JPH02289453A - Cement admixture and cement composition - Google Patents

Abstract

PURPOSE:To obtain a cement admixture enabling the production of concrete having freezing-thawing resistance, salt resistance and high durability by using specified fine powder of blast furnace slag and specified II-type anhydrous gypsum in combination. CONSTITUTION:A cement admixture is composed essentially of 100 pts.wt. fine powder (A) of blast furnace slag contg. >=60%, preferably >=80% particles of <=12mum particle size and having >=1.4, preferably >=1.7 basicity and >=50%, preferably >=90% rate of vitrification and 10-750 pts.wt. II-type anhydrous gypsum (B) having >=3,000cm<2>/g, preferably 4,000-7,500cm<2>/g Blaine value. A cement compsn. is obtd. by adding the cement admixture to cement by 4-35 pts.wt. per 100 pts.wt. cement so that the components A, B are preferably contained by 2-20 pts.wt. and 2-15 pts.wt., respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to cement admixtures and cement compositions containing the same.
The present invention relates to a cement admixture having high durability such as salt resistance, carbonation resistance, and corrosion resistance, and a cement composition containing the same.

<Prior art and its problems> Conventionally, as a method of increasing the strength of concrete molded bodies manufactured by atmospheric pressure steam curing, such as piles, poles, and humid pipes, it was sufficient to add a relatively large amount of Ceracola. is known to -C (Special Publication No. 56-4010)
Publication No. 4).

However, although this method has a great effect of increasing strength,
For example, sufficient effects cannot be obtained on the durability of concrete molded bodies, such as salt resistance, and problems such as the freeze-thaw durability cannot be improved unless high strength of 800 kgf/cm" or more is developed. there were.

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 pulverized blast furnace slag, fine aggregate of blast furnace slag, and a water reducing agent at ~85% by weight (Japanese Unexamined Patent Publication No. 61-281057).

However, with this method, when the concrete molded body is cured with atmospheric steam and then air-dried, 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 a decrease in long-term freeze-thaw durability. It was expected that this would lead to the promotion of carbonization, rusting of reinforcing bars, and a decrease in strength, and there were problems such as a small ratio of tensile strength to compressive strength.

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, Type A has a mixed amount of blast furnace slag of 30% or less, Type B has a mixed amount of more than 30% and less than 60%, and Type 0 has a mixed amount of blast furnace slag of more than 60% and not more than 70%. 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 4.0OOcn+"7g in Blaine value.
The amount of particles of 12μ or less in the front and back is less than 50%, and even if such coarse blast furnace slag is used in combination with type-type anhydrous gypsum, it will actually impair the ability of type-type anhydrous gypsum to develop high strength. This indicates a tendency toward

The inventors of the present invention have solved the above-mentioned problems and, as a result of intensive studies to improve various durability, have found that the above-mentioned problems can be solved by using a specific pulverized blast furnace slag powder and ■-type anhydrous gypsum together. As a result, the present invention was completed.

<Means for Solving the Problem> That is, the present invention provides 100 parts by weight of pulverized blast furnace slag powder containing 60% or more of particles of 12 μ or less, and 10 to 10 parts of type anhydrous gypsum.
A cement admixture whose main component is 750 parts by weight,
It is a cement TA composition whose main components are 100 parts by weight of cement and 4 to 35 parts by weight of the cement admixture.

The present invention will be explained in detail below.

The pulverized blast furnace slag powder (hereinafter referred to as main slag) in the present invention is blast furnace slag in which 60% or more of particles are 12 μm or less.

This slag is a fine powder obtained by crushing or crushing and classifying molten slag, which is a by-product from a blast furnace, which is rapidly cooled and vitrified. Slag that is normally used for blast furnace cement can also be used.

Basicity (CaO+A, 1zOs+Mg0)/5i, which represents the degree of latent hydraulicity of slag powder
In the present invention, Oz is preferably 1.4 or more, more preferably 1.7 or more.

In addition, the vitrification rate of this slag is preferably 50% or more,
More preferably 90% or more.

The particle size of this slag is preferably 60% or more, and more preferably 80% or more.If the particle size of 12μ or less is less than 60, sufficient strength development effect may not be obtained when used in combination with ■-type anhydrous gypsum. In some cases, this may impair the strength development ability of the ■-type anhydrous gypsum, which is not preferable.

