JP3290790B2 - Cement admixture and cement composition - Google Patents

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 Cement is an indispensable material for forming civil engineering and building structures.
It can be said that there is no material that can make a large structure less expensively than cement. However, there is a problem that a hardened body using cement has cracks.

There are several causes for this crack.
One is caused by drying shrinkage, and a number of cement expanders have been proposed for the purpose of compensating for the drying shrinkage (JP-B-53-13650, JP-B-53-31170, etc.).

A second cause of cracking is cracking due to heat of hydration.

Conventionally, as a method of reducing thermal cracking, use of a cement having a low calorific value of hydration, that is, a cement having a low heat generation has been closed up.

[0006] As the low heat-generating cement, a mixture of Portland cement and a large amount of pozzolanic substances such as blast furnace slag and fly ash is mainly used.
It is known that since the heat value of the initial hydration heat can be remarkably reduced, it is particularly effective in suppressing the thermal cracking of the mass concrete accompanying the casting of a dam or the like.

[0007] Since cracks that occur in an actual structure are a combination of cracks due to drying shrinkage and thermal cracks, a low heat-generating cement and a cement expanding material may be used in combination to suppress cracks comprehensively. Many.

However, the conventional cement expander is
There is a problem that when used for low heat cement mixed with pozzolanic substances such as blast furnace slag and fly ash, sufficient expansion properties are not exhibited. Has been strongly demanded.

The present inventor has made various efforts to solve the above-mentioned problems, and as a result, by combining a specific expansion component with dextrin, the cement admixture which is particularly used for low heat-generating cement and has a large crack-reducing effect. The present invention was completed based on the knowledge that a material can be obtained.

[0010]

Means for Solving the Problems That is, the present invention provides an expandable material that produced by heat-treating the formulation containing CaO raw material and CaSO ₄ material, CaSO ₄ is a total of 100 parts by weight of CaO and CaSO ₄ During ~
A cement admixture containing 10 to 30 parts by weight of an intumescent substance and 10 to 65% by weight of dextrin soluble in cold water , produced by heat-treating a mixture containing CaO and CaSO ₄ raw materials
CaSO ₄ is CaO and CaSO ₄ in total of 100
A cement admixture comprising 10-50 parts by weight of an intumescent substance and dextrin in an amount of 10-50 parts by weight , and further containing amorphous calcium aluminate, and a cement composition comprising the cement admixture and cement. .

Hereinafter, the present invention will be described in more detail.

The raw material of the expanding material of the present invention can be arbitrarily selected depending on the purity and cost, and is not particularly limited. For example, as a CaO raw material, CaCO ₃ such as limestone or slaked lime or Ca (OH) ₂ and the like, and as the CaSO ₄ raw material, anhydrous gypsum, hemihydrate gypsum, dihydrate gypsum and the like can be mentioned. SiO ₂ , Fe ₂ O ₃ , CaF present in raw materials
Impurities such as ₂ , MgO, and TiO ₂ are not particularly limited as long as the object of the present invention is not substantially inhibited.

In the present invention, the compounding ratio of the raw material of the expanding material is such that the chemical composition of the product expanding material is CaSO ₄ ,
The content is preferably 10 to 50 parts by weight, more preferably 20 to 40 parts by weight, based on a total of 100 parts by weight of aO and CaSO ₄ . If CaSO ₄ is less than 10 parts by weight,
For example, it shows rapid expansion by 1 day of age, and cracks occur in the cement hardened body using the expanded material,
In some cases, strength developability is reduced, and when the amount of CaSO ₄ exceeds 50 parts by weight, the swellability tends to be reduced.

In the present invention, the desulfurization decomposition temperature of gypsum varies greatly depending on the blending ratio of the raw material blend and the content of impurities. Therefore, the firing temperature during firing is not particularly limited. The temperature is preferably about 1,100 to 1,600 ° C.

The method for mixing the raw materials is not particularly limited, and a usual method can be used.

The heat treatment method for producing the expanding material of the present invention is not particularly limited, and any method such as a firing method using a rotary kiln or a melting method using an electric furnace is possible.

The amount of the expanding material used is 80 to 9 in 100 parts by weight of the cement admixture comprising the expanding material and dextrin described below.
8 parts by weight is preferred, and 90 to 95 parts by weight is more preferred. 80
If the amount is less than 10 parts by weight, the strength developability tends to decrease,
When used in excess of parts by weight, the effect of suppressing hydration heat generation tends to decrease. In addition, when the amorphous calcium aluminate described below is used in combination, the expanding substance, the amorphous calcium aluminate, and 100 parts by weight of the cement admixture composed of dextrin, 50 to 90 parts by weight, preferably 60 to 80 parts by weight. Parts are more preferred. If the amount is less than 50 parts by weight, the expandability may not be sufficient, and if the amount exceeds 90 parts by weight, cracks tend to occur in the cured product.

