JP2001114541A - Cement admixture and cement composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a cement admixture capable of imparting excellent expanding properties to a mortar or a concrete even if the formulated amount thereof is small, capable of preventing a pop out phenomenon and improving waterproof properties, and also capable of keeping a high quality over a long period because of good preservation stability, and further to provide a cement composition. SOLUTION: This cement admixture comprises an expanding material comprising a free lime, hauyne and anhydrous gypsum as essential constituent compounds, further having the percentage of a chemical composition of CaO, Al2O3 and SO3 regulated so as to be >=57 wt.% CaO, 5-15 wt.% Al2O3 and <=28 wt.% SO3, and containing <2 wt.% MgO in the percentage of the total chemical composition, a fatty acid and/or salts thereof, and a siliceous fine powder and/or a limestone fine powder. The cement composition is constituted of a cement and the cement admixture.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a cement admixture and a cement composition mainly used in the civil engineering and construction industries.

[0002]

2. Description of the Related Art Cement is an excellent material which is inexpensive and can be used to form a large concrete structure into an arbitrary shape. Furthermore, by using a cement admixture together, it is possible to improve the strength and durability of the structure. Many cement admixtures have been proposed so far, but the most used one is a cement admixture that imparts expandability to concrete. Here, concrete is
A generic term for cement, mortar and concrete.

[0003] As a cement admixture for imparting expandability to a concrete structure, for example, CaO-Al ₂ O ₃ -SO
₃ based compound as an active ingredient is known (JP-B
No. 42-21840, JP-B-4219473-JP, JP-B-53-160
No. 07 publication).

[0004]

However, since these cement admixtures are opened in a ready-mixed plant and mixed with concrete, in some cases, these cement admixtures are shipped without being sufficiently kneaded. Sometimes. In such a case, the cement admixture does not disperse evenly into the concrete and becomes lump, and the cured concrete causes local abnormal expansion, and the surface of the cured body macroscopically swells, peels, and falls. Or cause a so-called pop-out phenomenon.

[0005] As a method for preventing the pop-out phenomenon, an inert inorganic powder or the like is mixed in advance with the cement admixture so that the cement admixture may not be sufficiently kneaded.
A method is conceivable in which the expansion components do not agglomerate and do not lump, and a certain degree of dispersion can be expected.However, by mixing an inert inorganic powder, the expansion component is diluted to provide the required performance. Therefore, there is a problem that the compounding amount of the cement admixture increases.

[0006] In recent years, the performance required of a cement admixture that imparts expandability has been increasing more and more. That is, the reality is that the development of a cement admixture that can impart excellent expansion performance even with a small amount of compounding has been awaited. Therefore,
Although it is intended to prevent the pop-out phenomenon, a method in which the amount of the cement admixture is increased is not useful, and it is necessary to find a method that can prevent the pop-out phenomenon without increasing the amount.

On the other hand, a cement admixture for imparting waterproofness to concrete is also required. Thus, the present inventors
In view of such a situation, as a result of various investigations to solve the above-mentioned problems, the above-mentioned compound was obtained by blending a specific expanding substance, a fatty acid and / or a salt thereof, and a siliceous fine powder and / or a limestone fine powder. The inventors have found that a cement admixture that can solve the problem can be obtained, and have completed the present invention.

[0008]

That is, the present invention comprises free lime, auin, and anhydrous gypsum as the main constituent compounds, and in terms of the percentage of the chemical composition comprising three components of CaO, Al ₂ O ₃ and SO ₃ , 57% by weight or more of CaO, Al
5-15% by weight of ₂ O _3, 28% by weight or less of SO ₃ , and an expanding substance having less than 2% by weight of MgO in percentage of the chemical composition of all components; fatty acids and / or salts thereof; A cement admixture comprising a siliceous fine powder and / or a limestone fine powder, wherein the free lime content of the expansive substance is 30% by weight or more. Has an anhydrous gypsum content of 4
0% by weight or less of the cement admixture, further comprising a cement and the cement admixture.