The finer the particle size of this slag, the better.The particle size of the minimum blast furnace slag powder obtained by industrially and economically pulverizing or pulverizing/classifying is usually 1Oμ or less and D5.
The value of 0 is about 3μ, and it is more preferable to use such ultrafine powder slag.

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

The reason for such a synergistic effect is unknown, but
By pulverizing the blast furnace slag, the dissolution rate of the A1 element, which is present in large amounts in the blast furnace slag, becomes faster, which balances the dissolution rate of the type anhydrous gypsum and more efficiently generates ettringite in the liquid phase, creating voids. It is assumed that this is because, at the same time as filling and compacting the blast furnace slag, type anhydrous gypsum increases the elution amount of the ^1 element in the blast furnace slag, making the blast furnace slag particles porous and increasing the amount of hydration reaction of the entire blast furnace slag. be done.

In the present invention, the ■-type anhydrous gypsum (hereinafter referred to as the present gypsum) has an X-ray diffraction pattern in the form of UCa5Oa, and includes those obtained by firing two-type, semi-hydrous, and ■-type anhydrous gypsum, etc. It is also possible to use by-products from the hydrofluoric acid manufacturing process and natural anhydrous ceracola. Also,
The present gypsum is not limited to naturally or industrially contained impurities.

The fineness of this gypsum is Blaine value 3. '000cm'
/g or more, preferably 4,000 to 7,500 cm"
/g is more preferable. Blaine value is 3.000cm”7
If it is less than g, it tends to remain unreacted even after steam curing,
This is undesirable because it tends to react over a long period of time and cause the cement molded product to lack stability.

The amount of this gypsum used is based on 100 parts by weight of this slag.
The amount is 10 to 750 parts by weight.

The amount of the cement admixture of the present invention (hereinafter referred to as the present admixture) whose main components are the present slag and the present gypsum is as follows:
00 parts by weight, preferably 4 to 35 parts by weight. especially,
This slag is 2 to 20 ff per 100 parts by weight of cement.
It is more preferable to use it in an amount of 2 to 15 parts by weight.

If the wood slag or real gypsum is less than 2 parts by weight, the effect of improving strength development and durability is small; if the wood slag or real gypsum exceeds 20 parts by weight or the real gypsum exceeds 15 parts by weight,
There is a tendency that no increase in strength development can be expected. In particular, if this slag exceeds 20 parts by weight, even if a high strength of 1,000 kgf/cm" is achieved when the slag is left to dry for a long time, it will discolor to white on the surface and deep inside the cement compact, and will become alkali-based. As a result, problems such as neutralization, oxidation of the main slag, and rusting of reinforcing bars occur, and furthermore, a decrease in strength tends to occur, which is undesirable.

The most preferable amount of this admixture to be used is 5 to 16 parts by weight of this slag and 3 to 16 parts by weight of this slag to 100 parts by weight of cement.
8 to 2 formulated to be used in a range of 10 parts by weight
It is 6 parts by weight. The ratio of this slag and this gypsum used at this time is 19 parts of this gypsum to 100 parts by weight of this slag.
This corresponds to ~200 parts by weight.

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 carbonation, 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 this admixture, chemical admixtures such as water reducing agents, accelerators, and retarders can 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 condensates, salts of molecular weight polygeninsulfonates, polycarboxylate salts, etc. as main components.Specifically, for example, the product name [Mighty 150] manufactured by Kao ■, the product name manufactured by Denki Kagaku Kogyo ■ Examples include the product name EFT-500J and the product name rNL-4000J manufactured by Hozorisu Bussan.

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.

Mix this admixture with cement, sand, gravel, an appropriate amount of water, and a water reducing agent, knead mortar/concrete, and form it.
When producing cement molded bodies through normal pressure steam curing,
This 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 further 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 and vibration molding can be used.

If centrifugal force forming is performed using this admixture and a high-performance water reducer together, the mortar/concrete may not be compacted and a mushy sludge with a high solid content may be discharged. In that case, as a method to improve compaction, reduce solid content separation, and increase dewatering amount, inorganic substances such as quicklime, slaked lime, and/or sodium, potassium, and lithium sulfates and bisulfates can be added to It is preferable to use at most 1 part by weight per 00 parts by weight per day, and from the viewpoint of improving strength development, it is more preferable to use 0.05 to 0.5 parts by weight.

In addition, atmospheric pressure steam curing of cement molded bodies using this admixture is carried out in the range of 40 to 100°C, and 50 to 80°C.
The range is more preferable.

