JP3386225B2 - Method for producing carbonic acid-cured molded product and precursor thereof, and moisture absorbing / releasing material comprising the molded product - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention utilizes a reaction between calcium silicate hydrate and carbon dioxide gas to adjust the humidity inside a building, that is, a building material excellent in moisture absorption and desorption.
The present invention relates to a carbonic acid-cured molded product having a low specific gravity and high strength, which is useful as a civil engineering material or a filtering material, a method for producing a precursor effective for obtaining the same, and an application of the cured molded product.

[0002]

2. Description of the Related Art Conventionally, a technique for carbonating a molded body of lightweight cellular concrete is known (column of Comparative Example 2 of Japanese Patent Publication No. 55-23787). However, if this technique is carried out without particular ingenuity, the cured product obtained by the carbonation reaction (hereinafter referred to as the carbonation-cured molded product) may have reduced strength or cracks, There is a problem of so-called neutralization inferiority. For example, a molded product of ALC, which is a typical example of lightweight cellular concrete, is usually 15 to 1
It has a bending strength of 8 kgf / cm ^{2, but} the bending strength of the carbonation-cured molded product from this molded product is 0 to 10 kgf.
/ Cm ² and decrease. Furthermore, not only the bending strength is reduced,
There is also a problem that as the size of the material increases, more cracks occur and the utility value of the material itself is lost.

Moreover, in recent years, highly hermetically sealed and highly heat-insulated buildings suffer from adverse effects due to changes in humidity. For example, the moisture generated in the room is condensed on the wall surface, which causes (1) mold to spoil the appearance. (2) Shorten the life of the building itself. (3) Occurrence of mold and mites causes health problems of residents. On the contrary, when it is extremely dry, it may hurt the residents' throat and adversely affect buildings, furniture and paintings. In order to deal with such adverse effects and adverse effects, building materials having excellent moisture absorption and desorption properties have been conventionally used. Typical examples are wood, calcium silicate materials and zeolite composite materials. Wood has poor fire resistance and dimensional stability,
Since the calcium silicate material and the zeolite composite material do not have sufficient moisture absorption and desorption amount, there is a problem that the interior of the building using them becomes completely dry. An object of the present invention is to provide a method for producing a carbonate-cured molded product and a precursor thereof, which can suppress the above problems to a minimum, and an application of the molded product.

[0004]

In order to solve the above-mentioned problems, the invention according to the first aspect of the present invention comprises mixing powdery particles of lightweight cellular concrete with water, and molding the resulting mixture under pressure. And that the obtained molded body is cured in a carbon dioxide atmosphere. The invention of claim 6 is
The mixing granular material and water lightweight concrete and the resulting mixture employing a means of molding under pressure. A ninth aspect of the present invention is characterized in that the carbonic acid-cured molded product obtained in the first aspect is used as a moisture absorbing / releasing material such as an inner wall of a room of a building.

[0005]

The operation of the present invention is physically explained as follows. Once the light-weight cellular concrete compact is made into a powder, then the mixture of the powder and water is made into a compact again.
The reason why the decrease in bending strength is suppressed by subjecting it to a carbonation reaction as compared with the prior art that does not go through the granular material is not always clear, but it can be considered as follows.

Shrinkage phenomenon observed in carbonation reaction of ordinary concrete {"Comprehensive data on cracks in concrete" No. 29
9-900 pages (1977) Chubu Development Management Center Edition}
Is also found in the carbonation reaction of lightweight cellular concrete compacts made from siliceous raw materials, calcareous raw materials and water. When lightweight cellular concrete shrinks due to carbonation, it is sufficient that its structure shrinks uniformly and entirely, but as a concept, it shrinks while forming blocks. From now on, microscopic and macroscopic cracks will be created. In addition, when the molded product subjected to the carbonation reaction becomes large , the carbonation reaction occurs from the surface, and this becomes apparent as the strength of the entire carbonation-cured molded product decreases.

On the other hand, the precursor to be subjected to the carbonation reaction is a powder of light-weight cellular concrete which is pressure-solidified in the presence of water. The close-contacted granules reduce the shrinkage of the material due to the carbonation reaction and suppress cracking. Further, since the precursor is a solidified body of powder and granules, carbon dioxide gas is allowed to enter the inside of the precursor to uniformly promote carbonation of the molded body, and as a result, the strength of the carbonation-cured molded body as a whole is reduced. Suppress.