The dextrin according to the present invention is a dextrin having a cold water soluble content of 10 to 65% by weight, a starch obtained by adding a dilute acid to a starch and thermally decomposing it, a dextrin obtained by enzymatic decomposition of starch, Any one obtained by any method such as that obtained by condensation of glucose can be used in the present invention.

Here, the cold water soluble component of dextrin is
It means the amount of dextrin dissolved in distilled water at a temperature of 21 ° C. Specifically, 10 g of dextrin is added to 200 m
l, add 150 ml of distilled water at 21 ° C,
After keeping at 21 ± 1 ° C. for 1 hour, the filtrate was distilled to dryness, and the dextrin obtained was expressed as a ratio of dextrin to the test dextrin as the soluble component in cold water.

In the present invention, the dextrin soluble in cold water is
10 to 65% by weight, preferably 15 to 50% by weight, and 20 to 40% by weight.
% Is more preferred.

In the present invention, the amount of dextrin used is comprised of an intumescent substance and dextrin, or an intumescent substance,
In 100 parts by weight of the cement admixture composed of amorphous calcium aluminate and dextrin, 2 to 20 parts by weight is preferable, and 5 to 10 parts by weight is more preferable. If the amount is less than 2 parts by weight, the effect of suppressing the heat of hydration is small, and if it exceeds 20 parts by weight, strength developability tends to decrease.

The amorphous calcium aluminum according to the present invention
As a sample, a mixture of CaO raw material and Al ₂ O ₃ raw material is melted,
It is obtained by pulverizing the clinker obtained by quenching. The melting temperature of the amorphous calcium aluminate varies depending on impurities and is not particularly limited, but is usually preferably 1,500 to 1,700 ° C.

Here, the amorphous calcium aluminate
The CaO content is preferably from 35 to 45% by weight. 35
If the amount is less than 45% by weight, the expandability may be insufficient. If the amount exceeds 45% by weight, the workability of the cement composition may be impaired. Although the particle size of the amorphous calcium aluminate varies depending on the purpose of use, it is usually one with a Brain value of 1,
500-6,000 cm ² / g is preferred. If it is less than 1,500 cm ² / g, sufficient expandability may not be obtained, and if it exceeds 6,000 cm ² / g, workability may be deteriorated.

The amount of the amorphous calcium aluminate used is preferably 10 to 50 parts by weight, more preferably 20 to 40 parts by weight, per 100 parts by weight of the cement admixture. If the amount is less than 10 parts by weight, cracks tend to occur in the cured cement body using the same, and if it exceeds 50 parts by weight, the expandability may be insufficient.

The present invention is a cement admixture comprising a specific swelling substance and dextrin, or comprising a swelling substance, amorphous calcium aluminate and dextrin.

The particle size of the cement admixture of the present invention is not particularly limited because it depends on the purpose and use of the cement admixture, but is usually used in the range of a Brain value of 1,500 to 8,000 cm ² / g. Is preferred. If it is less than 1,500 cm ² / g, there is a possibility that the strength developability will decrease, and if it exceeds 8,000 cm ² / g,
In some cases, the expandability is not sufficiently exhibited.

Swelling substance and dextrin or swelling substance,
The method of mixing amorphous calcium aluminate and dextrin is not particularly limited, and a normal method is possible.Each material may be mixed at the time of construction, or a part of the material may be mixed in advance, or You can mix everything.

The amount of the cement admixture of the present invention varies depending on the purpose of use, but in the case of an intumescent substance and dextrin, it is preferably 3 to 12 parts by weight based on 100 parts by weight of the cement and the cement admixture in total. , 5 to 9 parts by weight. If the amount is less than 3 parts by weight, the expandability is not sufficient. If the amount exceeds 12 parts by weight, abnormal expansion may occur. In the case of expanding substances, amorphous calcium aluminate, and dextrin, the sum of cement and cement admixture
3 to 20 parts by weight, preferably 5 to 15 parts by weight, per 100 parts by weight
Parts by weight are more preferred. If the amount is less than 3 parts by weight, the expandability is not sufficient, and if it exceeds 20 parts by weight, abnormal expansion may occur.

Here, as cement, ordinary, early strength,
Various kinds of Portland cements, such as ultra-high strength, moderate heat, etc., various kinds of mixed cements in which pozzolan substances such as blast furnace slag and fly ash are mixed with these Portland cements,
And alumina cement. In the present invention, the effect is particularly remarkable in a mixed cement or a low heat cement based on the mixed cement.

