JPH0735272B2 - Cement admixture and cement composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a cement admixture and a cement composition containing the same, more specifically, high strength and freeze-thaw durability,
The present invention relates to a cement admixture having high durability such as salt resistance, neutralization and corrosion resistance, and a cement composition containing the same.

<Prior art and its problems> Conventionally, a relatively large amount of gypsum should be added as a method for increasing the strength of a concrete molded body manufactured by performing normal pressure steam curing such as piles, poles and fume tubes. However, it is generally known (Japanese Patent Publication No. 56-40104).

However, although this method has a large effect of increasing the strength,
For example, there is a problem that the concrete molded body does not have sufficient effects on durability such as salt resistance, and freeze-thaw durability cannot be improved unless high strength of 800 kgf / cm ² or more is exhibited. It was

In addition, as a method of simultaneously improving the strength and durability of the concrete molded body, with cement, 30 ~
It is known to add a considerably large amount of finely powdered blast furnace slag, fine aggregate of blast furnace slag and water reducing agent to 85% by weight (JP-A-61-281057).

However, in this method, when the concrete molded body is subjected to atmospheric pressure steam curing and then air-dried curing, large voids with a radius of 200 Å or more, which are thought to be due to drying shrinkage, are generated, resulting in long-term freeze-thaw durability deterioration and neutralization. However, there were problems such as accelerating the stress, rusting of the reinforcing bar and a decrease in strength, and a small ratio of tensile strength to compressive strength.

On the other hand, conventionally, blast furnace slag is often used as cement as blast furnace slag cement, and is classified into Class A, Class B and Class C depending on the blending amount of blast furnace slag. That is, the A type having a blast furnace slag mixing amount of 30% or less, the B type of more than 30% and 60% and the C type of more than 60% and 70% or less. From the viewpoint of preventing alkali-aggregate reaction, it is recommended that the mixing amount of blast furnace slag be 40% or more.

However, the grain size of blast furnace slag normally used for blast furnace cement is about 4,000 cm ² / g in terms of Blaine value, 12 μm.
The amount of the following particles is less than 50%, such a coarse blast furnace slag, even when used in combination with type II anhydrous gypsum, rather tends to impair the high strength development ability of type II anhydrous gypsum. It was shown.

The present inventors have solved the above problems, and as a result of extensive studies to enhance various durability, by using a specific blast furnace slag fine powder and type II anhydrous gypsum in combination, the knowledge that the above problems can be solved is obtained. As a result, the present invention has been completed.

<Means for Solving the Problems> That is, the present invention is a cement admixture containing 100 parts by weight of fine powder of blast furnace slag having a particle size of 12 μ or less and 60% or more and 10 to 750 parts by weight of type II anhydrous gypsum as a main component. Material and cement 100
A cement composition containing, as a main component, 4 parts by weight and 4 to 35 parts by weight of the cement admixture.

Hereinafter, the present invention will be described in detail.

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

The present slag is a fine powder obtained by crushing or crushing and classifying the molten slag by-produced from the blast furnace which is rapidly cooled and vitrified, and the one normally used for blast furnace cement can also be used.

In the present invention, the basicity (CaO + Al ₂ O ₃ + MgO) / SiO ₂ shown as indicating the degree of latent hydraulicity of the slag powder is preferably 1.4 or more, more preferably 1.7 or more.

The vitrification rate of this slag is preferably 50% or more,
% Or more is more preferable.

The particle size of the present slag is preferably 60% or more, and more preferably 80% or more, particles having a particle size of 12 μ or less. When the particles having a particle size of 12 μ or less are less than 60, when used in combination with type II anhydrous gypsum, the strength developing effect may not be sufficiently obtained, or in some cases, the strength expressing ability of type II anhydrous gypsum may be impaired, such being undesirable.

The finer the particle size of the slag, the finer the particle size of the minimum blast furnace slag powder obtained by crushing or crushing / classifying industrially and economically is usually 10 μD or less and D50.
Is about 3 μm, and it is more preferable to use such ultrafine slag.

