JP3230390B2 - Method for producing cement composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a high-strength cement composition having excellent fluidity.

[0002]

2. Description of the Related Art To obtain high-strength concrete,
Using a high-performance water reducing agent or a high-performance AE water reducing agent (hereinafter, these two types may be collectively referred to as a "high-performance water reducing agent"), and reduce the water-cement ratio as much as possible within a range where the kneaded material can be compactly formed. Is the most effective and common method. However, if the water-cement ratio is reduced, the viscosity of the kneaded material increases, resulting in a concrete with poor fluidity and workability.In addition, if the water-cement ratio is reduced,
The concrete no longer has fluidity and cannot be formed by ordinary pouring or compaction.

As a means for solving this, there is a method using silica fume as an admixture. Silica fume is a by-product from the production of metallic silicon and ferrosilicon.
It is spherical and ultrafine silica having a specific surface area of about 20 m ² / g and an average particle size of about 0.1 μm. By using silica fume and a high-performance water reducing agent together, the viscosity of the concrete is reduced and the fluidity can be improved, so that it is possible to produce concrete with a lower water cement ratio.

[0004] The action of this silica fume is attributed to the ball bearing effect derived from its spherical shape.
Further, since silica fume is a finer powder than cement particles, it is said that silica fume has an effect of filling the space between the cement particles to densify the structure of the cured product and an effect of increasing the strength of the cured product by a pozzolan reaction.

The effect of improving the fluidity and the effect of increasing the strength of the silica fume are remarkable when the water-cement ratio is small. Therefore, the compressive strength is 800 kgf / cm ²
At present, as a technology to impart fluidity to high-strength concrete with a low water cement ratio of about or more, the method of using silica fume as an admixture and adding a high performance water reducing agent is the most effective and general method at present. .

However, as compared with ordinary ordinary strength concrete, the concrete has high viscosity and is inferior in pumpability and workability. Therefore, there is a strong demand for the development of concrete having lower viscosity, and there is an example in which fly ash or blast furnace slag fine powder is used as an admixture to lower the viscosity and improve pumpability and workability.

[0007] There are three types of silica fume: powder, granule and slurry. Slurry silica fume has problems that silica fume easily precipitates, concentration is difficult to control, and there is a risk of freezing in winter. Furthermore, when applied to high-strength concrete, the unitary cement amount is large, and the unitary water amount is smaller than that.Therefore, the slurry-like silica fume must have a high concentration. It is not practical to apply to plants. Therefore, the silica fume used for practical use is a powdery or granular silica fume.

[0008] Granular silica fume has the advantage of being able to use the same transport, metering and charging equipment as powder materials such as cement. The effect of improving fluidity and strength properties is poor.

[0009] Powdered silica fume is superior to granules in the effect of improving fluidity and strength properties, but because it is difficult to handle with ultrafine powder, the existing transport, metering and addition equipment in a concrete manufacturing plant can be used as it is. Used and cannot be added to the mixer. For this reason, concrete mixers are either manually installed or newly installed with special addition equipment.

[0010]

The most common and effective method for increasing the strength of concrete is to reduce the water-cement ratio as much as possible within a range where compacting is possible. If silica fume and a high-performance water reducing agent are used in combination, it is possible to produce concrete with a lower water cement ratio, and in high strength concrete with a low water cement ratio of about 800 kgf / cm ² or more in compressive strength,
At present, as a technique for imparting fluidity, a method of using silica fume as an admixture and adding a high-performance water reducing agent is the most effective and general method. However, there are the following problems.

[0011] Since silica fume is ultrafine particles, it is usually in an aggregated state. At first glance, granular silica fume as well as powdered silica fume seem to have a small degree of aggregation, but are aggregates of ultrafine particles. Unless these agglomerated silica fumes are sufficiently dispersed in concrete, the effect of improving fluidity and strength cannot be effectively obtained.

Kneadability The conventional method of adding silica fume to Portland cement has a problem that kneadability in a mixer is poor.
In particular, the load on the mixer in the initial stage of kneading is extremely large until the silica fume and the high-performance water reducing agent are dispersed in the kneaded material. Therefore, in kneading with a mixer, kneading cannot be performed unless the amount of one kneading is considerably reduced below the capacity of the mixer.In addition, the kneading time is long to loosen agglomerated silica fume and to disperse it in concrete sufficiently homogeneously. It is necessary to take measures such as increasing the amount of a high-performance water reducing agent.

