JP3207956B2 - High strength 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 high-strength cement composition, and more particularly to a cement composition which exhibits good fluidity even when the water / cement ratio is reduced, and exhibits high initial and long-term strength.

[0002]

2. Description of the Related Art Conventionally, partially hydrated cement in which 0.1% to 5% by weight of water is homogeneously absorbed and partially hydrated by bringing steam into contact with the whole cement or spraying water by spraying. It is known that mortar or concrete obtained by adding a high-performance water reducing agent has a higher fluidity than mortar or concrete obtained by adding a high-performance water reducing agent to the original cement which has not been partially hydrated. (Japanese
No. 2-162506).

Further, mortar or concrete obtained by adding a high-performance water reducing agent to finely ground inert or low-activity cement to which limestone or slag has been added is more highly efficient than limestone or slag-free original cement. It is also known that fluidity is improved as compared with mortar or concrete to which a performance water reducing agent is added.

[0004] The mortar or concrete using partially hydrated cement or the mortar or concrete using finely ground inert or low-active limestone or slag-added cement according to these conventional methods has a fluidity as described above. If improved and fluidity is constant, water /
The cement ratio can be reduced by several percent.

On the other hand, in order to produce a high-strength hardened cement, it is generally practiced to reduce the water / cement ratio of the compound.

However, when the mortar or concrete according to the conventional method is used, although the water / cement ratio is reduced by several percent, the strength development of the cured product, particularly the strength development at the initial stage, is extremely low. For this reason, in order to obtain a high-strength hardened body, the amount of unit cement in the compounding must be increased, which causes drying shrinkage and temperature stress of the hardened body, leading to cracks and the durability of concrete. Is a problem.

[0007]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, and has a good fluidity even when the water / cement ratio is reduced, and exhibits not only an initial high strength but also a long term. An object of the present invention is to provide a high-strength cement composition that can also exhibit high strength.

[0008]

The high-strength cement composition of the present invention comprises a Portland cement having a maximum particle size of 5 to 15%.
μm and a coarse powder having a particle size exceeding 15 μm, and the fine powder is contacted with carbon dioxide gas and water vapor to increase the ignition loss by 0.1 to 5.0% by weight. Mixed with.

The portland cement used in the present invention includes ordinary portland cement, early-strength portland cement, moderately heated portland cement, sulfate-resistant portland cement, etc. conforming to JIS standards, and blast furnace slag powder, fly A mixed cement obtained by mixing one or two or more types of cement admixtures such as ash, silica powder, and silica fume is exemplified.

In producing the high-strength cement composition of the present invention, first, the above Portland cement is classified into fine powder and coarse powder using a conventional classifier.

At this time, the maximum particle size of the fine powder is 5 to 15 μm,
It is preferably 8 to 12 μm, and when the maximum particle size of the fine powder is less than 5 μm or more than 15 μm, the strength increase is small in any case.

Further, those having a particle size exceeding 15 μm are classified as coarse powder.

Examples of the classifier used for classification include those commonly used for classifying powders, such as starter band separators, cyclone separators, and turbo classifiers.

When Portland cement is classified using these conventional classifiers, it is not always classified completely at the target maximum particle size, and usually, the fine powder portion contains coarse particles exceeding the target classified particle size. Powder, while the coarse powder portion also contains fine powder having a particle size smaller than the target classified particle size.

In the present invention, the maximum particle size is 5 to 15 μm.
It is preferable that 5 to 50% by weight of the fine powder is classified in the fine powder.

Next, the fine powder obtained by the classification is contacted with carbon dioxide gas and water vapor to obtain a carbonized fine powder having an increase in ignition loss of 0.1 to 5.0% by weight.

That is, the fine powder is carbonated using a conventional apparatus, and the surface of the fine powder is partially carbonated.

The carbonation of cement minerals is about 50 relative humidity.
%, Water vapor does not proceed quickly, carbonation takes a long time and is not efficient, and the carbonation temperature is preferably high.

In the present invention, carbonation is carried out while spraying carbon dioxide gas containing water vapor while stirring the fine powder at a high speed or in a floating state so that the fine powder is uniformly carbonated.

In the carbonation, the increase in the ignition loss of the fine powder before and after the carbonation is 0.1 to 5.0% by weight, preferably 1.0 to 5.0% by weight.
The process is performed until the content becomes 3.0% by weight.

Further, the carbonized fine powder obtained by carbonation in this way and the coarse powder initially classified are mixed by a conventional mixer so as to be sufficiently homogeneous, whereby the high quality of the present invention is obtained. A strength cement composition is obtained.