When such fine ground blast furnace slag powder is used in combination with type II anhydrous gypsum, significantly higher strength is obtained than in the case of using slag powder alone or type II anhydrous gypsum alone, and a highly durable cement compact is obtained. .

The reason why such a synergistic effect is exhibited is unknown,
By pulverizing the blast furnace slag, the dissolution rate of a large amount of Al element in the blast furnace slag becomes faster, and it balances with the dissolution rate of type II anhydrous gypsum, producing ettringite more efficiently in the liquid phase, and forming voids. At the same time as filling and solidifying, the type II anhydrous gypsum increased the elution amount of Al element in the blast furnace slag, making the blast furnace slag particles porous and increasing the hydration reaction amount of the entire blast furnace slag. It

The type II anhydrous gypsum (hereinafter referred to as the present gypsum) in the present invention has a form in which the X-ray diffraction pattern is II-CaSO ₄ , and is obtained by firing dihydrate, semi-water or type III anhydrous gypsum. In addition, a by-product from the hydrofluoric acid production process or natural anhydrous gypsum can be used. The gypsum is not limited to impurities contained naturally or industrially.

The fineness of this gypsum is preferably 3,000 cm ² / g or more as a plain value, and more preferably 4,000 to 7,500 cm ² / g. When the plain value is less than 3,000 cm ² / g, it is not preferable because it tends to remain unreacted even when steam curing is performed, and this tends to react for a long period of time, resulting in lack of stability of the cement molded product.

The amount of gypsum used is 10 for 100 parts by weight of the slag.
~ 750 parts by weight.

The amount of the cement admixture of the present invention containing the present slag and the present gypsum as a main component (hereinafter referred to as the present admixture) is 10
4 to 35 parts by weight is preferable with respect to 0 parts by weight. In particular, it is more preferable to use 2 to 20 parts by weight of the present slag and 2 to 15 parts by weight of the present gypsum per 100 parts by weight of cement.

If this slag or this gypsum is less than 2 parts by weight, the effect of improving strength development and durability is small, and if this slag exceeds 20 parts by weight or this gypsum exceeds 15 parts by weight, the elongation of the strength development will increase. There is a tendency that cannot be expected. Especially, if this slag exceeds 20 parts by weight, if it is cured for a long time in an air-dried state,
Even if a high strength of 1.000 kgf / cm ² is obtained, the surface of the cement compact and the deep part will turn white and the alkalinity will decrease.
Therefore, problems such as neutralization, oxidation of the present slag, and rusting of reinforcing bars occur, and further, strength reduction easily occurs, which is not preferable.

The most preferable amount of the present admixture is 8 to 26 parts by weight, which is compounded to be used in the range of 5 to 16 parts by weight of the slag and 3 to 10 parts by weight of the gypsum per 100 parts by weight of cement. At this time, the use ratio of the main slag and the main gypsum corresponds to 19 to 200 parts by weight of the main gypsum per 100 parts by weight of the main slag.

Cement as used herein refers to various types of Portland cement 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 higher the hydraulic coefficient of cement and the higher the fineness of the cement, the higher the strength is, and the durability is improved.

In producing a cement molded product using this admixture, chemical admixtures such as a water reducing agent, an accelerator and a retarder can be used in combination, if necessary. In particular, the combined use of a water reducing agent is preferable, and among the water reducing agents, the combined use of a high performance water reducing agent is more preferable.

A high-performance water-reducing agent is a surfactant with a large dispersibility that does not cause excessive delay of condensation or excessive air entrainment even when added in a large amount, and is a salt of a naphthalene sulfonic acid formaldehyde condensate or melamine sulfonic acid formaldehyde. Condensate salts, high-molecular-weight lignin sulfonates, polycarboxylates, and the like as main components, and specifically include, for example, trade name "Mighty 150" manufactured by Kao Corporation, Electrochemical Industry ( Product name "FT-500" manufactured by Pozoris Bussan Co., Ltd., product name "NL-4000", etc.

