JP2016190771A - Cement composition and method for producing hardened cement body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cement composition which has a short set time even under hardening conditions of relatively low temperature.SOLUTION: The cement composition comprises cement, an additive containing at least one selected from the group consisting of blast-furnace slag and fly ash, and an alkali sulfate.SELECTED DRAWING: None

Description

  The present invention relates to a cement composition and a method for producing a hardened cement body using the cement composition.

  Cement compositions used for cement hardened bodies such as mortar and concrete structures may be applied by placing them in a formwork or support in a fresh state before hardening, and then removing them after hardening. is there. When such a cement composition is used, for example, in an outdoor concrete structure, it is cured in a relatively low temperature environment in a cold region or in winter. Generally, a cement composition tends to have a long curing time when the curing temperature is low. Accordingly, there is a problem that the number of days until the frame is removed becomes longer in the construction work of a concrete structure in a cold district or winter.

In order to shorten the setting time of the cement composition, it is known to add an admixture to the cement composition. For example, Patent Document 1 describes a cement composition containing quick lime as an admixture and further containing sulfate. Since sulfate promotes hardening of the cement composition, it can be removed from the frame in a short time.
However, in the cement composition described in Patent Document 1, it is difficult to shorten the curing time when the curing temperature is relatively low such as 5 ° C to 10 ° C.

Republished patent WO99 / 07647

  Therefore, in view of the conventional problems as described above, the present invention provides a cement composition and a method for producing a hardened cement body that have a relatively short curing time even when cured at a relatively low temperature. Let it be an issue.

  The cement composition according to the present invention includes cement, an admixture containing at least one selected from the group consisting of blast furnace slag and fly ash, and alkali sulfate.

  According to the present invention, by including an admixture containing at least one selected from the group consisting of cement, blast furnace slag and fly ash, and alkali sulfate, the curing time is short even when cured at a relatively low temperature. become.

  In the present invention, the alkali sulfate may be at least one selected from the group consisting of lithium sulfate, sodium sulfate, and potassium sulfate.

  When the alkali sulfate is at least one selected from the group consisting of lithium sulfate, sodium sulfate, and potassium sulfate, the curing time is shorter even when cured at a relatively low temperature.

  In the present invention, the alkali sulfate may be contained in an amount of 0.5 mass% to 4 mass%.

  When alkali sulfate is contained in the above range, the curing time is shorter even when cured at a relatively low temperature.

  In the present invention, the admixture may contain 5 mass% or more and 60 mass% or less.

  When the admixture is included in the above range, the curing time is short even when cured at a relatively low temperature.

The method for producing a hardened cement body according to the present invention comprises mixing a cement composition of any of the above and water to obtain a mixture, and a hardened cement body having a compressive strength of 10 N / mm ² or more within 4 days of age. To manufacture.

As described above, according to the present invention, it is possible to provide a cement composition having a relatively short curing time even when cured at a relatively low temperature.
Moreover, according to this invention, even when it hardens | cures at comparatively low temperature, the manufacturing method of the cement hardening body which manufactures the cement hardening body whose hardening time is comparatively short can be provided.

  Below, one Embodiment of the manufacturing method of the cement composition concerning this invention and a cement hardening body is described.

  The cement composition of this embodiment is a composition containing cement, an admixture containing at least one selected from the group consisting of blast furnace slag and fly ash, and alkali sulfate.

The cement used for the cement composition of the present embodiment is not particularly limited.
For example, normal Portland cement, early-strength Portland cement, ultra-high-strength Portland cement, moderately hot Portland cement, sulfate-resistant Portland cement, white Portland cement and other Portland cements, ultrafast cement, alumina cement and the like can be mentioned. Among these, early-strength Portland cement is preferable because desired strength can be obtained at an early stage.

The cement composition of the present embodiment includes an admixture containing at least one selected from the group consisting of blast furnace slag and fly ash.
The blast furnace slag is not particularly limited, and examples thereof include blast furnace granulated slag fine powder, blast furnace decooled slag fine powder, and the like, and as these blast furnace slag, those conforming to the provisions of JIS A 6206, etc. Can be mentioned.

  The fly ash is not particularly limited, and examples include fly ash type I, type II, type III, type IV, and the like, and examples of these blast furnace slag include those that comply with JIS A 6201. Can be mentioned.

In the cement composition of the present embodiment, the above-mentioned various admixtures may be used alone or in admixture of two or more.
Blast furnace slag or fly ash is preferably used alone as an admixture one by one.

Although content of an admixture is not specifically limited, For example, 5 to 60 mass%, Preferably 5 to 40 mass% etc. are mentioned.
When blast furnace slag is used as an admixture, the content thereof is, for example, 5% by mass to 60% by mass, preferably 5% by mass to 40% by mass.
When fly ash is used as the admixture, the content thereof is, for example, 5% by mass to 30% by mass, preferably 10% by mass to 20% by mass.
When the content of the admixture is within the above range, the curing time can be easily shortened even when cured at a relatively low temperature.