[0013] Fluidity and Viscosity [0013] Although an improvement in fluidity, which cannot be obtained only by using a high-performance water reducing agent, can be obtained by using silica fume, high-strength concrete to which silica fume is added has a large viscosity, and pumpability and construction efficiency are high. In order to ensure the fluidity, the fluidity must be as high as about 40 cm or more in slump flow. Therefore, the amount of the high-performance water reducing agent must be increased. In addition, slump flow 40cm
Even above, concrete is still more viscous than general-strength concrete, and concrete with lower viscosity is demanded in order to improve pumpability and workability.
Therefore, as a conventional technique, there is an example of using fly ash or blast furnace slag fine powder as an admixture to reduce viscosity, improve pumpability and workability, but the setting is delayed and the strength expression is reduced. There is a problem.

In order to make the concrete have a low water cement ratio and to have fluidity, it is necessary to add a high performance water reducing agent or a high performance AE water reducing agent having a strong powder particle dispersing action. No. However, high-performance water reducing agents and high-performance AE water reducing agents have both a strong dispersing action and a strong setting retarding action. As a result, concrete setting is greatly delayed.
In addition, the lower the water cement ratio, the more the amount of the high-performance water reducing agent used for obtaining the fluidity increases, so that the setting delay increases. If the setting delay becomes large, there arises a problem that defects such as cracks are liable to be generated in the concrete due to effects such as a long load burden on the formwork and a large settlement of the concrete. In addition, problems such as hindrance to the next construction process occur.

Production cost Concrete has poor kneading properties, the amount of kneading in the mixer must be small, and kneading must be performed for a long time.
Further, since it is necessary to add a large amount of an expensive high-performance water reducing agent, there arises a problem that the productivity of concrete is reduced, the supply capacity of concrete is reduced, and the production cost is increased.

Addition Method of Silica Fume Prior art addition of powdery silica fume or granular silica fume is carried out by charging the concrete mixer together with other concrete materials in batches. Granular silica fume can use conventional cement and admixture transport and metering equipment.However, compared to powdered silica fume, it is granular, so it has poor dispersibility, and it has the effect of improving the fluidity and strength properties of concrete. Inferior. Powdery silica fume is superior to granules in improving fluidity and strength properties, but because it is an ultrafine powder, its handling is poor, and it is not possible to use existing conveying and measuring equipment as it is. Therefore, it is necessary to input manually or to newly install a special conveying and measuring device.

[0017]

According to a first aspect of the present invention, there is provided a method for producing a cement composition, comprising 50 to 92 parts by weight of Portland cement, 5 to 25 parts by weight of silica fume and fine limestone powder.
A method for producing a cement composition comprising a total of 100 parts by weight to 25 parts by weight, wherein silica fume is charged into a finishing mill for pulverizing cement clinker or the like in a cement production step, And the like, while simultaneously mixing and dispersing silica fume, and then mixing a limestone fine powder having a specific particle size distribution with the pulverized product produced by the finishing mill.

As the Portland cement, ordinary Portland cement, early-strength Portland cement, ultra-high-strength Portland cement, moderately heated Portland cement and the like can be used.

Examples of the limestone powder, as claimed in claim 2,
Particles having a particle size distribution of 90% or more of particles of 20 μm or less, 65% or more of particles of 10 μm or less, 40% to 90% of particles of 5 μm or less, and 25% or less of 1 μm or less particles are preferable. This fine limestone powder is preferably obtained by pulverizing natural limestone and then classifying it into the above particle size.

The silica fume can be used in either powder or granular form. Further, silica fume, also contain SiO ₂ 80 parts by weight or more is <br/> the preferred.

[0021]

[Function] High-strength concrete, especially 800 kg of compressive strength
As a technique for imparting fluidity to high-strength concrete of about f / cm ² or more, a method of using silica fume as an admixture and adding a high-performance water reducing agent is the most effective and general method at present.

However, even with the above method, the viscosity is higher than that of ordinary ordinary strength concrete, so that the kneading property in the mixer is poor, the amount of the kneading material with respect to the mixer capacity is greatly reduced, and the mixing efficiency is lower than that of ordinary concrete. Unless the kneading time is significantly increased, it is not possible to obtain a homogeneous and sufficiently fluid concrete. Further, in order to make the concrete to have a low water cement ratio and to have fluidity, it is necessary to mix silica fume and add a high-performance water reducing agent having a strong action of dispersing powder particles. As a result, the setting of the concrete is greatly delayed due to the strong setting retarding action of the high-performance water reducing agent combined with the dispersing action. In addition, the lower the water cement ratio, the more the amount of the high-performance water reducing agent used for obtaining fluidity increases, and thus the longer the setting delay. Furthermore, the lower the water-cement ratio, the higher the cost of a high-performance water reducing agent required to obtain fluidity, and thus the higher the material cost of concrete.

