JP2002068794A - Cement admixture and cement composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cement admixture and cement compositions containing it with good expansion for prevention of pop-out and inhibition of heat of hydration. SOLUTION: The cement admixtures are obtained by firing CaO, Fe2O3, Al2O3, and CaSO4 raw materials and compose expansive additives, which contain free lime, calcium aluminoferrite, and anhydrous gypsum and dextrin having cold water soluble of <70%. The dextrin content is 0.5-15 parts in the cement admixture of 100 parts. The cement compositions comprise 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 self-sufficient in domestic production and is inexpensive because it is mass-produced. It is easy to handle and transport. In addition, it has high compressive strength, is excellent in durability such as fire resistance and water resistance, is easy to manufacture and apply, and can be made into any shape and size. Furthermore, there is an advantage that it can be used as a composite material in combination with various aggregates, steel materials, fibers, resins, and the like according to the purpose. Due to such features, cement is undoubtedly an indispensable material in forming civil engineering and building structures, but hardened materials using cement have the problem that cracks are likely to occur. . The cracks are mainly caused by drying shrinkage and heat of hydration. Although the mechanism of crack generation is different, the main cause is concrete shrinkage. Here, the concrete is a general term for cement, mortar and concrete. Therefore, for the purpose of reducing these cracks, a cement admixture that imparts expandability to a concrete structure has been proposed. As the cement admixture that imparts expandability, a CaO—Al ₂ O ₃ —SO ₃ system is used. Compounds containing a compound as an active ingredient are known (JP-B-42-21840, JP-B-42-19473, JP-B-53-16007, etc.). In addition, as a cement admixture that suppresses the heat of hydration while imparting expandability, a mixture of dextrin and a cement admixture that imparts expandability is effective.
57-00261).

[0003]

The cement admixture imparting expandability is used in a ready-mixed concrete production plant.
The main method is to mix with concrete by opening the bag, but since the opening of the bag is performed manually, there are cases where the timing and amount of the bag are incorrect. In such a case, in many cases, the cement admixture is not sufficiently kneaded in the concrete and is not uniformly dispersed but is in a lump. When such concrete hardens, massive cement admixture locally causes abnormal expansion, and the surface of the hardened body macroscopically swells, peels, and falls, causing a so-called pop-out phenomenon. ing.
As a method of preventing the pop-out phenomenon, an inert inorganic powder or the like is mixed in advance with the cement admixture, and even if the cement admixture is not sufficiently kneaded, the expanded components do not aggregate and form a lump. However, a method is conceivable in which a certain degree of dispersion can be expected. However, in this method, the swelling component is diluted by mixing an inert inorganic powder,
There is a problem that the amount of the cement admixture for imparting the required performance increases.

[0004] On the other hand, the performance required of a cement admixture that imparts expandability is increasing. That is, the development of a cement admixture that can provide excellent expansion performance even when the amount of admixture is smaller than the current level is awaited. Therefore,
The method of increasing the admixture amount of the cement admixture for preventing the pop-out phenomenon is not useful. It is necessary to find a method that can prevent the pop-out phenomenon without increasing the mixing amount. Furthermore, in order to prevent or reduce the cracks caused by the heat of hydration, it is desirable that a cement admixture that imparts expandability is additionally provided with an action of reducing the heat of hydration. In view of such a situation, the present inventors have made various studies to solve the above-mentioned problems, and as a result, by blending a specific swelling substance and dextrin having a cold water-soluble content of less than 70%, the above-mentioned problems have been solved. The inventors have found that a cement admixture that can be eliminated can be obtained, and have completed the present invention.

[0005]

That is, the present invention provides a C
aO raw material, Al_TwoO_ThreeRaw material, Fe_TwoO_ThreeRaw materials and CaSO _Four
A fired product obtained by heat-treating the raw material, free lime,
Contains calcium alumino ferrite and anhydrous gypsum
Swelling substance and dext with a cold water soluble content of less than 70%
A cement admixture containing phosphorus and cement
When the amount of dextrin in 100 parts of the admixture is 0.5 to 15 parts
The cement admixture, characterized in that
And a cement composition comprising the cement admixture
Things. The parts and percentages used in the present invention are especially
Unless otherwise indicated, it represents a mass unit.

