JP2000281419A - Production of mixed cement - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain mixed cement by simultaneously pulverizing cement clinker, gypsum and limestone along with mutually mixing so as to reduce unit quantity of water and/or admixture for achieving a specified consistency of the final mixed cement. SOLUTION: This mixed cement is obtained by simultaneously pulverizing cement clinker, gypsum and limestone in a grinding mill to a degree of fineness of about 4,200 cm2/g along with mutually mixing; wherein the cement clinker to be used is normal Portland cement one and the weight ratio of the normal Portland cement to the limestone is set at 9:1; alternatively, the above ratio is set at 7:3 and the degree of fineness at about 4,200 cm2/g, about 5,100 cm2/g or about 3,200 cm2/g, or the above ratio is set at 5:5 and the degree of fineness at about 4,200 cm2/g. Thereby, interstices in the cement and the coarse particle content of the pulverized limestone can be reduced, leading to dispensing with an exclusive silo and weighing machine for pulverized limestone.

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 mixed cement in which limestone fine powder is mixed.

[0002]

2. Description of the Related Art Generally, when using aggregates of low quality such as sea sand and crushed sand, the upper limit value of the unit water amount 185 k specified in the Building Construction Standards and Specifications (JASS 5) of the Architectural Institute of Japan.
To satisfy g / m ³ , cement mixed with limestone fine powder is used.

[0003] In the case of producing a mixed cement in which such limestone fine powder is mixed, conventionally, a method has been adopted in which limestone fine powder and Portland cement are individually pulverized and mixed by a mixer.

[0004] In this case, gypsum is added to Portland cement and pulverized.

[0005]

However, when the gypsum is added to Portland cement clinker and pulverized in this way, particles of 10 μm or less in the finished cement have pores (C ₃₎ that are relatively easily pulverized. A, C ₄ AF) and the content of gypsum increase.

[0006] The pores in the cement adsorb a large amount of the admixture, and thus cause a deterioration in the consistency of fresh concrete.

Further, there is a problem that a dedicated silo for limestone fine powder and a measuring instrument are required as equipment for mixing limestone fine powder and cement.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and can reduce the amount of water or admixture for obtaining a predetermined consistency, and can be used for a special silo for fine limestone powder. And to eliminate the need for a measuring instrument.

[0009]

The present invention focuses on the fact that limestone is easily crushed by cement clinker, and by mixing and crushing them simultaneously, relatively soft limestone is crushed first, and The present inventors have found that the content of interstitial material in cement and coarse particles in limestone fine powder, which are factors that worsen the tension, are reduced, and completed the present invention.

The present invention has been made to solve such a problem, and means for solving the problem are as follows.
It is to produce a cement clinker, gypsum and limestone by simultaneously pulverizing and mixing.

[0011]

Embodiments of the present invention will be described below.

(Example 1) Cement clinker, gypsum,
And limestone were placed in a pulverizing mill, pulverized to a fineness of 4200 cm ² / g, and mixed simultaneously.

As the cement clinker, clinker of ordinary Portland cement was used.

The ratio of ordinary Portland cement to limestone was 9: 1.

Example 2 In this example, the ratio of cement to limestone was 7: 3.

The fineness of the mixed cement is the same as in Example 1.
4200 cm ² / g.

(Embodiment 3) Also in this embodiment, the ratio of cement to limestone was 7: 3.

The fineness of the mixed cement was 5100 cm ² / g.

(Embodiment 4) Also in this embodiment, the ratio of cement to limestone was 7: 3.

The fineness of the mixed cement was 3200 cm ² / g.

Example 5 In this example, the ratio of cement to limestone was 5: 5.

The fineness of the mixed cement was 4200 cm ² / g.

Comparative Example 1 Cement clinker and gypsum were put into a ball mill, and the fineness of cement was 3300 cm ² / g.
And crushed.

On the other hand, the limestone was pulverized to 7400 cm ² / g to obtain a fine limestone powder, and this fine limestone powder was mixed with the above mixture of cement and gypsum.

The fineness of the mixed cement was 4150 cm ² / g.

The ratio of cement to limestone was 9: 1.

Comparative Example 2 Similar to Comparative Example 1, the cement was pulverized until the fineness became 3300 cm ² / g, and the fineness was 4100 cm ^2.
It was mixed with limestone fine powder ground to ² / g.

