JP2000281408A - Cement admixture and cement composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare a cement admixture which has the specific maximum particle diameter and can impart an excellent injection property, excellent material separation resistance, and an excellent strength to a cement composition, by formulating an inorganic sulfate and specific calcium aluminate having a specific Li2O content and a specified CaO/Al2O3 molar ratio. SOLUTION: This cement admixture comprises an inorganic sulfate and calcium aluminate having a Li2O content of from 0.1 to <1 wt.% and a CaO/Al2 O3 molar ratio of 1.5 to 2.0, and has the maximum particle diameter of <=40 μm. The calcium aluminate is crystalline or amorphous, is obtained by thermally treating a mixture of a CaO raw material, an Al2O3 raw material, a Li2O raw mate, and the like at 1,500 to 1,800 deg.C, has a Blaine specific surface area of preferably about 3,000 to 9,000 cm2/g, and is contained in an amount of about 30 to 90 pts.wt. per 100 pts.wt. of the cement admixture. The inorganic sulfate salt includes anhydrous gypsum, and is contained in an amount of 10 to 70 pts.wt. per 100 pts.wt. of the cement admixture. The cement admixture is used in an amount of about 10 to 50 pts.wt. per 100 pts.wt. of a cement composition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cement admixture and a cement composition mainly used in the fields of civil engineering and construction.

[0002]

2. Description of the Related Art In the field of civil engineering and construction, water stoppage and ground
For the purpose of stabilization, the gap between soil particles in the soil, the boundary of the soil layer,
In addition, injection material is widely used in cracks in rock
You. However, usually the injection material used is water
/ Cement ratio is large, so material separation easily occurs and coagulation
・ Curing is remarkably delayed and strength development is poor.
Was. In order to meet these issues, rapid-hardening
Is being developed. The present inventors have previously developed a rapid-hardening
And Li_TwoCa content of 1 to 15% by weight of CaO-Al _TwoO_Three−Li_TwoO type
Quality, inorganic sulphates and setting regulators, maximum
A cement admixture with a particle size of 40 μm or less was proposed (Japanese Unexamined Patent Publication No.
No. 310846). Injection material using this cement admixture
Has excellent material separation resistance and strength
Was.

[0003]

However, Li ₂ O, which is a raw material, is expensive as an industrial raw material and has been hardly popularized. The present inventors have conducted intensive studies in order to solve the above-described problems, and as a result, have used a cement admixture containing calcium aluminate having a specific composition range containing less than 1% by weight of Li ₂ O. Thus, the present inventors have found that a cement composition having excellent injectability, material separation resistance, and strength development properties can be obtained, and have completed the present invention.

[0004]

That is, the present invention comprises a calcium aluminate and an inorganic sulfate having a Li ₂ O content of 0.1 to less than 1% by weight and a CaO / Al ₂ O ₃ molar ratio of 1.5 to 2.0. Become,
It is a cement admixture with a maximum particle size of 40 μm or less.
A cement composition comprising a cement having a maximum particle size of 40 μm or less and the cement admixture.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail.

The calcium aluminate used in the cement admixture of the present invention has a Li ₂ O content of 0.1 to less than 1% by weight, and more preferably a Li ₂ O content of 0.25 to 0.9% by weight. The ratio of CaO to Al ₂ O _{3 in} the calcium aluminate is 1.5 in a CaO / Al ₂ O ₃ molar ratio (hereinafter, referred to as a C / A molar ratio).
It is in the range of ~ 2.0. If the composition of the calcium aluminate is not in the above range, the excellent material separation resistance and strength manifestation, which are the effects of the present invention, cannot be obtained.

The calcium aluminate of the present invention may be either crystalline or amorphous, and is obtained by heat-treating a mixture of a CaO raw material, an Al ₂ O ₃ raw material and a Li ₂ O raw material. The raw material is not particularly limited, but, for example, slaked lime or limestone powder or the like as a CaO raw material, bauxite or aluminum residual ash or the like as an Al ₂ O ₃ raw material, and Li ₂ CO ₃ or LiOH as a Li ₂ O raw material. Are used, respectively. The method of the heat treatment is not particularly limited, but for example, there is a method using a rotary kiln, an electric furnace, or the like. The heat treatment conditions (temperature and time) vary depending on the material composition, but usually the heat treatment temperature is about 1500 to 1800 ° C. Cooling of the heat-treated material
Any method such as a quenching method using water or high-pressure air or a slow cooling method using natural cooling may be used. Further, as other components or impurities, for example, Na ₂ O, K ₂ O, MgO, TiO ₂ , Fe ₂ O ₃ , B ₂ O ₃ , SiO
₂ , P ₂ O ₅ , SO ₃ and F _{2 and} other components are expected to be mixed, but these have the effect of lowering the melting point of the fired product or the melt, or increasing the activity, and also have a preferable surface. There is no problem as long as the effects of the present invention are not substantially impaired.