As in the cement composition produced by the method of claim 1, 50 to 92 parts by weight of Portland cement, 5 to 25 parts by weight of silica fume, and 3 to 25 parts by weight of limestone fine powder having a specific particle size distribution. By using the cement composition as a binder, the fluidity is improved as compared with the method of adding silica fume to Portland cement according to the prior art, and the amount of the high-performance water reducing agent required to obtain a constant concrete fluidity is reduced. Can be reduced. In addition, when mixing concrete, it has the effect of shortening the time required for the material to be homogeneously kneaded and to be in a fluid state, and further has the effect of reducing the load on the mixer.

Therefore, compared to the conventional technique of adding silica fume to Portland cement, the amount of the high-performance water reducing agent required to obtain the same fluidity can be reduced, which is advantageous in cost. In addition, since the fluidization at the time of kneading is quick and the load on the mixer can be reduced, the productivity can be improved because the amount of kneading at one time and the kneading time can be shortened,
It becomes industrially advantageous.

In the cement composition produced by the method of the first aspect, if the amount of Portland cement is less than 50 parts by weight, the high strength development is inferior.
If the amount is more than the parts by weight, the proportions of the silica fume and the limestone fine powder decrease, so that a cement composition having high strength, high fluidity, good kneading properties, and no large setting delay, which are features of the present invention, cannot be obtained. A particularly preferred amount of Portland cement is 70 to 90 parts by weight.

When the amount of silica fume is less than 5 parts by weight, the effect of improving the strength and fluidity by the silica fume is not obtained, and when the amount is more than 25 parts by weight, the improvement of the strength and fluidity by the silica fume is 5 to 25 parts by weight. It tends to be lower than in the case of the compounding amount, and silica fume is expensive and uneconomical. A particularly preferred amount of silica fume is 5 to 20 parts by weight.

If the amount of the limestone fine powder is less than 3 parts by weight, it is not possible to obtain a cement composition having high strength, high flowability, good kneading properties and no large setting delay, which are characteristics of the present invention. If the amount is more than 25 parts by weight, the strength development will be poor. The particularly preferable blending amount of the limestone fine powder is 3-1.
2.5 parts by weight.

The effect of improving the fluidity and kneading properties of the silica fume-added cement by the fine limestone powder is as follows:
It is remarkably expressed by the limestone fine powder having the specific particle size distribution described in claim 2 . The specific particle size distribution for exhibiting the above-mentioned effects cannot be specified only by the fineness (blaine specific surface area) based on the specific surface area by the air permeation method, which has been conventionally performed. That is, even if the limestone fine powder has the same Blaine specific surface area, it does not have the specific particle size distribution specified in claim 2 ,
A remarkable effect cannot be obtained on the improvement of the fluidity and the kneading property of the silica fume-added cement.

The high strength of the present invention, the kneading property with high flow is a good cement composition, limestone fine powder, claim 2
Particle size distribution of the limestone fine powder specified in the above, ie, 1 μm to 1
There is a peak of the frequency of the particle size distribution in a range of about 0 μm,
It cannot be obtained without a sharp particle size distribution in which the particle size is distributed in a relatively narrow range. The effect of the present invention can be obtained by combining the fine limestone powder having the specific particle size distribution with Portland cement and silica fume to produce a cement composition by the production method according to claim 1 . Therefore, when the particle size distribution is out of the particle size distribution specified in claim 2 , that is, when there is no peak of the frequency of the particle size distribution in the range of about 1 μm to 10 μm, and when the particle size is distributed over a wide range and has a flat particle size distribution, The high strength of the present invention,
A cement composition having high fluidity and good kneading properties cannot be obtained.

It is known that limestone fine powder generally has the effect of accelerating the setting of cement. However, the limestone fine powder originally has a setting promoting effect and the use of limestone fine powder having a specific particle size distribution delays the setting. The synergistic effect with the effect of reducing the amount of high-performance water reducing agent
The setting delay of concrete, which has been a problem in the prior art, can be greatly suppressed.

