JP6889395B2 - Method for producing highly fluid cement composition containing silica fume - Google Patents

Description

The present invention relates to a method for producing a silica fume-containing cement composition having high fluidity even at a low water-cement ratio.

It is generally known that the water-cement ratio can be reduced by blending silica fume with cement. For example, in Patent Document 1 (Japanese Patent Laid-Open No. 2005-170781), the amount of belite in the clinker mineral composition is 45 to 75% by mass, the aluminate phase is 4% by mass or less, and the specific surface area is 3000 to 4500 cm ² / g. A cement composition for high-strength concrete having high fluidity at a specific surface area of 12 to 30% with water cement by blending 16 to 30 parts by mass of silica fume with 70 to 84 parts by mass of low-heat Portland cement has been described.

In Patent Document 2 (Japanese Patent Laid-Open No. 2012-214330) _{, silica fume is replaced with cement having a C 2} S amount of 60 to 80% by mass, a C ₃ A amount of 4% or less, and a brain specific surface area of 3000 to 4500 cm ² / g, with a substitution rate of 7 Described is a highly fluid cement composition having a V funnel flow time of 40 seconds or less when a 0-stroke flow in a cement paste having a specific surface area of 10 to 13% is 250 to 270 mm and is blended in an amount of .5 to 15% by mass. Has been done.

Any cement compositions of Patent Documents 1 and 2, tricalcium aluminate content (hereinafter, _{C 3} A content abbreviated) suppressed to 4% or less, by limiting the specific surface area of the cement 3000~4500cm ² / g It enhances fluidity, but fluidity is also greatly affected by the amount of alkali. However, the amount of alkali is not taken into consideration in the cement compositions of Patent Documents 1 and 2.

In addition, cement containing silica fume is generally used for ultra-high-strength concrete, but polycarboxylic acid-based high-performance water reducing agents are often used for ultra-high-strength concrete, and this polycarboxylic acid-based high performance is used. ultra high strength concrete with water reducing agent, the more C _{3 a} content and water-soluble alkali content in the cement fluidity has been pointed out to be reduced.

On the other hand, regarding the amount of alkali in the cement composition, according to Patent Document 3 (Japanese Patent Laid-Open No. 2008-174414), C ₂ S is 34 to 45%, C ₃ S is 20 to 40.4%, and free lime is 0.43. % Or less, and a cement composition in which the amount of water-soluble alkali is limited to 0.3% or less is described. Further, in Patent Document 4 (Japanese Patent Laid-Open No. 2006-111493), a highly fluid concrete composition in which the total amount of alkali is limited to 0.5% or less in _{C 3} S 40 to 50% by mass and C _{2 S 25 to 40% by mass.} The thing is listed.

However, the cement composition of Patent Document 3 has a low fluidity when the water-soluble alkali content is 0.3% or less and the water-cement ratio is about 13%. Further, the concrete composition of Patent Document 4 is intended to have a high water-cement ratio (water-cement ratio of 20 to 45%), and the fluidity of a low-water-cement ratio of 15% or less is unknown. Moreover, since none of the compositions of Patent Documents 3 and 4 contains silica fume, the amount of alkali related to the fluidity of the silica fume-containing cement composition at a low water cement ratio is determined by the composition of Patent Documents 3 and 4. You can't tell from it.

Japanese Unexamined Patent Publication No. 2005-170781 Japanese Unexamined Patent Publication No. 2012-214330 Japanese Unexamined Patent Publication No. 2008-174414 Japanese Unexamined Patent Publication No. 2006-111493

Conventional silica fume-containing cement composition, but limits the C _{3 A} content and the like in the low heat Portland cement is based cements in order to maintain fluidity, the alkali content is not taken into consideration. However, it was also found that the fluidity of the silica fume-containing cement composition decreases when the total amount of alkali in the base cement is large. In order to obtain sufficient fluidity even in the silica fume-containing cement composition, there is a threshold value for the total amount of alkali in the base cement.

The present invention is a method for manufacturing a silica fume-containing cement compositions, by limiting the total amount of alkali with C _{3 A} content in the low heat Portland cement is based cement, fluidity be limited only C 3 _A content It solves the conventional problem of deterioration, and provides a method for producing a silica fume-containing cement composition having high fluidity with a high flow area ratio.

