JP2000072501A - Aggregate and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide, from the viewpoint of resource re-utilization, an aggregate having a good enough properties to used as a cement aggregate produced from fine concrete powder containing solid cement paste and a method for producing an aggregate having such properties stably and easily without making a strict control of the manufacturing conditions. SOLUTION: This aggregate is melted and cooled material of concrete fine power and has substantially noncrystalline structure. This method for producing the aggregate comprises melting concrete fine powder, cooling the melted concrete fine powder in the state having substantially amorphous structure, powdering or disintegrating the cooled material. In the production, the melting is preferably carried out by heating at >=1300 deg.C and further, the cooling is preferably carried out at a temperature-lowering rate of >=15 deg.C and particles obtained by powering or disintegrating the cooled material is classified and the classified particles comprise having >=0.6 mm particle diameter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aggregate made from concrete fine powder generated when crushing concrete or the like and a method for producing the aggregate.

[0002]

2. Description of the Related Art A large amount of concrete waste is generated as buildings are demolished or renovated. Approximately half of concrete waste is reused for roadbed materials and backfill materials, but as a new measure for recycling, it has been attempted to collect the aggregate contained in the waste material and reuse it as aggregate. Is being done. In order to recover the contained aggregate from the concrete waste material, it is generally considered that the concrete waste material is crushed or pulverized. However, this process usually generates a considerable amount of concrete fine powder having a size less than the size of the fine aggregate.

[0003] In general, the content of the cement paste component, which binds the aggregate in the concrete material, increases as the particle size of the fine powder becomes smaller. Is significantly reduced. For this reason, in order to use the fine powder as an aggregate, there is known a method of sintering the fine powder to increase the density and strength. However, in this method, the chemical components of concrete are not constant because the concrete-containing aggregate types and cement types and their contents are various, and the sintering temperature is considerably different due to a slight difference in the chemical components. It is not easy, and in this material system, the temperature range suitable for sintering is also disadvantageous in that it is disadvantageous. At a temperature below this range, the aggregate is not sufficiently densified and becomes a brittle aggregate. The properties of the obtained aggregates were greatly affected by subtle changes in firing conditions, such as softening and unstable properties.
In order to widen the sintering temperature range, it is necessary to adjust the components of the sintering raw material. For this purpose, it is necessary to recognize the chemical components of the target concrete fine powder and to add components for adjustment. However, in consideration of the treatment and utilization of fine powder as concrete waste material, the source of the concrete fine powder to be targeted is generally diversified, and almost no concrete fine powder of the same component and quality can be targeted at all times. Therefore, it is necessary to analyze the chemical composition of the target fine powder for each treatment, and it is necessary to add a chemical composition for adjustment in accordance with that, and to perform a pre-treatment that is very laborious in practice, such as mixing. was there.

[0004]

SUMMARY OF THE INVENTION The present invention relates to an aggregate which is mainly made of concrete fine powder comprising a solid cement paste component and an aggregate component generated when crushing and pulverizing concrete. Aggregate with properties equivalent to JASS 5N standard that can be used as aggregates for use, and stable aggregates without the need to adjust raw material components and without particularly strictly adjusting production conditions. And a production method which can be easily obtained.

[0005]

Means for Solving the Problems As a result of intensive studies for solving the above problems, the present inventors have melted concrete fine powder generated in the process of crushing or pulverizing concrete without adjusting the components, and melted the melt. What has been cooled so as to have a substantially amorphous structure is at least JASS 5
It has properties as an aggregate for cement equivalent to N, and has been found to have properties comparable to those of conventional natural aggregates and the like, and even if the temperature conditions during melting slightly vary, the above properties Found that it can be obtained stably,
The present invention has been completed.

