JP2003176160A - Cement composition for carbonized cured body - Google Patents

Abstract

(57) [PROBLEMS] To provide a carbonized hardened body which does not require pressure molding and can exhibit high strength even by casting, and a cement composition for realizing the same, and a blast furnace which is industrial waste. Provide effective use of granulated slag. A cement composition for a carbonated hardened body comprising crystallized slag obtained by heat treatment of granulated blast furnace slag and a hydraulic substance. The cemented composition for a carbonated cured body can be cast and produced, and can exhibit a cured body that exhibits excellent strength development in carbonation curing and does not generate cracks. At the same time, it is possible to improve the functionality of blast furnace slag, an industrial byproduct.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a cement composition for carbonation-cured products used in the civil engineering and construction industry. Parts and% in the present invention are based on mass unless otherwise specified.

[0002]

[Prior art and its problems] Regarding carbon dioxide emissions,
The civil engineering and construction industry accounts for an extremely large proportion of all industries, and there is a strong demand for reducing the environmental load. Most of the carbon dioxide emitted from the cement industry comes from the decarboxylation reaction of limestone, which is the raw material, and the combustion of fuel.

Therefore, in order to reduce carbon dioxide emission in the cement industry, reducing the amount of cement clinker fired is the most effective method, and it is extremely important to promote the use of various mixed cements. .

On the other hand, blast furnace slag produced as an industrial by-product from a steel mill is widely used in the concrete field. Blast furnace slag is roughly classified into blast furnace granulated slag that is rapidly cooled and vitrified, and blast furnace slowly cooled slag that is gradually cooled and crystallized.

Of these, granulated blast furnace slag is alkaline and has latent hydraulicity, and is similar to cement.
Alternatively, more finely pulverized material is used as a raw material for blast furnace cement.

[0006] Vitrified granulated blast furnace slag has latent hydraulicity and has an excellent property that long-term strength does not decrease even when mixed in a large amount with cement clinker. Studies in various fields are being conducted.

[0007] Recently, research on high functionality of blast furnace slag, which is an industrial by-product, is about to begin.

By the way, conventionally, "artificial stone" (Japanese Patent Laid-Open No. 49-88922) obtained by adding water to a converter slag and limestone and then hardening it under a carbon dioxide pressure atmosphere, a hydraulic material and a converter A "molded product by carbonation", in which water is added to a composition containing slag or the like as a component, pressure molding is performed, and then carbon dioxide gas is absorbed and cured (Japanese Patent Publication No. 56-36147 etc.), has been proposed.

However, the conventional "artificial stone" and "molded product by carbonation" do not exhibit sufficient strength unless they are pressure-molded. Nowadays, there is a strong demand for a cement composition that does not require pressure molding and can exhibit high strength even by casting.

The inventors of the present invention have made earnest studies on the improvement of the function of the cement for a carbonation hardening body using blast furnace slag, and as a result, when the hardening body of the hydraulic material produced using the crystallized slag is carbonated, the hardening occurs. It was found that carbonation contributes significantly to increasing the compressive strength in order to form a dense and hard layer near the body surface. Based on this finding, it was found that a high-strength carbonation cured product can be obtained, and the present invention was completed.

[0011]

[Means for Solving the Problems] That is, the present invention is a cement composition for a carbonation-cured product comprising a crystallized slag obtained by heat-treating granulated blast furnace slag, and a hydraulic substance, and the vitrification rate of the crystallized slag. Is 30% or less of the carbonized hardened body cement composition, the crystallized slag Blaine specific surface area is 3,000 cm ² / g or more of the carbonated hardened body cement composition. , 100 parts in total of hydraulic material and crystallized slag, the content of crystallized slag is 90 to 50
It is the cement composition for carbonation-cured products, characterized in that the content is at least 1 part.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
The crystallized slag of the present invention is a heat treatment of granulated blast furnace slag.
Means slag that has been crystallized. Blast furnace as an ingredient
It has the same chemical composition as granulated slag. Specifically, Si
O₂, CaO, Al₂O₃, And MgO are the main chemical components.
Other than TiO₂, MnO, Na ₂O, S, P₂O_Five, And Fe₂O₃Etc.
To be

As a compound of granulated blast furnace slag, glass is used.
In addition to quality, Gehrenite 2CaO ・ Al₂O₃・ SiO₂And Akermanai
2CaO ・ MgO ・ 2SiO₂The so-called melilite, which is a mixed crystal of
Including. Also, from the elemental composition, dicalcium silicate 2C
aO ・ SiO₂, Rankinite 3CaO ・ 2SiO₂, Wollastonite CaO
・ SiO₂Such as calcium silicate, merbinite 3CaO
MgO ・ 2SiO₂, Monticerite CaO / MgO / SiO₂Calci as
Ummmagnesium silicate, anorthite CaO / Al₂O₃・
2 SiO₂, Leucite (K₂O, Na₂O) ・ Al₂O₃・ SiO ₂, Sp
Flannel MgO / Al₂O₃, Magnetite Fe₃O_Four, Further, calcium sulfide
Presumed to contain sulfides such as Cadmium CaS and FeS FeS
ing.

