JPH05272111A - Method for crushing concrete waste - Google Patents

Abstract

PURPOSE:To improve the workability and the quality of coarse aggregate by heating concrete wastes to the specific temperature or above, or heating and cooling them, crushing them, and separating and recovering the coarse aggregate. CONSTITUTION:Concrete wastes are heated to 100 deg.C or above, preferably 150-500 deg.C, utilizing factory waste heat. They are quickly cooled as required, and the heating and quick cooling are repeated several times. They are crushed with a crusher. They are sifted, and the coarse aggregate and the coarse aggregate stuck with a small quantity of mortar are separated and extracted from mortar and reinforcing bars. The high-quality lump coarse aggregate stuck with little mortar can be easily recovered in a short time, crushing noises can be reduced, and the waste heat can be effectively utilized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for crushing concrete waste material, and more particularly to a method for crushing concrete waste material generated by dismantling a building and removing secondary concrete products, and effectively reusing it.

[0002]

2. Description of the Related Art Generally, concrete has a durable life of 30.
~ 40 years. Therefore, it is expected that a large amount of recovery work will be carried out on the concrete structures that have rapidly increased after the Second World War since the 1990s. On the other hand, environmental problems are becoming more and more important in the future, and it is becoming difficult to rely on mountain sand and river sand as an aggregate source used for concrete.

From the above, it is considered extremely important to reuse the waste concrete material as an aggregate for concrete in terms of effective use of resources and environmental protection.
Conventionally, the method of utilizing waste concrete or hardened concrete as recycled aggregate is a method of using crushed concrete as aggregate.

By the way, the quality required for such recycled aggregate is that the shape is round and the amount of adhered mortar is small. In addition, it is required from the environmental aspect that noise caused by crushing is small when the recycled aggregate is manufactured.

[0005]

However, the use of such recycled aggregate has a drawback that the shape of the aggregate becomes flat. In addition, since the amount of attached mortar is large, there is a problem that the water supply rate of recycled aggregate increases and the unit water amount of concrete increases. There is also the risk that noise generated during crushing will cause new environmental problems.

That is, when the concrete waste material is simply crushed, the shape of the crushed object tends to be flat. This is because it is difficult to separate the aggregate and the mortar part in the concrete. Therefore, the mortar remains attached to the aggregate, noise during crushing is great, and the time required for crushing is long.

The present invention solves the above-mentioned conventional problems, reduces the noise during crushing and the time required for crushing the concrete waste material for reuse of the concrete waste material, and reduces the amount of mortar adhered, An object of the present invention is to provide a method for crushing a concrete waste material, which can be a crushed material in a lump rather than a flat shape.

[0008]

A method for crushing a concrete waste material according to claim 1 is a method for crushing a concrete waste material to separate coarse aggregate into a concrete waste material at 100 ° C.
It is characterized in that it is crushed after being heated above.

A method of crushing a concrete waste material according to a second aspect is characterized in that, in the method of the first aspect, the concrete waste material is heated, rapidly cooled, and then crushed.

A method of crushing a concrete waste material according to a third aspect is characterized in that, in the method of the second aspect, heating and quenching are repeated a plurality of times and then the crushing is performed.

The present invention will be described in detail below.

In the method of the present invention, it is advantageous to use low temperature waste heat generated from various factories as a heat source for heating the concrete waste material. Although this low-temperature waste heat has a large total amount of generation, it has hitherto been mainly used as a method of utilizing it for drying a wet material, and has been regarded as a heat source that is difficult to effectively use. In the present invention, it is possible to efficiently heat concrete waste material by utilizing such low temperature waste heat, which has been conventionally difficult to effectively use.

When heating this concrete waste material, if the heating temperature is less than 100 ° C., the sufficient improvement effect according to the present invention cannot be obtained. Even if the heating temperature is excessively high, the workability is impaired and the processing cost rises. Therefore, the heating temperature is 100 ° C. or higher, preferably 150 to 50.
Set to 0 ° C. Moreover, the heating time is 3 after the temperature reaches the predetermined temperature.
0 minutes or more is suitable.

When the waste concrete is rapidly cooled after being heated, water or the like may be used for cooling. In this case, the cooling rate during the rapid cooling is preferably 5 ° C./minute or more.

In the present invention, even more excellent effects can be obtained by repeating heating and quenching twice or more, preferably 5 to 10 times.

