JP2000219558A - Lightweight aerated concrete excellent in carbonation resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress water repellency and to give excellent carbonation resistance and enough water absorbing property by incorporating a small amt. of a dimethylpolysiloxane having side chains all being methyl groups to a lightweight aerated concrete having a siliceous component and a lime component as the main components. SOLUTION: A siliceous source material such as quartzite and a lime source material such as a cement and quicklime are used in a fine powder state as the main materials, to which water and an additive such as aluminum powder are added to prepare a slurry. The slurry is aerated by the reaction of the aluminum powder, semi-hardened by the reaction of the lime source material, and then formed into a specified dimension. Then the product is subjected to high temp. high pressure steam cure in an autoclave to obtain a lightweight aerated concrete(ALC). Dimethylpolysiloxane having side chains all being methyl groups is added by 0.001 to 0.18 wt.% to the ALC to obtain the cobjectiver ALC having excellent carbonation resistance. Since the obtd. ALC has excellent carbonation resistance, it also has excellent ageing resistance and durability. Further, with enough water absorbing property, it does not cause frost damage.

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.

[0006] However, it has been confirmed that the improvement of the carbonation resistance by the surface finish of ALC is not sufficient, and that the carbonation progresses with the years of use.

[0007] Regarding the prevention of intrusion of moisture which causes carbonation, it is known that the addition of organopolysiloxane imparts water repellency to ALC. For example, JP-A-55-42272 discloses that dimethylpolysiloxane is added in an amount of 0.2 to 10% by weight.
JP-A-58148 describes that 0.05 to 10% by weight of an organopolysiloxane containing an alkyl group is added.

However, these water repellent ALCs are
Some include those having excellent resistance to carbonation, and others not. In addition, although it is generally said that the weather resistance is excellent, a frost damage phenomenon often occurs. The frost damage phenomenon is a phenomenon in which water is easily accumulated between the ALC and the paint finish layer on the outdoor side or the indoor side due to its excellent water repellency, and the water that has accumulated here freezes in winter and the paint peels off or swells. is there. This frost damage phenomenon is not seen in general ALC which is inferior in water repellency and carbonation resistance (has a corresponding amount of water absorption).

Therefore, the water-repellent ALC is excellent in weather resistance when viewed alone, but is problematic when viewed from the whole building. This is considered to be the reason that the water-repellent ALC is limited in its use range and is not widely used in buildings in general (the production amount is as very small as 1 to 2% of the total production amount).

[0010]

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide an ALC having reduced water repellency, excellent carbonation resistance, and sufficient water absorption.

[0011]

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, according to the present invention, A is excellent in carbonation resistance.
LC is A having a siliceous component and a calcareous component as main components.
The LC is characterized by containing 0.001 to 0.18% by weight of dimethylpolysiloxane whose side chains are all methyl groups.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Japanese Patent Application Laid-Open No. 55-42272 discloses that, as described above,
A water repellent ALC with an addition of 〜１０10% by weight is described.
The mechanism of exhibiting the water repellency of ALC is to change the contact angle between porous ALC and water by adding dimethylpolysiloxane, thereby preventing water from entering the ALC due to capillary action. It is considered that the above-mentioned amount of addition was necessary to sufficiently change the amount.

On the other hand, the ALC of the present invention having excellent resistance to carbonation
Contains 0.001 to 0.18% by weight of dimethylpolysiloxane in which all side chains are methyl groups. The fact that the carbonation resistance is excellent even with a small amount of dimethylpolysiloxane added is that the important thing in carbonation resistance is not water but liquid gas such as water vapor or surface-adsorbed water of about 6 molecular layers. In order to change the state in which the water vapor and the adsorbed water are present on the surface of tobermorite, the above-mentioned small amount is sufficient. " If the amount added is less than 0.001% by weight, the resistance to carbonation is not sufficient, while if it exceeds 0.18% by weight, the water absorption decreases.

[0015]

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

[Examples 1 to 7, Comparative Examples 1 to 3, Conventional Example 1] A siliceous raw material, a calcareous raw material and a repeated raw material were mixed, and the mixture was mixed with 40% by weight of a siliceous raw material, 40% by weight of a calcareous raw material, and 20% by weight. % Of a repeating raw material was obtained. At this time, silica stone was used as the siliceous raw material, and quicklime, cement and gypsum were used as the calcareous raw material. Also, 4
The breakdown of the 0% by weight calcareous raw material is 5% by weight of quicklime, 30% by weight of cement and 5% by weight of gypsum.