It has been confirmed by qualitative analysis by powder X-ray diffraction that the crystallized slag contains melilite.

The vitrification rate of the crystallized slag used in the present invention is preferably 30% or less, more preferably 10% or less. If the vitrification ratio exceeds 30%, the strength increase due to carbonation will be insufficient, and cracks will easily occur in the cured body. The lower limit of the vitrification rate is not limited, and a completely crystallized one is the most preferable.

The vitrification rate (X) referred to in the present invention is X (%)
= (1−S / S ₀ ) × 100. Where S
Is a major crystalline compound in crystallized slag obtained by powder X-ray diffractometry (mellenite 2CaO).
・ Al ₂ O ₃・ SiO ₂ and akermanite 2CaO ・ MgO ・ 2SiO ₂ mixed crystal)
The area of the main peak of S ₀ is slag at 1,000 ℃
The area of the main peak of melilite of the sample powder heated for 3 hours and then cooled at a cooling rate of 5 ° C./min is shown.

The Blaine specific surface area of the crystallized slag is not particularly limited, but preferably 3,000 cm ² / g or more,
4,000cm more preferably ^{2 / g~8,000cm 2 / g, 5,000cm} 2 / g~
Most preferred is 8,000 cm ² / g. Blaine specific surface area is 3,000c
If it is less than m ² / g, material separation resistance may not be obtained, or the effect of suppressing neutralization may not be sufficient. Also, 8,000c
When pulverizing to exceed m ² / g, the pulverizing power is large and it is uneconomical, and the crystallized slag tends to be weathered, and the deterioration of quality over time tends to be large.

The blending ratio of the crystallized slag is preferably 50 to 90 parts, and preferably 60 to 8 out of 100 parts in total of the hydraulic material and the crystallized slag.
0 part is more preferable. If it is less than 50 parts, the strength after carbonation may not be sufficient, and if it exceeds 90 parts, the strength of the cured body before carbonation and curing may be insufficient and the cured body may be damaged during demolding.

As the hydraulic material used in the present invention, various portland cements such as normal, early-strength, super-early-strength, low heat, and moderate heat, and granulated blast furnace slag, fly ash, or silica are added to these portland cements. Examples thereof include various mixed cements mixed, and filler cements mixed with limestone powder and the like, and one or more of these can be used.

The amount of the hydraulic material used in the cement composition of the present invention is not particularly limited, but usually, the hydraulic material is 10 to 5 in 100 parts in total of the hydraulic material and the crystallized slag.
0 part is preferable, and 20-40 parts is more preferable. If it is less than 10 parts, the strength of the cured product before carbonation is insufficient and the cured product may be damaged during demolding. Conversely, if the hydraulic substance exceeds 50 parts, the strength after carbonation is insufficient. There are cases.

The particle size of the cement composition of the present invention is not particularly limited because it depends on the purpose and application of use, but it is usually 3,000 to 8,000 cm ² / g in terms of Blaine specific surface area.
Is preferable, and 4,000 to 6,000 cm ² / g is more preferable. 3,000
If it is less than cm ² / g, sufficient strength development may not be obtained, and if it exceeds 8,000 cm ² / g, workability may deteriorate.

Although the amount of water used is not particularly limited, it is usually preferably 20 to 50 parts, and more preferably 30 to 40 parts, relative to 100 parts of the cement composition. If it is less than 20 parts, the flowability may be insufficient and it may be difficult to cast the kneaded product, and if it exceeds 50 parts, the strength of the obtained molded product may not be sufficient.

In the present invention, in addition to hydraulic materials and crystallized slag, aggregates such as sand and gravel, water reducing agents, AE water reducing agents,
High-performance water reducing agent, high-performance AE water reducing agent, defoaming agent, foaming agent, thickening agent, rust preventive agent, antifreezing agent, shrinkage reducing agent, polymer emulsion, setting regulator, clay mineral such as bentonite, and
It is possible to use one kind or two or more kinds of anion exchangers such as hydrotalcite and the like within a range not substantially impairing the object of the present invention.

In the present invention, the method of mixing the respective materials is not particularly limited, and the respective materials may be mixed at the time of construction, or some or all of them may be mixed in advance. .

The carbonation curing in the present invention means that the hardened body prepared by mixing the present cement composition and water is subjected to carbonation treatment in a gas atmosphere containing carbon dioxide gas.
Note that the gas atmosphere is not particularly limited as long as it contains carbon dioxide gas, and may contain gases such as nitrogen, oxygen, hydrogen, argon, and water vapor.

