JPH06219866A - Carbonation-resistant lightweight aerated concrete - Google Patents

Abstract

PURPOSE:To obtain a lightweight aerated concrete with the carbonation resistance improved and excellent in durability by impregnating the concrete with morpholine. CONSTITUTION:Bubbles are introduced by a foaming agent, frothing agent, etc., into a slurry with quartzite, portland cement, quick lime, etc., as the main material, and the slurry is hardened and cured with high-temp. and pressure steam to produce a lightweight aerated concrete. The concrete is impregnated with morpholine to produce a lightweight aerated concrete resistant to carbonation. The concrete is impregnated with morpholine by dipping the concrete in morphorine or in an aq. soln. of morpholine or spraying morpholine on the concrete. Consequently, the carbonation reaction rate of the concrete is drastically lowered, and the cracking of the concrete due to contraction as carbonation proceeds is retarded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to lightweight cellular concrete having excellent carbonation resistance.

[0002]

2. Description of the Prior Art Lightweight cellular concrete is non-combustible and fire resistant,
Since it has many features such as excellent heat insulation, light weight, and excellent workability, it is widely used as a building material for walls, floors, roofs, partitions and the like. Light-weight cellular concrete is generally produced by introducing bubbles into a slurry mainly made of silica stone, Portland cement, quicklime, etc. by a foaming agent, a foaming agent, etc. and curing it, followed by curing at high temperature and high pressure steam. Light-weight cellular concrete produced in this way generally has a specific gravity of about 0.5,
In this case about 50% by volume are bubbles, consisting of about 30% by volume of pores and the remaining about 20% by volume of solids. And the solid part is tobermorite crystals, CSH gel, and unreacted silica.

As described above, since lightweight cellular concrete has a structure in which bubbles communicate with innumerable pores existing from the surface to the inside, the lightweight cellular concrete easily absorbs water from the surface and absorbs the absorbed water. Carbon dioxide in the atmosphere dissolves into the water. The dissolved carbon dioxide gas reacts with the tobermorite crystals and CSH gel in the lightweight cellular concrete to generate calcium carbonate, which causes a so-called carbonation phenomenon. As carbonation progresses, the solid part shrinks and cracks in the lightweight cellular concrete, making it easier for water to enter through the cracks.
In addition, the strength of lightweight cellular concrete will be reduced.

Conventionally, in order to prevent the carbonation phenomenon of the lightweight cellular concrete, when the lightweight cellular concrete is used as a building material for a wall or the like, a coating material is applied to the surface thereof,
It is used so that water does not enter from the surface. However, it is necessary to apply a fairly thick coating in order to slow the progress of carbonation by suppressing the invasion of carbon dioxide by applying a surface treatment with paint, etc. Normally, such painting is not done on the indoor side. The carbonation of the light-weight cellular concrete gradually progressed, and after a long time, cracks might occur due to the carbonation.

For this reason, proposals have been made to improve the carbonation resistance of lightweight cellular concrete. This is disclosed in Japanese Patent Laid-Open No. 179090/1982.
As disclosed in a series of publications of Japanese Patent No. 179013 and the like, it is a technique of manufacturing by adding an organic phosphate ester or a strontium compound to a raw material slurry of lightweight cellular concrete.

Further, there is disclosed a method of impregnating a lightweight cellular concrete in a product state cured by high temperature and high pressure steam with a metal salt of acetic acid in a subsequent step (Japanese Patent Laid-Open No. 4-74778).

[0007]

However, the technique of adding an organic phosphoric acid ester or a strontium compound to a raw material slurry of lightweight cellular concrete does not provide sufficient degree of carbonation resistance, and these techniques are not sufficient. However, it takes a long time to obtain a lightweight cellular concrete in which the tobermorite crystals grow well by the method.

When light-weight cellular concrete that has been cured by high-temperature and high-pressure steam is impregnated with a metal salt of acetic acid in a later step, the carbonation rate becomes low when the water content of the lightweight cellular concrete is low, There is a problem that the effect of suppressing the carbonation reaction is small in a state where the water content is high. Light weight cellular concrete has a high water content at the beginning when it is built into a building, and it dries with age, and its water content decreases. On the other hand, the progress of carbonation is fast in the early stage when the water content is high, and when the water content is low, the carbonation and the progress are slow. Therefore, in order to slow down the progress of carbonation of lightweight cellular concrete, it is necessary to slow down the carbonation reaction in the initial high water content state. I can't get it.

An object of the present invention is to provide a lightweight cellular concrete whose carbonation progresses slowly not only in a low water content state but also in a high water content state.

[0010]

SUMMARY OF THE INVENTION The present invention is a carbonation-resistant lightweight foam concentrate impregnated with morpholine. The morpholine that can be used in the present invention is not particularly limited, and it is possible to use a morpholine stock solution or a diluted morpholine solution, so it is necessary to consider the amount and the treatment time to be impregnated. However, if the content is 30 wt% or more, the time for impregnating morpholine is short, and the water content of the panel does not need to be high, which is preferable.

The lightweight cellular concrete referred to in the present invention is
Calcium silicate hydrate such as tobermorite crystals and CSH gel produced by hydrothermal reaction and unreacted silica are solid components, and have a foaming agent such as metallic aluminum and bubbles introduced by a foaming agent. And having a bulk specific gravity after drying of 0.3 to 0.7. The shape of the product is not particularly limited, and a panel-shaped product or a product having another shape, for example, an unreinforced block-shaped product can be used. It is preferable to use a product in which a reinforcing material such as cage-shaped reinforcing bars and lath nets is contained in the product. However, since lightweight cellular concrete absorbs water up to the central portion, it is preferable that the reinforcing material be rustproofed.