Crushing after heating or after heating and quenching is
It can be performed according to a conventional method using a crusher or the like. After the crushing, the coarse aggregate and the coarse aggregate having a small amount of mortar adhered to the surface can be easily separated and taken out from the mortar portion and the reinforcing bars by dividing them into separate pieces.

Since the obtained coarse aggregate is the raw aggregate of the concrete waste material recovered without being crushed, its shape does not split into a flat shape and has a good lump shape. Moreover, since the amount of adhered mortar is extremely small, it can be effectively reused.

In the present invention, the concrete waste material does not always contain rebars, and the present invention can be effectively applied to the waste material of hardened concrete in which no rebars are arranged, and the adhered It is possible to recover good recycled coarse aggregate having a significantly small amount of mortar.

[0019]

The concrete waste material that has been heated once and the concrete waste material that has been heated once and then rapidly cooled with water or the like, and the concrete waste material that has been repeatedly heated and rapidly cooled will be distorted and can be easily crushed. This is because heating causes vaporization of water in waste concrete and dehydration of cement hydrate. Decrease in concrete strength due to volume change of water during vaporization and dehydration of water and decomposition of cement hydrate binding concrete. Since the mortar part and the coarse aggregate part have different volume change rates due to temperature changes, distortion may occur in concrete due to temperature changes.

By the action of the above. As a result, the concrete can be easily crushed, so that noise can be suppressed and the concrete can be crushed easily in a short time.

Further, since a large amount of strain in this concrete waste material occurs at the boundary between the coarse aggregate and the mortar,
After the crushing, the coarse aggregate and the coarse aggregate having a very small amount of mortar on the surface can be easily taken out by dividing it. Since this recycled coarse aggregate is collected without crushing the original coarse aggregate, the shape of the recycled coarse aggregate is not split and flat.

[0022]

EXAMPLES The present invention will be described more specifically with reference to Examples and Comparative Examples.

Examples 1 to 3 and Comparative Example 1 Concrete specimens having the compositions shown in Table 1 were prepared, a part of them was used for concrete strength test, and the rest was subjected to crushing treatment. Table 1 shows the concrete strength of each material.

The following treatment was performed on the specimen of 3 years old. Example 1: Concrete was heated at 100 ° C. for 30 minutes and then crushed.

Example 2: Concrete at 100 ° C. for 30
After heating for 1 minute, the mixture was rapidly cooled to 25 ° C in 10 minutes and then crushed. Example 3: Concrete was heated at 100 ° C. for 30 minutes and then rapidly cooled to 25 ° C. in 10 minutes, which was repeated 3 times and then crushed. Comparative Example 1: Concrete was crushed as it was without heating. For crushing, use a jaw crusher,
The minimum crushing interval was set to 30 mm.

Table 2 shows the grinding time of each concrete specimen and the noise generated during the grinding. Further, from the crushed material obtained after the treatment, a portion of 5 mm or more was taken out as coarse aggregate by a teacher, and the amount of mortar attached by the hydrochloric acid treatment was estimated. Table 2 shows the amount of mortar adhered (estimated value) and the shape of coarse aggregate.

From Table 2, it is clear that according to the method of the present invention, the crushing time can be shortened, the noise can be reduced, and the regenerated aggregate having a good shape and having a small amount of adhered mortar can be obtained. Is.

[0028]

[Table 1]

[0029]

[Table 2]

[0030]

As described in detail above, according to the method for crushing a concrete waste material of the present invention, noise can be easily suppressed in a short time, the amount of mortar adhered from the concrete waste material is remarkably small, and the shape is coarse aggregate. It is possible to efficiently recover the reusable coarse aggregate having the original shape. Moreover, not only can natural resources be saved by recovering coarse aggregate, but low-temperature waste heat from various factories, which was considered difficult to use effectively, can also be used effectively, enabling effective use of natural resources and energy at the same time. became.

Claims (3)

[Claims] 1. A method for crushing a concrete waste material, which comprises crushing a concrete waste material to separate coarse aggregate, wherein the concrete waste material is heated to 100 ° C. or higher and then crushed. 2. The method for crushing concrete waste according to claim 1, wherein the concrete waste is heated, then rapidly cooled, and then crushed. 3. The method for crushing concrete waste according to claim 2, wherein the crushing is performed after repeating heating and quenching a plurality of times and then crushing.