The particle size of calcium aluminate is such that the maximum particle size is 40 μm or less, preferably 20 μm or less.
It is more preferable that the thickness be not more than μm. When the maximum particle size of calcium aluminate exceeds 40 μm, the effect of the present invention is obtained.
Good injection property and material separation resistance cannot be obtained. Also, the specific surface area is usually 3000 to 9000 cm ² / g
And it is preferably about 4000 to 7000 cm ² / g. Three
If it is less than 000 cm ² / g, good injection properties and resistance to material separation may not be obtained, and if it exceeds 9000 cm ² / g, further improvement of the effect cannot be expected.

The amount of calcium aluminate is not particularly limited, but is preferably 30 to 90 parts by weight, more preferably 40 to 70 parts by weight, per 100 parts by weight of the cement admixture. If the amount is less than 30 parts by weight, sufficient rapid hardness and durability may not be obtained, and if it exceeds 90 parts by weight, sufficient pot life and strength development may not be obtained.

The inorganic sulfate of the present invention is a generic term for alkali metal sulfates such as gypsum, aluminum sulfate, sodium sulfate, etc., alkali metal sulfites and alkali metal bisulfites, and is particularly limited. Although not, gypsum and aluminum sulfate can be used,
The present invention is preferable from the viewpoint of great effect and economy. The gypsum is a general term for anhydrous gypsum, hemihydrate gypsum and dihydrate gypsum, and is not particularly limited, but it is preferable to use anhydrous gypsum because the effect of the present invention is the greatest. Anhydrite is
For example, it is possible to use natural anhydrous gypsum naturally produced, hemihydrate gypsum or dihydrate gypsum that is dehydrated by heat treatment, or those generated as industrial by-products. Aluminum sulfate includes anhydrous salts and hydrated salts, but from the viewpoint of economy, use of hydrated salts is preferred. The hydrated salt of aluminum sulfate has water of crystallization in the range of 20 mol or less, but any hydrate can be used.

The maximum particle size of the inorganic sulfate is 40 μm or less, preferably 20 μm or less, and more preferably 10 μm or less. If the maximum particle size exceeds 40 μm, the effects of the present invention, ie, good injectability and resistance to material separation, cannot be obtained.
The specific surface area is usually 3000 to 90 in terms of the Blaine specific surface area.
In the range of about 00cm ² / g, about 4000~7000cm ² / g are preferred. If it is less than 3000 cm ² / g, good injectability and resistance to material separation may not be obtained, and if it exceeds 9000 cm ² / g, further improvement of the effect cannot be expected.

The amount of the inorganic sulfate is not particularly limited, but is preferably 10 to 70 parts by weight, more preferably 30 to 60 parts by weight, per 100 parts by weight of the cement admixture. If less than 10 parts by weight, sufficient strength development may not be obtained,
If it exceeds 70 parts by weight, long-term durability may be deteriorated.

The particle size of the cement admixture of the present invention has a maximum particle size of 40 μm or less, more preferably 20 μm or less, and 10 μm or less.
μm or less is more preferable. If the maximum particle size of the cement admixture exceeds 40 μm, the effect of the present invention, that is, good injection property and material separation resistance cannot be obtained. The specific surface area is usually in the range of about 3,000 to 9000 cm ² / g, preferably about 4,000 to 7000 cm ² / g, in terms of Blaine specific surface area. If it is less than 3000 cm ² / g, good injectability and resistance to material separation may not be obtained, and if it exceeds 9000 cm ² / g, further improvement of the effect cannot be expected.

The amount of the cement admixture of the present invention is not particularly limited, but is preferably 10 to 50 parts by weight, based on 100 parts by weight of the cement composition containing cement and the cement admixture. -30 parts by weight are more preferred. If the amount is less than 10 parts by weight, the effect of developing strength is not sufficient, and even if the amount exceeds 50 parts by weight, further improvement of the effect cannot be expected.

