JP2001072476A - Light-weight cellular concrete having excellent resistance to carbonation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the resistance to carbonation of light-weight cellular concrete by including a specific amount of dimethylpolysiloxane bearing methyl groups as all of the side chains. SOLUTION: In an example, 40 wt.% of quartzite, as a raw material for siliceous substance, 5 wt.% of quick lime as a raw material for calciferous substance, 30 wt.% of cement, 5 wt.% of plaster and 20 wt.% of the repeatedly used raw materials are mixed; water, an Al powder and a surfactant are admixed to the mixture and they are kneaded to a slurry. After this slurry hardens by the hydration of the calciferous substance, the hardened product is steam-aged at elevated temperature and high pressure in an autoclave whereby objective light-weight cellular concrete. In this production process, when the slurry is mixed, 0.001-15 wt.% of an organopolysiloxane is admixed in an amount of 0.001-15 wt.%. As a result, the light-weight cellular concrete having a higher carbonation resistance than the usual cellular concrete is obtained. The organopolysiloxane may have a usual viscosity range, when it is usually used as a siliceous material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to lightweight cellular concrete excellent in carbonation resistance used for walls, roofs, floors and the like of buildings.

[0002]

2. Description of the Related Art Light-weight cellular concrete (hereinafter referred to as ALC) is widely used as a building material because it is lightweight and has excellent fire resistance, heat insulation and workability.

[0003] ALC is manufactured as follows. That is, a siliceous raw material such as silica stone and a calcareous raw material such as cement and quicklime are used as main raw materials, and water and an additive such as aluminum powder are added to these fine powders to form a slurry. The slurry is foamed by the reaction of the aluminum powder, semi-cured by the reaction of the calcareous raw material, and formed into a predetermined size. Thereafter, high-temperature and high-pressure steam curing is performed by an autoclave to obtain ALC.

[0004] The ALC thus produced contains a siliceous component and a calcareous component as main components, and the main constituent mineral is tobermorite. It has a microstructure with very large voids, in which bubbles and pores occupy about 80% of the total volume, and has a specific gravity of about 0.5 in absolute dryness.

[0005] As described above, ALC has a large number of bubbles and pores, so that moisture and gas (such as carbon dioxide) can be easily removed by ALC.
Infiltrate inside. Tobermorite, the main constituent mineral of ALC, reacts with the infiltrated water and carbon dioxide to decompose into silica gel and calcium carbonate. This is carbonation.
Carbonation causes ALC to undergo a carbonation phenomenon, that is, deterioration such as a decrease in strength and generation of cracks. So AL
In order to prevent or delay carbonation of C, it is required to (1) prevent the intrusion of moisture and carbon dioxide gas, and (2) to make tobermorite resistant to carbonation. As a means for the above (2), which can be a fundamental measure, no industrially effective means has been found despite various studies. Therefore, the means for the above (1), that is, the ALC surface finish (painting or the like) has been exclusively used until now. However, carbonation resistance by surface finishing is not always sufficient, and it has been confirmed that carbonation progresses with the life of ALC.

As a result of various studies and trial and error, the present inventors have found that a water-repellent ALC obtained by adding various organopolysiloxanes to a mixture slurry of a main raw material has excellent carbonation resistance. Although the cause of the excellent carbonation resistance has not yet been elucidated, not all ALCs having excellent water repellency are necessarily necessarily excellent in carbonation resistance, and the carbonation reaction proceeds in the presence of moisture. Therefore, it is considered that the cause may be that the organopolysiloxane changes the state of the presence of moisture on the surface of tobermorite.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide an ALC having excellent carbonation resistance in view of the above circumstances.

[0008]

In order to achieve the above-mentioned object, ALC having excellent carbonation resistance according to the present invention comprises an ALC containing a siliceous component and a calcareous component as main components, all of the side chains of which are methyl groups. It is characterized by containing 0.001 to 15% by weight of a certain dimethylpolysiloxane.

[0009]

Heretofore, organopolysiloxanes have been added to impart water repellency to ALC and siliceous building materials. Regarding the provision of water repellency, see
Dimethylpolysiloxane as described in JP-A-42272.
2 to 10% by weight, or an organopolysiloxane containing an alkyl group as described in JP-B-1-58148.
The addition amount of the organopolysiloxane was relatively large, such as addition of 05 to 10% by weight. This is because the expression mechanism of water repellency changes the contact angle between the material and water by the addition of organopolysiloxane, preventing water from entering the porous ALC or siliceous building material by capillary action, It is considered that a certain amount of addition was necessary for that purpose.

