JP2002003251A - Cement admixture and cement composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cement admixture excellent in expansiveness and quality stability in a long-term storage and a cement composition containing it. SOLUTION: The admixture contains an expansive substance comprising free lime, calcium aluminoferrite, hauyne and anhydrite, fatty acids and/or their salts. The cement composition contains cement and the 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 that is inexpensive and can be used to make large structures into any shape. In this cement,
Furthermore, by using a cement admixture together, it is possible to improve the strength and durability of the manufactured structure. Although many cement admixtures have been proposed, the one most frequently used is a cement admixture that imparts expandability to a concrete structure. Here, the concrete is a general 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
JP-B-42-21840, JP-B-4219473-, JP-B-53-160
No. 07 publication).

[0004]

However, a conventional cement admixture containing a CaO-Al ₂ O ₃ -SO ₃ compound as an active ingredient has a high SO ₃ content, and therefore, when the cement admixture is produced, the cement admixture is released into the atmosphere. The released SO _X was viewed as a problem. In recent years, the performance required of a cement admixture that imparts expandability has been increasing more and more. That is, the fact is that the development of a cement admixture capable of imparting excellent expansion performance even at a low admixture ratio has been awaited. Further, the conventional cement admixture imparting expandability has a problem that the expandability is greatly reduced by storage. This is largely due to weathering caused by water wetting and breakage of the bag, but even if the storage condition is relatively good, the swelling performance decreases when the storage period is about 6 months. In view of such a situation, the present inventors have conducted various studies to solve the above-mentioned problems. As a result, by blending a specific swelling substance and a fatty acid and / or a salt thereof, the swelling performance is excellent and the storage stability is improved. The present inventors have found that a cement admixture having good properties can be obtained, and have completed the present invention.

[0005]

That is, the present invention relates to a cement admixture containing an expanding substance containing free lime, calcium aluminoferrite, eauin and anhydrous gypsum, and a fatty acid and / or a salt thereof. Material
It is a cement composition containing cement and the cement admixture.

Hereinafter, the present invention will be described in detail.

[0007] The expanding substance of the present invention contains free lime, calcium alumino-ferrite, eauin and anhydrous gypsum, and the ratio thereof is not particularly limited. The free lime is preferably 30 to 70 parts, more preferably 40 to 60 parts. In addition, calcium alumino ferrite is 5-2
2.5 parts is preferable, and 10 to 15 parts is more preferable. The amount of the outer is preferably 5 to 22.5 parts, more preferably 10 to 15 parts. Further, the amount of anhydrous gypsum is preferably 5 to 30 parts, more preferably 10 to 25 parts. If the composition ratio of each compound in the cement admixture is not in the above range, excellent expansion characteristics may not be obtained. The parts and% used in the present invention represent mass units.

The free lime of the present invention is usually f-CaO
It is called. The calcium aluminof of the present invention
Ferrite is CaO-Al_TwoO_Three-Fe_TwoO_ThreeSystem compound
It is a general term and is not particularly limited,
Generally, CaO is C, Al _TwoO_ThreeTo A, Fe_TwoO_ThreeAnd F
Then C_FourAF and C₆A_TwoCompounds such as F are well known
I have. Usually, C_FourGood to think that it exists as AF
No. In the present invention, calcium alumino ferrite is
Bottom, C_FourAbbreviated as AF. The auin of the present invention is 3C
aO ・ 3Al_TwoO_Three・ CaSO_FourShows the compound represented by
Things.

When producing the cement admixture of the present invention, C
aO raw material, Al_TwoO_ThreeRaw material, Fe_TwoO_ThreeRaw materials and CaSO_Four
The raw material is heat-treated and free lime, C_FourAF, Auin and
It is possible to produce an expanding material containing anhydrous gypsum.
preferable. That is, free lime, C _FourAF, auin and nothing
Synthesize water gypsum separately and mix them,
CaO raw material, Al_TwoO_ThreeRaw material and Fe_TwoO_ThreeHeat-treat the raw materials
And free lime and C_FourA substance consisting of AF is synthesized and
The one made by mixing Auyne and anhydrous gypsum,
aO raw material, Al_TwoO_ThreeRaw material, Fe_TwoO_ThreeRaw materials and CaSO_Four
The raw material is heat-treated and free lime, C_FourAF and out?
Synthesize a substance consisting of
Manufactured products have reduced inflation performance when stored
Easy to do. CaO raw material, Al_TwoO_ThreeRaw material, Fe_TwoO_ThreeRaw materials and
CaSO_FourThe raw material is heat-treated and free lime, C_FourAF, Au
Synthesize swelling substance consisting of gypsum and anhydrous gypsum
As a method to confirm whether or not it was manufactured by grinding
Is, for example, coarse particles of cement admixture, specifically 10
Observation of particles larger than 0 μm with a microscope etc. and composition
Analyze the free lime, C_FourAF, Auin and
And anhydrous gypsum are mixed.
Can be easily determined.