  The ratio of the cement and the admixture is, for example, 5 to 150, preferably 5 to 67, etc. with respect to the cement 100 in terms of mass ratio.

  The alkali sulfate is not particularly limited as long as it is an alkali metal sulfate, and examples thereof include sodium sulfate, potassium sulfate, lithium sulfate, rubidium sulfate, and cesium sulfate. Among these, at least one selected from the group consisting of sodium sulfate, potassium sulfate, and lithium sulfate is preferable, and potassium sulfate is particularly preferable from the viewpoint of securing frost damage resistance.

The content of the alkali sulfate is not particularly limited, and examples thereof include 0.5% by mass or more and 4% by mass or less, preferably 1% by mass or more and 3% by mass or less.
When the content of the alkali sulfate in the cement composition is within the above range, the curing time can be shortened even in a relatively low temperature environment, and at the same time, the decrease in the strength of the cured body can be suppressed. Shrinkage can be suppressed, and temperature cracks during curing can be suppressed.

Next, a method for producing a hardened cement body using the cement composition of the present embodiment as described above will be described.
In the method for producing a hardened cement body according to this embodiment, the above-described cement composition and water are mixed to obtain a mixture, and the mixture is cured to have a compressive strength of 10 N / mm within 4 days of age. ^This is a method for producing a cement cured body having ^two or more.

The cement composition of the present embodiment includes, for example, a mixer together with aggregates such as coarse aggregate and fine aggregate, powder components such as admixtures, liquid components such as water, water reducing agents, retarders, and other chemical admixtures. It can be obtained as a mixture of fresh mortar, concrete, or the like by mixing with stirring.
In this case, for example, water is blended so that the water cement ratio is 35% by mass or more and 55% by mass or less. By mix | blending the water of the said range, the intensity | strength of the cement hardening body after mortar or concrete hardens | cures can be made into a preferable range.

When the cement composition of the present embodiment is blended in mortar or concrete, it is preferably blended so as to be contained in the mortar or concrete in an amount of 10% by mass to 50% by mass.
That is, it is preferable that the cement composition is blended so that alkali sulfate is contained in an amount of 0.05% by mass or more and 20% by mass or less in a hardened cement body such as mortar or concrete.
Or it is preferable to mix | blend a cement composition so that an admixture may be contained in 0.5% by mass or more and 30% by mass or less in mortar or concrete.

The hardened cement body using the cement composition of this embodiment is particularly suitable for use in the construction of concrete structures such as outdoors in winter and cold regions.
For example, a cement composition (mixture) in a fresh state is placed in a mold or a supporting work, cured, and demolded after curing to produce a hardened cement body such as a concrete structure. Usually, when the environmental temperature when curing is a low temperature such as less than 5 ° C. to 10 ° C., the number of days is 10 ° C. until a strength sufficient to demold the cement composition is obtained. It takes longer than when curing at the above temperature.
The hardened cement body using the cement composition of the present embodiment can develop high strength in a relatively short time even when cured at a low temperature such as 5 ° C. to less than 10 ° C., so the number of days until demolding is short. Tesumu.
Specifically, the hardened cement produced using the cement composition of this embodiment is compressed at an environmental temperature of 5 ° C. to 10 ° C. measured by the method described in JIS A 1108 within 4 days of age. intensity becomes 10 N / mm ² or more, preferably, within 20 N / mm ² or more and 6 days, the 30 N / mm ² or more within 8 days.
In addition, the age as used in this embodiment means the elapsed days from immediately after preparation of a mixture. That is, the hardened cement body that has passed 24 hours from immediately after the preparation of the mixture is called a material age of 1 day.

In addition, the cement composition of this embodiment can suppress an increase in temperature cracks even when cured under conditions where temperature cracks are likely to occur.
When the cement composition hardens, the cement and water undergo a hydration reaction and harden. However, when the heat generated by the hydration reaction is accumulated inside the cement composition, the hardened material expands. When the heat is released after the reaction is completed, the cured product tends to shrink. However, if the cured product is constrained by surrounding members (such as natural bedrock or adjacent concrete structures), the shrinkage is prevented. Therefore, cracks (temperature cracks) occur. Such temperature cracks are more likely to occur when attempting to increase the compressive strength of the cement composition or curing a large-capacity cement composition.

In particular, when used for the construction of concrete structures such as outdoors in the winter or in cold regions, it may be attempted to remove the mold quickly by shortening the curing time by performing heat curing or heat insulation curing. When heat curing or heat insulation curing is performed, temperature cracks are more likely to occur.
The cement composition of this embodiment can suppress the occurrence of temperature cracks even under such conditions.

  Furthermore, the cement composition of this embodiment can also suppress shrinkage of the cured body due to self-shrinkage and drying shrinkage. Therefore, it is particularly suitable as a cement composition for producing a large-capacity concrete structure.