Water, aluminum powder and a surfactant were added to the main raw material mixture and kneaded to prepare a slurry. At this time, slurries without addition of dimethylpolysiloxane in which all side chains were methyl groups (Conventional Example 1) and slurries with addition (Examples 1 to 7 and Comparative Examples 1 to 3) were prepared. The amount of addition to the slurry was 0.0005% by weight (Comparative Example 1), 0.001% by weight (Example 1), 0.005% by weight.
% By weight (Example 2), 0.01% by weight (Example 3),
0.05% by weight (Example 4), 0.10% by weight (Example 5), 0.15% by weight (Example 6), 0.18% by weight
(Example 7), 0.20% by weight (Comparative Example 2) and 0.1% by weight.
30 wt% (Comparative Example 3). The water / solid ratio (weight) 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.

About the prepared ALC sample,
(1) Carbonation resistance and (2) water absorption were examined.

(1) Carbonation Resistance A sample was formed into a size of 10 mm in thickness, 40 mm in height and 80 mm in length, and subjected to an accelerated carbonation test. In the accelerated carbonation test, the temperature was 20 ° C., the relative humidity was 90%, and the carbon dioxide concentration was 3
It was left for 20 days under a constant atmosphere of volume%. The degree of carbonation of each sample was calculated, and the carbonation resistance index was calculated from the degree of carbonation. Formulas for calculating the degree of carbonation and the index of resistance to carbonation are as follows.

Carbonation degree (%) =） (C-Co) / (Cm
ax-Co)｝ × 100 where C is the carbon dioxide binding amount (weight) of the sample, C
o is the amount of carbon dioxide binding of the sample which has not been subjected to the accelerated carbonation test, and the amount of reduction (weight) of carbon dioxide due to decomposition into carbon dioxide at 600 to 800 ° C. for both C and Co was measured by thermal analysis. Cmax is the amount of carbon dioxide bound when all of the calcium in the sample becomes calcium carbonate, and was calculated by analyzing the calcium content in the sample.

Carbonation resistance index = (degree of carbonation of Conventional Example 1) /
(Degree of Carbonation of Sample) The larger the calculated index of carbonation resistance, the better the carbonation resistance. Table 1 shows the results.

The determination of carbonation resistance is as follows:
"Unsuitable" for less than 5 and "OK" for 1.5 or more and less than 2.0
And 2.0 or more was regarded as “suitable”. Table 1 shows the results. In Table 1, "unsuitable" is indicated by a triangle, "acceptable" is indicated by a circle, and "appropriate" is indicated by ◎.
Indicated by the mark.

(2) Water Absorption A sample was formed into a cubic shape having a side length of 100 mm, and the overall water absorption was measured. In the measurement, the sample which became constant weight in a 70 ° C. drier was placed in water at a temperature of 20 ± 2 ° C.
The whole surface was immersed for 4 hours. When the sample was immersed, the foaming direction was directed upward, and the upper surface was positioned 30 mm below the water surface. Thereafter, the overall water absorption (volume increase) of each sample was calculated by the following equation.

Total water absorption (volume%) = ｛(V−Vo) /
Vo｝ × 100 Here, V is the volume of the sample after immersion for 24 hours, and Vo is the volume (1000 cm ³ ) of the sample before immersion (initial).

The higher the calculated total water absorption, the better the water absorption. Table 1 shows the results.

The determination of water absorption was made by determining that the total water absorption was 18% by volume.
Less than 18% by volume and less than 20% by volume was considered as "Poor", and less than 20% by volume was "Appropriate". Table 1 shows the results
Shown in In Table 1, "Inappropriate" is indicated by a triangle, "OK" is indicated by a circle,
“Appropriate” is indicated by a mark ◎.

[0028]

[Table 1]

The following can be seen from Table 1.

(1) When the addition amount of dimethylpolysiloxane in which all the side chains are methyl groups is 0.001 to 0.18% by weight (Examples 1 to 7), compared with ordinary ALC (Conventional Example 1), Excellent carbonation resistance and comparable water absorption.

(2) When the amount of dimethylpolysiloxane in which all side chains are all methyl groups is 0.0005% by weight (Comparative Example 1), the carbonation resistance is insufficient, and the amount is 0.20% by weight.
(Comparative Example 2) and 0.30% by weight (Comparative Example 3) have insufficient water absorption.

[0032]

According to the present invention, an ALC which is excellent in deterioration resistance and durability due to excellent carbonation resistance and which does not cause the frost damage phenomenon often observed in water repellent ALC due to sufficient water absorption. Can be provided. 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 0.001 to 0.
Lightweight cellular concrete excellent in carbonation resistance characterized by containing 18% by weight.