JPH02302349A - Cement additive and cement composition using the same - Google Patents

Abstract

PURPOSE:To provide the subject cement additive capable of improving the mechanical strength and durability of concrete forms, comprising anhydrous gypsum (II), active silica and blast furnace-slag powder of specific particle distribution at specified proportion. CONSTITUTION:The objective cement additive comprising (A) 100 pts.wt. of anhydrous gypsum (type II), (B) 20 to 500 pts.wt. of active silica and (C) 20 to 500 pts.wt. of blast furnace slag powder containing >=60wt.% of particles <=12mu in size. The other objective cement composition comprises (1) 100 pts.wt. of cement and (2) 6 to 30 pts.wt. of the present cement additive. The use of the present cement composition as raw material will obtain concrete forms of both high mechanical strength and durability.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a cement admixture and a cement composition containing the same.

<Prior art and its problems> Conventionally, as a method of obtaining high strength under steam curing conditions, type water gypsum and, for example, silica powder have been used.

A method is known in which a cement admixture is used which is a mixture of siliceous substances such as clay, silicate clay, and fly ash (Japanese Patent Publication No. 49504/1983).

However, with this method, although the effect of increasing the strength can be obtained, there are problems such as not being able to obtain a sufficient effect with respect to durability, especially resistance to chlorine ion penetration (salt resistance).

In addition, as a method for simultaneously improving the strength and durability of concrete molded bodies, we have developed
It is known to mix a considerably large amount of finely powdered blast furnace slag, blast furnace slag fine aggregate, and a water reducing agent in an amount of ~85% by weight (Japanese Patent Laid-Open No. 61-281057).

However, with this method, when the concrete molded body is cured with atmospheric steam and then air-dry, large voids with a radius of 200 Å or more are generated, which is thought to be due to drying shrinkage, resulting in a decrease in long-term freeze-thaw durability and carbonation. It is expected that this will lead to the promotion of corrosion, rusting of the reinforcing bars, and a decrease in strength, and the ratio of tensile strength to compressive strength is also small.

On the other hand, conventionally, blast furnace slag has been widely used in cement as blast furnace slag cement, and is classified into type A, type B, and type 0 depending on the amount of blast furnace slag blended. That is, if the mixed amount of blast furnace slag is 30% or less, it is type A, if it exceeds 30% and not more than 60%, it is type B, and if it exceeds 60% and not more than 70%, it is type 0. In order to prevent alkali-aggregate reaction, it is recommended that the amount of blast furnace slag mixed is 40% or more.

However, the particle size of blast furnace slag used for blast furnace cement is usually around 4.000 cm2/g in Blaine value, and the amount of particles of 12μ or less is less than 50%. Even when used in combination with ■-type anhydrous gypsum and activated silica, the effect of improving strength development and durability was small, and the ability of ■-type anhydrous gypsum to develop high strength was rather impaired.

The inventors of the present invention have solved the above problems, and as a result of intensive studies to improve various durability, the above problems can be solved by using specific blast furnace slag powder and activated silica in combination with type anhydrous gypsum. Based on this knowledge, we have completed the present invention.

Means for Solving the Problems> That is, the present invention comprises 100 parts by weight of type anhydrous gypsum, 20 to 500 parts by weight of activated silica, and 6 parts by weight of particles of 12μ or less.
A cement admixture whose main components are 20 to 500 parts by weight of blast furnace slag powder of 0% or more, and a cement composition whose main components are 100 parts by weight of cement and 6 to 30 parts by weight of the cement admixture. .

The present invention will be explained in detail below.

The ■ type anhydrous gypsum in the present invention is one whose X-ray diffraction pattern shows the form of II CaSO4, and has two
In addition to those obtained by firing half-water and type anhydrous gypsum, those produced by-product from the hydrofluoric acid production process and natural anhydrous ceracola can also be used. In addition, type 2 anhydrous gypsum is not limited to impurities that are naturally or industrially contained.

■The powder degree of molded anhydrous gypsum is 3,000 in Blaine value.
cm”/g or more, preferably 4.000 to 7.500c
m”/g is more preferable. Blaine value is 3,000 cm
If it is less than ``/, 8, it is undesirable because it tends to remain unreacted even after steam curing, and this tends to react over a long period of time, resulting in a lack of stability of the cement molded body.

Activated silica in the present invention includes silica hume, Aerosil, and the like.

Silica fume is, for example, an ultrafine powder whose main component is amorphous Sing of about 200 to 0.5 microns, which is produced as a by-product during the production of ferrosilicon, metal silicon, and the like.