[0009]

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

[0010] The expanding material of the present invention comprises CaO, Al_TwoO_ThreePassing
And SO_ThreeFree lime, eauin and anhydrous
Gypsum is the main constituent compound, CaO, Al_TwoO_Threeas well as
SO _ThreeIn the percentage consisting of the three components
Weight% or more, Al_TwoO_ThreeIs 5 to 15% by weight, SO_ThreeIs 28
% By weight or less and the percentage of the chemical composition of all components
And the MgO content is less than 2% by weight.
ing. CaO is preferably 60 to 80% by weight, and 65 to 80% by weight.
75% by weight is more preferred. Also, SO_ThreeIs 10-25
% By weight is preferred, and 15-20% by weight is more preferred.
MgO content is less than 2% by weight, preferably 1.5% by weight or less.
Is more preferable. When the MgO content is 2% by weight or more, long-term resistance
There is a risk that durability will deteriorate.

[0011] The constituent compound of the swelling substance of the present invention,
The main constituents are free lime, auin and anhydrous gypsum. The _{Auin, 3CaO · 3Al 2 O 3 ·} C
It means a compound represented by aSO ₄ . In the present invention, the free lime content is preferably 30% by weight or more,
It is more preferably at least 40% by weight. Free lime content is 30
If the amount is less than the weight percentage, excellent expansion performance may not be obtained. The content of anhydrous gypsum is preferably 40% by weight or less, more preferably 35% by weight or less. When the content of anhydrous gypsum exceeds 40% by weight, not only SO _X generated during production increases, but also excellent expansion performance may not be obtained.

The intumescent material of the present invention comprises a CaO raw material, Al ₂
It can be produced by blending an O ₃ raw material and a CaSO ₄ raw material and subjecting them to a heat treatment. Examples of CaO raw materials include limestone and slaked lime, and examples of Al ₂ O ₃ raw materials include bauxite and aluminum residual ash. Examples of CaSO ₄ raw materials include
Gypsum dihydrate, hemihydrate gypsum, anhydrous gypsum and the like can be mentioned. The heat treatment can be performed by using a rotary kiln or an electric furnace, and the heat treatment temperature is preferably in a range of about 1100 to 1600 ° C.
A temperature of about 00 to 1400 ° C. is more preferable. If the temperature is lower than 1100 ° C., the obtained cement admixture may not have sufficient expansion performance. If the temperature exceeds 1600 ° C., not only the amount of SO _X which evaporates, but also excellent expansion performance may not be obtained.

[0013] In the present invention, the presence of inflation material
Pure substance, the total amount of which does not substantially inhibit the object of the present invention
It is preferably within a range, for example, about 10% by weight or less.
No. Specific examples of impurities include SiO_Two, Fluorinated compound
Material, chlorine compound, TiO_Two, Na _TwoO, K_TwoO, MgO,
Fe_TwoO_Three, B_TwoO_Three, P_TwoO_FiveAnd the like. Among these
In particular, the MgO content is less than 2% by weight as described above.
But SiO_TwoThe amount is also preferably 5% by weight or less,
% By weight or less is more preferable. SiO_TwoThe amount exceeds 5% by weight
Thus, the effect of the present invention, that is, excellent expansion performance is obtained.
May not be.

The particle size of the expanded material of the present invention is not particularly limited, but is usually 1500 in terms of a Blaine specific surface area.
6000 cm ² / g is preferable, and 2500 to 4000
cm ² / g is more preferred. 1500cm is less than ² / g, may strength development is deteriorated, 6000 cm ²
/ G, excellent expansion performance may not be obtained.

