JP2000178056A - Aerated lightweight concrete excellent in carbonization resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an aerated lightweight concrete(ALC) which does not undergo the deterioration of durability because it is excellent in resistance to carbonization phenomenon as one of deteriorations. SOLUTION: The aerated lightweight concrete contains 1×1013-2×1018, preferably 1×1016-1×1018 organopolysiloxane molecules per 1m2. All side chains of the organopolysiloxane are functional groups having no oxygen atom. Each side chain of the organopolysiloxane preferably has one or more >=2C alkyl groups in one molecule.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to lightweight cellular concrete (AL) used for walls, roofs, floors and the like of buildings.
With respect to C), A is particularly excellent in carbonation resistance against the carbonation phenomenon, which is one of the deteriorations, and therefore does not deteriorate in durability.
LC.

[0002]

2. Description of the Related Art A steel plate having a reinforcing bar built therein and formed in a plate shape.
ALC panels made of LC are used for building walls, roofs, floors, and the like.

[0003] The ALC panel mainly comprises a siliceous raw material such as silica stone and a calcareous raw material such as cement and quicklime.
After adding additives such as water and aluminum powder to these fine powders to form a slurry, the mixture is poured into a mold in which reinforcing steel bars are arranged, foamed by the reaction of the aluminum powder, and semi-cured by the reaction of the calcareous raw material. Then, after being formed to a predetermined size, it is manufactured by performing high-temperature and high-pressure steam curing using an autoclave. The ALC panel is widely used as a building material because it is lightweight and has excellent fire resistance, heat insulation, and workability.

[0004] As described above, ALC contains air bubbles and pores therein, and it is advantageously used as lightweight concrete having an absolute dryness of specific gravity of about 0.5. Occupies 80% and has a microstructure with very large voids, so that moisture and gas easily enter the ALC. The main constituent mineral of ALC is tobermorite, which reacts with carbon dioxide in the presence of moisture to decompose into silica gel and calcium carbonate. This is carbonation.

[0005] Carbonation causes deterioration of ALC such as a decrease in strength and generation of cracks. Therefore, in order to prevent or delay carbonation, means for preventing intrusion of moisture or carbon dioxide gas, or means for imparting a function of carbonation resistance to tobermorite is required. Heretofore, means for preventing the intrusion of moisture or carbon dioxide gas has been exclusively used by ALC surface finishing. However, the improvement of the carbonation resistance by the surface finish is not sufficient, and it has been confirmed that even in the ALC having the surface finish, the carbonation proceeds with the service life. On the other hand, no industrially effective means has been found as a means for imparting a function of carbonation resistance to tobermorite, which is expected as a fundamental measure, despite various studies.

[0006]

SUMMARY OF THE INVENTION In view of the above problems, the present invention provides an ALC having excellent carbonation resistance.

[0007]

In order to solve the above-mentioned problems, a lightweight cellular concrete (ALC) having excellent carbonation resistance according to the present invention comprises an organopolysiloxane having a molecular weight per unit surface area of 1 × 10 ^{13. ２2} × 10 ¹⁸ / m ² , preferably 1 × 10 ¹⁶ to 1 × 10 ¹⁸ / m ² .

In the organopolysiloxane, it is preferable that all the functional groups on the side chains are functional groups having no oxygen atom.

Furthermore, it is preferable that the functional group of the side chain of the organopolysiloxane has at least one alkyl group having 2 or more carbon atoms in one molecule.

[0010]

DETAILED DESCRIPTION OF THE INVENTION Heretofore, organopolysiloxanes have been added to impart water repellency to ALC and siliceous building materials. Regarding water repellency, the addition of organopolysiloxane has mainly been used to change the contact angle between the material and water to prevent water from entering the porous ALC or siliceous building material by capillary action. .

On the other hand, the problem in carbonation is not liquid water, but gaseous water vapor or surface-adsorbed water of about six molecules, and the effect of carbonation resistance by organopolysiloxane has not been confirmed. Was.

However, as a result of various studies, the present inventors have found that the addition of an organopolysiloxane has an effect on the carbonation resistance of tobermorite. It was found to be different from the more effective organopolysiloxanes.

[0013] In various patent publications,
An invention has been disclosed which regulates the amount of an organopolysiloxane to be added to a raw material in an early stage of production of ALC or a siliceous building material. However, ALC and siliceous building materials exhibit strong alkalinity in the production stage and are cured by high-temperature and high-pressure steam in an autoclave, so that a part of the organopolysiloxane which decomposes at an acid, alkali and high temperature is decomposed. And that the degree of decomposition varies depending on the type of organopolysiloxane.

Therefore, in order to determine the amount of the organopolysiloxane to be added, it is necessary to quantify the amount of the organopolysiloxane in the ALC or the siliceous building material at the end of the production process. In addition, when the number of molecules per unit surface area of the organopolysiloxane is determined from the content of the organopolysiloxane and the specific surface area of the material, the relationship between the organopolysiloxane and the type of the organopolysiloxane is largely unaffected. Becomes clear.

