JP2001097750A - Aggregate utilizing waste gypsum and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an aggregate utilizing a waste gypsum and excellent in mechanical strength without affecting hardening physical properties of a cement and to provide a method for producing the aggregate. SOLUTION: This aggregate utilizes a waste gypsum and is produced by covering the surface of a gypsum-based waste material such as a gypsum board with a hardened cement material subjected to a carbonating treatment. The method for producing the aggregate utilizing the waste gypsum comprises pulverizing the gypsum-based waste material, as necessary, granulating the resultant particles, then covering the surface with a cement-based raw material comprising a cement raw material and water, exposing the coated particles or grains to gaseous carbon dioxide under heating and pressurizing and carrying out a carbonating treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waste gypsum-based aggregate capable of effectively utilizing waste gypsum generated from gypsum board waste and the like, and a method for producing the same.

[0002]

2. Description of the Related Art At present, a gypsum board (gypsum board) having excellent fire resistance is used as a wall material for a house. Gypsum board used for a house is one of the waste materials generated in large quantities among the house waste materials generated when demolishing a house. Since such waste gypsum board is used after being bonded and combined with other materials at the time of commercialization and construction, it is difficult to use it again as gypsum board, and it is currently treated as waste. It is.

Further, when gypsum board powder obtained by pulverizing a gypsum board is directly added to a cement material and used, there is a problem that the physical properties of the cured product are deteriorated due to additives at the time of gypsum board production. Japanese Patent Application Laid-Open No. 10-45446 discloses a method for suppressing a decrease in physical properties at the time of addition to such a problem. However, when gypsum is directly added to the cement raw material, not only the sulfuric acid component has a large effect on the setting behavior of the cement, but also if added in large amounts, it may adversely affect long-term physical properties. However, the amount of gypsum is limited to a small amount, and a more effective field of application has been demanded.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in view of the state of use of the above-mentioned conventional gypsum material. For use in concrete materials,
It is an object of the present invention to provide a waste gypsum-based aggregate excellent in mechanical strength without affecting the hardened physical properties of cement and a method for producing the same.

[0005]

In order to achieve the above object, the present invention according to claim 1 is characterized in that the surface of a gypsum waste material is coated with a hardened cement which has been subjected to a carbonation treatment. To provide waste gypsum utilizing aggregate. Claim 2
The present invention according to claim 1, wherein the surface of the particles obtained by pulverizing the gypsum-based waste material is coated with a cement-based material composed of a cement raw material and water, and carbonized. An aggregate manufacturing method is provided.

Hereinafter, the present invention will be described in more detail. The gypsum-based waste material (hereinafter sometimes referred to as waste gypsum) in the present invention refers to waste when a material mainly composed of a gypsum component becomes unnecessary. The gypsum component may be any of anhydrous gypsum, gypsum hemihydrate and gypsum, and is not particularly limited as long as it is a material mainly containing a calcium sulfate component. The gypsum-based waste material may contain impurities other than gypsum. For example, when a gypsum board for a house wall material is used as the gypsum-based waste material, usually, a wallpaper, an adhesive, and the like are simultaneously contained.

In the present invention, the carbonized cement hardened body refers to a hardened body structure obtained by carbonating an unhydrated cement raw material and a cement hydrate. The carbonized hardened cement covers the surface of the gypsum-based waste material, and it is preferable that almost the entire surface be coated. Although the coating thickness is not particularly limited, it is preferable that the average film thickness be 0.5 mm or more in consideration of the fact that the coating does not collapse during handling when used as an aggregate.

[0008] In the present invention, the cement used for the production of the carbonized cement hardened body is not particularly limited as long as calcium hydroxide is produced with hydration. For example, ordinary portland cement, special portland cement Although portland cement and alumina cement can be used, Portland cement is preferable in that the effect of densification during the carbonation treatment is large.

Here, the Portland cement is a cement mainly composed of an unhydrated calcium silicate compound generally called alite (C3S: 3CaO.SiO2) or belite (C2S: 2CaO.SiO2). Portland cement such as ordinary Portland cement, early-strength Portland cement, ultra-high-strength Portland cement, moderate-heat Portland cement, low-heat Portland cement, sulfate-resistant Portland cement, various low-alkali portland cements, and blast furnace cement,
Examples thereof include mixed cements such as silica cement and fly ash cement, and white cements.

[0010] In the method for producing an aggregate utilizing waste gypsum according to the present invention, the surfaces of particles obtained by pulverizing gypsum waste are coated with a cement raw material composed of a cement raw material and water and subjected to a carbonation treatment. The method for grinding the gypsum waste material is not particularly limited, and an appropriate method may be used depending on the state of the waste material to be used. However, if the crushed waste material does not have an appropriate particle size as an aggregate (generally 25 mm or less in the case of coarse aggregate), an appropriate shape and strength, it may be granulated by an appropriate granulation method. preferable.

[0011] As an example of a method for granulating the gypsum-based waste material, a pulverized gypsum-based waste material is charged into a rolling-type granulator.
A method of granulating by adding water may be mentioned. When granulation is difficult using only gypsum waste and water, a binder such as cement may be added.

As a method of coating the surface of the particles obtained by pulverizing the above-mentioned gypsum-based waste material, if necessary, with a cement-based material composed of a cement raw material and water, preferably, after the granulation of the gypsum-based waste material, A method of coating the surface of the particles with a cement composition in which water is added to a raw material using a tumbling granulator. At this time, after adding only the cement first to the tumbling type granulator, water may be added as necessary, but the surface of the particles obtained by pulverizing the gypsum-based waste material finally has It is necessary to be coated with a cement-based raw material composed of a cement raw material and water.