The fatty acid of the present invention generally means RCOOH
(R is a saturated or unsaturated hydrocarbon), and is a general term for a compound represented by the formula (I), and is not particularly limited.
Specific examples thereof include, for example, lauric acid, myristic acid, stearic acid, oleic acid, behenic acid, palmitic acid and the like. In the present invention, salts of these fatty acids can also be used, and specific examples thereof include sodium salts, potassium salts, calcium salts, magnesium salts, and aluminum salts. Further, fatty acids can also be obtained as natural fats and oils, and specific examples thereof include, for example, soybean oil, coconut oil, palm oil, olive oil, linseed oil, cottonseed oil, rapeseed oil, drill oil, castor oil, tallow, squalane, Lanolin, hardened oil and the like. In the present invention, one or more of these can be used (hereinafter referred to as fatty acids).

Fatty acids not only promote the effect of suppressing pop-out, but also have the effect of improving storage stability. That is, it suppresses weathering of the expansive substance contained in the cement admixture of the present invention.

Although the silica fine powder of the present invention is not particularly limited, it is a general term for silica fume, blast furnace slag, fly ash, diatomaceous earth, silica dust such as fused silica, and the like. The siliceous fine powder has not only the effect of suppressing the pop-out phenomenon but also the effect of improving the waterproofness of concrete.

Although the limestone fine powder of the present invention is not particularly limited, it is a general term for ore mainly composed of naturally occurring calcium carbonate. The limestone fine powder does not have the effect of improving the waterproofness unlike the silica-based fine powder, but has a sufficient effect of suppressing the pop-out phenomenon, and has the advantage that it can be obtained at low cost in some areas.

The siliceous fine powder and / or limestone of the present invention
The particle size of the fine powder is not particularly limited.
Normally, the specific surface area of the brane is 3000-9000cm^Two/ G
Is preferably 3500-6000 cm^Two/ G is more preferred
New 3000cm^Two/ G is insufficient pop-out
In some cases, the effect of suppressing the phenomenon of
m ^Two/ G cannot be expected to further increase the effect.
The financial burden also increases.

An expanding substance in the cement admixture of the present invention;
The mixing ratio of the fatty acid and the silica fine powder and / or limestone fine powder is not particularly limited, but usually, the expanding material is preferably 50 to 95 parts by weight, and preferably 60 to 95 parts by weight in 100 parts by weight of the cement admixture. ~ 90 parts by weight is more preferred. If the amount of the intumescent substance is less than 50 parts by weight, sufficient inflation performance may not be obtained, and if it exceeds 95 parts by weight, a sufficient effect of suppressing a pop-out phenomenon and an effect of improving waterproofness may not be obtained. is there. The mixing ratio of fatty acids is 0.005 to
5 parts by weight is preferable, and 0.05 to 1 part by weight is more preferable. If the amount is less than 0.005 parts by weight, a sufficient pop-out suppressing effect and storage stability may not be obtained. If the amount exceeds 5 parts by weight, strength development may be deteriorated. The amount of the fine silica powder and / or the fine limestone powder is preferably 5 to 50 parts by weight, more preferably 10 to 40 parts by weight. If the amount is less than 5 parts by weight, a sufficient effect of suppressing the pop-out phenomenon,
In some cases, the effect of improving waterproofness may not be obtained, and when it exceeds 50 parts by weight, sufficient expansion performance may not be obtained.
However, in the compounding ratio in 100 parts by weight of the cement admixture, the compounding amount of the fatty acids is adjusted by subtracting from the compounding amount of the expanding material.

[0021] The particle size of the cement admixture of the present invention is not particularly limited.
500-6000 cm ² / g is preferable, and 3000-5
000 cm ² / g is more preferred. Is less than 2500 cm ² / g, there is a case where the effect of suppressing sufficient pop-out phenomenon can not be obtained in some cases expanded performance and excellent more than 6000 cm ² / g is not obtained.

The amount of the cement admixture of the present invention is not particularly limited, but is usually 3 to 1 in 100 parts by weight of the cement composition comprising cement and the cement admixture.
2 parts by weight is preferable, and 5 to 9 parts by weight is more preferable. Three
If the amount is less than 10 parts by weight, the effect of the present invention may not be sufficiently obtained. If the amount is more than 12 parts by weight, the strength development may be deteriorated.