The method of impregnating morpholine of the present invention comprises:
For example, there are a method of immersing lightweight cellular concrete in morpholine and its aqueous solution, a method of spraying and impregnating lightweight cellular concrete. The content of morpholine can be changed by increasing the concentration of the morpholine aqueous solution, prolonging the immersion time in the aqueous solution, or prolonging the spraying time.

It is essential that the surface layer of the lightweight cellular concrete is impregnated with morpholine, and the content thereof is preferably 1 to 20%, more preferably 5 to 15%.
Is the range. It suffices that the surface of the light-weight cellular concrete is substantially uniformly impregnated by visual observation, and the inside is not necessarily impregnated uniformly. By impregnating morpholine, the carbonation rate of the lightweight cellular concrete can be reduced not only in a dry state with a water content of about 5 wt% but also in an undried state with a water content of 20 wt% or more.

[0014]

[Function] As described above, when morpholine is impregnated in lightweight cellular concrete, the lightweight cellular concrete has a structure in which bubbles are connected to the numerous pores from the surface to the inside, but carbon dioxide resistance is improved. The chemical conversion is improved. Although this effect is not clear, the presence of morpholine on the surface of bubbles and pores hinders the contact between carbon dioxide gas and tobermorite crystals, or the dissolution of calcium from the surface of tobermorite crystals into water. It is considered that this is suppressed and the subsequent reaction with carbon dioxide becomes slower.

[0015]

The present invention will be further described based on the following examples. The accelerated carbonation test and the measurement of carbonation degree in Examples and Comparative Examples were carried out as follows. Accelerated carbonation test (I) The lightweight cellular concrete after various treatments obtained in Examples and Comparative Examples was dried at 20 ° C. and RH 60% until a constant weight was obtained, which was used as a sample. This test piece is heated to 20
The reaction was carried out for 14 days in a plastic chamber set at a temperature of 60 ° C., a relative humidity of 60% and a carbon dioxide concentration of 10%.

Accelerated carbonation test (II) The light-weight cellular concrete obtained in each of the Examples and Comparative Examples after various treatments was used as a test sample without being dried, and the test sample was used at a temperature of 20 ° C., a relative humidity of 90% and a carbon dioxide gas. The reaction was performed for 3 days in a plastic chamber set to a concentration of 10%. Measurement of carbonation degree Each of the test pieces obtained in the above was dried at 105 ° C. for 24 hours, pulverized, and precisely weighed. 5 accurately weighed specimens
The carbon dioxide gas contained in a specified aqueous hydrochloric acid solution was decomposed, the amount of carbon dioxide gas generated was measured, and the gas generation amount (v) per gram of the test piece was determined. (Amount of carbon dioxide gas included in the above test) On the other hand, after crushing a part of each test piece, carbonation was carried out for 7 days under the conditions of a temperature of 20 ° C., RH of 100% and carbon dioxide gas of 2 kgf / cm 2. Next, this was dried at 105 ° C. for 24 hours, and then an appropriate amount was precisely weighed. Further, carbon dioxide gas contained in a 5N hydrochloric acid aqueous solution was decomposed, and the amount of carbon dioxide gas generated was measured to obtain the gas generation amount (V) per gram of the test piece. (Amount of carbon dioxide gas that can be contained in the sample) The carbonation degree was calculated using the following formula.

Carbonation degree = (v / V) × 100 (%) Moisture content Before starting the accelerated carbonation test, the weight (W) of each sample was measured. The weight (w) of this test piece when dried to a constant weight at 105 ° C. was measured. The water content was calculated using the following formula.

Water content = {(W−w) / w} × 100 (%)

[0019]

Example 1 45 parts by weight of silica stone, 44 parts by weight of ordinary Portland cement, 11 parts by weight of quick lime, 70 parts by weight of molding water were added and mixed with stirring, and 60 parts of mortar containing 0.07 parts by weight of aluminum powder was added thereto. The light-weight cellular concrete was obtained by foaming and curing in a curing tank at a temperature of ℃, and curing the mortar block having reached a predetermined hardness by autoclaving (180 ° C., 10 hours). Two pieces of the obtained lightweight cellular concrete cut into a size of 20 × 40 × 160 mm were prepared, immersed in a 50% aqueous solution of morpholine for 1 minute, and then the aqueous solution on the surface was wiped off. Was used for accelerated carbonation tests (I) and (II). The results are shown in Table 1. The surface layer of the sample was almost uniformly impregnated with morpholine, and the impregnation amount of the entire sample was 6.7 wt%.

[0020]

Comparative Example 1 Two lightweight cellular concretes were prepared in the same manner as in Example 1 and used for accelerated carbonation tests (I) and (II) without impregnation with morpholine. The results are shown in Table 1.
It was shown to.

[0021]

[Comparative Example 2] Two lightweight cellular concretes were prepared in the same manner as in Example 1, and instead of being impregnated with morpholine, they were immersed in a 10% aqueous solution of magnesium acetate for 1 minute, and then the surface aqueous solution was wiped off. Was used for accelerated carbonation tests (I) and (II). The results are shown in Table 1.
The surface layer of the specimen was substantially uniformly impregnated with magnesium acetate, and the impregnation amount of the entire specimen was 6.7 wt%.

[0022]

[Table 1]

[0023]

As described above, according to the method of the present invention, the carbonation reaction rate of lightweight cellular concrete not only in the dry state but also in the non-dried state is significantly reduced. Therefore, it is possible to delay the progress of carbonation in the early stage when the lightweight cellular concrete was built and high water content, and it is possible to delay the occurrence of cracks due to carbonation shrinkage that occurs with the progress of carbonation. As a result, a lightweight cellular concrete having excellent durability can be provided.

Claims (1)

[Claims] 1. A carbonic acid resistant light weight air bubble concentrate impregnated with morpholine.