The organopolysiloxane is adsorbed on the surface of the material by an intermolecular force or a hydrogen bond.
Since the specific surface area of LC and siliceous building materials greatly varies depending on the raw materials and manufacturing conditions, it is unscientific to simply specify the addition amount, and it was originally specified as the molecular weight per unit surface area and added. I should have done.

Here, the number of molecules per unit surface area is defined by the following equation (Equation 1).

[0017]

## EQU1 ## Number of molecules per unit surface area (pieces / m ² ) = (AL
C. Content of organopolysiloxane in 1 g (g) / molecular weight of organopolysiloxane) × Avogadro number / ALC specific surface area (m ² / g)

As a result of the studies described above, the ALC having excellent resistance to carbonation according to the present invention has a molecular weight of 1 × 10 ¹³ to 2 × 10 ¹⁸ / m ² , based on the number of molecules per unit surface area of organopolysiloxane. Contains 1 × 10 ¹⁶ to 1 × 10 ¹⁸ pieces / m ² . If the number of molecules per unit surface area is less than 1 × 10 ¹³ / m ² , the carbonation resistance will not be exhibited. If it exceeds 2 × 10 ¹⁸ / m ² , the carbonation resistance will not be further improved.

Examples of the functional group having no oxygen atom include an alkyl group. Examples of the functional group having an oxygen atom include an alkoxy group and a carboxyl group.

Further, when there is no oxygen atom in the functional group of the side chain of the organopolysiloxane, the resistance to carbonation is further improved.

In particular, when the organopolysiloxane has one or more alkyl groups having 2 or more carbon atoms in one molecule, the carbonation resistance is improved.

(Example 1) Silica 40 was used as a siliceous raw material.
5% by weight, quicklime as a calcareous raw material, cement 3
0% by weight, 5% by weight of gypsum, and 20% by weight of the raw material repeatedly, and water and aluminum powder,
A surfactant was added, and an organopolysiloxane having an average of 40 siloxane units and all side chains of which were methyl groups was added in various amounts, and kneaded to prepare a slurry. The water solids ratio was 0.6.

After the slurry is hardened by the hydration of the calcareous raw material, it is subjected to high-temperature and high-pressure steam curing in an autoclave at 185 ° C. and 11 atm for 6 hours. Ten samples with different values within the range of × 10 ¹¹ to 1 × 10 ²¹ / m ² were obtained.

Each sample was 10 mm × 40 mm × 80 mm
And subjected to an accelerated carbonation test. The test conditions were 20 ° C, 90% relative humidity, and 3 vol% carbon dioxide concentration.
20 days. The degree of carbonation of each sample was calculated by the following equation (Equation 2).

[0025]

## EQU2 ## Degree of carbonation (%) = (C-C ₀ ) / (Cmax-
C ₀ ) × 100

Here, C is the carbon dioxide binding measured as the weight loss of each sample after the accelerated carbonation test in the range of 600 to 800 ° C. measured by DTA-TG (gravimetric analysis in differential thermal analysis). C ₀ is the amount of carbon dioxide binding measured in the same manner for each uncarbonated sample before the accelerated carbonation test. Cmax is the amount of carbon dioxide binding when all the calcium is converted into calcium carbonate by chemically analyzing the calcium content in each sample.

FIG. 1 shows the relationship between the number of molecules per unit surface area of organopolysiloxane and the degree of carbonation in each sample.
(Marked with ●).

Example 2 In Example 2, an organosiloxane having an average of 40 siloxane units, 6 of the side chains being ethyl groups, and all of the remaining side chains being methyl groups was added. A sample was obtained in the same manner as in Example 1, except that the amount was changed in 10 ways, and the results of the evaluation were shown in FIG.

Comparative Example 1 As Comparative Example 1, an average of 40 siloxane units and one of the side chains was a methoxy group,
A sample was obtained in the same manner as in Example 1, except that organopolysiloxane in which three of the side chains were ethyl groups and all of the remaining side chains were methyl groups was added in various amounts. The results of similar evaluation are shown in FIG.

Comparative Example 2 As Comparative Example 2, an organopolysiloxane in which one of the side chains was an alkyl group modified with a carboxyl group and all of the remaining side chains were methyl groups was added in an amount of 10%. A sample was obtained in the same manner as in Example 1 except that the addition was performed in the same manner as in Example 1, and the result of the evaluation was similarly shown in FIG.

The degree of carbonation of the sample to which no organopolysiloxane was added was 60%, and the degree of carbonation of Examples 1 and 2 was almost 60%. Is 1 × 10 ¹¹ -1
At × 10 ¹² / m ² , it can be seen that the effect of improving the resistance to carbonation is extremely small or hardly observed.

The effect of improving the carbonation resistance is clearly seen when the carbonation resistance is 1 × 10 ¹³ / m ² or more. Is 1 × 10 ¹⁶ / m ² or more. Further, in Example 1 in which the side chain contains only a methyl group and Example 2 in which the side chain contains an ethyl group,
At 2 × 10 ¹⁸ particles / m ² or more, the progress of carbonation hardly progresses, and even if added more, the effect does not increase.