As the cement of the present invention, ordinary, early strength,
Various portland cements, such as ultra-high strength, low heat and moderate heat, and various kinds of mixed cements obtained by mixing these portland cements with pozzolanic substances such as silica, fly ash and blast furnace slag, and alumina cement can be used. And its maximum particle size is 40μm
It is as follows.

As the mixing device used in the production of the cement admixture and the cement composition of the present invention, any existing stirring device can be used.
There are an omni mixer, a V-type mixer, a Henschel mixer and a Nauta mixer. Also, as a mixing method,
The respective materials may be mixed separately at the time of construction, or a part or all of them may be mixed in advance.

The blending amount of water is not particularly limited, but is preferably in the range of 50 to 500%, more preferably 100 to 400%, in a water / cement composition ratio. If it is less than 50%, sufficient injectability may not be obtained, and if it exceeds 500%, sufficient strength expression may not be obtained.

In the present invention, if necessary, a setting retarder can be used in combination. Examples of the setting retarder include organic acids such as citric acid, tartaric acid, gluconic acid, and malic acid or salts thereof, phosphoric acid or salts thereof, alkali metal carbonates, and boric acid. However, it is preferable to use an organic acid or a salt thereof in combination with an alkali metal carbonate since the strength developability is improved. The amount of the setting retarder depends on the purpose and use of the setting retarder, but is usually more preferably 0.5 to 10 parts by weight based on 100 parts by weight of the cement admixture. If the amount is less than 0.5 part by weight, a sufficient pot life may not be obtained, and if the amount exceeds 10 parts by weight, the strength may be reduced.

The cement admixture and cement composition of the present invention may be added to aggregates such as sand and gravel, as well as reinforcing fiber materials, cement expanders, water reducing agents, high performance water reducing agents, high performance AE water reducing agents, and thickening agents. Rust preventives and antifreezes, soluble alkali salts such as sodium hydroxide, calcium compounds such as calcium oxide and calcium hydroxide, clay minerals such as bentonite and montmorillonite, ion exchangers such as zeolite, hydrotalcite and hydrocalumite Can be used together within a range that does not substantially inhibit the object of the present invention.

[0020]

The present invention will be described below in detail with reference to examples.

Example 1 A CaO raw material, an Al ₂ O ₃ raw material and an alkali metal oxide (hereinafter referred to as R ₂
O) is melted at 1600 ° C for 30 minutes in an electric furnace, then the melt is quenched and the resulting clinker is ground with a vibrating ball mill to obtain the maximum particle size. It was adjusted to 40 μm and a specific surface area of brane of 6500 ± 200 cm ² / g to obtain various calcium aluminates shown in Table 1.
The composition of calcium aluminate was measured by chemical analysis.

50 parts by weight of this calcium aluminate and 50 parts by weight of inorganic sulfate a are mixed to form a cement admixture having a maximum particle size of 40 μm and a specific surface area of brane of 6500 ± 200 cm ² / g,
A cement composition was prepared by mixing with cement ground to a maximum particle size of 40 μm. In 100 parts by weight of the cement composition, 25 parts by weight of the cement admixture and 0.5 part by weight of the setting modifier were blended, and a water / cement composition ratio of 300% was kneaded with a mortar mixer for 60 seconds to obtain a cement paste. Prepared. About this cement paste, the separation water rate was measured in order to measure the compressive strength at 20 ° C. and evaluate the material separation resistance. Table 1 shows the results. For comparison, a similar test was performed for those containing an alkali metal oxide other than Li ₂ O. <Materials> CaO raw material: reagent primary calcium carbonate Al ₂ O ₃ raw material: reagent primary aluminum oxide R ₂ O (A) raw material: reagent primary lithium carbonate R ₂ O (B) raw material: reagent primary sodium carbonate R ₂ O (C) raw material: Reagent 1st grade potassium carbonate Cement: Ordinary Portland cement manufactured by Denki Kagaku Kogyo Co., Ltd. crushed with a vibrating ball mill to a maximum particle size of 40 μm. Inorganic sulfate a: natural anhydrous gypsum, maximum particle size 40 μm Setting retarder: mixture of 75 parts by weight of potassium carbonate and 25 parts by weight of citric acid Water: tap water <Measurement method> Particle size: laser diffraction particle size distribution analyzer Separated water Rate: Polyethylene 5cm bag, height 15c
m, and the height of the floating water separated after 24 hours was measured, and the water separation rate (%) was calculated from (height of the floating water / 15) × 100. Compressive strength: Measured according to JIS A 1108.