The addition of silica fume, the high-strength concrete that is a low water-cement ratio with a superplasticizer, a very small the Most Probable inorganic substance reactive such as powder limestone fines, the strength reduction is added inner split It is feared that it will occur. However, in the present invention using the limestone fine powder having the specific particle size distribution, there is no significant reduction in strength, and particularly when the amount of the limestone fine powder having the specific particle size distribution is 10% or less, it is equivalent to the case where no limestone fine powder is added. It develops the above strength.

Further, in the present invention using limestone fine powder having a specific particle size distribution, the viscosity of the concrete becomes small, and there is an effect that the workability can be improved as compared with the case where no concrete is used.

Further, in the present invention using a limestone fine powder having a specific particle size distribution, the limestone fine powder does not generate heat of hydration, so that it has an effect of reducing heat generation of concrete and has a high unit cement amount and a high strength concrete. This has the effect of suppressing strength reduction and crack generation due to temperature rise, which are problems.

[0034]

EXAMPLES Examples of mortar and concrete using the cement composition produced according to the present invention will be described below. First, the experimental method will be described for each item.

1. Materials Used (Including Materials Used in Comparative Examples) 1.1 Materials Used in Cement Composition (1) Portland Cement NP (Normal Portland Cement) (Specific gravity: 3.1)
6) HP (early strength Portland cement) (specific gravity: 3.1)
4) MP (Medium heat Portland cement) (specific gravity: 3.
20) (2) Silica fume: 940 U from Elchem (specific gravity 2.
2)  (3) Limestone fine powder having a specific particle size distribution
It was prepared to have a distribution.

A) Limestone fine powder having a specific particle size distribution used in Examples and Reference Examples GL: The particle size distribution of 95 wt% for 20 μm or less, 65 wt% for 10 μm or less, 40 wt% for 5 μm or less, and 13 wt% for 1 μm or less. Have. Blaine specific surface area is 5
280 cm ² / g.

GL: 98 wt% of 20 μm or less,
87 wt% for 10 μm or less, 55 wt% for 5 μm or less,
1 μm or less has a particle size distribution of 15 wt%. The Blaine specific surface area is 7730 cm ² / g.

GL: 100 μm for 20 μm or less
%, 99 wt% for 10 μm or less, 87 wt% for 5 μm or less
% And 1 μm or less have a particle size distribution of 25 wt%. Blaine specific surface area is 17000 cm ² / g.

B) Limestone fine powder having no specific particle size distribution used in the comparative example BL: particle size distribution of 66 wt% for 20 μm or less, 49 wt% for 10 μm or less, 38 wt% for 5 μm or less, and 19 wt% for 1 μm or less. Blaine specific surface area is 5
040 cm ² / g.

BL: 77 wt% at 20 μm or less,
62 wt% for 10 μm or less, 47 wt% for 5 μm or less,
1 μm or less has a particle size distribution of 16 wt%. The Blaine specific surface area is 7670 cm ² / g.

BL: 98 wt% for 20 μm or less,
86 wt% for 10 μm or less, 75 wt% for 5 μm or less,
1 μm or less has a particle size distribution of 32 wt%. The Blaine specific surface area is 16820 cm ² / g.

BL: 64 wt% for 20 μm or less,
40 wt% for 10 μm or less, 26 wt% for 5 μm or less,
1 μm or less has a particle size distribution of 7 wt%. The Blaine specific surface area is 3710 cm ² / g.

1.2 Materials other than the cement composition used for mortar and concrete Fine aggregate: mountain sand from Kisarazu (specific gravity 2.63, water absorption 1.
Coarse aggregate: crushed stone from Hachioji (maximum size 20 mm, specific gravity 2.68, water absorption 0.83%) High-performance AE water reducing agent: polycarboxylic acid kneading water: tap water

2. Measurement method of particle size distribution of limestone fine powder having specific particle size distribution Measurement of particle size distribution of limestone fine powder having specific particle size distribution is carried out using a laser diffraction / scattering type particle size distribution measuring device (France, CI
This was performed using LAS CILAS 850B). At the same time, the fineness (specific surface area) by the Blaine air permeation method was also measured.

3. Manufacturing method of cement composition The manufacturing method of the cement composition is as follows.

(1) Production Method 1 ( Reference Example ) Various powder materials such as Portland cement, silica fume, and limestone fine powder were mixed with a ski-type shovel blade type high-speed mixer (pro-share mixer manufactured by Taiheiyo Kiko Co., Ltd.). . However, this method merely shows an example of the mixer, and does not limit the type and model of the mixer.

