JP3230378B2 - Cement composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to 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.

Dispersion of Silica Fume Since silica fume is an ultrafine particle, 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]

The cement composition of the present invention comprises 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 in a total amount of 100 parts by weight. The limestone fine powder contains 90% or less of particles of 20 μm or less.
Above, 65% or more and 5μm or less of particles of 10μm or less
Particles having a particle size of 1 μm or less within a range of 40% to 90%.
% Or less.

As the Portland cement, ordinary Portland cement, early-strength Portland cement, ultra-high-strength Portland cement, moderate heat Portland cement and the like can be used. It is.

As the limestone fine powder, particles of 20 μm or less are 90% or more, particles of 10 μm or less are 65% or more, and 5% or less.
Particles having a particle size distribution in which particles having a particle diameter of 1 μm or less are within a range of 40% to 90% are used.
You . This fine limestone powder is preferably obtained by pulverizing natural limestone and then classifying it into the above particle size.

In order to produce the cement composition of the present invention, powdery or granular silica fume is put into a mill for pulverizing and finishing the cement clinker and the like, and the silica fume is dispersed at the same time as the pulverization of the cement clinker and the like. Then, it is preferable to add limestone fine powder after grinding and finishing by a mill.

In order to produce the cement composition of the present invention, powdery or granular silica fume is added to Portland cement ground and finished by a finishing mill,
You may make it mix limestone fine powder using a mixer. Furthermore, in order to produce the cement composition of claim 1, powdery or granular silica fume and limestone crushed stone are charged into a mill for pulverizing and finishing cement clinker and the like, and the silica fume is dispersed at the same time as the cement clinker and the like are pulverized. And grinding of limestone may be performed. In addition, in order to produce the cement composition of claim 1, limestone crushed stone is put into a mill for grinding and finishing cement clinker, etc., and crushing of limestone is performed simultaneously with grinding of cement clinker and the like. After the pulverization adjustment, the silica fume may be mixed using a mixer.

[0022]

[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 currently the most effective and general method.

However, even with the above-mentioned 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 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.

A cement composition comprising 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 as in the cement composition of claim 1 is used. By using as a binder, the flowability is improved as compared with the conventional method of adding silica fume to Portland cement, and the amount of the high-performance water reducing agent required to obtain a constant flowability of concrete 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 with 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 of the first aspect, if the blending amount of Portland cement is less than 50 parts by weight, the high strength developability is inferior, and if it is more than 92 parts by weight, the proportion of silica fume and limestone fine powder is low. Therefore, 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.

If 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. If 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, 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. 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 of the silica fume-added cement by the fine limestone powder is as follows:
The limestone powder with Japanese Teitsubu distribution of the present invention are intended to be prominently expressed. 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 Blaine specific surface area of the limestone fine powder is the same, if it does not have the specific particle size distribution specified in the present invention, a remarkable effect on improving the fluidity and kneading property of the silica fume-added cement. Can not get.

In order to obtain the cement composition of the present invention having a high strength, a high fluidity and a good kneading property, the fine limestone powder has a particle size distribution of the fine limestone powder specified in the present invention , that is, 1 μm to 10 μm.
There is a peak in the frequency of the particle size distribution in a range of about μm, and the particle size distribution is relatively narrow, so that it cannot be obtained unless the particle size distribution has a sharp particle size distribution. A limestone fine powder having the specific particle size distribution, combined with Portland cement and silica fume, the effect of the present invention can be obtained by a cement composition of the present invention. Therefore, when the particle size distribution specified in the present invention is out of the range, that is, 1 μm to 10 μm
In the case where there is no peak of the frequency of the particle size distribution in the range of about, and in the case where the particle size is distributed in a wide range and has a flat particle size distribution, the cement composition of the present invention having high strength, high flowability and good kneading properties is obtained. I can't.

It is known that limestone fine powder generally has a setting promoting effect of cement. However, the setting promoting effect inherent in the limestone fine powder and the setting delay due to the use of limestone fine powder having a specific particle size distribution are known. 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 to a high-strength concrete with a low-water cement ratio using a high-performance water-reducing agent reduces the strength by adding an inorganic substance, such as limestone fine powder, which is considered to have extremely low reactivity. 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 is 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 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 content and a high strength concrete. This has the effect of suppressing strength reduction and crack generation due to temperature rise, which are problems.

[0035]

EXAMPLES Examples of mortar and concrete using the cement composition 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, BET specific surface area 20. 0m ² / g) (3) limestone powder limestone having a specific particle size distribution was ground in a ball mill and adjusted to be a specific size distribution by using a classifier.

A) Limestone fine powder having a specific particle size distribution used in Examples GL: 95 μm 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. 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 wt% 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%. The Blaine specific surface area is 17000 cm ² / g.

B) Limestone fine powder without specific particle size distribution BL used in the comparative example: BL: 20 μm or less has 66% by weight, 10 μm or less has 49% by weight, 5 μm or less has 38% by weight, and 1 μm or less has 19% by weight. 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% of 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.
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 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 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.).

