JP2001122653A - Production process of carbonate hardened body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbonate hardened body production process for producing a carbonate formed body having sufficient material strength by forming a calcareous raw material and a siliceous raw material into a formed body and subjecting the formed body to carbonation to promote the carbonization to the inside of the formed body. SOLUTION: This process comprises forming a grainy powder in which a calcareous material and a siliceous material coexist into a formed body, and curing the formed body in the presence of gaseous carbon dioxide to form calcium carbonate within the formed body and to harden the formed body. The grainy powder, before formed into a formed body, is subjected to pulverization treatment causing a mechanochemical reaction in the powder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a carbon dioxide cured product of a molded product made of calcareous and siliceous raw materials, which is a material used for interior / exterior building or civil engineering material for buildings. Things.

[0002]

2. Description of the Related Art As a technique for hardening by reacting a raw material granule mainly composed of a calcium silicate compound obtained by mixing a calcareous raw material powder and a siliceous raw material powder with carbon dioxide gas,
There has been proposed a method for producing a hardened carbonic acid product in which a mixture of light-weight cellular concrete (ALC) or a cement-based hardened material granule and water is pressure-formed, and the formed body is reacted in a carbon dioxide gas atmosphere to be solidified. ing. (Japanese Patent Laid-Open No. 7-25
No. 679, Japanese Unexamined Patent Publication No. Hei 7-284628) These molding and solidifying techniques are based on the fact that a calcium component in a raw material is precipitated as calcium carbonate by a carbonation reaction, and is filled in voids between the raw material particles to form a binder. It is interpreted that the compact is solidified by performing the function. In addition, the more closely the calcium carbonate is filled into the voids, the more the resulting carbonized hardened material has a material strength (mechanical properties).
Is also known to increase.

[0003]

However, in the course of the carbonation reaction of the compact, a sufficient amount of cured carbon dioxide cannot be obtained even if a large amount of calcium carbonate is precipitated. The following speculation has been made for this reason. Calcite, one of the polymorphs of calcium carbonate, has a molar volume of 36.9 cc / m, while the molar volume of calcium hydroxide is 33.1 cc / mol.
ol and about 1.1 times, and the volume of the crystal lattice of the calcium carbonate crystal is larger than that of the calcium hydroxide crystal.
Therefore, even if the calcareous raw material powder and the siliceous raw material powder, which have been separately ground in advance, are simply mixed to produce a raw material, it is difficult to mix them at the molecular level, and a portion where the calcareous raw material is concentrated remains. When calcium carbonate crystals are generated in a portion where the calcareous raw material is concentrated in the molded body, the structure of the cured body is destroyed from the inside due to the volume expansion. As a result, the material strength of the cured body itself cannot be improved.

[0004] When a compact is formed from fine powder, the bulk density of the compact increases. Therefore, when the molded body is subjected to carbonation curing with carbon dioxide gas, the permeability of carbon dioxide gas into the molded body is reduced, and the carbonation inside the molded body is less likely to proceed. As a result, it was not possible to obtain a carbonic acid cured product having sufficient strength. Insufficient material strength of the cured body as described above causes a problem in long-term durability when used as a building material or the like. Therefore, an object of the present invention is to solve the above-mentioned problems, and to promote carbonation to the inside of a molded product formed from calcareous and siliceous raw materials, thereby producing a method for producing a cured carbonic material having sufficient material strength. Is to provide.

[0005]

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention is to form a granule in which calcareous and siliceous substances coexist and cure the formed body in the presence of carbon dioxide gas.
In a method for producing a cured carbonic acid product in which calcium carbonate is formed in a molded product and the molded product is cured, a method for producing a cured carbonic acid product in which a pulverizing treatment for causing a mechanochemical reaction on the powder before molding is performed.

[0006]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, after a pulverization treatment for causing a mechanochemical reaction is performed on a raw material powder in which calcareous material and siliceous material coexist, a molded material formed by the molding treatment is subjected to carbon dioxide gas. Curing to produce calcium carbonate in the molded product to produce a cured carbonic acid product.