On the other hand, the carbonation reaction is caused not by liquid water but by surface-adsorbed water, and it is thought that the effective addition amount may be different due to a different mechanism of action. Therefore, the addition amount of the organopolysiloxane is set to 0.0001 to
When the experiment was carried out by changing the content to 20% by weight, it was found that the carbonation resistance was exhibited even at 0.001% by weight where no water repellency was exhibited.

[0011]

The present invention will be described in more detail with reference to the following examples.

40% by weight of silica as a siliceous raw material, 5% by weight of quicklime, 30% by weight of cement, 5% by weight of gypsum, and 20% by weight of a repetitive raw material are mixed as calcareous raw materials. A surfactant was added and kneaded to prepare a slurry. The water solids ratio was 0.6. After the slurry was hardened by hydration of the calcareous raw material, it was subjected to high-temperature and high-pressure steam curing in an autoclave at 185 ° C. and 11 atm for 6 hours.

At the time of mixing the raw material slurry, an ALC was prepared in which the addition amount of the organopolysiloxane was changed from 0.0001 to 20% by weight. For comparison, an ALC (hereinafter, abbreviated as a blank sample) containing no organopolysiloxane was also prepared. Here, the organopolysiloxane has a viscosity of 5, 10, 20, or
A total of six types of 50, 100, and 200 cs were used.

To examine the carbonation resistance of each sample,
It was molded into a size of 0 mm × 40 mm × 80 mm and subjected to an accelerated carbonation test. The test conditions were 20 ° C. and 90% relative humidity.
% And a carbon dioxide gas concentration of 3% by volume in a constant atmosphere for 20 days. The degree of carbonation of each sample was calculated by the following equation.

Degree of carbonation (%) = ｛(C-Co) / (Cm
ax-Co)｝ × 100 Here, C and Co are analyzed by analyzing the amount of carbon dioxide binding of each sample and the uncarbonated sample as the weight loss due to decomposition of carbon dioxide at 600 to 800 ° C. by thermal analysis.
ax was obtained by analyzing the calcium content in each sample, and was defined as the amount of carbon dioxide binding in the case of carbon dioxide when all of the calcium became calcium carbonate. Based on the analysis results of the degree of carbonation of each sample, a value obtained by dividing the degree of carbonation of the blank sample by the degree of carbonation of each sample was defined as a carbonation resistance index.

In addition to the carbonation resistance, the basic physical properties of ALC such as compressive strength and dry shrinkage were measured in accordance with JIS A5416.

Table 1 shows the measurement results of the carbonation resistance index with respect to the viscosity and addition amount of the organopolysiloxane of each sample.
Shown in

[0018]

[Table 1] Here, regarding the carbonation resistance, if it is determined that the carbonation resistance index is 1.5 or higher, 2.0 or higher is suitable, and the other is inappropriate, the addition amount of all kinds of organopolysiloxane is 0.1.
001% or more is sufficient for carbonation resistance. In particular, at an addition amount of 1 to 2% by weight, carbonation did not proceed at all, and the carbonation index became infinite. However, when the content was 17.5% by weight or more, it was found that the drying shrinkage ratio was out of the JIS standard, so that it was not suitable as ALC. That is, when the organopolysiloxane was added in an amount of 0.001 to 15% by weight, a resin having more excellent carbonation resistance than ordinary ALC was obtained. The desired ALC could be obtained by controlling the amount of all the organopolysiloxanes used in the tests so far. This time, the organopolysiloxane having a viscosity range usually used for siliceous materials such as ALC is used. If the organopolysiloxane has a viscosity within the range normally used, the addition amount is controlled to obtain the desired ALC.
Can be obtained.

[0019]

As described above in detail, according to the present invention, regarding the carbonation phenomenon which is one of the deteriorations of ALC,
AL with excellent resistance to deterioration and durability due to excellent carbonation resistance
C can be obtained. Therefore, it is possible to extend the service life of the ALC building, reduce the cost of repair and repair, and meet social demands for reducing the amount of industrial waste.

Claims (1)

[Claims] 1. A lightweight cellular concrete mainly composed of a siliceous component and a calcareous component, wherein dimethylpolysiloxane having all methyl groups in the side chains is 0.001 to 15%.
Lightweight cellular concrete with excellent carbonation resistance characterized by containing by weight.