As the cement according to the present invention, various portland cements such as ordinary, fast, super fast and moderate heat are used.
Various mixed cements obtained by mixing blast furnace slag, fly ash, and silica with these Portland cements, low-heat cements, filler cements obtained by mixing limestone powder, etc., and alumina cements can be mentioned.
Species or two or more can be used.

In the present invention, in addition to the cement admixture and cement of the present invention, aggregates such as sand and gravel, water reducing agents, AE water reducing agents,
High-performance water reducing agent, high-performance AE water reducing agent, defoamer, thickener, rust inhibitor, anti-freezing agent, shrinkage reducing agent, polymer emulsion, setting regulator, cement hardened material, clay minerals such as bentonite and zeolite One or two or more of ion exchangers and the like such as hydrotalcite can be used within a range that does not substantially inhibit the object of the present invention.

In the present invention, the method of mixing each material is not particularly limited, and each material may be mixed at the time of construction, or a part or all may be mixed in advance. . As the mixing device, any existing device can be used, and for example, a tilting cylinder mixer, an omni mixer, a Henschel mixer, a V-type mixer, a Nauta mixer and the like can be used.

[0026]

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

Example 1 A special grade of CaO raw material, Al ₂ O ₃ raw material and CaSO ₄ raw material were blended and heat-treated at 1350 ° C. for 2 hours using an electric furnace to obtain various compositions shown in Table 1. An intumescent material is produced and the specific surface area of the brane is 3500 ± 200 cm ² /
g. 74.5 parts by weight of these intumescent substances, 0.5 part by weight of fatty acid A, and 25 parts by weight of limestone fine powder were mixed to form a cement admixture, and 100 parts by weight of a cement composition comprising cement and cement admixture were used. 7 parts by weight of the cement admixture is mixed, and the unit cement composition amount is 300
Concrete having a kg / m ³ , a water / cement composition ratio of 62%, and an s / a of 45% was prepared, and the expansion rate was measured and a pop-out test was performed. In addition, the expansive substance was identified by powder X-ray diffraction (XRD), and it was confirmed that free lime, eauin and anhydrous gypsum were the main constituent compounds.
The chemical composition was determined by chemical analysis, and the compound composition was calculated from the result of chemical analysis. Table 2 shows the compound composition calculated from the chemical composition, and Table 3 shows the test results.

<Materials Used> Cement α: Commercial ordinary Portland cement Fatty acids A: Commercially available stearic acid Limestone fine powder: Limestone from Aomi mine, Niigata prefecture, crushed to a Blaine specific surface area of 5000 cm ² / g. Water: tap water Sand: from Himekawa, Niigata prefecture, specific gravity 2.62 Gravel: from Himekawa, Niigata prefecture, specific gravity 2.64 CaO raw material: reagent grade calcium carbonate Al ₂ O ₃ raw material: reagent grade aluminum oxide CaSO ₄ raw material: reagent grade anhydrous Gypsum <Measurement method> Chemical analysis: Measured according to JIS R 5202. Compound composition: Free lime content was measured according to JIS R 5202, and other compounds were determined by calculation.
That is, the C ₄ AF amount is calculated from the Fe ₂ O ₃ amount, and the total Al ₂ O ₃
Subtracting the amount of Al ₂ O ₃ contained in C ₄ AF from the amount,
The amount of the air in was calculated from the remaining amount of Al ₂ O ₃ . Then
By subtracting the SO ₃ content contained in Auin from total SO ₃ content was calculated anhydrous gypsum amounts from the remaining SO ₃ amount. Expansion coefficient: Measured according to JIS A 6202 B. Pop-out test: Concrete was prepared in advance without adding a cement admixture, this concrete was put into a tilting mixer, and the cement admixture was added later while agitating the mixer at a rate of 12 revolutions / minute. After a minute, it was discharged and poured into a mold having a length of 1 m, a width of 50 cm and a height of 10 cm, and a pop-out phenomenon was observed.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

[Table 3]

From Table 3, it can be seen that the cement admixture of the present invention has excellent expansion performance and prevents the pop-out phenomenon.