Further, the action of the present invention is chemically understood as follows. When powder and particles of lightweight cellular concrete are mixed with water, not only water acts as a fluidizing agent for fluidizing the particles, but also acts as a binder for strength development of the precursor, in addition, During the subsequent carbonation reaction, carbon dioxide is dissolved into carbon dioxide. Then, the obtained mixture is molded under pressure to obtain a molded product having a predetermined shape.
When this molded product is aged in an atmosphere of carbon dioxide gas, the calcium silicate hydrate of the light-weight cellular concrete forming the molded product is attacked by hydrogen ions of carbonic acid to elute calcium ions.

This calcium ion reacts with hydrogen carbonate ion or carbonate ion to form calcium hydrogen carbonate or calcium carbonate, and reinforces the strength of the carbonic acid-cured molded product. Calcium silicate hydrate, from which calcium ions have been eluted, turns into a silica skeleton gel with many pores, and these pores increase the specific surface area of the carbonation-cured molded product, exerting the function of absorbing and releasing moisture. To do. The silica skeleton is obtained by observing the cross section of the carbonic acid-cured molded article with an electron microscope and X-ray diffraction, and by wet analysis in which a part of the molded body is sequentially treated by salicylic acid treatment, hydrochloric acid treatment, alkaline solution treatment and the like. You can judge. For details, see “The 47th Cement Technology Conference Lectures”, 450-455.
Page (1993) and "Proceedings of the 45th Cement Technology Conference", pages 270-275 (1991).

The scope of application of the present invention will be described below. The lightweight cellular concrete used in the present invention is obtained by mixing aluminum metal powder, an organic foaming agent or a lightweight aggregate into a water slurry containing siliceous raw materials and calcareous raw materials as main components, and setting it in a mold to cure it. After that, it is produced by autoclaving or steam curing, and contains 10 to 35% by weight of calcium in terms of calcium oxide. ALC is a typical example of such lightweight cellular concrete.

The precursor material of the present invention is a powder or granular material obtained by crushing and crushing the lightweight cellular concrete compact produced as described above. It is possible to utilize the grinding powder particles that are generated during the process. The powder particle size of the powder granules greatly affects the physical properties of the precursor and the carbonic acid-cured molded product, particularly the strength. In order to obtain a carbonation-cured molded product having high strength, it is used as a powder of light-weight cellular concrete in 0.5 by the Blaine measurement method.
It is better to adjust the powder particle size so that the powder particle size is about 1.2 m ² / g (Blaine value).

When the Blaine value is less than 0.5 m ² / g, the frequency of contact between the powder and granules due to pressure molding becomes low, so that the strength of the precursor becomes low and, as a result, the carbon dioxide is obtained by subsequent carbonation. Also, the strength of the molded body becomes low. Therefore, when the large-sized carbonation-cured molded product is manufactured, the cured molded product is easily cracked. On the other hand, when powder particles having a Blaine value of more than 1.2 m ² / g are used, the energy required for pulverization becomes large. In addition, a press machine having a large pressurizing capacity is required for press molding.

Further, the water mixed with the particles of the lightweight cellular concrete may be used in an amount of 40 to 60 parts by weight with respect to 100 parts by weight of the particles in order to exert the above-mentioned effects. desirable. If the amount of water mixed is less than 40 parts by weight, the strength of the precursor itself is reduced and the strength of the precursor itself is reduced because the bond between particles due to water is insufficient during the production of the precursor, that is, during press molding. In the carbonation reaction, especially the forced reaction of compressed carbon dioxide,
The precursor is damaged and becomes less strong. Also, the precursor
When the size is increased, cracks are likely to occur from the peripheral portion toward the center.

On the other hand, if the amount of water mixed exceeds 60 parts by weight, extra pressurizing energy is required to produce excess water during the molding of the precursor. In some cases, the raw material flows out with excess water, the pressure does not rise, and the specific gravity and strength of the carbonation-cured molded product decrease. Further, the carbonation-cured molded product causes delamination. As a pressure molding method, pressure molding such as uniaxial pressing, rolling, and extrusion can be used. However, since the pressurizing condition has a great influence on the physical properties of the precursor and the carbonation-cured molded product, the pressing force for manufacturing the precursor is 50 to 300 k.
A range of gf / cm ² is desirable.