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

Formulation I: W / C = 22% S / C = 1.
4. Addition amount of high-performance AE water reducing agent: C x 1.2% Formulation II: W / C = 25% S / C = 1.6 Addition amount of high-performance AE water reducing agent: C x 1.2% Mixing of concrete The mixing of concrete used in Examples and Comparative Examples is as follows.

[0049]

[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.

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 for 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, the 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 conducted in accordance with a test for measuring the setting time of concrete by the ASTM C 403 Proctor penetration resistance method.

(5) Compressive Strength Properties 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. Examples and Comparative Examples Using Mortar 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 was used. Table 2 shows the results
Shown in

Also, in 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.

[0059]

[Table 2]

From the comparison between Examples 1 to 3 and Comparative Example 5, it can be seen that mixing limestone fine powder with the cement composition containing silica fume improves the fluidity of the cement composition containing silica fume. However, from the comparison between 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 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 Examples 4 and 5 and Comparative Examples 8 and 9, it can be seen that when NP and HP other than MP were used, the effect of improving fluidity was obtained as in Examples 1 to 3. Further, from the comparison between 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.

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.

[0064]

[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. Examples and Comparative Examples Using Concrete Examples 10, 11, Comparative Examples 12 to 14 A cement composition of the present invention in which moderately heated Portland cement, silica fume and limestone fine powder having a specific particle size distribution were mixed and prepared for 7 minutes by the production method 1. (Examples 10 and 11) and a comparative cement composition mixed and prepared in the same manner except that a comparative limestone fine powder having no specific particle size distribution was used instead of the limestone fine powder having the specific particle size distribution (comparative example) 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 the same as the production method except that the mixing ratio of the cement composition was changed to moderate heat Portland cement: silica fume 9: 1.
1 and mixed for 7 minutes.

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 at a water cement ratio of 22% in the mixing 2, and the amount of the high-performance AE water reducing agent added was constant at C × 1.3% (C is the amount of the cement composition ). Table 4 shows the slump flow measurement results.

When Examples 10 and 11 in Table 4 are compared with Comparative Example 14, 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. 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. the, it is seen that <br/> effect causes improved the fluidity of the concrete is poor.

[0070]

[Table 4]

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 a high-performance AE water reducing agent required to obtain a slump flow of 60 cm when the mixing ratio of 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 Examples 12 to 17 and Comparative Examples 15 and 16 is A where the mixing ratio of ordinary Portland cement and silica fume is 9: 1, 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.

As shown in Table 5, the cement compositions of Examples 12 to 17 mixed with limestone fine powder having a specific particle size distribution were 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 3% or more of limestone fine powder having a specific particle size distribution is mixed as compared with 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 by using a cement composition mixed with limestone fine powder having a specific particle size distribution in Comparative Example 15.
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 achieving 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%.

[0078]

[Table 5]

Examples 18 to 23, Comparative Examples 17 and 18 Table 6 shows the results of investigation on 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, up to a mixing ratio of 10%, as compared with the case where no limestone is added.

[0082]

[Table 6]

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.

From Table 7, it can be seen that the concrete using the cement composition of the present invention, even in the early-strength Portland cement and ordinary Portland cement, uses a cement composition which does not use 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.

[0085]

[Table 7]

[0086]

As described above, according to the cement composition of the present invention , a method of using silica fume as an admixture for Portland cement, which has been practiced with conventional high-strength concrete, and reducing the water-cement ratio with a high-performance water reducing agent. A mortar or concrete excellent in fluidity and kneading properties that could not be obtained by the method can be produced. In addition, according to the cement composition of the present invention, a small amount of a high-performance water reducing agent is added and the fine limestone powder in the composition has a coagulation accelerating action. The delay in setting by the 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 in 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. Advantageously high strength
High fluidity concrete can be manufactured.

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.

Continuation of the front page (51) Int.Cl. ⁷ Identification code FI C04B 18:14 C04B 18:14 Z 14:28 14:28 20:00) 20:00) B (72) Inventor Etsuro Asakura Omiya-shi, Saitama 1-297 Kitabukuro-cho, Cement Research Institute, Mitsubishi Materials Corporation (56) References JP-A-6-199549 (JP, A) JP-A-2-102152 (JP, A) JP-A-5-286746 (JP, A) JP-A-7-277785 (JP, A) 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-5-147798 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C04B ^7/ 00-28/36

Claims (1)

(57) [Claims] 1. Portland cement 50-92 weight
Parts, 5 to 25 parts by weight of silica fume and fine limestone powder 3
~ 25 parts by weight so that the total is 100 parts by weight
Cement compositionAnd In the limestone fine powder, particles having a particle size of 20 μm or less are 90% or more,
65% or more of particles having a particle size of 0 μm or less are 4% or less.
25% or less of particles of 1 μm or less in the range of 0% to 90%
Cement composition characterized by having a certain particle size distribution
object.