(2) Manufacturing method 2 ( Example ) In a cement plant, silica fume is supplied together with Portland cement raw materials such as clinker and gypsum to a finishing mill in a cement manufacturing process, and the silica fume is mixed with Portland cement particles. Further, limestone fine powder having a specific particle size distribution was added to and mixed with the silica fume-mixed cement obtained by the dispersion.

(3) Manufacturing Method 3 (Comparative Example) As a comparative method, a method of separately feeding a cement, silica fume, and the like separately into a concrete mixer for comparison is hereinafter referred to as a manufacturing method 3.

4. Mixing of mortar The mixing of mortar used in Examples , Reference Examples and Comparative Examples is as follows. W is the amount of water, C is the amount of the cement composition,
S is the fine aggregate amount.

Formulation I: W / C = 22% S / C = 1.4 High-performance AE water reducing agent addition amount: C × 1.2% Formulation II: W / C = 25% S / C = 1.6 high Performance AE water reducing agent addition amount: C x 1.2%

5. Mixing of concrete The mixing of concrete used in Examples , Reference Examples and Comparative Examples is as follows.

[Table 1]

6. Mortar kneading method The mortar was kneaded using a Hobart mixer (4.7 liter capacity) for 3 minutes.

7. Concrete kneading method For the kneading, a forced kneading pan-type mixer (capacity: 50 liters) was used, and the kneading was performed by mortar kneading.
After the addition of coarse aggregate, kneading was further performed for 2 minutes.

[0054] 8. Evaluation method of various properties of mortar and concrete (1) Evaluation method of fluidity of mortar The fluidity of mortar was evaluated by mini-slump cone (cone shape of top surface φ5cm, bottom surface φ10cm, height 15cm).
The mortar was filled with the mortar, and the final spread diameter (mini-slump flow) of the mortar when the cone was pulled up was evaluated.

(2) Method of Evaluating the Fluidity and Viscosity of Concrete The fluidity of concrete is determined by examining the spread of the sample after the slump test of concrete, ie, slump flow, when the amount of the high-performance AE water reducing agent is fixed. Was evaluated. When the amount of the high-performance AE water reducing agent added was adjusted so as to obtain a slump flow of 60 ± 3 cm, the fluidity was evaluated based on the amount of the high-performance AE water reducing agent added. In addition, even if the slump flow was the same, the properties of concrete greatly differed depending on the viscosity. Therefore, the O funnel flow time was measured as an index of the viscosity.

(3) Method of evaluating kneading property In the case of mortar or concrete with a small water-cement ratio, it takes a certain time after the start of kneading by the mixer until the fluidity of the kneaded material is developed. The longer the time, the greater the load on the mixer and the longer the kneading. Therefore, in this example, the kneading property of the concrete was evaluated by measuring the time required for the mortar material to fluidize (mortar kneading time) in one minute of the mortar kneading, and evaluating the kneading property as an evaluation index. did. That is, the shorter the mortar kneading time, the better the kneading properties. The mortar kneading time was measured under the condition that the concrete slump flow after kneading with the amount of the high-performance AE water reducing agent was kept constant at 60 ± 3 cm.

(4) Setting behavior of concrete The test was carried out in accordance with a test for measuring the setting time of concrete by the ASTM C403 Proctor penetration resistance method.

(5) Compressive Strength After the concrete was kneaded, it was poured into a steel mold having a diameter of 10 × 20 cm, and the mold was lightly beaten with a wooden hammer and compacted. The mold was demolded on one day of age, and thereafter was cured in water at 20 ° C. until the age of the test material. For the compressive strength test, the loading surface is polished and the loading speed is JI
The test was performed according to the SA 1108 concrete compressive strength test method.

9. Reference Examples and Comparative Examples by Mortar Reference Examples 1 to 5 and Comparative Examples 1 to 9 The fluidity test of a mortar using a cement composition in which moderately heated Portland cement, silica fume and limestone fine powder were mixed and prepared for 7 minutes by the production method 1 Table 2 shows the results.

In Comparative Examples 5, 8, and 9 in which no comparative limestone powder was added as shown in Table 2, the cement composition was similarly treated for 7 minutes by the production method 1 except that the limestone fine powder was not used. A mixture was prepared. The composition of the mortar is Formulation I.