That is, the present invention provides (1) a molten and cooled concrete fine powder, which is characterized in that it has a substantially amorphous structure. And its production method represented by the following (2) to (5). (2) A method for producing an aggregate, comprising melting concrete fine powder, cooling the powder in a substantially amorphous structure, and pulverizing or crushing the cooled product.
(3) The method for producing an aggregate according to (2), wherein the melting is performed by heating at 1300 ° C. or more. (4) The method for producing an aggregate according to the above (2) or (3), wherein the cooling is performed at a cooling rate of 15 ° C./min or more. (5) The above-mentioned (2) to (4), wherein the particles obtained by pulverizing or crushing the cooled material are classified and composed of particles having a particle diameter of 0.6 mm or more.
Any one of the methods for producing an aggregate.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The amorphous aggregate of the present invention is capable of removing concrete fine powder generated during concrete crushing or crushing treatment, for example, when collecting contained aggregate from concrete waste or dismantling concrete structures. Raw materials. The fine powder is composed of particles such as aggregate for cement, aggregate to which cement paste is adhered, and cement paste separated from the aggregate. The concrete powder of the present invention refers to an aggregate of such individual particles. Particles having an extremely high aggregate content are not subject to the present invention, and can be generally reused as aggregates by collecting them as they are. Particularly suitable are fine powders containing a large amount of components. However, even fine powder having a small content ratio of cement paste can be a target. Further, when the fine powder is used as a raw material, it is not necessary to adjust the components by adding a chemical component, and it is preferable to adjust the fine powder diameter. That is, the size of the fine powder is desirably approximately 2.5 mm or less, from the viewpoint of reducing the content of the aggregate mixed as the fine powder and increasing the melting reaction efficiency.

[0008] Such fine powder is melted so that the crystal structure disappears and a glass state is obtained. Melting is preferably 1300
Heat to above ℃. If the heating temperature is lower than 1300 ° C., it is not preferable that the material having a large CaO content is not completely melted in some cases. The heating device is not particularly limited as long as it can be heated at a desired temperature, but for example, an arc furnace, an electric arc furnace, or the like may be used from the viewpoint of production efficiency. After the heating, the melt is cooled so as not to crystallize. In general, the precipitation of crystals in an amorphous body causes the material to become brittle, and thus it is necessary to suppress the precipitation of crystals as much as possible. Therefore, cooling is preferably performed at a cooling rate of at least 15 ° C./min for at least 5 minutes.
The temperature may be reduced to around 00 ° C., and then the temperature may be gradually cooled. More preferably, the temperature is lowered at a rate of 20 ° C./min or more. High-speed cooling can sufficiently suppress crystal re-precipitation, and it can be seen that the cooling material is crushed into small blocks due to strong thermal strain. Or it leads to labor saving regarding the crushing process. The cooling means is, for example, a known quenching method such as a method of blowing compressed air or the like onto the melt or a method of throwing into the water is recommended, but it is also possible to put the melt in a heat-resistant container near room temperature and allow it to cool naturally. However, there is no particular limitation. The cooling material obtained by such cooling has a structure close to a liquid in a supercooled state that has not yet been formed into a complete vitreous or crystalline or solid solution arrangement, and has a clear crystal structure. It has a substantially amorphous structure with almost no composition.

[0009] After cooling, the solidified substantially solid mass of the cooled material is pulverized, while the cooled material that has been crushed by cooling is broken up. Any device or method may be used for crushing or crushing, but generally crushed vitreous crushed material has a shell-like rupture surface. The shape is adjusted to a smooth shape, more preferably a spherical shape, using a device that can also perform the above. Preferably, the ground or crushed particles are classified to exclude particles smaller than 0.6 mm. After classification, particles of 0.6 mm or more and less than 5 mm are collected as fine aggregates, if there are particles of 5 mm or more, as coarse aggregates. The aggregate having a substantially amorphous structure of the present invention is such fine aggregate and / or coarse aggregate. Note that 0.6
Particles smaller than mm are removed because it is difficult to adjust the particle shape to a shape suitable for the aggregate, but they can be reused as a cement raw material or the like by further pulverizing.

