JP2001072459A - Lightweight cellular concrete with high resistance to carbonation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject cellular concrete to be used as the wall, roof, flooring, etc., of buildings. SOLUTION: This lightweight cellular concrete based on both siliceous and calcareous components contains 0.0005-10 wt.% of an organopolysiloxane having in one molecule at least one siloxane unit shown by R(CH3)SiO2/2, R(CH3)2SiO1/2, or RSiO3/2 (R is a >=2C alkyl group).

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.

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 been elucidated yet, not all ALCs having excellent water repellency are necessarily necessarily excellent in carbonation resistance. Therefore, since the carbonation reaction proceeds in the presence of water, it is considered that the cause may be that the organopolysiloxane changes the state of the presence of water on the tobermorite surface.

[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]

Means for Solving the Problems The present inventor has conducted various studies and trial and error in order to achieve the above object, and as a result, it has been found that "ALC containing a small amount of various organopolysiloxanes is
The water repellency is reduced and the water absorption is improved, and at the same time, the carbonation resistance is still excellent. "

That is, A of the present invention which is excellent in carbonation resistance
LC is A having a siliceous component and a calcareous component as main components.
In LC, R (CH ₃ ) SiO _2/2 , R (CH ₃ )
₂ SiO _1/2 or RSiO _3/2 (where R is an alkyl group having at least 2 carbon atoms (n) (C _n H _{2n + 1} ))
At least one siloxane unit represented by
Of organopolysiloxanes having a number of
It is characterized by containing 0% by weight.

[0010]

Heretofore, organopolysiloxanes have been added to impart water repellency to ALC and siliceous building materials. Regarding the provision of water repellency, see
No. 42272, polydimethylsiloxane was added to a solution of 0.
The addition amount of organopolysiloxane was relatively large, for example, addition of 2 to 10% by weight or addition of 0.05 to 10% by weight of an organopolysiloxane containing an alkyl group as disclosed in Japanese Patent Publication No. 1-58148. 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 site of the carbonation reaction is not the liquid water but the surface adsorbed water, and it is thought that the effective amount of addition may be different because the action mechanism is different. Therefore, the addition amount of the organopolysiloxane is set to 0.0001 to
The experiment was carried out with the content changed to 15% by weight, and it was found that the carbonation resistance was exhibited even at 0.0005% by weight where no water repellency was exhibited.

[0012]

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

As a siliceous raw material, 40% by weight of silica stone, as a calcareous raw material, 5% by weight of quick lime, 30% by weight of cement, 5% by weight of gypsum, and 20% by weight of a repeating material are mixed.
A slurry was prepared by adding water, aluminum powder and a surfactant to these main raw materials and kneading them. 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 for 6 hours in an autoclave at 185 ° C. and 11 atm.

At the time of mixing the raw material slurry, the addition amount of the organopolysiloxane containing an alkyl group is set to 0.0001 to
An ALC was added varying up to 15% by weight.
For comparison, an ALC (hereinafter, abbreviated as a blank sample) containing no organopolysiloxane was also prepared. Here, a total of six types shown in Table 1 were tried as organopolysiloxanes containing an alkyl group.

[0015]

[Table 1] 10 mm × 40 to examine the carbonation resistance of each sample
It was formed into a size of mm × 80 mm and subjected to an accelerated carbonation test. The test was performed under a constant atmosphere of 20 ° C., a relative humidity of 90% and a carbon dioxide gas concentration of 3% by volume for 20 days. The degree of carbonation of each sample was calculated by the following equation.

Degree of carbonation (%) = Ｃ (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 a weight loss due to decomposition of carbon dioxide at 600 to 800 ° C. by thermal analysis, respectively.
“x” was obtained by analyzing the calcium content in each sample, and was defined as a carbon dioxide gas binding amount when all the calcium was converted into calcium carbonate. Based on the carbonation degree analysis results of each sample,
The value obtained by dividing the carbonation degree of the blank sample by the carbonation degree of each sample was defined as the carbonation 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 2 shows the measurement results of the carbonation resistance index with respect to the type and addition amount of the organopolysiloxane of each sample.
Shown in

[0019]

[Table 2] Here, regarding the carbonation resistance, the carbonation resistance index is 1.5.
When it was judged that the above was acceptable, that 2.0 or more was appropriate, and that the others were inappropriate, all the organopolysiloxane addition amounts were 0.000.
When the content is 5% by weight or more, the carbonation resistance is sufficient.

In particular, when the addition amount was 1 to 2% by weight, carbonation did not proceed at all, and the carbonation index became infinite. However, when the content was 12% by weight or more, the drying shrinkage ratio was out of the JIS standard, and thus it was found to be inappropriate as ALC.
That is, 0.0005 to 10
With respect to those added by weight%, those having excellent carbonation resistance as compared with ordinary ALC were obtained.

The desired ALC could be obtained by controlling the amounts of all the organopolysiloxanes containing alkyl groups used in the tests so far. However, since the types of organopolysiloxane containing an alkyl group can be produced indefinitely, it is impossible to confirm all types by tests. However, we used AL
C is an organopolysiloxane containing an alkyl group in a range usually used for siliceous materials such as C. If the organopolysiloxane contains an alkyl group in a range usually used, the desired ALC can be obtained by controlling the amount of addition. Obtainable.

[0022]

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 R (CH ₃ ) Si
O _2/2 , R (CH ₃ ) ₂ SiO _1/2 or RSiO _3/2
(Wherein, R is an alkyl group having at least 2 carbon atoms)
At least one siloxane unit represented by
Of organopolysiloxanes having a number of
A lightweight cellular concrete excellent in carbonation resistance characterized by containing 0% by weight.