[0061]

[Table 2]

From the comparison between Reference Examples 1 to 3 and Comparative Example 5, it can be seen that mixing the fine limestone powder with the cement composition containing silica fume improves the fluidity of the cement composition containing silica fume. However, from the comparison between Reference Examples 1 to 3 and Comparative Examples 1 to 4, even when the specific surface area of the limestone fine powder is almost the same, the fluidity improving effect is greatly different, and the limestone fine powder having the specific particle size distribution of the present invention is obtained. It can be seen that fluidity is extremely good in the mixed cement composition.

That is, 90% or more of particles having a size of 20 μm or less and 65% of particles having a size of 10 μm or less in the fine limestone powder.
% And particles having a particle size of 5 μm or less have a particle size distribution of 40 to 90%, and particles having a particle size of 1 μm or less have a particle size distribution of 25% or less. Is 95% or more and 10%
80% or more of particles having a particle size of not more than 80 μm and 50 to 90% of particles having a particle size of not more than 5 μm and 2% of particles having a particle size of 1 μm or less.
When the particle size distribution is 5% or less, a greater fluidity improving effect can be obtained.

From the comparison between Reference Examples 4 and 5 and Comparative Examples 8 and 9, it can be seen that when NP and HP other than MP are used, the effect of improving the fluidity can be obtained as in Reference Examples 1 to 3. Also, from the comparison between Reference Examples 4 and 5 and Comparative Examples 6 and 7,
The cement composition obtained by mixing the limestone fine powder having the specific particle size distribution of the present invention has a remarkably good fluidity, and even if the specific surface area of the limestone fine powder is about the same, it does not have the specific particle size distribution of the present invention. It can be seen that limestone fine powder does not show an effective improvement in fluidity.

Reference Examples 6 to 9 and Comparative Examples 10 to 11 In the mortar, the mixing ratio of silica fume in the cement composition was changed in the range of 0 to 30 parts by weight, and the strength properties thereof were examined. The production of the cement composition was carried out by mixing and preparing for 7 minutes by the production method 1. The composition of the mortar was Formulation II, and the fine limestone powder in the cement composition was GL.
Was fixed at 10 parts by weight. Table 3 shows the compressive strength of the mortar at the age of 28 days.

[0066]

[Table 3]

According to Table 3, the mixing ratio of silica fume is 5
It can be seen that up to 25 parts by weight is effective for improving the strength. When the mixing ratio of silica fume is more than 25 parts by weight and becomes 30 parts by weight, there is no longer a large strength improving effect, and silica fume is expensive and uneconomical. The mixing ratio of silica fume in the cement composition is preferably 5 to 25 parts by weight of the present invention, more preferably 5 to 20 parts by weight.

10. Reference Examples and Comparative Examples Using Concrete Reference Examples 10 and 11, Comparative Examples 12 to 14 Cement composition of the present invention in which moderately heated Portland cement, silica fume and limestone fine powder having a specific particle size distribution are mixed and prepared for 7 minutes by Production Method 1. (reference examples 10 and 11), and in place of the powder limestone fines having a specific particle size distribution, specific particle size except that distribution was used for comparison limestone powder having no comparative cement composition prepared by mixing prepared analogously (compare The fluidity of concrete using Examples 12 and 13) was examined.

A comparative example was also carried out when no fine limestone powder was added (Comparative Example 14). Comparative Example 14 was prepared by mixing for 7 minutes in the same manner as in Production Example 1 except that the mixing ratio of the cement composition was changed to medium heat Portland cement: silica fume 9: 1.

The concrete was mixed except that the type of the cement composition was different, and the other conditions were the same. Concrete mixing was carried out with the water cement ratio of the mixing 2 being 22% and the amount of the high-performance AE water reducing agent added being constant at C × 1.3% (C is the amount of the cement composition). Table 4 shows the slump flow measurement results.

Comparison between Reference Examples 10 and 11 in Table 4 and Comparative Example 14 shows that the fluidity of concrete using the cement composition of the present invention using limestone fine powder having a specific particle size distribution is as follows. It can be seen that it is greatly improved as compared with those not used. Further, Reference Examples 10 and 11 and Comparative Example 12,
13 compared with limestone fine powder having a specific surface area similar to that of limestone fine powder having a specific particle size distribution which is a feature of the present invention, in the case of limestone fine powder having a particle size distribution different from that of the present invention. Shows that the effect of improving the fluidity of concrete is inferior.

