JPH08175856A - Method for treating concrete waste material - Google Patents

Abstract

PURPOSE: To effectively recover an aggregate and having the same characteristics as those of an aggregate and a cement component from a concrete waste material. CONSTITUTION: A concrete waste material is coarsely ground into a concrete bulk, which is calcined preferably at 300-700 deg.C, ground, sieved into an aggregate part and a mortar part and recovered as a concrete aggregate and/or a cement raw material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention separates concrete aggregate and / or cement raw material from concrete waste material.
Regarding the method of collecting.

[0002]

2. Description of the Related Art In recent years, with the dismantling of concrete structures, a large amount of waste concrete is generated, and its treatment has become a problem. A part of it is used as a material for land reclamation and roadbed paving, but most of it is left in the natural world and left abandoned, causing environmental problems. Further, from the viewpoint of resource saving, concrete aggregates and / or raw materials for cement are separated and recovered from concrete waste materials and reused as new concrete raw materials. As a method for recycling concrete waste material, a method has been proposed in which mechanical crushing is performed, and the material is sieved into a large-diameter aggregate portion and a fine powder mortar portion, and then recovered as a concrete aggregate and a raw material for cement, respectively.

[0003]

However, in the method of merely physically crushing and sieving as in the conventional treatment method, the cement hydrate remains on the surface of the recovered aggregate, and the new aggregate is Compared with, the specific gravity is smaller, the water absorption is larger, and the abrasion is larger. At the same time, the amount of cement raw material recovered also decreases. In this way, the aggregate recovered by the conventional treatment method lacks durability as an aggregate for concrete, so that the range of use is limited to the amount used that does not deteriorate the concrete quality, or a structure that does not particularly require high strength. Its use is extremely limited, such as when it is used in a product. Therefore, most of the recycled products of concrete waste materials are currently used as so-called low-treated products such as recycled crusher runs and grain-crushed stone substitutes. The present invention has been made in view of the above problems, and an object of the present invention is to effectively recover an aggregate and a cement component having the same properties as a new aggregate from a concrete waste material.

[0004]

In order to achieve the above object, a method for treating a concrete waste material according to the present invention is a method in which a concrete mass obtained by roughly crushing a concrete waste material is calcined, then crushed and sieved. It is characterized in that it is separated into an aggregate part and a mortar part and recovered as a concrete aggregate and / or a cement raw material. In order to achieve the same object, the method for treating a concrete waste material according to the present invention is characterized in that the calcination treatment is performed in a temperature range of 300 to 700 ° C.

[0005]

The problem with the prior art is that the aggregate part and the cement hydrate part cannot be effectively separated. That is,
Although downsizing is possible by mechanical crushing,
The crushed material (even in the same particle size group) is a mixture of aggregate and cement hydrate, and both cannot be separated. And, by mixing such aggregate and cement hydrate,
The characteristics (specific gravity, water absorption, abrasion) of the aggregate are deteriorated, which limits its use as an aggregate. According to the method for treating a concrete waste material according to the present invention, a lump obtained by roughly crushing the concrete waste material is calcined in a temperature range of 300 to 700 ° C., preferably 450 to 600 ° C., thereby giving a thermal strain to the concrete lump. Then, the strength of the aggregate is reduced, the adhesive force between the aggregate and the cement is reduced to make it easily crushed, and then this is mechanically crushed. As a result, the amount of cement hydrate remaining on the aggregate surface after crushing is greatly reduced compared to the previous one, and an aggregate with the same properties as the new aggregate is obtained, and the cement component is also effective. Can be collected.

The present invention will be described in detail below. Figure 1
It is process drawing which shows the processing method of the concrete waste material based on this invention. The concrete waste material is first crushed by a crusher into lumps having an appropriate diameter. The size of the lump of concrete obtained by this crushing is not particularly limited, but it is preferably small in diameter in consideration of the efficiency of the calcination treatment described later.

Next, this concrete block is put into a calcining furnace and calcined at a predetermined temperature for a predetermined time. When concrete is heated, it generally becomes brittle in proportion to its heating temperature. It is known that the hydrate of cement paste contained in concrete causes dehydration at about 300 ° C, and that slaked lime thermally decomposes at about 500 ° C. It is considered that voids are generated due to the volume reduction when slaked lime is converted into quick lime, and as a result, pores in the concrete are expanded or cracks are generated to reduce the adhesive force between the cement component and the aggregate. Therefore, if it is not heated at a temperature below 300 ° C. for a long time, it will not be sufficiently dehydrated, but even if it is completely dehydrated, there will be few voids,
It is not possible to reduce the adhesive strength to such an extent that the cement paste and the aggregate can be easily separated. On the other hand, when heated at a high temperature of 700 ° C or higher, the concrete becomes brittle and the paste part,
Although it is easy to separate fine and coarse aggregates, when sandstone or granite type aggregates are used as aggregates, they are not preferable because they cause thermal deterioration. Particularly recently, limestone is increasingly used as coarse aggregate, and pyrolysis fracture occurs at high temperatures of 700 ° C. or higher.