  In addition, although the manufacturing method of the cement composition and cement hardened body concerning this embodiment is as above, it is thought that embodiment disclosed this time is an illustration and restrictive at all points. Should. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The cement composition according to the present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to the following examples.

(Test 1)
A cement composition was prepared by blending the following materials as shown in Table 1. As the binder, blast furnace cement type B (BB) or fly ash cement type B (FB) was used.

・ Cement: Blast furnace cement type B (BB) or fly ash cement type B (FB), both manufactured by Sumitomo Osaka Cement Co., Ltd. ・ Water: tap water ・ Fine aggregate: Land sand ・ Coarse aggregate: Sandstone crushed stone

(Measurement of compressive strength)
Cement compositions were prepared by changing the binder according to the formulation shown in Table 1. Each cement composition was poured into a cylindrical mold having an inner diameter of 10 cm and a height of 20 cm, and cured at an environmental temperature of 5 ° C. or 10 ° C. (Test Examples 1 to 4). The number of days when the compressive strength of the cement composition of each test example reached 10, 20, 30 N / mm ² was measured. The compressive strength was measured according to the method described in JIS A 1108.
The results are shown in Table 2.

  As shown in Table 2, when comparing cement compositions using the same type of binder, it takes longer to achieve any compressive strength when the environmental temperature is 5 ° C than when the environmental temperature is 10 ° C. Is clear.

(Test 2)
Next, concrete was produced using a cement composition in which the following materials were mixed in the formulation shown in Table 3 as the binder shown in Table 1.
Each concrete was cured at an environmental temperature of 5 ° C. or 10 ° C. in the same manner as described above (Examples 1 to 20, Comparative Examples 1 and 2). The number of days that the compressive strength of the concrete of each example and comparative example reached 10, 20, and 30 N / mm ² was measured in the same manner as described above. The results are shown in Table 3.

・ Haya strong Portland cement (HC) (manufactured by Sumitomo Osaka Cement)
・ Super fast cement (JC) (manufactured by Sumitomo Osaka Cement)
・ Blast furnace slag fine powder (BFS): Blast furnace slag fine powder 4000 (manufactured by Sment Kanto)
・ Fly ash (FA): Fly ash type II (Tohoku Electric Power Noshiro Thermal Power Plant)
・ Sodium sulfate (Na ₂ SO ₄ ): Reagent (manufactured by Kanto Chemical Co., Inc.)
Potassium sulfate (K ₂ SO ₄ ): Reagent (manufactured by Kanto Chemical Co., Inc.)

As is apparent from Table 3, each example had fewer days to reach the desired compressive strength, particularly 30 N / mm ² , compared to the comparative example. Therefore, even when cured in a relatively low temperature environment of 5 ° C. or 10 ° C., each example has a shorter curing time than each comparative example.

(Test 3: Measurement of temperature crack index)
Next, Table 3 shows the results of the three-dimensional FEM temperature stress analysis using the cement compositions of Test Example 2, Comparative Example 2 and Example 2, Example 4, Example 12, Example 14, and Example 14. 4 shows. The temperature cracking index is the ratio of tensile stress to the tensile strength (proof strength) of concrete, and the smaller the value, the higher the risk of temperature cracking.

  As shown in Table 4, the temperature cracks of concrete using the cement compositions of Example 2, Example 4, Example 12, and Example 14 were the same as those of Test Example 2 and Comparative Example 2. That is, it is clear that the above examples have a short curing time and the risk of temperature cracking is not high.

(Test 4: Measurement of self-shrinkage and dry shrinkage)
Next, the amount of self-shrinkage and the amount of dry shrinkage were measured using the cement compositions of Test Example 2, Comparative Example 2, Example 2, Example 4, and Example 14. The results are shown in Table 4.
The amount of self-shrinkage was measured according to the Japan Concrete Institute (tentative name) high-fluidity concrete self-shrinkage test method, and the amount of dry shrinkage was measured according to the method described in JIS A1129.

  As shown in Table 5, the concrete using Example 2, Example 4, and Example 14 had smaller self-shrinkage and dry shrinkage than Test Example 2 and Comparative Example 2. That is, it is clear that the above examples have a short curing time and that self-shrinkage and drying shrinkage are suppressed.

Claims (5)

  A cement composition comprising cement, an admixture containing at least one selected from the group consisting of blast furnace slag and fly ash, and alkali sulfate.   The cement composition according to claim 1, wherein the alkali sulfate is at least one selected from the group consisting of lithium sulfate, sodium sulfate, and potassium sulfate.   The cement composition according to claim 1 or 2, comprising the alkali sulfate in an amount of 0.5 mass% to 4 mass%.   The cement composition as described in any one of Claims 1 thru | or 3 which contains the said admixture 5 mass% or more and 60 mass% or less. The cement composition according to any one of claims 1 to 4 is mixed with water to obtain a mixture, and the mixture is cured to have a compressive strength of 10 N / mm ² or more within 4 days of age. The manufacturing method of the cement hardened body which manufactures the cement hardened body which becomes.