The fineness of the mixed cement was 4250 cm ² / g.

The ratio of cement to limestone was 7: 3.

(Comparative Example 3) As in Comparative Example 1, the cement was crushed until the fineness of the cement became 3300 cm ² / g, and the fineness was 9700 cm.
^It was mixed with limestone fine powder ground to ² / g.

The fineness of the mixed cement was 5170 cm ² / g.

The ratio of cement to limestone was 7: 3.

(Comparative Example 4) In the same manner as in Comparative Example 1, the cement was pulverized until the fineness was 3300 cm ² / g, and the fineness was 1100 cm.
^It was mixed with limestone fine powder ground to ² / g.

The fineness of the mixed cement was 3150 cm ² / g.

The ratio of cement to limestone was 7: 3.

(Comparative Example 5) In the same manner as in Comparative Example 1, the cement was pulverized until the fineness became 3300 cm ² / g, and the fineness was reduced to 4300 cm ² / g.
^It was mixed with limestone fine powder ground to ² / g.

The fineness of the mixed cement was 4050 cm ² / g.

The ratio of cement to limestone was 5: 5.

(Test Example) The mixed cements of Examples 1 to 5 and Comparative Examples 1 to 5 were mixed with concrete, and those using ordinary cement alone were also mixed with concrete. The index of concrete consistency was considered by the slump test method.

Specifically, comparison of the unit water amount to obtain a slump of 18 cm was performed for Examples 1 to 5, and Comparative Examples 1 to 5, and for the case of using cement alone.

Examples 1 to 5 for obtaining a slump of 18 cm
Table 1 shows the blending of the mixed cements of Comparative Examples 1 to 5 and those using the ordinary cement alone with concrete.

[0042]

[Table 1]

[0043] In Table 1, W / C represents a water / cement ratio, s / a is shows the ratio of the volume of sand in the volume of sand and gravel fine aggregate (m ³⁾ (m ³⁾ is there.

As the fine aggregate, sea sand having a surface dry specific gravity of 2.56 was used.

As the coarse aggregate, crushed stone having a specific gravity of 2.70 was used.

The unit water amount obtained in Table 1 is graphed in FIG. 1, and the unit water amount of each example and the comparative example was compared.

As is clear from FIG. 1, those having the same additive amount (Example 1 and Comparative Example 1, Example 2 and Comparative Example 2, Example 3 and Comparative Example 3, and Example 4 When Example 4 and Example 5 were compared with Comparative Example 5), it was confirmed that each example had a smaller amount of unit water for obtaining a predetermined consistency than each Comparative Example.

As a result, it was confirmed that when the unit water amount was the same in each example and each comparative example, the amount of the admixture could be reduced in the example as compared with the comparative example.

[0049]

As described above, according to the present invention, it is possible to reduce the amount of unit water for obtaining a predetermined consistency when the admixture addition rate with respect to the cement weight is the same, as compared with the prior art. And the addition rate of the admixture can be reduced when the unit water amount is the same.

As described above, since the unit water amount for obtaining a predetermined consistency can be reduced, there is an effect that the strength can be expressed more than before.

In addition, equipment such as a silo for exclusive use of limestone fine powder and a measuring instrument, which are conventionally used, becomes unnecessary.

Further, since the limestone and the cement clinker are simultaneously crushed, the relatively soft limestone is crushed first, so that there is an effect that the crushing time for obtaining a predetermined fineness as the mixed cement can be shortened. .

[Brief description of the drawings]

FIG. 1 is a graph showing a unit water amount in each of Examples and Comparative Examples.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Naoki Nishida 7-55 Minamionkajima, Taisho-ku, Osaka Sumitomo Osaka Cement Co., Ltd. Cement Concrete Research Laboratory (72) Inventor Yu Yu Honda Chiyoda-ku, Tokyo F-term (reference) in Sumitomo Osaka Cement Co., Ltd. 1 No. 1 Kanda Midoriyocho 4G012 PB11 PC06 PD03 PE01

Claims (1)

[Claims] 1. A method for producing a mixed cement in which limestone fine powder is mixed, the method comprising simultaneously pulverizing and mixing cement clinker, gypsum and limestone to produce a mixed cement.