The method of mixing the cement admixture is not particularly limited, and a usual method can be used. The expanding material and the dextrin, or the expanding material, the amorphous calcium aluminate, and the dextrin are premixed and mixed. Swelling substance and dextrin,
Alternatively, the swelling material, the amorphous calcium aluminate, and the dextrin can be separately mixed into the cement. Further, the respective materials may be mixed at the time of construction, or a part or all may be mixed in advance.

The amount of water used in the present invention can be appropriately changed depending on the type and amount of the material used.

The kneading method of the kneaded material containing the cement composition of the present invention and water is not particularly limited, and may be a commonly used method. Specifically, as the mixing and kneading apparatus, any existing stirring apparatus can be used. For example, a tilting mixer, an omni mixer, a V-type mixer,
A Henschel mixer, a Nauta mixer and the like can be used.

The method of curing the kneaded material containing the cement composition of the present invention and water is not particularly limited, and is generally performed at ordinary temperature and normal pressure, steam curing, high temperature and high pressure steam curing, and pressurization. Any curing method such as curing can be applied.

In the present invention, in addition to cement and a cement admixture, a setting regulator, a water reducing agent, a high-performance water reducing agent, an AE agent,
E water reducer, high-performance AE water reducer, thickener, aggregate such as sand and gravel, cement hardened material, rust preventive, antifreeze, polymer emulsion, clay minerals such as bentonite and montmorillonite, zeolite, One or more of ion exchangers such as hydrotalcite and hydrocalumite, inorganic sulfates such as aluminum sulfate and sodium sulfate, inorganic phosphates, and boric acid are used in the present invention. It is possible to use them together within a range that does not substantially impair the purpose.

[0035]

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

Example 1 A clinker obtained by calcining limestone and gypsum as raw materials at a maximum calcining temperature of 1,400 ° C. using a rotary kiln has a Brain value of 3,000 ± 200 cm ² / g. As shown in Table 1, various swelling substances having different amounts of CaSO ₄ were obtained. The chemical composition of the intumescent material was determined by chemical analysis.
Obtained from the values of O and CaSO ₄ , CaO is obtained from total CaO, CaSO ₄
This is the value obtained by subtracting the CaO content. A cement admixture consisting of 93 parts by weight of various intumescent substances and 7 parts by weight of dextrin a was mixed with 7 parts by weight based on a total of 100 parts by weight of cement α and cement admixture, and a water / (cement + cement admixture) ratio of 50 was used. %, (Cement + cement admixture) / sand = 1/2
Then, a mortar of 20 ± 0.3 ° C. was prepared and the temperature of the mortar center and the expansion coefficient were measured. Table 1 shows the results.

<Materials used> Limestone: Limestone powder from Aomi mine, Denki Kagaku Kogyosha Co., Ltd., Blaine value: 3,840 cm ² / g Gypsum: Anhydrite gypsum manufactured by Shin-Akita Chemical Co., Ltd., Blaine value
4,210cm ² / g Dextrin a: Nissei Chemical Co., Ltd. product name “MF30”, soluble in cold water 30% by weight Cement α: Ordinary Portland cement manufactured by Denki Kagaku Kogyo Co., Ltd. Fine aggregate: Himekawa river sand, Niigata prefecture :Tap water

<Measurement method> Mortar central temperature: mortar is 30 cm in height, 13 cm in inner diameter,
Approximately 3.5 liters are placed in a 10 cm thick styrofoam cylindrical container, and the temperature of the mortar center is automatically measured with a thermocouple when cured in a constant temperature room at 20 ° C. Expansion coefficient: JIS A 6202 (Method B) According to.

[0039]

[Table 1]

Example 2 The amount of the cement admixture using the expanding material of Experiment No. 1-5 of Example 1 was changed to 10
The procedure was performed in the same manner as in Example 1 except that the amount was changed as shown in Table 2 with respect to 0 parts by weight. The results are also shown in Table 2.

[0041]

[Table 2]

Example 3 The same operation as in Example 1 was carried out except that blast furnace cement was used as the cement. Table 3 shows the results.

<Materials> Cement β: Blast furnace cement manufactured by Denki Kagaku Kogyo Co., Ltd. (Class B)

[0044]

[Table 3]

Example 4 A swelling substance having a CaSO ₄ content of 30% by weight was used, the total amount of the swelling substance and dextrin was fixed, and the type of dextrin and the amount of dextrin in 100 parts by weight of the cement admixture were shown. Example 4 was carried out in the same manner as in Example 3 except that the conditions were changed as shown in FIG. The results are also shown in Table 4.