The heat treatment temperature for producing the cement admixture of the present invention is preferably in the range of 1100 to 1600 ° C, more preferably in the range of 1200 to 1500 ° C. 1
If the temperature is lower than 100 ° C., the obtained cement admixture has insufficient expansion performance. If the temperature exceeds 1600 ° C., anhydrous gypsum may be decomposed.

Examples of the CaO raw material include limestone and slaked lime. Examples of the Fe ₂ O ₃ raw material include copper karami, iron powder, and commercially available iron oxide. Examples of the Al ₂ O ₃ raw material include bauxite and aluminum residual ash. Examples of CaSO ₄ raw materials include dihydrate gypsum, hemihydrate gypsum and anhydrous gypsum. There are impurities in these raw materials. Specific examples thereof include SiO ₂ , MgO, TiO ₂ , P ₂ O ₅ , Na ₂ O, K ₂
O, etc., are not particularly problematic as long as the object of the present invention is not substantially impaired. Among them, it is particularly preferable that SiO ₂ has a silicate ratio of less than 0.5. If the silicate ratio is 0.5 or more, excellent expansion performance may not be obtained. The silicic acid ratio in the present invention is calculated from the following formula based on the amounts of SiO ₂ , Al ₂ O ₃ and Fe ₂ O _{3 in} the expanded material. Silicic acid ratio = SiO ₂ / (Al ₂ O ₃ + Fe ₂ O ₃ ) Further, the amount of SiO ₂ in the cement admixture is preferably 5.0% or less, more preferably 3.0% or less. If it exceeds 5.0%, excellent expansion performance may not be obtained.

The fatty acid of the present invention generally means RCOOH
(R is a saturated or unsaturated hydrocarbon group) and is a general term for a compound represented by the general 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 can be mentioned. 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. Furthermore, 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, hydrogenated oil and the like.
In the present invention, one or more of these can be used (hereinafter referred to as fatty acids). Among them, in the present invention, the case where stearic acid is used is most preferable.

The mixing ratio of the intumescent substance and the fatty acids in the cement admixture is not particularly limited, but usually, the intumescent substance is 95 to 99.99 in 100 parts of the cement admixture.
5 parts is preferable, and 99-99.95 parts is more preferable.
If the amount is less than 95 parts, the strength developability may deteriorate, and 9
If it exceeds 9.995 parts, the storage stability may deteriorate. The compounding ratio of the fatty acids is preferably from 0.005 to 5 parts, more preferably from 0.05 to 1 part. If the amount is less than 0.005 part, the storage stability may be deteriorated, and if the amount is more than 5 parts, the strength expression may be deteriorated.

The particle size of the cement admixture of the present invention is not particularly limited.
500-6000 cm ² / g is preferable, and 2500-4
000 cm ² / g is more preferred. If it is less than 1500 cm ² / g, the strength development may be poor and 6000 c
If it exceeds m ² / g, excellent expansion performance may not be obtained.

Although the amount of the cement admixture of the present invention is not particularly limited, it is usually 3 to 100 parts per 100 parts of the cement composition comprising the cement and the cement admixture.
12 parts is preferable, and 5 to 9 parts is more preferable. If the amount is less than 3 parts, the effect of the present invention may not be sufficiently obtained.
If it is used beyond the part, the strength expression may be deteriorated.

The cement composition of the present invention includes the cement admixture of the present invention, various portland cements specified in JIS R 5210, various mixed cements specified in JIS R 5211, JIS R 5212 and JIS R 5213, Combine with one or more of blast furnace cement, fly ash cement and silica cement, filler cement mixed with limestone powder, etc., and alumina cement etc. prepared with the admixture ratio of JIS or higher. It was done.

In the present invention, the cement admixture and the cement composition of the present invention may be added to aggregates such as sand and gravel, as well as a water reducing agent, an AE water reducing agent, a high performance water reducing agent, a high performance AE water reducing agent and a defoaming agent , Thickeners, rust inhibitors, anti-freezing agents, shrinkage reducing agents, polymer emulsions, setting regulators, cement hardened materials, clay minerals such as bentonite and zeolite, and ion exchangers such as hydrotalcite Species or two or more species can be used as long as the object of the present invention is not substantially inhibited.

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. . 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.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below.