The amount of the high-performance water reducing agent used is not particularly limited, but is preferably about 0.2 to 2 parts by weight based on 100 parts by weight of cement in terms of solid content.

Mixing this admixture with cement, sand, gravel, an appropriate amount of water and a water reducing agent, kneading and molding mortar and concrete,
In producing a cement molded product by curing under atmospheric pressure steam,
This admixture may be mixed with preliminarily cemented cement to prepare a cement composition, or the admixture or each component may be mixed separately into a mixer directly at the time of kneading, and further dispersed in water to form a slurry. You may mix with.

The kneading method is not particularly limited, and a method usually practiced for mortar and concrete can be used.

Cement molding methods are centrifugal molding, press molding,
Conventional methods such as extrusion molding and vibration molding can be used.

If centrifugal mixing is performed using this admixture and a high performance water reducing agent, the mortar / concrete may have poor tightness, and sludge with a high solid content may be discharged. In that case, as a method of improving tightening and reducing the separation of solid content to increase the dehydration amount, quick lime / slaked lime and / or inorganic substances such as sodium, potassium and lithium sulfates and bisulfates are cemented. It is preferable to use at most 1 part by weight with respect to 100 parts by weight, and it is more preferable to use together at 0.05 to 0.5 part by weight from the viewpoint of improving strength development.

Further, the atmospheric pressure steam curing of the cement molded product using the present admixture is performed in the range of 40 to 100 ° C, more preferably in the range of 50 to 80 ° C.

As the cement molded product molded as described above, for example, a concrete pile, a pole, a centrifugal force molded product such as a fume pipe and a steel pipe lining, a box culvert, a concrete sleeper, a sheet pile, a precast molded product such as a bridge pier and a bridge girder. Can be mentioned.

<Example> Hereinafter, the present invention will be described with reference to Examples.

Example 1 Using concrete mix B shown in Table-1, as shown in Table-2, the amount of this slag used was changed, and the mixing ratio with this gypsum and the addition amount to cement were changed to prepare concrete. did.

The amount of this admixture and water reducing agent added is all cement.
The weight is 100 parts by weight, and atmospheric pressure steam curing is
After pre-curing for 4 hours, the temperature was raised to 65 ° C. at 15 ° C./h, kept for 4 hours, allowed to cool naturally, and taken out from the steam curing tank the next morning for various tests.

<Materials used> Cement: Normal Portland cement manufactured by Denki Kagaku Kogyo Co., Ltd. (specific gravity 3.16) Water: Groundwater Sand: River sand from Himekawa, Niigata (specific gravity 2.65) Gravel: 〃 Crushed stone (specific gravity 2.68) Water reducing agent: High performance water reducing agent , Denki Kagaku Co., Ltd. product name "FT-500" (specific gravity 1.20) This gypsum: Shin-Akita Kasei Co., Ltd. hydrofluoric acid generating by-product gypsum, Blaine value 6,000 cm ² / g (porosity 0.5), specific gravity 2 .
93 Main slag: Kawatetsu Riverment slag for blast furnace slag cement (no gypsum dihydrate, particles of 12μ or less 48%) re-adjusted as follows with a vibration mill or a vibration mill and a classifier Specific gravity 2.95 α: 12μ or less 53%, D50 is less than 12μ β: 〃 60% 〃 9μ γ: 〃 80 〃 6μ δ: 〃 100 〃 3μ The water / cement ratio is simply water and cement weight%, and this admixture is sand The volume of the mixed material was outside the target slump, and the slump was adjusted by adjusting the amount of water.

<Test method> (1) Measurement of slag particle size It was dispersed in ethanol using a laser diffraction powder particle size analyzer Granulometer Model 715 (measurement range 0 to 192 µ) manufactured by Cirrus.