Example 2 CaO raw material, Al ₂ O ₃ raw material and CaSO
Mix ₄ raw materials and use a rotary kiln at a temperature of 1
The procedure was performed in the same manner as in Example 1 except that clinkers having various compositions shown in Table 4 were produced by heat treatment at 400 ° C. Table 5 shows the compound composition calculated from the chemical composition. Table 6 shows the measurement results of the coefficient of expansion.

<Materials Used> CaO raw material: Limestone from Aomi mine, Niigata Prefecture Al ₂ O ₃ Raw material: bauxite from China CaSO ₄ raw material: Natural anhydrous gypsum from Thailand Commercial products: free lime, awyn and anhydrous gypsum as main constituent compounds Cement admixture.

[0035]

[Table 4]

[0036]

[Table 5]

[0037]

[Table 6]

From Table 6, it can be seen that the cement admixture of the present invention has excellent expansion performance and prevents the pop-out phenomenon.

Example 3 The same as Example 2 except that the expanding substance c and the fine limestone powder were used, and the kinds of fatty acids and the mixing ratio in 100 parts by weight of the cement admixture were changed as shown in Table 7. I went to. However, when the blending amount of the limestone fine powder was fixed at 25 parts by weight and the amount of the fatty acids was changed, the amount of the expanding substance c was adjusted.
In order to confirm the storage stability of the cement admixture, the cement admixture was put in a paper bag, closed with a sewing machine and closed at a temperature of 20 ° C.
Stored in a test room at 80 ° C. and 80% relative humidity. During the storage period shown in Table 7, the expansion rate of concrete was measured to confirm the storage stability. The results are shown in Table 7.

<Materials Used> Fatty acids B: Commercial oleic acid Fatty acids C: Commercial lauric acid Fatty acids D: Commercial coconut oil Fatty acids E: Commercial palm oil Fatty acids F: Commercial beef tallow Fatty acids G: Commercial sodium stearate fatty acid Class H: commercially available sodium oleate Fatty acids I: Equiweight mixture of fatty acids A and fatty acids D Fatty acids J: Equiweight mixture of fatty acids A, fatty acids D and fatty acids H

[0041]

[Table 7]

From Table 7, it can be seen that the cement admixture of the present invention has a small decrease in the expansion coefficient even when the storage period is long, and also prevents the pop-out phenomenon, as compared with the comparative example in which no fatty acid is used. .

Example 4 Example 4 was repeated except that the cement admixture was prepared by using the expanding substance c and the fatty acid A and changing the type and amount of the siliceous fine powder and / or limestone fine powder shown in Table 8. Performed similarly to 2. However, the mixing ratio of the fatty acids A was fixed at 0.5 parts by weight. The waterproof test was also performed. Table 8 also shows the results.

<Material used> Silica fine powder b: Commercial blast furnace slag obtained by pulverizing a blast furnace slag to a specific surface area of 5000 cm ² / g. Silica fine powder b: Commercial silica fume, Blaine specific surface area 200,000 cm ² / g. Silica fine powder C: Commercial fly ash ground to a specific surface area of 5000 cm ² / g. Silica fine powder d: Commercial diatomaceous earth ground to a Blaine specific surface area of 5,000 cm ² / g. Silica fine powder e: Equal weight mixture of siliceous fine powder a and siliceous fine powder b, Blaine specific surface area 102500 cm
² / g. Silica fine powder F: Equiweight mixture of siliceous fine powder b and limestone fine powder, Blaine specific surface area 102500 cm ² /
g. <Measurement method> Waterproof test: φ15 × 30 cm, center hole diameter 2.0c
A m-shaped hollow specimen was prepared, demolded at the age of 1 day, subjected to water curing for 6 days until the age of 7 days, and then subjected to a water permeability test. The test was performed using the output method. A water pressure of 10 kg / cm ² was applied from the outside of the specimen for 48 hours, the amount of water oozing out of the center hole was measured, and the relative value when the water permeability of concrete not mixed with the cement admixture was taken as 100 was measured. Expressed as a ratio.