[0006]

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

The swelling substance of the present invention contains free lime, calcium aluminoferrite and anhydrous gypsum, and the ratio thereof is not particularly limited. 30-60
Part is preferable, and 40 to 50 parts is more preferable. The content of calcium alumino ferrite is preferably 10 to 40 parts, more preferably 15 to 35 parts. Further, the amount of anhydrous gypsum is preferably 10 to 40 parts, more preferably 20 to 35 parts. If the composition ratio of each compound in the cement admixture is not in the above range, excellent expansion performance may not be obtained.

[0008] The expanding material of the present invention contains impurities.
Specifically, SiO ₂ , Al ₂ O ₃ , MgO, TiO ₂ , P
₂ O _5, Na ₂ O, and contains K ₂ O, etc., purposes does not particularly problematic within a range that does not substantially inhibit the range of less than 0.5 silicate rate for SiO ₂ of the present invention It is preferred that If the silicate ratio is 0.5 or more, excellent expansion performance may not be obtained. The silicic acid ratio in the present invention means the amount of SiO _{2, the} amount of Al ₂ O _{3 and the} amount of F in the cement admixture.
It is calculated from the following equation from the amount of e ₂ O ₃ . Silicic acid ratio = SiO ₂ / (Al ₂ O ₃ + Fe ₂ O ₃ ) The amount of SiO ₂ in the expanding material is preferably 5.0% or less, more preferably 3.0% or less. If it exceeds 5.0%, excellent expansion performance may not be obtained.

[0009] The calcium alumino ferrite of the present invention
Is CaO-Al_TwoO_Three-Fe_TwoO_ThreeGeneric term for compounds
Although it is not particularly limited, CaO
C, Fe _TwoO_ThreeTo F, Al_TwoO_ThreeIs A, generally
C_FourAF and C₆A_TwoCompounds such as F are well known. Book
In the invention, since the expansion performance is improved, C_FourAF
It is preferred to use. Below, calcium aluminoff
Cellite to C_FourAbbreviated as AF.

When producing the cement admixture of the present invention, C
aO raw material, Al ₂ O ₃ raw material, Fe ₂ O ₃ raw material and CaSO ₄
It is preferable that the raw material is heat-treated to synthesize a calcined product composed of free lime, C ₄ AF and anhydrous gypsum, which is then pulverized for production. Free lime, C ₄ AF, and anhydrous gypsum are separately synthesized, and a mixture of these is not preferred because storage may greatly reduce the swelling performance. CaO raw material, Al ₂ O ₃ raw material, Fe ₂ O ₃ raw material and CaSO ₄ raw material are heat-treated to produce a burned product composed of free lime, C ₄ AF and anhydrous gypsum, and then pulverized to produce As a method for confirming the presence or absence, for example, coarse particles of a cement admixture, specifically, coarse particles of 100 μm or more are observed with a microscope (SEM-EDS) or the like to analyze the composition, and free lime is contained in the particles. , C ₄ AF and anhydrous gypsum can be easily identified.

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 Al ₂ O ₃ raw material include bauxite and aluminum residual ash, and examples of the Fe ₂ O ₃ raw material include copper kerami, iron powder, and commercially available iron oxide. Further, examples of the CaSO ₄ raw material include dihydrate gypsum, hemihydrate gypsum and anhydrous gypsum.

[0013] The particle size of the expanded material of the present invention is not particularly limited, but is usually 1500 in terms of 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 dextrin used in the present invention is generally called a modified starch, and is usually obtained by hydrolyzing starch. Above all, acid-roasted dextrin obtained by adding a dilute acid and thermally decomposing is most common. However, those obtained by the acid immersion method, maltodextrin obtained by enzymatic decomposition of starch, British gum obtained by non-roasting, or those obtained by adding water to starch, or a solution of alkali or concentrated salts One or more of the pregelatinized starch obtained by rapidly dehydrating and drying the pregelatinized product can be used as long as the object of the present invention is not impaired.

The dextrin of the present invention preferably has a cold water soluble content at 20 ° C. of less than 70%, more preferably a cold water soluble content of 20 to 50%. preferable. If it is 70% or more, although effects can be obtained with respect to suppression of heat of hydration and prevention of pop-out, curing failure may be caused, which is not preferable. Here, the cold water-soluble component of dextrin means the amount of dextrin dissolved in distilled water at a temperature of 21 ° C. Specifically, 10 g of dextrin is placed in a 200 ml flask, and the temperature of 21 ° C. Add 150 ml of distilled water,
After maintaining at a temperature of 21 ° C. for 1 hour, the mixture was filtered off, and the filtrate was evaporated to dryness. The dextrin obtained was expressed in terms of the ratio to the test dextrin as a soluble component in cold water.