If the applied pressure is less than 50 kgf / cm ² , the molded body will not be dense, and it will be difficult to handle the molded body itself, and cracks will occur due to carbonation. On the other hand, if it exceeds 300 kgf / cm ² , the precursor becomes too dense and the carbonation reaction slows down, and a huge press machine is required to prepare a large-sized compact.

The precursor produced as described above suppresses the decrease in bending strength even if it is subjected to a carbonation reaction alone, and becomes an excellent intermediate product for producing a carbonation-cured molded article. Therefore , this intermediate product is subsequently subjected to a carbonation reaction in a carbon dioxide atmosphere. The reaction conditions include the concentration of carbon dioxide, temperature, relative humidity, pressure, presence or absence of a vacuum step before the reaction, etc., but normally the concentration of carbon dioxide is 2 to 100%, and the temperature is room temperature to
100 ° C, relative humidity 80% or more, pressure is atmospheric pressure to 10
The range of atmospheric pressure is industrially preferable.

[0017]

Comparative Example 1 Next, the effects of the present invention will be specifically described with reference to Comparative Examples and Examples. First, a method for obtaining a compact of lightweight cellular concrete from a starting material and an experiment in which the compact is subjected to a carbonation reaction without crushing are shown as comparative examples. 60 parts by weight of silica powder, 17 parts by weight of lime powder, 20 parts by weight of cement and 3 parts by weight of gypsum were stirred and mixed with 70 parts by weight of water, and the mixture was poured into a mold in the presence of aluminum powder. The raw material slurry obtained by casting was left as it was for about 3 hours to be foam-cured. The obtained foamed cured product was placed in an autoclave and cured in a steam atmosphere at 180 ° C. and about 10 atm for about 6 hours to produce an ALC molded body.

It was found from the X-ray diffraction pattern that the main product of the ALC molded product was tobermorite. Further, the shaped body is a specific gravity 0.52, compressive strength 62kgf / cm ^2, the flexural strength 15 kgf / cm ^2, the specific surface area by BET method was 20.5 m ² / g. 100 × this molded body
After cutting into a size of 100 × 20 mm to make it saturate, it was placed in a container controlled to have an atmosphere of a temperature of 30 ° C. and a relative humidity of 98%, and carbon dioxide gas having a concentration of 3% was fed. After carrying out the carbonation reaction for 20 days, the carbonation rate with respect to the amount of calcium in the obtained carbonation cured product was determined from the amount of carbon dioxide gas generated by the acid treatment. In addition, the carbonation cured product is 100 × 25 × 20
It was cut into a size of mm and its specific gravity and bending strength were measured. The results are shown in Table 1 as Comparative Example 1.

[0019]

Example 1 Next, an example in which the present invention is embodied using the ALC molded body produced in Comparative Example 1 will be shown. First, the ALC molded body manufactured in Comparative Example 1 was crushed. At this time, the Blaine values of 0.87 and 1.07 were changed by changing the time required for crushing.
And 1.15 m ² / g of granules were produced. 50% by weight of water based on 100 parts by weight of these powders and granules was added and uniformly mixed, and then placed in a mold to obtain 100 kgf.
Pressure molding was performed at a pressure of / cm ² to obtain a molded body having the same size as in Comparative Example 1. The specific gravity of the obtained molded product when dried was 1.
0, the bending strength was 15 to 17 kgf / cm ² . This molded body was allowed to stand still in a container set in an atmosphere having a temperature of 30 ° C. and a relative humidity of 98%, and carbon dioxide gas having a concentration of 3% was fed. After changing the carbonation reaction time variously, the carbonation-cured molded product was taken out of the container and dried at 105 ° C. for 24 hours,
The reaction rate, specific gravity and bending strength were measured. The results are shown in Table 1. The specific gravity and bending strength increased with the carbonation reaction. Particularly increased Blaine Then, a large strength increase reaction rate even identical.