The carbonation treatment in the present invention refers to a treatment in which an alkali component, particularly a calcium component, of a raw material or a cement hydrate during a cement hydration reaction undergoes a carbon dioxide reaction to be carbonated. As a method of the carbonation treatment, a method of exposing the particles coated with the cement-based raw material to carbon dioxide at an arbitrary concentration, preferably carbon dioxide under pressure, and in some cases, supercritical carbon dioxide may be mentioned. The carbonation treatment is performed after the surface of the particles is coated with the cement-based raw material to a final shape, and further, if necessary, the mold is retained to obtain the desired waste gypsum-based aggregate. Can be.

(Function) In the waste gypsum-based aggregate of the present invention, the surface of the gypsum waste material is coated with a hardened cement which has been subjected to a carbonation treatment, so that the coating film is very dense and has high strength. . In addition, the surface of the particles obtained by pulverizing the gypsum-based waste material is coated with a cement-based material and subjected to a carbonation treatment, so that the intended gypsum-based aggregate having a hard coating film formed thereon can be easily obtained. -It can be obtained easily. Since the surface of such waste gypsum-based aggregate is formed of a dense carbonated cement coating film, the amount of sulfate ion eluted when used as a cement or concrete material is suppressed. In addition, the strength of the granulated particles themselves increases if necessary. Further, according to the method for producing waste gypsum-based aggregate of the present invention, the surface of particles obtained by pulverizing gypsum-based waste material is coated with a cement-based material and subjected to a carbonation treatment to obtain a target hard material. A waste gypsum-based aggregate having a suitable coating film formed thereon can be obtained easily and simply.

[0015]

EXAMPLES (Example 1) Gypsum board generated as waste was pulverized by a pulverizer, and the obtained waste gypsum powder was averaged in a tumbling granulator (New Gla Machine manufactured by Seishin Co., Ltd.). Granulated to a diameter of about 3 mm. Thereafter, 60 parts by weight of ordinary Portland cement and 5 parts by weight of water are added to 100 parts by weight of the waste gypsum granule, and the surface of the gypsum waste material is coated with a cement raw material using a tumbling granulator. A granulated product was obtained. Thereafter, the granulated product was put in an autoclave, and the temperature was 100 ° C.
Carbon dioxide treatment was performed for 15 minutes under the condition of a pressure of 100 kg / cm 2 to obtain an aggregate.

(Comparative Example 1) A granulated product was produced in the same manner as in Example 1 except that the carbonation treatment was not performed, and natural curing was performed at room temperature for one week to obtain an aggregate. Comparative Example 2 The waste gypsum granulated in Example 1 was directly used as an aggregate without coating with cement.

* Aggregates produced according to Example 1 and Comparative Examples 1 and 2 were evaluated as follows, and the results are shown in Table 1. [Measurement of crush strength of aggregate] The obtained aggregate was crushed by a compression tester, and the load at the time of crush / cross-sectional area of aggregate (calculated from aggregate diameter) was measured as crush strength.

[Aggregate running test] The obtained aggregate was immersed in water for 1 month under running water, and the weight change before and after the test was measured. [Coagulation test of cement material] 50 parts by weight of the obtained aggregate was mixed with 100 parts by weight of cement and 30 parts by weight of water,
This mixture was subjected to a setting test. The setting test was performed by a setting test method using a general Vicat needle device, and the end time was measured. In parallel with this test, cement 100
When a coagulation test was carried out on a mixture containing only 30 parts by weight of water and 30 parts by weight of water, the termination time was 3 hours.

[Dimension change of cement material] 50 parts by weight of the obtained aggregate was mixed with 100 parts by weight of cement and 30 parts by weight of water to produce a square piece having a length of 150 mm and a length of 40 mm.
Room-temperature curing was performed for 28 days. After drying the obtained square bar at 60 ° C. for one day and measuring the initial size, it was heat-treated at 120 ° C. for 2 weeks, the size after the heat treatment was measured, and the shrinkage from the initial size was measured.

[0020]

[Table 1]

As can be seen from Table 1, the lightweight aggregate using waste gypsum produced in the examples is an aggregate having high strength and little elution components. Also, in the setting test, the hardening behavior was almost the same as the hardened state of the ordinary cement paste, indicating that the hardening behavior was hardly affected. In addition, the hardened cement body using these has a small dimensional change in the example, whereas the hardened body has a large dimensional change in the comparative example.

[0022]

The aggregate using waste gypsum of the present invention is constituted as described above, and the surface of the gypsum waste is covered with a dense, high-strength, carbonized cement hardened material, so that the aggregate can be used. In addition to its excellent mechanical strength, the dissolution of the calcium sulfate component is suppressed, so that it does not adversely affect the hardening behavior when mixed into the cement material or the durability of the manufactured hardened body. Therefore, gypsum-based material as waste can be recycled as aggregate, and in particular, since waste is used as a main material of aggregate, it is very useful from the viewpoint of effective use of waste. It is. Further, according to the method for producing waste gypsum-based aggregate of the present invention, the surface of particles obtained by pulverizing gypsum-based waste material is coated with a cement-based material and subjected to a carbonation treatment to obtain a target hard material. A waste gypsum-based aggregate having a suitable coating film formed thereon can be obtained easily and simply.

Claims (2)

[Claims] 1. An aggregate utilizing waste gypsum, wherein the surface of a gypsum waste material is coated with a cement hardened body subjected to a carbonation treatment. 2. The bone using waste gypsum according to claim 1, wherein the surface of the particles obtained by pulverizing the gypsum waste material is coated with a cement raw material consisting of a cement raw material and water and subjected to a carbonation treatment. The method of manufacturing the material.