<Materials used> Dextrin b: 10% by weight of soluble in cold water Dextrin c: 45% by weight of soluble in cold water Dextrin d: 65% by weight of soluble in cold water Dextrin e: 70% by weight of soluble in cold water Dextrin f: 5% by weight soluble in cold water

[0047]

[Table 4]

Example 5 A cement admixture consisting of 94 parts by weight of an intumescent material having a CaSO ₄ content of 30% by weight and 6 parts by weight of dextrin a was added in an amount of 7 parts by weight to 100 parts by weight of cement and cement admixture. Combined with 352 parts by weight of aggregate and 255 parts by weight of fine aggregate,
(Cement + Cement admixture) 49% of the mixture, the kneading temperature was adjusted to 20 ° C, and the thickness was 10%.
Insulated on four sides with foam styrol of 50 cm, heat dissipation on two sides 50 ×
The temperature in the center of the concrete when placed in a 50 × 50 cm iron mold and cured in a constant temperature room at 20 ° C. was automatically measured with a thermocouple. The expansion rate was also measured. Table 5 shows the results.

<Materials> Coarse aggregate: Gravel from Himekawa, Niigata, Gmax = 25mm

[0050]

[Table 5]

Example 6 69 parts by weight of various swelling substances, amorphous calcium aluminate
(A-CA) Cement admixture consisting of 25 parts by weight and 6 parts by weight of dextrin was added to the sum of cement α and cement admixture.
10 parts by weight are mixed with 100 parts by weight, and water / (cement +
50% of (Cement admixture), (Cement + Cement admixture)
The procedure was the same as in Example 1 except that mortar was prepared at a rate of 20 ± 0.3 ° C. after kneading with ／/ sand = １ ／. Table 6 shows the results
Shown in

<Materials Used> A-CA: An amorphous calcium aluminate, a raw material obtained by mixing reagent grade calcium carbonate and aluminum oxide in a molar ratio of CaO and Al ₂ O ₃ of 10: 8, Melted at 1,650 ° C and quenched, the resulting clinker was obtained with a Blaine value of 3,41.
One crushed to 0 cm ² / g.

[0053]

[Table 6]

Example 7 The mixing amount of the cement admixture using the expanding material having a CaSO ₄ content of 30% by weight was adjusted to a total of 100% for cement and cement admixture.
The same procedures as in Example 6 were carried out except that the weight parts were changed as shown in Table 7. The results are also shown in Table 7.

[0055]

[Table 7]

Example 8 The same operation as in Example 6 was carried out except that cement β was used as cement. Table 8 shows the results.

[0057]

[Table 8]

Example 9 Using an intumescent substance having a CaSO ₄ content of 30% by weight, the amount of dextrin and the total amount of the intumescent substance and A-CA were kept constant, and A-CA in 100 parts by weight of cement admixture was used. Of Example 6 except that the amount of was used as shown in Table 4. The results are also shown in Table 9.

[0059]

[Table 9]

Example 10 Using an expanding material having a CaSO ₄ content of 30% by weight and a constant amount of cement admixture, the type of dextrin and the amount of dextrin in 100 parts by weight of cement admixture were as shown in Table 10. The same operation as in Example 6 was performed except that the amount was changed. However, when changing the amount of dextrin, the swelling substance and A-
The amount of CA was increased or decreased by an equal amount. The results are shown in Table 10.

[0061]

[Table 10]

Example 11 A cement admixture comprising 69 parts by weight of an intumescent substance having a CaSO ₄ content of 30% by weight, 25 parts by weight of A-CA, and 6 parts by weight of dextrin a was added to a total of 100 parts by weight of cement and cement admixture. And 10 parts by weight, 352 parts by weight of coarse aggregate and 255 parts by weight of fine aggregate, and a water / (cement + cement admixture) ratio of 49%
Example 5 was carried out in the same manner as in Example 5 except that a concrete adjusted to a kneading temperature of 20 ° C. was used. Table 1 shows the results
It is shown in FIG.

[0063]

[Table 11]

By using the cement composition of the present invention, good expandability and an effect of reducing heat of hydration can be obtained.

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI // C04B 103: 60 C04B 103: 60 (56) References JP-A-55-75951 (JP, A) Japanese Patent Publication No. 52-41285 (JP, B1) JP 50-13816 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) C04B 22/06-22/16

Claims (3)

(57) [Claims] 1. An expanding material formed by heat-treating a composition containing a CaO raw material and a CaSO ₄ raw material, wherein CaSO ₄ is composed of CaO and CaSO _4.
4. A cement admixture containing an intumescent substance in an amount of 10 to 30 parts by weight in 100 parts by weight in total and dextrin having a soluble content of cold water of 10 to 65% by weight. 2. An expanding substance produced by heat-treating a composition containing a CaO raw material and a CaSO ₄ raw material, wherein the CaSO ₄ comprises CaO and CaSO _4.
4. A cement admixture comprising an expanding substance in an amount of 10 to 50 parts by weight in 100 parts by weight in total, amorphous calcium aluminate, and dextrin having a soluble component in cold water of 10 to 65% by weight. 3. A cement composition comprising a cement and the cement admixture according to claim 1 or 2.