[0045]

[Table 8]

From Table 8, it can be seen that the cement admixture of the present invention has excellent expansion performance, prevents pop-out phenomenon, and has high waterproofness.

Example 5 74.5 parts by weight of cement admixture c and fatty acids A0.5
Example 2 except that a cement admixture consisting of 25 parts by weight of a silica fine powder and 25 parts by weight of a siliceous fine powder was used, and the blending amount of the cement admixture with respect to 100 parts by weight of the cement composition was changed as shown in Table 9. The same was done. Table 9 also shows the results.

[0048]

[Table 9]

From Table 9, it can be seen that the concrete containing the cement admixture of the present invention has an increased coefficient of expansion as the compounding amount increases, thereby preventing the pop-out phenomenon and increasing the waterproofness.

Example 6 CaO raw material, Al ₂ O ₃ raw material, CaSO ₄
The raw material and the MgO raw material were blended and heat-treated at a temperature of 1400 ° C. using a rotary kiln.
Intumescent materials having different MgO contents shown in FIG. 0 were produced and pulverized to a Blaine specific surface area of 3500 ± 200 cm ² / g. 74.5 parts by weight of the intumescent material, 0.5 part by weight of fatty acid A, and 25 parts by weight of siliceous fine powder are mixed to form a cement admixture, and 100 parts by weight of a cement composition comprising cement and cement admixture And a cement admixture in an amount of 10 parts by weight to prepare a mortar having a water / cement composition ratio of 25% and a sand / cement composition ratio of 1/2, and observed the long-term stability of the mortar. However, a commercially available high-performance water reducing agent was used in an amount of 1.2% based on the cement composition. The mortar was cured at 20 ° C. for 6 months after demolding at the age of 1 day. Table 11 shows the results.

<Materials> MgO raw material: Chinese dolomite High-performance water reducing agent: Commercial polycarboxylic acid

[0052]

[Table 10]

[0053]

[Table 11]

From Table 11, it can be seen that the low water cement composition ratio mortar blended with the cement admixture of the present invention has excellent expansion performance, but the concrete of the comparative example blended with the cement admixture having a high MgO content. It can be seen that cracking and expansion failure occurred.

[0055]

Industrial Applicability The cement admixture of the present invention not only provides excellent expansion performance, prevents pop-out phenomena, and improves waterproofness, even if the compounding amount in mortar or concrete is small. Since the storage stability is good, it is possible to maintain high quality for a long time. In addition, even when used at a low water cement composition ratio, a mortar or concrete excellent in long-term stability that does not cause expansion failure due to remaining unreacted materials can be obtained.

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[Procedure amendment]

[Submission date] November 8, 1999 (1999.11.
8)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Name of invention

[Correction method] Change

[Correction contents]

[Title of the Invention] Cement admixture and cement composition

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C04B 24/08 C04B 24/08 28/02 28/02

Claims (4)

[Claims] 1. Free lime, eauin and anhydrous gypsum are the main constituent compounds, and CaO is 5% by percentage of the chemical composition consisting of three components of CaO, Al ₂ O ₃ and SO _3.
7 wt% or more, Al ₂ O ₃ is 5 to 15 wt%, SO ₃ 2
Not more than 8% by weight, containing, in percentage of the chemical composition of all components, less than 2% by weight of MgO, a swelling substance, fatty acids and / or salts thereof, and siliceous fine powder and / or limestone fine powder. Made of cement admixture. 2. The swelling substance has a free lime content of 30% by weight.
The cement admixture according to claim 1, characterized in that: 3. The cement admixture according to claim 1, wherein the content of the anhydrous gypsum in the expanding substance is 40% by weight or less. 4. A cement composition comprising a cement and the cement admixture according to claim 1.