[0010]

EXAMPLES Example 1 Concrete waste material was crushed with a jaw crusher, and was roughly composed of the chemical components shown in Table 1.
Concrete fine powder of 5 mm or less was collected. The collected fine powder was heated and melted at 1600 ° C. for 20 minutes using an arc furnace having an inner volume of 0.3 m ³ . The melt was poured into water to obtain a finely divided cooled product. The cooled product was crushed by a KM Super Mill (manufactured by Kansai Matech Co., Ltd.), and the crushed material was classified to collect particles having a size of 0.6 mm or more. As a result of analyzing the particles by powder X-ray, no particular diffraction peak was observed. The absolute density and the 24-hour water absorption of the particles were measured according to JIS A1109 in accordance with JIS A1109.
The unit volume mass was measured by a method according to SA1104, and the stability as an aggregate was measured by a method according to JIS A1122. As a result, the absolute dry gravity was 2.67, the 24-hour water absorption was 0.53%, and the unit volume mass was 1.56 kg /
1. The stability as aggregate was good.

[0011]

[Table 1] Chemical Ingredients Chemical Component Name _{SiO 2 Al 2 O 3 Fe 2} O 3 CaO MgO Na 2 0 K 2 O SO 3 ig.loss content (wt%) 45.8 12.7 4.3 21.8 1.6 1.7 1.2 0.7 10.2

Example 2 The same concrete fine powder as in Example 1 was heated and melted at 1600 ° C. for 20 minutes using the same arc furnace. The melt was gently placed in a heat-resistant container, allowed to cool naturally, and then taken out of the mass of the cooled product, which was pulverized by a jaw crusher. The pulverized material was adjusted for particle size using an aerofractron (manufactured by Tokai Techno Co., Ltd.) and then classified to collect particles having a size of 0.6 mm or more. As a result of analyzing the particles by powder X-ray, there was no particular diffraction peak except for a very slight diffraction peak which was considered to be a gehlenite compound. The characteristic values of the particles measured in the same manner as in Example 1 were as follows: the absolute dry gravity was 2.69, the 24-hour water absorption was 0.35%, the unit volume mass was 1.65 kg / l, The stability as a material was good.

Example 3 The same concrete fine powder as in Example 1 was heated and melted at 1400 ° C. for 40 minutes using the same arc furnace. The melt was poured into water, and the obtained cooled product was crushed by a KM super mill (manufactured by Kansai Matech Co., Ltd.), and the crushed material was classified to collect particles having a size of 0.6 mm or more. As a result of analyzing the particles by powder X-ray, there was no particular diffraction peak except for a slight diffraction peak which was considered to be a gehlenite compound. The absolute specific gravity of the particles measured in the same manner as in Example 1 was 2.69, the 24-hour water absorption was 0.35%, the mass per unit volume was 1.65 kg / l, and the stability as aggregate was as follows. Was good.

Example 4 The same concrete fine powder as in Example 1 was melted by heating at 1600 ° C. for 20 minutes using an electric furnace. The melt was cooled to about 600 ° C. at a rate of temperature drop of about 16 to 17 ° C./min, and then allowed to cool naturally. This was ground with a jaw crusher. The pulverized material was classified after adjusting the particle shape using an aerofractron.
Particles of 6 mm or more were collected. The particles were analyzed by powder X-ray. As a result, no particular peak was recognized except for a slight diffraction peak which was considered to be a gehlenite compound. The characteristic values of the particles measured by the same method as in Example 1 were as follows: the absolute dry gravity was 2.66, the 24-hour water absorption was 0.75%, the unit volume mass was 1.63 kg / l,
The stability as aggregate was good.