An expanding substance in the cement admixture of the present invention;
The blending ratio of dextrin is not particularly limited, but usually, in 100 parts of the cement admixture, the expansive substance is 85%.
It is preferably from 9 to 99.5 parts, more preferably from 90 to 99 parts. If the amount of the swelling substance is less than 85 parts, sufficient swelling performance may not be obtained. If the amount exceeds 99.5 parts, a sufficient effect of suppressing the pop-out phenomenon or a sufficient effect of suppressing hydration heat may not be obtained. is there. Also, dextrin is 0.5 to 15
Part is preferable, and 1 to 10 parts is more preferable. If the amount is less than 0.5 part, a sufficient effect of preventing pop-out and the effect of suppressing hydration heat generation may not be obtained, and if the amount exceeds 15 parts, poor curing may occur.

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 can not be obtained in some cases expanded performance and excellent more than 6000 cm ² / g is not obtained.

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

The cement composition of the present invention refers to JIS R 5210
Various Portland cements specified in JIS R 5211,
JIS R 5212, or various mixed cement specified in JIS R 5213, blast furnace cement, fly ash cement, silica cement, and alumina cement or white cement manufactured with an admixture ratio of more than that specified in JIS,
One or more of special cements such as oil well cements, filler cements mixed with limestone powder and the like, and cement-based solidifying materials are used in combination with the cement admixture of the present invention.

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 auxiliaries,
AE water reducer, high performance water reducer, high performance AE water reducer, defoamer, thickener, rust preventive, antifreeze, fluidizer, shrinkage reducer,
Substantially inhibits the object of the present invention by one or more of polymer emulsions, setting modifiers, cement hardened materials, clay minerals such as bentonite and zeolite, and ion exchangers such as hydrotalcite. It is possible to use it in the range that does not.

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 may be partially or entirely mixed in advance. . As the mixing device, any existing device can be used, for example, a forced kneading mixer, a tilting mixer, an omni mixer, a Henschel mixer,
It is possible to use a V-type mixer, a Nauta mixer and the like.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments.

Example 1 CaO raw material, Al ₂ O ₃ raw material, Fe ₂ O ₃ raw material and CaSO
_{The four} raw materials were blended, mixed and pulverized, and then heat-treated at 1350 ° C. for 2 hours to produce expanded materials having various compositions as shown in Table 1, and pulverized to a Blaine specific surface area of 3500 ± 200 cm ² / g. In 100 parts of a cement admixture composed of an expanding substance and dextrin, 95 parts of an expanding substance and 5 parts of dextrin are mixed to form a cement admixture. In 100 parts of a cement composition composed of cement and a cement admixture, the cement admixture is mixed. Using 7 parts, a mortar having a water / cement composition ratio = 50% and a cement composition / sand ratio = 1/3 was prepared and subjected to measurement of expansion coefficient, measurement of mortar center temperature, and pop-out test. Table 2 shows the results.

Incidentally, the expanded material was subjected to powder X-ray diffraction (XR).
D), and it was confirmed that free lime, C ₄ AF 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.

<Materials Used> Cement: Commercial ordinary Portland cement Dextrin E: Commercial product, 40% soluble in cold water Water: Tap water Sand: ISO679 compliant, standard sand CaO raw material: reagent grade 1 calcium carbonate Al ₂ O ₃ raw material: Reagent primary aluminum oxide Fe ₂ O ₃ Raw material: Reagent primary ferric oxide CaSO ₄ Raw material: Reagent primary dihydrate gypsum Expanding substance a: Commercial calcium sulfoaluminate-based expanding material Expanding substance b: Commercial lime-based expansion Material Free lime: calcined reagent 1 grade calcium carbonate at 1350 ° C for 2 hours. C ₄ AF: 4 mol of CaO, 1 mol of Al ₂ O ₃ , Fe ₂ O
_A mixture obtained by mixing the reagent primary calcium carbonate, the reagent primary aluminum oxide, and the reagent primary ferric oxide so that ₃ becomes 1 mol, and baking at 1350 ° C. for 2 hours. Anhydrite: Reagent grade 1 dihydrate gypsum at 1350 ° C
Fired for hours.