[0023]

[Table 1]

The cement composition containing the cement admixture of the present invention exhibited good material separation resistance and compressive strength. On the other hand, a comparative example containing no Li ₂ O (Experiment No. 1
-1), Comparative Example with high Li ₂ O content (Experiment No. 1-7), Na ₂ O
Examples (Experiment Nos. 1-8 and 1-9) containing Ca and K ₂ O, and Comparative Examples using calcium aluminate having a C / A molar ratio of 2.2 (Experiment Nos. 1-10 and 1-13) In the case of (), the material separation resistance and the compressive strength development are remarkably inferior.

Example 2 The same procedure as in Example 1 was carried out except that the amount of the cement admixture of Experiment No. 1-4 of Example 1 in 100 parts by weight of the cement composition was changed as shown in Table 2. I went to. Table 2 shows the results.

[0026]

[Table 2]

The cement composition containing the cement admixture of the present invention exhibited good material separation resistance and compressive strength. On the other hand, in the comparative example (Experiment No. 2-1) in which the cement admixture was not blended, the material separation resistance and the compressive strength development were remarkably inferior.

Example 3 Table 3 shows the types and amounts of calcium aluminate and inorganic sulfate in the cement admixture of Experiment No. 1-4 of Example 1.
The procedure was performed in the same manner as in Example 1 except that the conditions were changed as shown in FIG. Table 3 shows the results. <Materials> Inorganic sulfate a: Natural anhydrous gypsum, maximum particle size of 40 μm Inorganic sulfate b: Reagent primary grade aluminum sulfate 18 hydrate, maximum particle size of 40 μm Inorganic sulfate c: Reagent primary grade dihydrate gypsum, maximum particle size 40 μm inorganic sulfate d: reagent grade 1 hemihydrate gypsum, maximum particle size 40 μm

[0029]

[Table 3]

The cement composition containing the cement admixture of the present invention exhibited good material separation resistance and compressive strength. On the other hand, in the comparative example in which the inorganic sulfate was not blended (Experiment No. 3-1), the material separation resistance and the compressive strength development were remarkably inferior.

Example 4 In the cement admixture of Experiment No. 1-4 of Example 1, the maximum particle size was changed as shown in Table 4, and the injection permeability was measured in addition to the compressive strength and the water separation rate. Other than that, it carried out similarly to Example 1. Table 4 shows the results. <Measurement method> Injection permeability: Spread cloth on the bottom of a cylinder of φ10 × 20cm, specific gravity
2.63, particle size 0.3-1.2mm, showing the porosity per unit volume, filled with sand of 43% porosity 15cm in height from the lower part, poured 500cc of the prepared cement paste for injection from the upper part of the cylinder, 24 hours later The mold was removed, and the penetration depth was measured.

[0032]

[Table 4]

The cement composition containing the cement admixture having a maximum particle size of 40 μm or less according to the present invention exhibited good injection permeability, material separation resistance and compressive strength. On the other hand, in the comparative example in which the maximum particle diameter of the cement admixture is 50 μm (Experiment No. 4-1), the material separation resistance, the compressive strength development, and the injection permeability are remarkably inferior.

Example 5 In the cement admixture of Experiment No. 1-4 of Example 1, the maximum particle size was changed to 40 μm, and the maximum particle size of cement was changed as shown in Table 5. The same was done. Table 5 shows the results.

[0035]

[Table 5]

The cement admixture of the present invention has a maximum particle size of 40.
The cement composition containing the cement of not more than μm showed good injection permeability, material separation resistance and compressive strength. On the other hand, in the comparative example (Experiment No. 5-1) in which the maximum particle diameter of the cement is 50 μm, the material separation resistance, the compressive strength development, and the injection permeability are remarkably inferior.

[0037]

By using the cement admixture of the present invention, a cement composition having excellent injectability, resistance to material separation and strength development can be obtained.

Claims (2)

[Claims] Claims: 1. A Li ₂ O content of 0.1 to less than 1% by weight, CaO / Al ₂ O
_3. A cement admixture having a maximum particle size of 40 μm or less, comprising calcium aluminate and inorganic sulfate in a molar ratio of 1.5 to 2.0. 2. A cement composition comprising a cement having a maximum particle size of 40 μm or less and the cement admixture according to claim 1.