FIG. 2 shows a concrete specimen (diameter 100
2 mm by changing the calcination temperature.
It is a graph showing the compression strength ratio when calcined for a time,
As is clear from the figure, the compressive strength ratio gradually decreases with increasing calcination temperature, confirming the effect of calcination.
Further, FIG. 3 is a graph showing the weight loss of the test piece under the same calcination condition by the abrasion test, and it can be seen that the abrasion loss increases as the calcination temperature increases.

Thus, the calcination temperature is preferably in the range of approximately 300 to 700 ° C. regardless of the type of concrete raw material. When considering making it possible to recover the paste portion, fine and coarse aggregate without adversely affecting the aggregate,
It is desirable to set it in the range of 450 to 600 ° C. Also,
The calcination time is not particularly limited, and is appropriately set depending on the size of the crushed concrete lump, the treatment amount, and the like.

After the calcination, the concrete mass is crushed again by a crusher, sieved to a predetermined particle size group, and collected as an aggregate and a cement raw material according to the particle size. By this sieving, for example, a component having a particle size of 0.15 mm or less is recovered as a cement raw material, and a component having a particle size of 0.6 mm or more is recovered as an aggregate.

[0011]

The present invention can be further clarified by the following examples. [Example 1] A concrete waste material of a construction about 40 years after casting using river sand and river gravel as an aggregate was roughly crushed by a crusher and calcined at 550 ° C, and then the waste material lump 3
00 kg was put into an empty mill having an inner diameter of 1000 mm and a length of 1500 mm and rotated at a rotation speed of 30 rpm for 30 minutes. After the rotation, the waste concrete material was discharged and sieved into each particle group, and the amount of CaO in the particle group was measured. Table 1 shows the measurement results.

[0012]

[Table 1]

From Table 1, large-diameter particles having a particle size of 0.6 mm or more are aggregate components, but since the CaO content is extremely low, almost no cement hydrate remains on the surface and the aggregate part is It can be seen that the mortar part and the mortar part are separated very well. In addition, when subjected to an aggregate test, it was confirmed that the recovered aggregate was sufficiently usable as a concrete material. Further, particles having a particle size of 0.6 mm or less are mortar components, but particles having a particle size of 0.15 mm or less are Ca.
It has a high O content and can be sufficiently reused as a cement raw material.

[Example 2] A crushed concrete waste material of about 20 years old was roughly crushed by a crusher and calcined at 600 ° C, and then 350 kg of the waste material and an iron ball 5 of 30 mmφ
0 pieces were put into an empty mill having an inner diameter of 1000 mm and a length of 1500 mm, and were rotated at a rotation speed of 30 rpm for 10 minutes. After the rotation, the waste concrete material was discharged and sieved into each particle group, and the amount of CaO in the particle group was measured. The measurement results are shown in Table 2.

[0015]

[Table 2]

As in Example 1, it can be seen from Table 2 that the aggregate portion and the mortar portion are separated very well.

[0017]

As described above, according to the method for treating a concrete waste material according to the present invention, a lump obtained by roughly crushing the concrete waste material is calcined to give a thermal strain to the concrete lump to increase its strength. The amount of cement hydrate remaining on the aggregate surface after crushing was reduced as a result of mechanically crushing it after reducing the adhesive force between the aggregate and cement to make it crushable. The aggregate is significantly reduced compared to the conventional one, and an aggregate having the same characteristics as the new aggregate can be obtained, and the cement component can also be effectively recovered.

[Brief description of drawings]

FIG. 1 is a process drawing showing a method for treating a concrete waste material according to the present invention.

FIG. 2 is a graph in which a compressive strength ratio with respect to a calcination temperature of a concrete sample is measured.

FIG. 3 is a graph in which the amount of abrasion loss with respect to the calcination temperature of a concrete sample is measured.

Claims (2)

[Claims] 1. A method of calcination, crushing and sieving a concrete block obtained by roughly crushing waste concrete to separate it into an aggregate part and a mortar part, and recovering as concrete aggregate and / or cement raw material. A method for treating a concrete waste material, which is characterized by: 2. The method for treating concrete waste according to claim 1, wherein the calcination treatment is performed in a temperature range of 300 to 700 ° C.