[0007] Further, by performing a pulverization treatment for causing a mechanochemical reaction on a raw material powder in which calcareous and siliceous substances coexist, amorphous calcium silicate hydrate (CSH) is contained in the powder. ) Is generated. This amorphous calcium silicate hydrate (CSH) is unstable in terms of energy because it has a disordered crystal structure unlike crystalline calcium hydroxide (such as tobermorite). For this reason, Ca ²⁺ ions are easily eluted with respect to carbon dioxide gas curing, and calcium carbonate is precipitated more quickly than crystalline calcium silicate hydrate. By this action, the carbonation reaction easily and easily proceeds not only to the surface layer portion of the molded body but also to the inside of the molded body.

Further, fine particles of amorphous calcium silicate hydrate (CSH) produced by the pulverizing treatment are:
When Ca ²⁺ ions are eluted to further precipitate calcium carbonate, Ca ²⁺ ions eluted in the gap between the raw material particles precipitate calcium carbonate so as to fill the gap, so that the particles are closely bonded. It plays the role of a binder function to make it work.

In addition, the mixing and pulverization of the raw materials ensures sufficient mixing at the molecular level, thereby eliminating the concentrated portion of the calcareous raw material. As a result, tissue destruction from the inside of the hardened body caused by the difference in the crystal volume between calcium carbonate and calcium hydroxide is extremely reduced unlike the conventional case.
Furthermore, since the precipitated calcium carbonate crystal is sufficiently small, the bonding force between the particles is also increased. In addition, silica gel produced by elution of Ca ²⁺ ions from amorphous calcium silicate hydrate (C—S—H) shrinks in volume by itself, so that the internal structure of the cured product becomes more dense and the entire structure becomes denser. Improve material strength. It is known that the siliceous raw material basically does not react during the carbonation curing, and that the influence of the siliceous raw material on the material shrinkage is extremely small. For the above reasons, it is presumed that the material strength as a carbonic acid cured product can be improved.

The pulverizer for causing a mechanochemical reaction on the raw material powder is not particularly limited, and for example, a ball mill, a vibration mill, an attritor mill, a disk mill, or the like can be used. Further, a material having a large impact force during pulverization is preferable because a mechanochemical reaction can be caused in a short time. The particle size of the powder after the pulverization treatment is not particularly limited because it is crushed during pressure molding,
An average of 5 mm to 1 μm is desirable in terms of productivity or carbonation efficiency. When the particle size exceeds 5 mm, pressure molding becomes difficult. When the particle size is less than 1 μm, it becomes difficult for the carbonation gas to penetrate into the material. The pulverization can be either dry pulverization or wet pulverization. In the case of dry grinding, water, ethanol, ethylene glycol, triethanolamine and the like can be used as grinding aids.

The molar ratio of Ca / Si of the raw material powder is 0.2 to
A value of 4.0 is preferable because sufficient material strength can be obtained.
If the Ca / Si molar ratio is smaller than 0.2, a sufficient amount of calcium carbonate is not generated, so that the binder function cannot be sufficiently performed. The Ca / Si molar ratio is 4.
If it is larger than 0, the amount of calcium carbonate filled in the voids in the molded body becomes excessive, and the structural increase (crack) inside the cured body occurs due to the increase in the molar volume. Further, the molar ratio of Ca / Si is 0.3-1.
When the value is 0, the most appropriate carbonation state is obtained, so that the specific strength (strength / specific gravity) increases, and an inexpensive siliceous raw material can be sufficiently used. This Ca / S
The i molar ratio can also be obtained by mixing two or more types of raw material particles described in the following paragraph 0012, or adjusting the raw material particles by adding a calcareous and / or siliceous component to the raw material particles as necessary. it can.