The present invention relates to a method for producing a highly fluid cement composition containing silica fume, which solves the above problems by the following constitution.
[1] In a method for producing a cement composition containing silica fume using low-heat Portland cement as a base cement, an apparatus for automatically analyzing chemical components in the base cement is provided in the production line, and the C in the base cement is provided by the analyzer. ₃ a weight 3.6% by weight or less, the total amount of alkali is 0.23 to 0.32 mass%, and _{C 3} S content of the base in the cement is fed back raw materials blended so that 20 to 30 wt% the base cement adjusted Te feeding the silica fume mixing step, silica fume-containing substitution ratio in the mixing step is characterized by preparing a mixture of silica fume so that 7.5 to 15% by weight cement composition A method for producing a highly fluid cement composition.

The cement composition according to the production method of the present invention (hereinafter, may be referred to as the cement composition of the present invention) is a cement composition containing silica fume based on low-heat Portorand cement, and has a substitution rate of silica fume. There is a 7.5 to 15 wt%, based _{C 3} a content in cement 3.6% by weight or less, based the total alkali content in the cement 0.23 to 0.32 wt%, and said base cement a C _{3 S} content is 20 to 30 wt% of the cement composition, in the ratio (S / C) 0.6 fine aggregate to said cement composition (C) (S), 2 of the cement composition A high-fluidity cement containing silica fume, which exhibits a flow area ratio of 5.0 or more at a water-cement ratio of 15% or less when a cement mortar containing a high-performance water reducing agent of .5 to 2.7% by mass is produced. It is a composition.

Specifically, the cement composition of the present invention has a high fluidity with a flow area ratio of 5.0 or more at a water-cement ratio of 15% or less, and a flow area ratio of 5. at a water-cement ratio of 13%. It is a highly fluid cement composition having a flow area ratio of 5.0 or more at 5 or more and a water-cement ratio of 12%.

In the conventional silica fume-containing cement composition, when the water-cement ratio is 15% or less, the influence of the quality difference of the base cement becomes remarkable and the fluidity is greatly reduced. Therefore, the water-cement ratio is lower than 15% for high-strength concrete. It was difficult to apply to. On the other hand, the cement composition of the present invention, the water-cement ratio has a high flowability even at a low water-cement ratio of 15% or less is suitable as a high-strength concrete, also, C _{3 A} content of the base cement And since the total amount of alkali is limited, there is less variation in the quality of concrete and the like than in the conventional silica fume-containing cement composition.

Further, the cement composition of the present invention, by providing a device for automatically analyzing a chemical component of the base cement during the manufacturing process, C _{3 A} content 3.6 mass% or less and the total amount of alkali in the base cement a 0.23 to 0.32 wt%, it is possible to further _{C 3} S in said cement feedback control of the raw materials blended so that 20 to 30 wt%.

In the past, the amount of water-soluble alkali, which is the main factor affecting fluidity, was often controlled, but since the amount of water-soluble alkali needs to be wet-analyzed, it is difficult to manage the manufacturing process online. It was. On the other hand, the cement composition of the present invention, the total amount of alkali and C _{3 A} content of the base in the cement since it automatic analysis, it is possible online control of the manufacturing process.

A graph showing the relationship between the total amount of alkali in the base cement and the flow area ratio. Graph showing the relation between C _{3 A} content and flow area ratio of the base cement. Graph showing the relationship between the SO ₃ content and flow area ratio of the base cement. The flow chart which shows the outline of the manufacturing method.

Hereinafter, the present invention will be specifically described based on the embodiments.
Cement composition according to the production method of the present invention is a cement composition containing silica fume low heat Portland cement as a base, C _{3 A} content of the base in the cement, C _{3 S} content of the base in the cement, and the total amount of alkali The present invention relates to a method for producing a cement composition having high fluidity by limiting the amount to a certain range.