[0072]

[Table 4]

Reference Examples 12 to 17, Comparative Examples 15 and 16 According to the composition of the present invention, a large slump flow can be obtained as compared with the case where a conventional cement composition is used. Therefore, when the slump flow is the same, the amount of the high-performance AE water reducing agent required for improving the fluidity may be small.

To prove this, the amount of the high-performance AE water reducing agent required to obtain a slump flow of 60 cm when the mixing ratio of the limestone fine powder was changed was measured. Table 5 shows the results.

The concrete mixing conditions are those of the water cement ratio of the mixing 2 of 22%. For the limestone fine powder having a specific particle size distribution, GL was used and the mixing ratio was changed.
Assuming that the mixing ratio of the cement composition in Reference Examples 12 to 17 and Comparative Examples 15 and 16 is 9: 1 with the mixing ratio of ordinary Portland cement and silica fume being A, limestone having a specific particle size distribution with respect to A The mixing ratio of the fine powder was adjusted so as to be 0 to 25%. The method for producing the cement composition was in accordance with Production Method 1. Also,
The mixing time was 7 minutes.

From Table 5, the cement compositions of Reference Examples 12 to 17 mixed with limestone fine powder having a specific particle size distribution are as follows:
The amount of the high-performance AE water reducing agent required to obtain a slump flow of 60 cm may be smaller than that of the case where no limestone fine powder for comparison (Comparative Example 15) or a small amount of limestone fine powder (Comparative Example 16) is added. It can be seen that the larger the amount of powder added, the smaller the required amount of water reducing agent.

The kneading time of the mortar is shorter in the cement composition of the present invention in which limestone fine powder having a specific particle size distribution is mixed by 3% or more than in the non-mixed comparative example, and the kneading property is remarkably improved. You can see that. Especially 5%
It is effective when mixed.

The flow time of the O funnel, which is an index of the viscosity of the concrete, was determined in Comparative Example 15 using a cement composition mixed with limestone fine powder having a specific particle size distribution.
It can be seen that the falling time is shorter and the viscosity of the concrete is lower than when no is added. The lower the viscosity, the greater the mixing ratio of the fine limestone powder having the specific particle size distribution.

As described above, the cement composition mixed with limestone fine powder having a specific particle size distribution can reduce the high-performance AE water reducing agent required for obtaining a predetermined slump flow, improve the kneading properties, and improve the viscosity. Although having a reducing effect, the mixing ratio of the limestone fine powder having a specific particle size distribution is 3% of the present invention.
Effective at ~ 25%.

[0080]

[Table 5]

REFERENCE EXAMPLES 18-23, COMPARATIVE EXAMPLES 17, 18 Table 6 shows the results of examination of the setting and strength properties of concrete using the cement composition of the present invention prepared by mixing and adjusting limestone fine powder having a specific particle size distribution. Show. The composition of the concrete and the like are the same as those in Table 5.

It can be seen that the setting time of concrete decreases as the mixing ratio of limestone fine powder having a specific particle size distribution increases. Acceleration of the setting time is effective at a mixing ratio of fine limestone powder of 3% or more.

Further, it can be seen that the compressive strength does not decrease even when limestone fine powder having a specific particle size distribution is mixed, as compared with no addition, up to a mixing ratio of 10%.

[0084]

[Table 6]

Reference Examples 24 and 25, Comparative Examples 19 and 20 Cement compositions with different types of Portland cement were produced by mixing for 7 minutes in Production Method 1, and their concrete properties were examined. High performance A with W / C = 25% formulation 1
E The amount of the water reducing agent was adjusted so that the slump flow was 60 cm. GL was used as the limestone fine powder having a specific particle size distribution. The composition of the cement composition of the example is Portland cement: silica fume: GL = 80: 10: 10,
The composition of the cement composition of the comparative example is Portland cement: silica fume = 90: 10. Table 7 shows the results.

[0086] From Table 7, it can be seen that even in the early-strength Portland cement and ordinary Portland cement, concrete using the cement composition of the present invention uses a cement composition not using limestone fine powder having a specific particle size distribution for comparison. It is clear that the kneading property and the fluidity are excellent as compared with the concrete that was used.

[0087]

[Table 7]

Reference Examples 26 to 29 , Example 1, Comparative Examples 21 and 22 Table 8 shows the results of examining the properties of cement compositions obtained by changing the production method using concrete. Here, in the composition 2 having a water cement ratio of 22%, the amount of the high-performance AE water reducing agent added was C × 1.
The test was performed at a constant value of 3% (C is the amount of the cement composition).