The blast furnace slag powder in the present invention is blast furnace slag containing 60% or more of particles with a size of 12 μ or less.

Blast furnace slag powder is a fine powder obtained by pulverizing or crushing and classifying molten slag, which is a by-product of a blast furnace, which is rapidly cooled and vitrified, and the powder normally used for blast furnace cement can also be used.

Basicity (CaO+^1203 +Mg0)/St, which is shown as an expression of the degree of latent hydraulicity of slag powder
In the present invention, ow is preferably 1.4 or more, more preferably 1.7 or more.

Moreover, the vitrification rate of blast furnace slag powder is preferably 50% or more, more preferably 90% or more.

The particle size of the blast furnace slag powder is preferably 60% or more, more preferably 80% or more of particles having a size of 12 μm or less. If the number of particles of 12 μ or less is less than 60, when used in combination with ■-type anhydrous gypsum or activated silica, sufficient strength development effect may not be obtained, or in some cases, the strength development ability of ■-type anhydrous gypsum may be impaired, which is not preferable. .

The finer the particle size of blast furnace slag powder, the better.
The minimum particle size of blast furnace slag powder that can be industrially and economically obtained by crushing or crushing/classifying is usually 10 μ or less, and the D50 value is about 3 μ. Use is more preferred.

゛When such fine blast furnace slag powder is used in combination with ■-type anhydrous gypsum or activated silica, significantly higher strength can be obtained than when using blast furnace slag powder alone, ■-type anhydrous gypsum alone, or activated silica alone, and A highly durable cement molded body can be obtained.

The reason for such a synergistic effect is unknown, but
It is inferred as follows. In other words, the high strength is due to the thringite produced by the reaction between the aluminate phase in the cement and the type anhydrous gypsum.
3CaO・A1z03・3CaSO4・32)1zO)
is obtained by filling the voids and promoting compaction, and activated silica reacts with portlandite (Ca (OH) z) to generate tobermorite and promoting compaction. However, by using blast furnace slag powder, A
As the absolute amount of the I acid component increases and the blast furnace slag is pulverized, the dissolution rate of the AI acid component, which is present in large amounts in the blast furnace slag, becomes faster, and in balance with the dissolution rate of the type II anhydrous gypsum, the liquid phase At the same time, the type anhydrous gypsum increases the elution amount of the ^l component in the blast furnace slag, makes the blast furnace slag particles porous, and increases the overall density of the blast furnace slag. This is presumed to be due to increasing the amount of hydration reaction.

In addition, salt resistance is due to the small ionic radius of chlorine ions.
Denseness alone is not enough; over a long period of time, the fixation of chlorine ions that gradually penetrate deep can be achieved using Friedel's salt (3CaO.Al
zO+・CaC1g408zO), but ettringite is stable against chlorine, and adding a large amount of type anhydrous gypsum to change the aluminate phase to ettringite will lose its ability to fix chlorine. .

The amount of activated silica and blast furnace slag powder to be used is 20 to 500 parts by weight each based on 100 parts by weight of type 1 anhydrous gypsum.

The amount of the cement admixture of the present invention, which is mainly composed of type (1) anhydrous gypsum, activated silica, and blast furnace slag powder, is preferably 6 to 30 parts by weight per 100 parts by weight of cement. In particular, 2 to 10 parts of each component per 100 parts by weight of cement.
It is more preferable to use parts by weight.

■ If molded anhydrous gypsum, activated silica, and blast furnace slag powder are each less than 2 parts by weight, the effect of improving strength development and durability is small, and if each exceeds 10 parts by weight, portolan in the hardened concrete There is a concern that all of the dyte will disappear and rusting of the reinforcing bars (particularly in prestressed products, stress corrosion due to the tension of the steel rod is also added, so a decrease in the alkalinity of the hardened product is dangerous).

Based on activated silica (as the unit water amount increases, the improvement effect on strength and salt resistance does not increase and tends to decrease).
This is not only uneconomical, but also increases slump drop, making workability difficult. In addition, when the total amount of activated silica and blast furnace slag powder exceeds 20 parts by weight, the portlandite in the hardened concrete becomes depleted and the alkalinity decreases. There is a concern that the PCfi rod of the prestressed molded body will rust, which is not preferable.

Preferably, the amount of each of type 1 anhydrous gypsum, activated silica, and blast furnace slag powder is 3 to 9 parts by weight, more preferably 4 to 8 parts by weight, based on 100 parts by weight of cement.