Examples of cement compacts formed as described above include centrifugal force compacts such as concrete piles, poles, humid pipes, and steel pipe linings, and precast compacts such as box culverts, concrete sleepers, sheet piles, bridge piers, and bridge girders. Can be mentioned.

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

Example 1 Using concrete mix B shown in Table 1, concrete was produced by changing the amount of this slag used, changing the mixing ratio with this gypsum, and changing the amount added to cement as shown in Table 2. did.

The amounts of the admixture, water reducing agent, etc. are all parts by weight relative to 100 parts by weight of cement, and the atmospheric pressure steam curing is performed at 15"C/h after pre-curing for 4 hours. 65
After bringing the temperature to ambient temperature to °C and holding it there for 4 hours, it was allowed to cool naturally, and the next morning it was taken out from the steam curing tank and various tests were conducted.

Table-1 Materials used> Cement: Ordinary Portland cement made by Denki Kagaku Kogyo ■ (specific gravity 3.16) Water: Groundwater sand: Niigata prefecture Himeyo river sand (specific gravity 2.65) gravel
: Crushed stone (specific gravity 2.68) Water reducing agent : High performance water reducing agent, Denki Kagaku Kogyo Product name rFT-500J (
Specific gravity 1.20) Genuine gypsum: manufactured by Shin-Akita Kasei, Ceracola, a by-product of hydrofluoric acid generation, Blaine value 6.000 cm”/g (1
oshi 40.5), specific gravity 2.93 This slag: Blast furnace slag cement slag made by Yotetsu Barment Co., Ltd. (no Sansui Ceracola, 48% particles of 12μ or less)
A vibration mill or a vibration mill and a classifier were combined and readjusted as follows: Specific gravity: 2.95 α: 12μ or less 53%, D50: about 12μ or less β:
〃 60 9μ T: 〃 80 〃 6μ δ: 〃100〃3μ The water/cement ratio is simply the weight% of the amount of water and the amount of cement.
The main admixture was replaced by sand by volume, and if the slump was outside the target slump depending on the amount of the main admixture, the slump was adjusted somewhat by the water amount m.

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

(2) Measurement of Strength Test Compressive strength was determined using a vibrating cylindrical specimen measuring φ1010×20, and tensile strength was determined by splitting the cylindrical specimen measuring φ15×15 cm.

(3) Measurement of the amount of chlorine ion penetration A φ10 x 20C11 cylindrical specimen was demolded after one day of age, and then cured for 28 days in a curing box controlled at 20°C ± 3 and R1 160% ± 5. , 3% NaCl
After 91 days, the central part of the specimen was immersed in an aqueous solution.
．． The pieces were cut out to a size of 5 cm, dried at 300°C for 24 hours, crushed, and the amount of chlorine permeated was measured by fluorescent X-ray analysis.

(4) Measurement of carbonation depth A cylindrical specimen of φ1010×20 was cured for 28 days in the same manner as in the measurement of the amount of chlorine ion penetration, and then R11100%.
Cured for 91 days in a curing box with a COt gas concentration of 18% by volume,
Phenolphthalene was applied to the circular cut surface at the center and the average carbonation depth was measured.

(5) Measurement of freeze-thaw durability A specimen measuring 10 x 10 x 40 cm was demolded the next morning, and after standard curing for 14 days, a rapid freeze-thaw test was conducted in water to determine the durability index DF value.

Here, the DF value is expressed by the following formula.

DF value (χ') = P N/M P: Relative dynamic elastic modulus at N cycles P = n-/n'' n: Primary deflection frequency at the start of the test - - order deflection frequency at the nth arbitrary cycle Number of cycles M when NAP reaches 60% or ends the test: The test results for the number of cycles at which the freeze-thaw test ends are shown in Table 2.

This admixture is expressed in parts by weight based on 100 parts by weight of cement, and the 14-day strength is standard curing, and the 28-day strength is 20°.
After curing at C±3 and RH60%±5, the strength at the start of each durability test was measured and shown.

As is clear from Table 2, compared to the use of the present slag and the present gypsum alone, in the examples of the present invention in which both are used in appropriate amounts, the strength is increased synergistically and various durability is also improved.

In addition, regarding the particle size of blast furnace slag, the combination of 60% or more particles of 12μ or less and this gypsum has a remarkable effect of improving strength and durability, and it is said that the finer the particle size of blast furnace slag, the better. Recognize.