[0020]

[Table 1]

[0021]

Example 2 In this example, how the water content in the ALC molded product affects the physical properties of the carbonation cured product is examined.
The ALC molded body produced in Comparative Example 1 had a Blaine value of 0.
It was crushed to 87 cm ² / g. The obtained granular material was dried at 105 ° C. for about 24 hours until the weight became constant. 25 to 65 parts by weight of water was added to the dried powdery granules every 5 parts by weight, and they were mixed so as to be uniform. Put the mixed powder and granules in a mold and put 100kgf /
It was pressure molded at a pressure of cm ² . Put the demolded compact into a closed container and degas it with a vacuum pump to about -50 mmHg.
Subsequently, carbon dioxide gas was fed up to 2 atm. The temperature was not controlled, and the carbonation reaction was carried out at room temperature in the range of 20 to 28 ° C. Even under these conditions, the molded body generated heat due to the carbonation reaction, and the temperature was 60
Temperature rises to ~ 80 ° C. After sending pressurized gas, about 10
The carbonation-cured molded body was taken out for a certain period of time, dried at 105 ° C. for 24 hours, and then the reaction rate, specific gravity and bending strength of the carbonated cured molded body were measured, and the results shown in FIG. 1 were obtained.

In this example, the carbonation rate of the carbonation-cured molded product was 90% or more. If the amount of water added to the granules is less than 40 parts by weight, the specific gravity is low and the strength is not high under the same pressure condition. Further, as in the present example, the rapid reaction by the compressed gas damaged the carbonation-cured molded product, and it was confirmed that cracks were generated from the peripheral portion of the cured molded product toward the center. On the other hand, if the amount of water added to the granules exceeds 60 parts by weight,
The fluidity of the granular material sharply increased, and part of the granular material itself flowed out as the water was discharged. In this case, the strength is also low, and cracks such as breaking occur or delamination occurs. It is considered that delamination occurs because excess water moves in a direction orthogonal to the pressing direction during pressure molding.

[0023]

[Example 3] When a mixture of powder and granules and water was pressure-molded to produce a molded body, it was observed how the applied pressure affects the physical properties of the carbonation-cured molded body. The ALC molded body prepared in Comparative Example 1 was pulverized to a Blaine value of 1.07 m ² / g. Water was added so that the water content was 50 parts by weight per 100 parts by weight of the obtained powder and granules, and both were uniformly mixed. The granules mixed with water were put into a mold and pressure-molded.

A molded body as a precursor obtained after demolding was placed in a closed container and deaerated to about -50 mmHg by a vacuum pump, and then carbon dioxide gas was fed up to 2 atm to carry out a carbonation reaction. It was The reaction temperature is not controlled and the room temperature is 20 to
Carbonation reaction was carried out in the range of 28 ° C. About 1 hour after feeding the pressurized gas, the carbonation-cured molded product was taken out and kept at 105 ° C.
After drying for 24 hours, the reaction rate of the carbonation-cured molded product,
The specific gravity and bending strength were measured and the results shown in Table 2 were obtained.
In this embodiment , 70% or more of the precursor is carbonated under the above curing conditions to form a carbonation-cured molded product. Applied pressure is 50kg / cm
^When it was ² or less, not only the specific gravity and the strength were low, but also cracks were generated from the peripheral portion to the central portion of the carbonation-cured molded product. Further, it was observed that a part of the powder and granules could not be formed into a compact and remained on the surface.

[0025]

[Table 2]

[0026]

Example 4 Sample No. 2 described in Table 1 of Example 1
Under the same conditions as in -9, a molded body made of a carbonation-cured molded body having dimensions of 100 x 100 x 12 mm was prepared. For comparison, well-known ALC, gypsum board, cypress wood, lauan plywood (plywood), fiber-reinforced calcium silicate-based artificial wood (artificial wood), and zeolite cement panel (zeolite board) were cut into the same size as above. These test specimens at 60 ° C
100 x 100 after drying for 24 hours under
The remaining 5 surfaces were covered with an aluminum adhesive tape, leaving one mm surface. These test pieces were weighed and then placed in a constant temperature and constant humidity chamber, and the conditions of 20 ° C., relative humidity 60% and 20 ° C. relative humidity 30% were alternately held for 96 hours respectively, and the moisture absorption amount was measured by weighing over time. It was measured. The result is shown in FIG. 2 as the amount of moisture absorption per unit area.