The cement mentioned here includes various Portland cements such as normal, early strength, super early strength, moderate heat, and white. Further, blast furnace cement cannot be used because it has problems such as neutralization, oxidation, and discoloration, but silica cement and fly ash cement can be used. The greater the cement's hydraulic coefficient and the greater its fineness, the higher its strength and improved durability.

When producing a cement molded body using the cement admixture of the present invention, chemical admixtures such as a water reducing agent, an AE water reducing agent, an accelerator, and a retarder may be used in combination, if necessary. In particular, it is preferable to use a water reducing agent in combination, and among these water reducing agents, it is more preferable to use a high performance water reducing agent in combination.

A high-performance water reducing agent is a surfactant with a large dispersion ability that does not cause excessive delay in condensation or excessive air entrainment even when added in large amounts, and is a surfactant that does not cause excessive condensation delay or excessive air entrainment even when added in large amounts. These include salts of reduced metals, high molecular weight lignin sulfonates, and polycarboxylate salts as their main ingredients.Specifically, examples include "Mighty 150," a product manufactured by Kao Corporation, and "Mighty 150," manufactured by Denki Kagaku Kogyo Corporation. Examples include product name rFT-5001 and Hozorisu Bussan Choko product name rNL-4000J.

The amount of high-performance water reducing agent used is not particularly limited, but it is 0.2 to 2 parts by weight per 100 parts by weight of cement in terms of solid content.
Parts by weight are preferred.

In manufacturing a cement molded body by mixing the cement admixture of the present invention with cement, sand, gravel, an appropriate amount of water, and a water reducing agent, kneading mortar/concrete, molding, and curing with atmospheric pressure steam, the present invention The cement admixture may be mixed in advance with cement to form a cement composition, or the admixture or each component may be mixed separately into a mixer directly during kneading, or it may be dispersed in water to form a slurry. You can also mix it with

The kneading method is not particularly limited, and methods commonly used for mortar and concrete can be used.

Forming methods for cement compacts include centrifugal force forming, press forming,
Conventional methods such as extrusion molding, paper forming, vibration molding, and centrifugal force molding after vibration molding can be used.

Further, atmospheric pressure steam curing of the cement molded body using the cement admixture of the present invention is carried out in the range of 40 to 100'C,
The range of 50 to 80°C is more preferable.

The cement molded bodies formed as described above include, for example, concrete piles, balls, humid pipes, steel pipe composite piles, centrifugal force molded bodies such as steel pipe linings, box culverts, segments, concrete sleepers, sheet piles, etc.
Examples include precast molded bodies such as bridge piers and bridge girders.

<Example> The present invention will be explained below with reference to Examples.

Example 1 Using the concrete formulation shown in Table 1, concrete was kneaded in a conventional manner by changing the type 1 water Ceracola, activated silica, and blast furnace slag powder as shown in Table 2. Thereafter, the kneaded product was molded into a specimen measuring 10 cm in diameter and 20 cm in diameter.

Table 1: After pre-curing for 4 hours, the specimens were heated to 65°C at a rate of 15°C/h, steam-cured at normal pressure, kept for 4 hours, allowed to cool naturally, and then steamed the next morning. It was taken out of the curing tank and various tests were conducted. The test results are shown in Table-2.

In addition, the water/cement ratio is simply the amount of water and the amount of cement (wt%), and the cement admixture of the present invention is replaced by sand and volume.
If the slump was outside the target slump depending on the amount of the cement admixture of the present invention, the slump was adjusted by slightly adjusting the amount of water.

Test method> (1) Measurement of slag particle size Laser diffraction powder particle size analyzer Granulometer manufactured by Cirrus Co., Ltd., Model 715 (Measurement range 0 to 192
u) was used and dispersed in ethanol.

(2) Measurement of strength test The compressive strength was determined using a vibration-packed cylindrical specimen of φ1010×20 when demolded on the 1st day of age.

(3) Measurement of salt resistance test A cylindrical specimen of φ1010×20 was demolded after 1 day of age, and then cured for 28 days in a curing box controlled at 20°C ± 3 and R1 (60% ± 5). % NaCl aqueous solution, removed at 1.3 and 12 months of age, and cut out the center part of the specimen with dimensions of φ10 x 1 cm.
After drying at °C for 24 hours, the entire amount was pulverized, and the amount of chlorine permeation was measured by fluorescent X-ray analysis.