The raw material particles are not particularly limited as long as they are mainly composed of calcareous materials, those mainly composed of siliceous materials, and those mainly composed of calcareous materials and siliceous materials. Powdered granules mainly composed of calcareous materials include slaked lime, quicklime, limestone and the like. Further, examples of the powdery granules mainly composed of siliceous materials include silica sand, fly ash, silica fume, glass, clay, and diatomaceous earth. In addition, powders mainly composed of calcareous and siliceous materials are used as cement, cement by-product (γ-C2S), granulated blast furnace slag, raw corn sludge, concrete, or cement-based secondary products (ALC (lightweight cellular concrete)). ,
Caical board, siding) and the like. Among them, fly ash, concrete waste, cement 2
It is preferable from the viewpoint of recycling to use industrial waste such as waste material of the next product, and furthermore, in the case of concrete waste material containing a large amount of calcareous material, the amount of calcium carbonate generated by carbonation increases, so that carbonation hardening with high material strength is performed. Being able to gain body is more desirable. The raw material particles may contain components other than calcareous and siliceous materials.

When diatomaceous earth mainly composed of siliceous material is used for the raw material powder, the cured carbonic acid product has a high material strength and has a pore structure of calcium carbonate and silica gel produced by the carbonation reaction. Thus, it is possible to obtain a member (cured body) having a humidity control function. Therefore, by processing this member into a board shape, for example, it can be used as an interior wall material having a humidity control function in a room, and is more suitable.

Further, it is more preferable that the calcareous substance be slaked lime, since water molecules in the component are easily released and amorphous calcium silicate hydrate (CSH) is easily formed. Further, when slaked lime is generated by reacting quicklime and water during or before the pulverizing treatment, heat of hydration is generated and the mechanochemical reaction rate by wet pulverization is increased, which is more preferable.

During the formation of the molded article, it is possible to simultaneously add additives such as reinforcing fibers, aggregates and pigments which do not affect the carbonation reaction. However, since these may be destroyed by pulverization, it is desirable to add them after the pulverization treatment. In addition, the water required for forming the molded body is:
If added before the pulverizing treatment, the powder and granules easily adhere to the inner wall of the pulverizer. Therefore, it is desirable to add water after the pulverizing treatment. Examples of the method for forming the molded body include pressure molding, casting, and papermaking. However, since pressure molding has a small amount of water, the drying time of the molded body can be shortened and the carbonation rate is increased. Further, press molding and extrusion molding can be applied as the pressure molding, but it is preferable because press molding can be easily performed even if the water content is low. If the pressing force at this time is in the range of 5 to 30 MPa, appropriate hardness for handling is obtained, and the molding apparatus can be downsized.

There are the following methods for carbonating and curing the compact in the presence of carbon dioxide gas. Reaction conditions are temperature 0-100 ° C,
The mixture is sealed and cured in a vessel having a carbon dioxide gas concentration of 2 to 100% to be cured. This method is industrially preferable, but it is also possible to use carbon dioxide gas or the like in the exhaust gas generated during combustion. In addition, the carbon dioxide gas pressure may be a negative pressure condition, but a high pressure is desirable because the reaction speed becomes faster.

The presence or absence of occurrence of a mechanochemical reaction can be confirmed by, for example, a change in lattice irregularity by X-ray diffraction, electron diffraction, solubility, thermal analysis, infrared spectrum, Raman spectroscopy, radial distribution analysis, ESR, It can be measured using a method such as NMR.

[0018]

EXAMPLES Examples of the present invention and comparative examples are shown below. (Example 1) ALC mainly composed of calcareous and siliceous substances
A case where a raw material granule in which a mechanochemical reaction is caused by mixing (lightweight cellular concrete) and slaked lime (having a calcareous component as a main component) is used is shown below. After crushing the autoclaved ALC and classifying it to 2 mm or less, 95 to 50 parts by weight of powdery granules, and slaked lime 5 to 50 parts
Parts by weight and an alumina ball mill (internal volume 1.
6L) to produce raw material particles pulverized for 2 hours and 4 hours. Analysis of this powder by X-ray diffraction shows that the diffraction intensity of slaked lime and tobermorite, which is a constituent of ALC, is low and the half-width of the diffraction line is large with the grinding time, and a mechanochemical reaction is occurring. It could be confirmed.