In Comparative Examples 1 and 2 in which the side chain of the organopolysiloxane to be added has a functional group containing oxygen such as a methoxy group or a carboxyl group, a methyl group or an alkyl group consisting only of carbon and hydrogen is added to the side chain. It can be seen that the carbonation resistance is inferior at all the added amounts as compared with Examples 1 and 2 having the same.

Therefore, the addition of an organopolysiloxane having a functional group containing oxygen in the side chain is not preferable from the viewpoint of the resistance to carbonation of ALC, and the organopolysiloxane having no oxygen atom in the functional group of the side chain. Is 1 × 10 ¹³ to 2 × 10 ¹⁸ molecules / m ² as the number of molecules per unit surface area,
The ALC of the present invention, which preferably contains 1 × 10 ¹⁶ to 1 × 10 ¹⁸ particles / m ² , has excellent carbonation resistance.

Further, the second embodiment is different from the first embodiment in that
Since carbonation resistance is good, an alkyl group having 2 or more carbon atoms is added to the side chain of the organopolysiloxane.
It is preferable to have one or more in the molecule.

(Example 3) In the case of organopolysiloxanes having only methyl groups, there are infinite types depending on the number of siloxane units. Conversion was confirmed.

FIG. 2 shows the relationship between the number of molecules per unit surface area of organopolysiloxane and the degree of carbonation in a sample in which the number of siloxane units was changed. Even when the average number of siloxane units is changed to 25, 40, or 80, the relationship between the number of molecules per unit surface area of the organopolysiloxane and the degree of carbonation is almost the same. From this, the resistance to carbonation is
It can be seen that regardless of the size of the organopolysiloxane, it is uniquely determined by the number of molecules per unit surface area of the organopolysiloxane.

Example 4 In the case of an organopolysiloxane containing an alkyl group having 2 or more carbon atoms, the number of types is infinite depending on the number of siloxane units, the number of carbon atoms of the alkyl group, and the number of the alkyl groups. However, almost the same resistance to carbonation was confirmed for all types tested in the previous studies.

FIG. 3 shows the relationship between the degree of carbonation and the number of molecules per unit surface area of organopolysiloxane in a sample in which the number of siloxane units, the number of carbon atoms in the alkyl group, and the number of alkyl groups were changed. Regardless of the type of the organopolysiloxane, the relationship between the number of molecules per unit surface area of the organopolysiloxane and the degree of carbonation is almost the same. This indicates that the carbonation resistance is uniquely determined by the number of molecules per unit surface area of the organopolysiloxane, regardless of the structure and size of the organopolysiloxane.

From the above results, the number of molecules per unit surface area of organopolysiloxane is 1 × 10 ¹³ to 2 × 1
0 ¹⁸ / m ^2, preferably 1 × 10 ¹⁶ ~1 × 10 ¹⁸ pieces /
m ² , and further, the organopolysiloxane has no oxygen atom in the side chain functional group. In addition, the organopolysiloxane has one or more alkyl groups having 2 or more carbon atoms.
AL of the present invention characterized by having at least one in the molecule
With C, a remarkable effect of obtaining excellent carbonation resistance can be obtained.

[0041]

As described above in detail, according to the present invention, regardless of the presence or absence of a surface finish, carbonation resistance is superior to ordinary ALC. As a specific effect, since it is possible to obtain an ALC having excellent durability and little or no deterioration phenomenon such as a decrease in strength and generation of cracks, it is possible to extend the service life of the ALC building, repair and repair the ALC building.
The cost of renovation can be reduced and social demands for reduction of industrial waste can be met.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the number of organopolysiloxanes per unit surface area and the degree of carbonation.

FIG. 2 is a graph showing the relationship between the number of organopolysiloxanes per unit surface area and the carbonation resistance in a sample in which the number of siloxane units is changed.

FIG. 3 is a graph showing the relationship between the number of organopolysiloxanes per unit surface area and the degree of carbonation in a sample in which the number of siloxane units, the number of carbon atoms in an alkyl group, and the number of alkyl groups are changed.

Claims (5)

[Claims] 1. An organopolysiloxane having a molecular weight per unit surface area of 1 × 10 ¹³ to 2 × 10 ¹⁸ particles / m ^2.
Including lightweight aerated concrete. 2. An organopolysiloxane having a number of molecules per unit surface area of 1 × 10 ¹⁶ to 1 × 10 ¹⁸ particles / m ^2.
Including lightweight aerated concrete. 3. The lightweight cellular concrete according to claim 1, wherein the organopolysiloxane has a functional group in which all side chain functional groups have no oxygen atom. 4. The lightweight cellular concrete according to claim 1, wherein the organopolysiloxane has at least one alkyl group having 2 or more carbon atoms in one molecule. 5. The lightweight cellular concrete according to claim 3, wherein the functional group having no oxygen atom comprises an alkyl group.