(4) Measurement of portlandite A cylindrical specimen of φ1010×20 was demolded after 1 day of age, and the center part of the specimen was cut out with dimensions of φ10×1cm.
After drying at 00°C for 24 hours, the entire amount was pulverized and chemically analyzed. Furthermore, portlandite is f-Ca
It is shown in terms of O.

<Materials used> Cement: Manufactured by Denki Kagaku Kogyo Co., Ltd., ordinary Portland cement, specific gravity 3.16 ■Type water gypsum: Manufactured by Shin-Akita Kasei ■, hydrofluoric acid generation by-product Ceracola, plain value 6.000 cm"/g (porosity 0
．． 5), specific gravity 2.93 Activated silica-A rainbow hydroxide, manufactured by Nippon Heavy Chemical Industry ■, specific gravity 2.20 〃 -B: Product name "Aerosil 50", manufactured by Nippon Aerosil ■, specific gravity 2.20 Slag: Steel barment Blast furnace slag Cement slag made by Sanshui Gypsum (no Sansui gypsum, 48% particles of 12μ or less)
A vibrating mill or a readjusted combination of a vibrating mill and a classifier, specific gravity 2.95 α: 12 μ or less 53%, D50 approximately 12 μ or less β:
〃 60 9μ T: /l 80 6μδ:〃
100〃3μ Water: Groundwater Sand: Niigata prefecture Himeyo river sand (specific gravity 2.65) gravel
: Crushed stone (specific gravity 2.68) Water reducing agent 2 High performance water reducing agent, manufactured by Denki Kagaku Kogyo Part name rFT-500J (
Specific gravity: 1.20) In Table 2, Experiments Nα1-1 to Nα1-9 and Experiment No. 1-28 are comparative examples.

As shown in Table 2, each of type 1 water gypsum, activated silica, and blast furnace slag powder was added separately (Experiment No. 1-2).
-4) and the combination of only Type gypsum and silica hume (Experiment Nα1-7) and the present invention examples (Experiments Nα1-14.1-30 and 1-33) in which the same amounts of each were mixed, the strength was It can be seen that the penetration resistance to chlorine is also significantly improved.

In addition, with the same formulation as the above invention example, the amount of particles of 12μ or less was 5
Comparative example using 3% blast furnace slag powder (α) (experiment Nα1
-28), in Experiment Nα1-28, the effect of improving strength and resistance to chlorine was small, and as in the example of the present invention, when the amount of particles of 12μ or less is 60% or more, the finer the effect is, the more pronounced the effect is. is recognized.

Example 2 Using the concrete of Experiment Nα1-1.1-7 and 1-14 in Example 1, a PC resistor with an outer diameter of 300 mm x thickness of 601 x length (for bending moment) and 1 m (for compression) was constructed. It was molded using the usual method, preheated for 6 hours, raised to 75°C in 3 hours, cured with normal pressure steam, kept as it was for 4 hours, then the steam valve was turned off, allowed to cool naturally, and demolded the next morning. After applying prestress, the specimens were left to cure indoors for up to 7 days, and then subjected to bending and compression tests.

The test results are shown in Table-3.

For the reinforcement of the PC shaft, the straight bars are made of high-frequency hot wire ■ PC steel rods φ13mm x 4 and φ11 plates x 4 (straight bars), and the spiral bars are φ3mm ordinary iron wire 10cm long.
Insert at intervals1. The initial tension stress of the PC steel bar was set to 160 kgf/cm'' with respect to the cross section.

Table 3 Example 3 Using the same concrete as in Example 2 and using the same curing conditions, centrifugal force forming was performed by a conventional method to obtain an inner diameter of 1, 0OOn.
An A-type humid pipe with v+

The results are shown in Table 4.

In addition, the reinforcement ratio of straight reinforcement was 0.26%, and the ratio of double spiral reinforcement was 1.49%.

Table 4 <Effects of the invention> As shown in the examples, by using the cement admixture of the present invention, concrete with high strength and high durability can be manufactured. A cement molded body using this cement admixture also has significantly improved performance as a molded body.

Claims (2)

[Claims] (1) Type II anhydrous gypsum 100 parts by weight and activated silica 2
A cement admixture whose main components are 0 to 500 parts by weight and 20 to 500 parts by weight of blast furnace slag powder containing 60% or more of particles of 12 microns or less. (2) A cement composition whose main components are 100 parts by weight of cement and 6 to 30 parts by weight of the cement admixture according to claim 1.