The carbonation-cured product in the present invention means a product obtained by hydrating and hardening the present cement composition to obtain a cured product, which is further cured by carbonation.

As the mixing device, any existing device can be used, for example, a tilt cylinder mixer, an omni mixer,
A Henschel mixer, a V-type mixer, a Nauta mixer or the like can be used.

[0028]

EXAMPLES The present invention will be further described below based on experimental examples of the present invention.

Experimental Example 1 Cement compositions were prepared by mixing 25 parts of cement with 75 parts of various slag powders or limestone powders shown in Table 1. To 100 parts of this cement composition, 30 parts of water was added and kneaded to prepare a paste. Pour this paste into the formwork, 24
It was removed from the mold after a lapse of time, and thereafter, it was cured in water at 20 ° C for 6 days until the age of 7 days (this is called pre-curing). After that, 30 ℃,
Accelerated carbonation was carried out in an environment with relative humidity of 60% and carbon dioxide concentration of 5%. Cut the specimen into slices, apply a phenolphthalein alcohol solution to the cross section to confirm the neutralization depth, and make the completely neutralized specimen a specimen after carbonation curing,
The cracks and the like of the specimen after carbonation curing were observed, and the compressive strength of the specimen without cracks was measured.

For comparison, the same experiment was carried out in the case where the underwater curing was continued after the completion of the precuring (hereinafter referred to as standard curing). The results are also shown in Table 1.

<Materials used> Hydraulic substance a: Early strength Portland cement, Slag A (Crystalline slag) manufactured by Denki Kagaku Kogyo Co., Ltd .: Granulated blast furnace slag heat-treated at 1000 ° C. for crystallization, vitrification 5%, Blaine specific surface area 4,000 cm ² / g, Slag B: Blast furnace slowly cooled slag, vitrification rate 5%, Blaine specific surface area 4,000 cm ² / g, Slag C: Granulated blast furnace slag, vitrification rate 95%, Blaine specific surface area 4,000 cm ² / g, limestone powder: main component calcium carbonate. Blaine specific surface area
4,000 cm ² / g. Water: Tap water

<Measurement method> Compressive strength: 2 × 2 × 8 cm Measured by making a specimen.

[0033]

[Table 1] ・ ○ indicates that there are no cracks, and × indicates that there are many cracks.

Experimental Example 2 The procedure of Experimental Example 1 was repeated, except that the compounding ratio of slag A (crystallized slag) in the cement composition was changed as shown in Table 2. The results are also shown in Table 2.

[0035]

[Table 2] ・ ○ in the column of the state of the test piece indicates that there is no crack, x indicates that many cracks occur, and − indicates that the test piece cannot be created because it does not cure.

Experimental Example 3 In this cement composition, slag A (crystallized slag) was used.
Slag A with 75 parts and 25 parts hydraulic material a
Was carried out in the same manner as in Experimental Example 1 except that the Blaine specific surface area was changed as shown in Table 3. The results are also shown in Table 3.

[0037]

[Table 3] ・ ○ in the column of the condition of the specimen is no crack

Experimental Example 4 Slag A (crystallized slag) having a Blaine specific surface area of 4,000 cm ² / g was used, and the mixing ratio of slag A in the cement composition was 75 parts, and 25 parts of the hydraulic material was 100 parts in total. In the same manner as in Experimental Example 1, except that the addition amount of water was changed as shown in Table 4. The results are also shown in Table 4.

[0039]

[Table 4] ・ ○ in the column of the condition of the specimen is no crack

Experimental Example 5 A mixed slag was prepared by mixing slag A and slag C so that the vitrification rate was as shown in Table 5. The mixing ratio of the above mixed slag is 75 parts, and the hydraulic material is 25
Part of the cement composition was mixed, and the same evaluation as in Experimental Example 1 was performed. The results are also shown in Table 5.

[0041]

[Table 5] ・ ○ in the column of the condition of the specimen is no crack

[0042]

EFFECTS OF THE INVENTION By using the cement composition of the present invention, it is possible to obtain a cured product which can be cast by casting, exhibits excellent strength development in carbonation curing and does not cause cracks. Further, the blast furnace slag, which is an industrial by-product, can be made highly functional, and a high-strength cured product can be obtained even if the amount of cement, which has a large environmental load, is reduced.

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Claims (3)

[Claims] 1. A cement composition for a carbonation-cured product, which comprises crystallized slag obtained by heat-treating granulated blast furnace slag to crystallize it, and a hydraulic substance. 2. The crystallized slag has a Blaine specific surface area of 3,000.
The cement composition for a carbonation-cured product according to claim 1, wherein the cement composition is 0 cm ² / g or more. 3. The carbonated cured product according to claim 1, wherein the content of the crystallized slag is 90 to 50 parts in 100 parts in total of the hydraulic material and the crystallized slag. Cement composition.