[Cement composition]
The cement composition according to the production method of the present invention is a cement composition containing silica fume using low heat Portorland cement as a base cement, and the substitution rate of the silica fume is 7.5 to 15% by mass in the base cement. The amount of C ₃ A in the base cement is 3.6% by mass or less, the _{amount of C 3} S in the base cement is 20 to 30% by mass, and the total amount of alkali in the base cement is 0.23 to 0.32% by mass. Cement mortar containing a high-performance water reducing agent of 2.5 to 2.7% by mass of the cement composition at a ratio (S / C) of 0.6 of the fine aggregate (S) to the cement composition (C). It is a silica fume-containing high-fluidity cement composition showing a flow area ratio of 5.0 or more at a water-cement ratio of 15% or less. Specifically, as the above-mentioned high-performance water reducing agent, as shown in Table 2 of Examples described later, a Chuball SSP104 improved product manufactured by Takemoto Oil & Fat Co., Ltd. and a mass dergrenium product manufactured by BASF Japan Co., Ltd. at a water-cement ratio of 13%. SP8HU and Floric SF500U, a product of Floric, are used, and an improved version of Chuball SSP104, a product of Takemoto Oil and Fats, is used at a ratio of 12% to water cement.

The cement composition of the present invention uses low-heat Portland cement as the base cement. Low heat Portland cement is a cement with a belite C _{2 S} content more than 40 mass% suppressing heat of hydration, superior for expression of long strength, low heat concrete, is suitable for high strength and high fluidity .. In the cement composition of the present invention, the content of low-temperature Portland cement is preferably 85.0 to 92.5% by mass. Other is mineral composition of the low thermal Portland cement _{C 3} A content, may be those having a general mineralogy, for example, _{C 2} S is 60 to 80 mass%, _{C 3} S in the range of 20 to 30 wt% is there.

The cement composition of the present invention is a cement composition obtained by blending silica fume with low-heat Portland cement as a base, and the substitution rate of silica fume is 7.5 to 15% by mass. The substitution rate of silica fume is expressed by the ratio of the weight of silica fume to the total weight of cement (C) and silica fume (SF) [SF / (C + SF) × 100%]. If the substitution rate of silica fume is less than 7.5% by mass, the effect of increasing fluidity and strength is insufficient, and if this substitution rate exceeds 15% by mass, it is necessary to add a large amount of silica fume in the manufacturing process, and the manufacturing efficiency. Not only is the amount of cement reduced, but the amount of cement is relatively small, which may result in a decrease in strength.

In the cement composition of the present invention, the total amount of alkali in the base cement is 0.23 to 0.32% by mass. The total amount of alkali (R ₂ O) is the total amount of _{Na 2} O and K ₂ O, and is expressed by the formula _{R 2} O = Na ₂ O + 0.658 · K _{2 O.} When the total amount of alkali exceeds 0.32 % by mass, the fluidity drops sharply.

The flow area ratio (Гp) is generally used as an index showing the fluidity of mortar or paste, and is expressed by the following equation [1]. Fp of the formula is a flow value (0 stroke flow: mm) when no falling motion is performed in the flow value measuring method specified in the standard (JIS R 5201 “Physical test method for cement”).
Гp = [Fp / 100] ² -1 ... [1]

In the cement composition of the present invention, for example, when the total amount of alkali in the base cement is 0.23 to 0.32% by mass, the flow area ratio is 5.5 or more (mostly 6) at a water cement ratio of 13%. Above), it is possible to have a high fluidity with a flow area ratio of 5.0 or more at a water-cement ratio of 12%. On the other hand, when the total amount of alkali exceeds 0.32% by mass, the flow area ratio at a water-cement ratio of 13% drops to less than about 5.

C _{3 A} content of the base in the cement of the cement composition of the present invention is preferably 3.6 mass% or less. Specifically, _{C 3} A content is preferably 3.2 to 3.6 mass%. C 3 _A content tends to decrease the fluidity exceeds 3.6 mass%, is significantly reduced, the fluidity exceeds 4.0 mass%. Specifically, C at 3 _A weight 3.6 wt% or less, the flow area ratio in the water-cement ratio of 13% is 5.5 or more, depending on the type of superplasticizer, the flow area ratio 6 It is .5 or more. On the other hand, _{C 3} A quantity at 4.0 to 4.1 mass%, the flow area ratio in the water-cement ratio of 13% is reduced to about 4-5.

In ultrahigh-strength concrete using the cement composition of the present invention, a polycarboxylic acid-based high-performance water reducing agent is usually added. In ultra-high-strength concrete with the addition of this superplasticizer, based C _{3 A} content in cement 3.6% by weight or less, and the base total alkali content in the cement from 0.23 to 0.32 wt%, further _{When C 3} S in the cement is 20 to 30% by mass, it is possible to have a high fluidity with a water cement ratio of 15% or less and a flow area ratio of 5.0 or more.