The granules were adjusted to a water content of 40%, pressed under a press pressure of 20 MPa, and subjected to a carbon dioxide gas concentration of 100%.
Carbonation was performed in the presence of a carbon dioxide gas pressure of 0.2 MPa for 24 hours. Table 1 shows the relationship between the crushing time and the bending strength of the cured product obtained as described above. As shown in Table 1, when the pulverizing treatment is performed and the time is lengthened, a carbonated cured product having greatly improved bending strength can be obtained, and the same tendency is observed regardless of the mixed composition ratio. Was done. In addition, the bending strength of the cured product tended to increase as the mixing ratio of slaked lime was increased. Further, from the results, it was confirmed that a sufficient bending strength to handle the cured body as a predetermined member was obtained by the pulverization treatment for 4 hours.

[0020]

[Table 1]

(Example 2) A case in which fly ash mainly composed of siliceous material and slaked lime (mainly calcareous material) are mixed to use a raw material granule in which a mechanochemical reaction is caused is used. Shown in 90 to 60 parts by weight of fly ash and 10 to 40 parts by weight of slaked lime were mixed and pulverized by an alumina ball mill for 2 hours and 4 hours to produce raw material particles. When this powder was analyzed by X-ray diffraction, it was confirmed that the slaked lime had a low diffraction intensity and a large half-value width of the diffraction line with the pulverization time, and that a mechanochemical reaction had occurred.

The powder was adjusted to a water content of 5%, pressed under a press pressure of 20 MPa, and carbonized for 24 hours in the presence of a carbon dioxide gas concentration of 100% and a carbon dioxide gas pressure of 0.2 MPa. Table 2 shows the relationship between the pulverization time and the bending strength of the obtained cured product. As shown in Table 2,
The following results similar to those in Example 1 were obtained. 1) When the pulverizing treatment is performed and the time is extended, the bending strength of the cured product is greatly improved, and the same tendency is observed in any case of the mixed composition ratio. 2) As the mixing ratio of slaked lime was increased, the flexural strength of the cured product increased.

[0023]

[Table 2]

(Example 3) A case in which raw material granules in which a mechanochemical reaction is caused is used for raw consludge mainly composed of calcareous and siliceous materials is described below. The raw consludge was dried, coarsely crushed by a jaw crusher, and then pulverized by an alumina ball mill for 1 hour to produce raw material particles. When the powder and granules were analyzed by X-ray diffraction, it was confirmed that the diffraction intensity of slaked lime, which is a constituent of raw con sludge, was low and the half-value width of the diffraction line was large, and that a mechanochemical reaction had occurred.

This granule was adjusted to a water content of 20%, and pressed under a press pressure of 20 MPa to obtain a carbon dioxide gas concentration of 100%.
Carbonation was performed in the presence of a carbon dioxide gas pressure of 0.2 MPa for 24 hours. Table 3 shows the relationship between the crushing time and the bending strength of the cured product obtained as described above. As shown in Table 3, it was confirmed that the pulverization treatment significantly improved the bending strength of the cured product.

[0026]

[Table 3]

(Example 4) The following describes a case in which raw material granules having a mechanochemical reaction are used as waste concrete containing lime and silicate as main components. 17 parts by weight of ordinary Portland cement, 32 parts by weight of fine aggregate, 44 parts by weight of coarse aggregate, and 7 parts by weight of water were kneaded, cast into a mold, and cured in a room for one year. The bulk density of this concrete is 228
The bending strength was ³ kg / m ³ and the bending strength was 5.33 MPa. After coarsely crushing this concrete to remove coarse aggregate, it was pulverized by an alumina ball mill for 1 hour and 2 hours to produce raw material particles. Analysis of this powder by X-ray diffraction confirmed that the mechanochemical reaction occurred as the diffraction intensity of slaked lime, which is a constituent of concrete, decreased and the half-width of the diffraction line increased with the crushing time. Was.

This powder was adjusted to a water content of 5%, pressed under a press pressure of 20 MPa, and carbonized for 72 hours in the presence of a carbon dioxide gas concentration of 100% and a carbon dioxide gas pressure of 0.2 MPa. Table 4 shows the relationship between the pulverization time and the bending strength of the cured product obtained as described above. As shown in Table 4, it was confirmed that when the pulverizing treatment was performed and the time was extended, the bending strength of the cured product was greatly improved.