Example 5 Concrete waste materials different from those in Examples 1 to 4 were crushed by a jaw crusher, and concrete fine powder having a chemical composition shown in Table 2 and having a size of about 2.5 mm or less was recovered. This fine powder was heated and melted at 1700 ° C. for 40 minutes using the same arc furnace as in Example 1. The melt was poured into water, and the obtained cooled product was crushed by a KM super mill (manufactured by Kansai Matech Co., Ltd.), and the crushed material was classified to collect particles having a size of 0.6 mm or more. The particles were analyzed by powder X-ray. As a result, no diffraction peak was observed except for a diffraction peak slightly considered to be gehlenite. The absolute dry weight of the particles measured by the same method as in Example 1 was 2.61, the 24-hour water absorption was 0.69%, the mass per unit volume was 1.61 kg / l, and the stability as aggregate was as follows. Was good.

[0016]

[Table 2] Chemical Ingredients Chemical Component Name _{SiO 2 Al 2 O 3 Fe 2} O 3 CaO MgO Na 2 0 K 2 O SO 3 ig.loss content (wt%) 63.7 13.4 2.7 8.5 1.9 1.9 1.5 0.5 6.8

Comparative Example 1 Concrete fine powder similar to that of Example 1 was heated at 1100 ° C. for 30 minutes using an arc furnace having an inner volume of 0.3 m ³ . The heated product was gently placed in a heat-resistant container, allowed to cool naturally, and then a mass of cooled product was taken out and crushed by a jaw crusher. The pulverized product was classified, and particles of 0.6 mm or more were collected. The particles were analyzed by powder X-ray. As a result, diffraction peaks of wollastonite, anorthite and a gehlenite compound were detected. Further, observation by a polarizing microscope revealed that the glass quality was almost half or less. The particles had an absolute dry gravity of 2.43 and a 24-hour water absorption of 4.5 measured in the same manner as in Example 1 above.
5%, the unit volume mass was 1.45 kg / l, and the stability as aggregate was poor.

Comparative Example 2 Concrete fine powder having a chemical composition similar to that of Example 5 and having a size of about 5 mm or less was recovered. This fine powder was heated and melted at 1700 ° C. for 40 minutes using an electric furnace. The melt is cooled to a temperature of about 4-5 ° C. for 60
The mixture was cooled to 0 ° C. and allowed to cool naturally, and the resulting cooled product was disintegrated with a KM supermill. The crushed material was classified, and 0.6
Particles of mm or more were collected. As a result of analyzing the particles by powder X-ray, diffraction peaks of wollastonite, anorthite and a gehlenite compound were detected, and further, observation by a polarizing microscope revealed that the glassy abundance was about half of the whole.
The absolute dry weight of the particles measured by the same method as in Example 1 was 2.42, the 24-hour water absorption was 3.16%, the unit volume mass was 1.46 kg / l, and the stability as aggregate was obtained. Although it was good, it was of low quality which was not as far as JASS 5N.

[0019]

According to the present invention, it is possible to reuse a large amount of concrete fine powder containing a large amount of cement paste which is often discarded. The component area is quite wide,
It is possible to use concrete fine powder generated from most concrete crushed materials used in the world as raw materials without adjusting the components, and furthermore, the heating conditions at the time of manufacturing are wide, and JASS 5N equivalent is excellent. A high quality aggregate can be obtained with extremely high reproducibility.

Claims (5)

[Claims] 1. An aggregate comprising a melt-cooled concrete fine powder and having a substantially amorphous structure. 2. A method for manufacturing an aggregate, comprising melting concrete fine powder, cooling the same while maintaining a substantially amorphous structure, and pulverizing or crushing the cooled product. 3. The method for producing an aggregate according to claim 2, wherein the melting is performed by heating at 1300 ° C. or higher. 4. The method for producing an aggregate according to claim 2, wherein the cooling is performed at a cooling rate of 15 ° C./min or more. 5. The method for producing an aggregate according to claim 2, wherein particles obtained by pulverizing or pulverizing the cooled material are classified, and are composed of particles having a particle diameter of 0.6 mm or more.