〔Production method〕
The cement composition of the present invention, the low thermal Portland cement-based, C _{3 A} content of 3.6 wt% or less and the total alkali content the 0.23 to 0.32 wt% of this base in the cement, the cement After controlling the C ₃ S of the above to 20 to 30% by mass, silica fume can be mixed and produced. C _{3 A} content and total alkali amount of the base in the cement, so can be quantified by an automated analysis of the fluorescent X-ray analysis, it is possible to line manages manufacturing process.

FIG. 4 shows an outline of the manufacturing method. As shown in the figure, the base cement (low heat Portland cement) prepared in the raw material blending step is sent to a composition analysis step equipped with a fully automatic chemical analyzer, and the composition of the base cement is quantified. _{Here, the amount of C 3} A in the base cement is 3.6% by mass or less, the total amount of alkali is 0.23 to 0.32% by mass, and the _{amount of C 3} S in the cement is 20 to 30% by mass. Is sent to the next silica fume mixing step. On the other hand, those outside the above range are removed from the production line, and the data is fed back to the raw material blending process, and the blending of the raw materials is adjusted so that the base cement is within the above range. Silica fume is mixed with the base cement sent to the silica fume mixing step so that the substitution rate is 7.5 to 15% by mass, and the silica fume-containing cement composition of the present invention is completed.

[Example 1]
_{C 3} A quantity of cement, SO ₃ content, Na ₂ O weight, _{K 2} O content, silica fume is added to the water-soluble alkali amount varying the low heat Portland cement (based cements), silica fume content of substitution of 10 wt% by silica fume Cement was prepared. The composition of the base cement is shown in Table 1.
A fine aggregate (S) and a high-performance water reducing agent (A to D) were mixed with the silica fume-containing cement (C), and water was added to prepare a mortar sample. The compounding conditions of the mortar are shown in Table 2. The mortar was first kneaded with silica fume-containing cement and fine aggregate for 15 seconds, then water and a high-performance water reducing agent were added, and the mortar was kneaded for 120 seconds. The mortar in the mixer was scraped off, kneaded for another 220 seconds, allowed to stand in the mixer for 5 minutes, discharged, and subjected to a flow test.
For this mortar sample, the flow area ratio was determined according to the JIS standard (JIS R 5201). The results are shown in Table 1. Further, for a sample having a water-cement ratio of 13% for the high-performance water reducing agent A and a water-cement ratio of 12% for the high-performance water reducing agent A, the relationship between the total alkali amount in the base cement and the flow area ratio is shown in FIG. the relationship between the C _{3 a} content and flow area ratio in the cement are shown in Figure 2. Further, the water-cement ratio of 13% of the samples of superplasticizer A, showing the relationship between the SO ₃ content and flow area ratio of the base cement in FIG.

Table 1 and Figure 1, as shown in FIG. 2, C _{3 A} content 3.6 mass% or less of the sample total alkali content is not more than 0.35 mass%, the flow area ratio in the water-cement ratio of 13% Is generally 5.5 or higher, and most are 6 or higher. Further, these samples have a flow area ratio of 5.0 or more at a cement ratio of 12%.
When the total amount of alkali exceeds 0.35% by mass, the flow area ratio drops sharply. Furthermore, most except for a part when the C 3 _A content is more than 3.6 mass% the flow area ratio decreases.
On the other hand, as shown in FIG. 3, for SO ₃ amount and the flow area ratio of the base cements, not seen a particular relationship.

Claims (1)

A method for producing a cement composition containing silica fume low heat Portland cement as a base cement, provided a device for automatically analyzing a chemical component of the base cement production line, C _{3 A} content of the base in the cement by the analyzer There 3.6 wt% or less, the total amount of alkali is 0.23 to 0.32 mass%, and _{C 3} S content of the base in the cement is adjusted by feeding back the material blended so that 20 to 30 wt% and the base cement feeding the silica fume mixing step, silica fume-containing high fluidity substitution ratio in the mixing step is characterized by preparing a mixed to the cement composition silica fume to be 7.5 to 15 wt% A method for producing a cement composition.

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