[0022]

The mortar and hardened concrete obtained by using the high-strength cement composition of the present invention exhibit remarkably high strength not only in long-term aging but also in initial aging.

The fine powder classified in the present invention is originally a part of cement, and contains a large amount of tricalcium silicate, tricalcium aluminate and tetracalcium aluminate having high fineness and high activity. Due to the hydration of the fine powder, the fluidity of the mortar or concrete decreases over time.

Therefore, in the present invention, the fine powder is carbonated to form a carbonated fine powder. The surface of the carbonized fine powder is partially carbonated by the carbonation, and its core is clinker of cement, but only its surface is covered with inert calcium carbonate.

That is, in the cement composition of the present invention, the calcium carbonate coating improves the initial fluidity of the mortar or concrete, reduces the amount of kneading water for obtaining the same fluidity, and reduces the long-term age. In
Hydration of the clinker of the core covered with calcium carbonate also improves the long-term strength development.

Hereinafter, the present invention will be described in detail with reference to examples.

[0027]

【Example】

 Examples 1 to 5 and Comparative Examples 1 to 4

Preparation of Cement Composition Four kinds (maximum) of ordinary Portland cement (manufactured by Sumitomo Cement Co., Ltd., loss on ignition 1.0%) using a turbo classifier (TC-15N manufactured by Nisshin Engineering Co., Ltd.) The particles were classified into fine powder and coarse powder having a particle size of 5, 10, 15, and 20 μm). Table 1 shows the maximum particle size of each fine powder.

Each classified fine powder is put into a fluidized bed mixer,
Carbonation was performed using pure carbon dioxide gas and steam as a fluid medium. At this time, the carbonation time in the fluidized bed with steam and carbon dioxide was appropriately increased or decreased to obtain each carbonized fine powder having an increased ignition loss as shown in Table 1.

Each of the carbonized fine powders thus obtained,
Each of the initially classified corresponding coarse powders was
The mixture was sufficiently mixed with a mold mixer to obtain each high-strength cement composition of the present invention.

For comparison, an original cement using only ordinary Portland cement as a raw material (Comparative Example 1), a coarse powder, a fine powdered limestone powder having the same amount as a fine powder classified at a maximum particle size of 10 μm (fineness: 15,000 cm ²⁾ / G), a cement composition (Comparative Example 3) containing a carbonized fine powder having an increase in ignition loss exceeding the range of the present invention, and a maximum particle size within the range of the present invention. Thus, a cement composition (Comparative Example 4) using a fine powder exceeding the above was obtained.

Using each cement composition obtained by mortar production and strength measurement, cement: sand = 1: 3, β-naphthalenesulfonic acid formalin condensate-based high-performance water reducing agent (Mighty 150 manufactured by Kao Corporation, solid content 40 (% By weight) was added to the cement composition, and the amount of kneading water was changed so that the mortar flow value became 200 ± 2 mm to obtain a mortar kneaded product.

The sand used at this time was Toyoura standard sand (particle size: 0.10 to 0.30 mm) and No. 4 sand (particle size: 0.42 to 0.42 mm).
1.68mm) No. 3 sand (particle size 0.84 to 2.38m)
m) in equal amounts.

The mortar kneaded material thus obtained is molded into a size of 4 × 4 × 16 cm.
After the RH was cured in a wet air and demolded, it was cured in water at 20 ° C. until a predetermined material age to obtain a test specimen for strength measurement.

Each specimen is JIS R
The compressive strength was measured according to the mortar strength test of No.5201. Table 1 shows the obtained results.

[0036]

[Table 1]

From the results shown in Table 1, it can be seen that the high strength cement composition of the present invention has not only the initial strength but also the long-term strength, which is significantly better than the ordinary Portland cement as a raw material, while In the case of Comparative Example 1,
In the case of Comparative Example 2, the amount of water for obtaining the target flow value was large, and the strength development was lower than that of the example.
Although the amount of water can be reduced, especially the initial strength development is low, and in the case of Comparative Example 3 or 4, the strength development is better than the case of ordinary Portland cement as a raw material, but not as much as in the examples. Also, it can be seen that the amount of water is large.

[0038]

According to the high-strength cement composition of the present invention, even if the water / cement ratio is reduced, the fluidity is good and not only the initial high strength is exhibited but also the long-term high strength is exhibited. Can be.

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C04B 7/02

Claims (1)

(57) [Claims] 1. Portland cement having a maximum particle size of 5 to 5.
15 μm fine powder and coarse powder having a particle size exceeding 15 μm are classified, and the fine powder is brought into contact with carbon dioxide gas and water vapor to increase the ignition loss by 0.1 to 5.0% by weight. And a high-strength cement composition.