Example 1 Raw materials of CaO, Al ₂ O ₃ , Fe ₂ O ₃ and CaSO
_{The four} raw materials were blended and heat-treated at 1350 ° C. for 2 hours in an electric furnace to produce expanded materials having various compositions as shown in Table 1. 99.5 parts of these expanding materials and 0.5 part of fatty acid a were mixed and pulverized using a pot-type ball mill to obtain a cement admixture having a Blaine specific surface area of 3500 ± 300 cm ² / g.

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 stored in a test room at a temperature of 20 ° C. and a relative humidity of 80%. 7 parts of cement admixture is used for 100 parts of cement composition composed of cement and cement admixture, water / cement composition ratio = 50%, cement composition / sand ratio = 1 /
The mortar No. 3 was prepared, the expansion rate was measured, and the storage stability of the cement admixture was evaluated by confirming the relationship between the storage period and the length change rate of the cement admixture.

The cement admixture was identified by powder X-ray diffraction (XRD), and it was confirmed that free lime, C ₄ AF, Auyne and anhydrous gypsum were the main constituent compounds. The chemical composition was determined by chemical analysis, and the compound composition was calculated by calculation from the result of chemical analysis.

Table 2 shows the measurement results of the rate of change in length. For comparison, a similar experiment was performed on a commercially available expander without blending the fatty acids a.

<Materials Used> Fatty acids a: Commercially available stearic acid Cement: Commercial ordinary Portland cement Water: Tap water Sand: ISO679 compliant, standard sand CaO raw material: Reagent primary calcium carbonate Al ₂ O ₃ Raw material: Reagent primary oxidation Aluminum Fe ₂ O ₃ Raw material: Reagent 1st grade iron oxide CaSO ₄ Raw material: Reagent 1st grade anhydrous gypsum Expanding material: Commercial calcium aluminate based expanding material Expanding material: Commercial lime based expanding material

<Measurement method> Chemical analysis: Measured according to JIS R 5202. Compound composition: First, the free lime content was measured according to JIS R 5202, and other compounds were determined by calculation. That is, the amount of C ₄ AF was calculated from the amount of Fe ₂ O ₃ , then the amount was calculated from the amount of Al ₂ O _{3, and the} amount of anhydrous gypsum was calculated from the amount of SO ₃ . Length change rate: Measured according to JIS A 6202.

[0026]

[Table 1]

[0027]

[Table 2]

From Tables 1 and 2, it can be seen that the cement admixture of the present invention exhibits excellent expansion performance, and the deterioration of expansion performance is extremely small even when the storage period is long.

Example 2 The procedure of Example 1 was repeated, except that the expanding substance D of Example 1 was used, and the types of the fatty acids and the mixing ratio in the cement admixture were changed as shown in Table 3. . The results are also shown in Table 3.

<Materials Used> Fatty acids b: commercially available oleic acid fatty acids c: commercially available lauric acid fatty acids d: commercially available coconut oil fatty acids e: commercially available palm oil fatty acids f: commercially available tallow fatty acids g: commercially available sodium stearate fatty acids Class h: Commercially available sodium oleate Fatty acids i: Equivalent mixture of fatty acids a and fatty acids d Fatty acids j: Equivalent mixture of fatty acids a, fatty acids d, and fatty acids h

[0031]

[Table 3]

From Table 3, it can be seen that the compound containing fatty acids, such as the cement admixture of the present invention, has a very small decrease in expansion performance even when the storage period is long.

Example 3 99.5 parts of the intumescent substance D shown in Table 1 of Example 1 and fatty acids a
Example 1 was repeated except that 0.5 part of the cement admixture was used and the amount of the cement admixture in 100 parts of the cement composition was changed as shown in Table 4. The results are also shown in Table 4.

[0034]

[Table 4]

From Table 4, it can be seen that as the amount of the cement admixture of the present invention increases, the expansion performance is improved, and the reduction in expansion performance is extremely small even when the storage period is long.

[0036]

Industrial Applicability The cement admixture of the present invention not only has excellent expansion performance, but also has good storage stability, and can maintain high quality for a long period of time.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C04B 28/02 C04B 28/02 // C04B 103: 60 103: 60 (72) Inventor Mitsuo Takahashi Nishikubiki, Niigata 2209 Aomi, Aomi-gun, Gunma F-term (reference) in the Aomi Plant of Denki Kagaku Kogyo Co., Ltd. 4G012 MA00 MB23 MB33 PB03 PB05 PB11 PB12 PB18 PC09 PC14 PD02

Claims (2)

[Claims] 1. A cement admixture containing a swelling substance containing free lime, calcium alumino-ferrite, eauin and anhydrous gypsum, and a fatty acid and / or a salt thereof. 2. A cement composition comprising a cement and the cement admixture according to claim 1.