[0029]

[Table 4]

(Example 5) A case where a raw material granule in which a mechanochemical reaction is caused is used for lightweight cellular concrete (ALC) mainly composed of calcareous and siliceous materials is described below. Powder and granules 10 crushed ALC and classified to 2 mm or less
0 parts by weight using an alumina ball mill for 30 minutes and 1
The raw material powder was produced by pulverizing for a time. Analysis of this powder by X-ray diffraction shows that ALC
It was confirmed that the diffraction intensity of tobermorite, which is a component of the above, was low and the half width of the diffraction line was large, and that a mechanochemical reaction had occurred.

The powder was adjusted to a water content of 40%, pressed under a press pressure of 20 MPa, and subjected to a carbon dioxide gas concentration of 100%.
Carbonation was performed in the presence of a carbon dioxide gas pressure of 0.2 MPa for 24 hours. Table 5 shows the relationship between the crushing time and the bending strength of the cured product obtained as described above. As shown in Table 5, it was confirmed that when the pulverizing treatment was performed and the time was extended, the bending strength of the cured product was greatly improved.

[0032]

[Table 5]

(Comparative Example) Slaked lime and fly ash were separately pulverized by an alumina ball mill for 4 hours to produce two types of powders. Then, the obtained two kinds of granules were mixed at a ratio of 10 to 40 parts by weight of slaked lime and 90 to 60 parts by weight of fly ash to produce raw material granules. Even when the powder and granules were analyzed by X-ray diffraction, the diffraction intensity of slaked lime and the half-value width of the diffraction line hardly changed from those before the pulverization treatment, and the occurrence of a mechanochemical reaction was not confirmed.

The granules were adjusted to a water content of 5%, pressed under a press pressure of 20 MPa, and further pressurized at a carbon dioxide gas concentration of 100% and a carbon dioxide gas pressure of 0.2 MPa.
Carbonation was performed for hours. Table 6 shows the relationship between the pulverization time and the bending strength of the cured product obtained as described above. In comparison with the results of Table 2 (Example 2) in which a mechanochemical reaction was caused in the raw material granules by the pulverization treatment, as shown in the results of Comparative Examples in Table 6, in any case of the mixture composition ratio,
A remarkable difference was found in the bending strength of the cured product. That is, by causing a mechanochemical reaction to occur in the raw material particles, it is possible to obtain a hardened carbonic acid material having significantly increased bending strength.

[0035]

[Table 6]

[0036]

According to the present invention, carbonation is sufficiently advanced to the inside of a compact in which calcareous and siliceous materials coexist, and the raw material particles are closely bonded to each other. Can be obtained. Thereby, when the present carbonated cured product is used for a building material, it has an effect of being excellent in long-term durability.

Continued on the front page (72) Inventor Kenji Inagaki 2035 Shimoi-machi, Shioi-machi, Owariasahi-shi, Aichi F-Term in Building Materials Techno-Laboratory Co., Ltd. 4G012 PA30 PB03 PE03 PE05 RA02

Claims (5)

[Claims] 1. Carbonation hardening in which a granule in which calcareous and siliceous materials coexist is formed, and the formed body is cured in the presence of carbon dioxide gas, thereby generating calcium carbonate in the formed body and hardening the formed body. A method for producing a carbonic acid cured product, comprising: performing a pulverizing treatment for causing a mechanochemical reaction on a granular material before molding. 2. The Ca / Si molar ratio of the powder is 0.2
2. The method for producing a cured carbonic acid product according to claim 1, wherein 3. The granules are: 1) slaked lime, quicklime, limestone mainly composed of calcareous material, 2) silica sand, fly ash, silica fume, glass, clay, diatomaceous earth mainly composed of silicate, 3) calcareous And one or more of the powdery and granular materials described in Cement, cement by-product (γ-C2S), granulated blast furnace slag, raw concrete sludge, concrete, or cement-based secondary products The method for producing a cured carbonic acid product according to claim 1 or 2, wherein calcareous and / or siliceous materials are added as necessary. 4. The method according to claim 1, wherein the calcareous material is slaked lime.
Or a method for producing a cured carbonic acid product according to item 3. 5. The method for producing a cured carbonic acid product according to claim 1, wherein said slaked lime is produced by reacting quicklime and water during or immediately before the pulverizing treatment.