushima-ku, Osaka-shi, Osaka F-term in Sera Tech Co., Ltd. (reference) 4D004 AA33 BA02 CA04 CA08 CB13 4D065 AA05 BB04 EB01 EB04 EB05 EC05 EC09 ED14 ED45 EE02

Claims (6)

[Claims] A step of crushing the concrete waste into a predetermined size; a step of crushing the obtained crushed material into finer sand; And recycling the concrete waste. 2. A step of crushing the concrete waste to a predetermined size, and crushing the obtained crushed material into finer sand using a cage type mill or a pin mill provided with a ceramic striking pin. A method for recycling concrete garbage, comprising: a step; and a step of separating sand and powder from the obtained sandy pulverized material using a wind separation device. 3. A step of crushing the concrete waste with a crusher so that the size becomes about 40 mm or less, and crushing the obtained crushed material by using a cage type mill equipped with ceramic striking pins. Crushing with a crusher so that the crushed sand is about 10 mm or less, and a step of separating sand and powder from the obtained crushed material with a wind separation device. Method. As wherein ceramics constituting the striking pin cage mill, bending strength 30 Kg / mm ² or more and using Vickers hardness 1200 Kg / mm ceramics having ² or more, of concrete glass according to claim 2 or 3, wherein Recycling method. 5. The ceramic constituting a striking pin of a cage type mill is any one of alumina ceramics, alumina-titanium carbide ceramics, zirconia ceramics, silicon carbide ceramics and silicon nitride ceramics. Recycling method of concrete waste. 6. The concrete waste is left to dry for a predetermined period of time before being crushed by a crusher.
The method for recycling concrete waste according to any one of the above.