On the contrary, it can be seen that when the particle size of blast furnace slag is coarse, with less than 60% of particles having a size of 12μ or less, the effect of combined use with this gypsum is extremely reduced.

Furthermore, in the combination of this slag and this gypsum,
Combinations outside the scope of the present invention (Experiment N11l-13,1-
19, 1-20), it can be seen that either the strength effect is small, the elongation of strength is almost unchanged, or one of the various durability tends to be worse.

In addition, the concrete of experiments NcLl-4, 1-9 and 1-16 was formed into a φ10 x 20C11 cylinder,
Although the 14-day compressive strength was 603 kgf/cm for experiment Nα1-4 and 603 kgf/cm for experiment Nα1-4,
9 is 785 kgf/cm", experiment Nα1-16 is 803
kgf/cm2, and it was found that the present invention shows remarkable effects in normal pressure steam curing.

Example 2 Experiment N in Table 2 was carried out using the concrete mixes A to D in Table 1.
Using the concrete shown as α1-4.1-9 and 1-16, specimens of φ10×20 were formed in the same manner as in Example 1, and the compressive strength of each material age was measured. Table 3 shows the results.
Shown below.

After steam curing, the specimens which were demolded the next morning were left in a room adjusted to a room temperature of 20°C±3.

As shown in Table 3, even if the unit cement amount is small, the strength effect is remarkable, and the unit cement amount is 300 kg / m
However, it can achieve high strength of over 800kgf/cn+.

Example 3 The concrete shown in Experiment Nα2-4 to Nα2-6 in Table 3 in Example 2 was prepared by pulverizing quicklime fired in a gas-fired lime furnace to a size of 88μ or less (Q), and adding water to it for digestion. dried slaked lime (R), primary reagents sodium sulfate (S), potassium sulfate (T), lithium sulfate (IJ
) and the amount of sodium bisulfate (V) added, φ20
A centrifugally formed specimen of X 5 x 30 cm was formed, and the amount of sludge generated, the solid content of the dried sludge, the thickness of the slag (the thickness of the part of the inner surface of the centrifugally formed specimen that did not tighten), and one day after steam curing. Compressive strength was measured. Table 4 shows the results.
Shown below.

The centrifugal force forming was performed for 2 minutes at 3G, 4 minutes at 9G, and 3 minutes at 30G, a fixed amount of 18 kg of concrete was poured, and the hollow part was covered to prevent the separated sludge from getting wet.

As can be seen from Table 4, it is effective to use inorganic substances in combination to improve the formability of concrete centrifugally formed bodies using this admixture.

Note that even when inorganic substances are used in combination with Experiments Nα3-1 and Nα3-2, which are comparative examples, there is no significant effect in the examples of the present invention.

Example 4 Using the concrete of experiment Nα2-4 to 6 in Example 2, the outer diameter was 300IIIn×thickness 60In [I+ length was 4m]
(for bending moment) and 1 m (for compression) were molded by a conventional method and cured under the same curing conditions as in Example 2. Thereafter, a bending test and a compression test were conducted when the material was 7 days old. The results are shown in Table-5.

In addition, the reinforcement of the PC shaft is made of high-frequency hot wire φ13a PC steel rod.
4 mX and 4 φ11 wires (straight bars), spiral bars were made by inserting φ3mm iron wires at 10cm intervals, and the initial tensile stress of the PC steel bars was 160 kgf/cm2 with respect to the pile cross section.

Table 6 Example 5 Using the same concrete as in Example 4 and using the same curing conditions, centrifugal force forming was performed using a conventional method to create a humm pipe.
An external pressure strength test was conducted when the material was 7 days old.

The results are shown in Table-6.

In addition, the Huyum tube has an inner diameter of 100 mm, a thickness of 82 mm, and a length of 2 mm.
, 43On+m, the reinforcement ratio is 0.26% for straight bars, and 1.49% for double spiral bars.
It is a type tube.

<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. The performance of the cement molded product using this method is also significantly improved.

Claims (2)

[Claims] (1) A cement admixture whose main components are 100 parts by weight of pulverized blast furnace slag powder containing 60% or more of particles of 12 μm or less and 10 to 750 parts by weight of type II anhydrous gypsum. (2) A cement composition whose main components are 100 parts by weight of cement and 4 to 35 parts by weight of the cement admixture according to claim 1.