<Measurement method> Chemical analysis: Measured according to JIS R5202. Compound composition: First, the free lime content was measured according to JIS R 5202, and other compounds were determined by calculation. That is, from the amount of Fe ₂ O ₃ or Al ₂ O _{3 to the} amount of C ₄
The AF amount was calculated, and then the anhydrous gypsum amount was calculated from the SO ₃ amount. Length change rate: Measured according to JIS A6202. Pop-out test: A mortar was prepared in advance using a material other than the cement admixture, and the mortar was charged into the tilting mixer. Then, the cement admixture was added while agitating the mixer at a speed of 12 revolutions / minute. Discharged later, 50 vertical
cm, a width of 30 cm, and a height of 6 cm were placed in a mold, and it was observed whether or not a pop-out phenomenon occurred. Mortar center temperature: depth of mortar 30 cm, inner diameter 13
Approximately 3.5 liters were placed in a styrofoam cylindrical container having a thickness of 10 cm and a thickness of 10 cm, and cured at 20 ° C. in a constant temperature chamber.

[0027]

[Table 1]

[0028]

[Table 2]

Tables 1 and 2 show that the cement admixture of the present invention has an excellent expansion performance as compared with commercially available expandable materials and those obtained by separately synthesizing and mixing free lime, calcium aluminoferrite and anhydrous gypsum. It can be seen that the mortar was added, the pop-out phenomenon was prevented, and the temperature at the center of the mortar was reduced.

Example 2 The same procedure as in Example 1 was carried out except that the expanding substance D shown in Example 1 was used and the type and amount of dextrin were changed as shown in Table 3 to obtain a cement admixture. In addition, the compressive strength of the mortar was measured, and a similar experiment was performed on a commercially available expandable material not containing dextrin. The results are also shown in Table 3.

<Materials> Dextrin A: 0% soluble in cold water Dextrin B: 5% soluble in cold water Dextrin C: 10% soluble in cold water Dextrin D: 20% soluble in cold water Dextrin E: soluble in cold water 40% dextrin F: cold water soluble 50% dextrin G: cold water soluble 65% dextrin H: cold water soluble 69% dextrin I: cold water soluble 70% dextrin J: cold water soluble 80% dextrin K: 90% soluble in cold water

<Measurement Method> Compressive strength of mortar: Measured at 7 days of age in accordance with JIS R5201.

[0033]

[Table 3]

From Table 3, it can be seen that the cement admixture of the present invention has excellent expansion performance and, at the same time, admixes with dextrin, thereby preventing the pop-out phenomenon and reducing the temperature of the central part of the mortar. It can be seen that the content of dextrin increases as the amount of cold water-soluble components or the amount of dextrin used increases. However, the cold water soluble content of dextrin is 7
If the content is out of the range of 0% or more of the present invention, the strength developability tends to be extremely reduced.

Example 3 95 parts of the swelling substance D used in Example 1 and dextrin E
Example 2 was repeated except that a cement admixture consisting of 5 parts was used and the amount of the cement admixture was changed as shown in Table 4 with respect to 100 parts of the cement composition. The results are also shown in Table 4.

[0036]

[Table 4]

From Table 4, it can be seen that the cement admixture of the present invention shows excellent expansion performance as the amount used increases, prevents the pop-out phenomenon, reduces the temperature at the center of the mortar, and develops the strength. It can be seen that there is almost no decrease in the properties.

[0038]

The cement admixture of the present invention has excellent expansion performance as compared with the conventional expansion material, and also has an effect of preventing pop-out phenomenon and suppressing heat of hydration, and has a strength developing property. There is almost no decrease.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // C04B 103: 60 C04B 103: 60 (72) Inventor Minoru Morioka 2209 Aomi, Aomi-cho, Aomi-cho, Nishikubiki-gun, Niigata Prefecture Inside the Aomi Plant of Denki Kagaku Kogyo Co., Ltd. (72) Inventor Toshiyuki Tamaki 2209 Aomi, Aomi-cho, Nishikubiki-gun, Niigata F term in the Aomi Plant of Denki Kagaku Kogyo Co., Ltd. 4G012 MA00 MB12 PB05 PB11 PB39

Claims (3)

[Claims] 1. A calcined product obtained by heat-treating a CaO raw material, an Al ₂ O ₃ raw material, an Fe ₂ O ₃ raw material, and a CaSO ₄ raw material, wherein the expanded product contains free lime, calcium aluminoferrite and anhydrous gypsum. Substance and cold water soluble matter 70
% Dextrin and a cement admixture. 2. The dextrin content in 100 parts of the cement admixture is 0.5 to 15 parts.
A cement admixture according to claim 1. 3. A cement composition comprising a cement and the cement admixture according to claim 1 or 2.