Table 8 shows that the longer the mixing time in Production Method 1, the shorter the mortar kneading time and the greater the concrete slump flow. This, in a cement composition containing silica fume,
This indicates that the flocculation of silica fume is sometimes loosened and the more homogeneously dispersed, the better the kneading property of mortar and the fluidity of concrete in mortar kneading. Further, the cement composition mixed and manufactured by the manufacturing method 2 in which silica fume was charged into a finishing mill at the time of manufacturing the cement exhibited the same kneading property and fluidity as those mixed for 7 minutes or more in the manufacturing method 1.

A comparison of Comparative Example 22 with Reference Examples 26 to 29 and Example shows that a conventional limestone fine powder having a specific particle size distribution is not used and cement and silica fume are separately charged into a concrete mixer. It can be seen that Production Method 3 is inferior in both kneading properties and fluidity as compared with the case where the cement composition produced according to the present invention is used. In addition,
In Comparative Example 22, since the flow time of the mortar exceeded 1 minute in the pre-kneading of the mortar of the concrete, the kneading time after the coarse aggregate was added was reduced to 20 minutes by 1 minute and 40 seconds, and the total kneading time was the same as the others. Adjusted to 3 minutes.

Comparative Example 21, Examples 26 to 29 and Reference Example
Configuration Comparing 1 and portland cement of Examples 26-29 and Reference Example 1, a cement composition comprising a limestone fine powder having a silica fume and the specific particle size distribution, by according to the manufacturing method of the present invention, the cement composition It can be seen that the kneading property and the fluidity are remarkably improved by the method of separately charging the respective constituent materials into the concrete mixer.

[0092]

[Table 8]

[0093]

As described above, according to the cement composition manufactured by the manufacturing method of the present invention , silica fume is used as an admixture in Portland cement, which has been used for conventional high-strength concrete, and water is added to the high-performance water reducing agent. It is possible to produce mortar or concrete excellent in fluidity and kneading properties, which cannot be obtained by the method of reducing the cement ratio. Moreover, according to the cement composition produced by the method of the present invention, the amount of the high-performance water reducing agent to be added is small, and the fine limestone powder in the composition has a coagulation promoting action. The setting delay caused by the existing high-performance water reducing agent can be greatly reduced. Further, as compared with the conventional method of using silica fume as an admixture in Portland cement, the strength is equal to or higher than that of the conventional method, and the heat of hydration can be reduced. In addition, compared to the conventional method of using silica fume as an admixture for Portland cement, the cement composition of the present invention has a high fluidity of the kneaded material at the time of kneading the concrete, and does not apply a large load to the mixer. High strength and high fluidity concrete can be advantageously produced.

Conventionally, special equipment was required to separately add silica fume to the mixer. However, if the composition of the present invention mixed with silica fume is used, the existing concrete plant equipment can be used, and no special equipment is required. It also has an effect.

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification code FI C04B 14:04 C04B 14:04 Z 14:28) 14:28) (72) Inventor Etsuo Asakura 1-chome Kitabukurocho, Omiya City, Saitama Prefecture 297 Address, Mitsubishi Materials Corporation Cement Research Institute (56) References JP-A-6-199549 (JP, A) JP-A-2-102152 (JP, A) JP-A-5-286746 (JP, A) JP JP-A-4-321546 (JP, A) JP-A-3-5347 (JP, A) JP-A-3-261638 (JP, A) JP-A-5-238788 (JP, A) JP-A-5-1477984 (JP , A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C04B ^7/ 00-28/36

Claims (2)

(57) [Claims] 1. Portland cement 50 to 92 parts by weight, silica fume 5 to 25 parts by weight and limestone fine powder 3
A method for producing a cement composition comprising a total of 100 parts by weight of ２５25 parts by weight, comprising: adding silica fume to a finishing mill in which cement clinker or the like is crushed in a cement production step; A method for producing a cement composition, comprising mixing and dispersing silica fume simultaneously with pulverization, and then mixing a limestone fine powder having a specific particle size distribution with a pulverized product produced by a finishing mill. Wherein Oite to claim 1, wherein the specific particle size distribution of limestone powder with the, 20 [mu] m or less of particles of 90% or more, 10 [mu] m is less than 65% or less of the particles, 5 [mu] m or less of particles 40% to 90% 25% of particles of 1 μm or less within the range
A method for producing a cement composition having the following particle size distribution.