As a result, as is clear from FIG. 2, the initial moisture absorption from the dry state is about 30 g / gypsum board.
m ^2, ALC Te about 60 g / ^{m 2,} about 200 g / ^{m 2} of natural wood such as Hinoki and plywood, whereas about 200 g / ^{m 2} in artificial wood and zeolites plate, the molded article of the present invention It was as large as about 630 g / m ² . Further, moisture absorption change natural wood with humidity changes, while the change in the moisture absorption of artificial wood and zeolite plate is about 150 g / m ^2, moisture absorption amount of change of a molded article according to the present invention is about 33
It is as large as 0 g / m ² and exhibits a moisture absorption / release property superior to that of natural wood. The present invention can be carried out by partially modifying the above-described embodiment within the scope of not significantly impairing the effects of the invention by following the fundamental technical idea. For example, reinforcing fibers, fillers, binders and the like can be mixed in the precursor, the carbonation-cured molded product or the moisture absorbing / releasing material. In this case, as the reinforcing fibers, it is possible to use organic fibers such as wood fibers and synthetic fibers, inorganic fibers such as glass fibers, carbon fibers and various mineral fibers. The carbonation reaction is preferably performed at room temperature and neutrality. This is because glass fibers and synthetic fibers can be used. The reinforcing fiber is added in an amount of 0.5 to 5.0% by volume to improve the strength and toughness of the molded product.

The filler can be used for ordinary cement moldings such as silica sand, diatomaceous earth, clay minerals other than the above, amorphous silica, slag, fly ash, shirasu balloon, lightweight aggregate, resin particles and the like. Various fillers can be used in the range of 50% by volume or less. When manufacturing a large-sized molded product, a high strength is required for the precursor, and thus it is better to use a binder. In that case, polyvinyl alcohol, polyethylene glycol, or the like is used as the hydrophilic binder.

Since the molded product according to the present invention exhibits excellent moisture absorption and desorption properties as described above, it is used as a building material for interiors of houses such as partitions, floors, ceilings, wall surfaces of closets, storage containers for works of art, exhibits in museums and museums. It can be effectively used for interior walls of rooms and warehouses.

[0030]

As described above in detail, unlike the prior art in which the lightweight cellular concrete compact is carbonated as it is,
After the molded body is once formed into a powder and granules, the powder and granules are mixed with a specific medium, molded, and then subjected to a carbonation reaction. Not only can the problems of so-called neutralization inferiority, such as strength reduction and cracking, be solved, but the moisture absorption and desorption properties can be significantly enhanced, which is an excellent effect.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between water content, flexural strength and specific gravity in Example 3.

FIG. 2 is a diagram showing the moisture absorptive and desorptive properties of a molded article in Example 4.

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Claims (10)

(57) [Claims] 1. Carbonation-hardening molding comprising mixing powder of light-weight cellular concrete with water, molding the mixture obtained under pressure, and curing the obtained molding in a carbon dioxide atmosphere. How to make a body. 2. The method for producing a carbonate-cured molded article according to claim 1, wherein the lightweight cellular concrete contains tobermorite. 3. The method for producing a carbonic acid-cured molded article according to claim 1, wherein the specific surface area of the powdery or granular material is 0.5 to 1.2 m ² / g by the Blaine measurement method. 4. The mixture is 50 to 300 kgf / cm.
^Two The carbonic acid-cured molded article according to claim 1, which is pressurized at a pressure of
Method of manufacturing. 5. Water is added to 40 parts by weight of 100 parts by weight of powder and granules.
The method for producing a carbonic acid-cured molded article according to claim 1, wherein the carbonic acid-cured molded article is mixed in a proportion of about 60 parts by weight. 6. A method for producing a precursor for a carbonate-cured molded body, which comprises mixing water-mixed powder of light-weight cellular concrete with water and molding the resulting mixture under pressure. 7. A method of lightweight cellular concrete to produce a precursor for carbonated cured molded article of claim 6 wherein containing the tobermorite. 8. The specific surface area of the powder or granular material is 0.5~1.2m ² / g in Blaine assay, wherein the mixture 50
The method for producing a precursor for a carbonate-cured molded article according to claim 6 , wherein the precursor is pressurized at a pressure of 300 kgf / cm ² . 9. Water is added to 40 parts by weight of 100 parts by weight of powder and granules.
The method for producing a precursor for a carbonate-cured molded article according to claim 6 , wherein the precursor is mixed in a proportion of about 60 parts by weight. 10. A moisture absorbing / releasing material, which is a carbonate-cured molded product of a lightweight cellular concrete powder, the molded product containing a silica skeleton gel.