(2) Measurement of strength test Compressive strength was obtained using a vibration-filled cylindrical specimen of φ10 × 20 cm, and tensile strength was measured using a cylindrical specimen of φ15 × 15 cm.
It was calculated by the split.

(3) Measurement of permeation amount of chloride ion A cylindrical specimen of φ10 × 20 cm was demolded in 1 day of age, then 20
After curing for 28 days in a curing box controlled to ℃ ± 3, RH60% ± 5, soak in 3% NaCl aqueous solution, and 91 days later, cut out the central part of the test piece with a size of φ10 × 0.5cm, and at 24 ℃ at 300 ℃ The whole that had been dried for a period of time was ground and the amount of chlorine permeated was measured by fluorescent X-ray analysis.

(4) Measurement of Neutralization Depth A cylindrical specimen of φ10 × 20 cm was aged for 28 days in the same manner as the chlorine ion permeation measurement, and then 100% RH and a CO ₂ gas concentration of 18
It was aged in a volume% curing box for 91 days, and phenolphthalene was applied to the circular cut surface of the central part to measure the average neutralization depth.

(5) Measurement of freeze-thaw durability A sample of 10 × 10 × 40 cm was demolded the next morning, standard-cured for 14 days, and then subjected to a rapid freeze-thaw test in water to obtain a durability index DF value.

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

DF value (%) = PN / MP: Relative dynamic elastic modulus at N cycles P = n ₁ ² / n ² n: First-order flexural frequency at the start of test n ₁ : First-order flexural frequency at any cycle N: Cycle number when P reaches 60% or when the test is terminated M: Cycle number when the freeze-thaw test is terminated Table 2 shows the test results.

This admixture is shown in parts by weight relative to 100 parts by weight of cement, 14 days strength is standard curing, 28 days strength is 20 ℃ ± 3, RH
The strength at the beginning of each durability test was measured after curing at 60% ± 5.

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

Also, regarding the particle size of blast furnace slag, particles of 12μ or less
By combining 60% or more with this gypsum, the effect of improving strength and durability becomes remarkable, and it can be seen that the finer the grain size of the blast furnace slag, the better.

On the contrary, if the particle size of the blast furnace slag is less than 60% with particles 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 No. 1-13, 1-19, 1-2
In 0), it can be seen that the strength effect is small, the elongation of strength is hardly changed, or any of various durability tends to be deteriorated.

In addition, the concrete of Experiment Nos. 1-4, 1-9 and 1-16 was
Molded in a 20 cm cylinder, without atmospheric steam curing,
Although it was cured in a room at 20 ° C until the next day and demolded for standard curing, the 14-day compressive strength was 603 kgf / cm ² in Experiment Nos. 1-4 and Experiment No.
1-9 is 785 kgf / cm ² , Experiment No. 1-16 is 803 kgf / cm ² ,
It has been found that the present invention shows a remarkable effect in normal pressure steam curing.

Example 2 The concrete composition of A to D of Table-1 and the experiment N of Table-2
Using the concrete shown in o.1-4, 1-9 and 1-16, a specimen of φ10 × 20 was molded in the same manner as in Example 1 and the compressive strength of each material was measured. The results are shown in Table-3.

After steam curing, the specimen that was demolded the next morning was cured at room temperature.
It was left in a room adjusted to 20 ° C ± 3.

As can be seen from Table-3, the strength effect is remarkable even when the unit cement amount is small, and 800 kg even when the unit cement amount is 300 kg / m ^3.
High strength of f / cm ² or more can be obtained.

Example 3 In Example 2, concrete shown in Experiment Nos. 2-4 to 6 of Table 3 was crushed with quick lime in a gas-fired lime furnace to a size of 88 μ or less (Q), and water was further added to digest it. Dried slaked lime (R), primary reagents sodium sulfate (S), potassium sulfate (T), lithium sulfate (U) and sodium bisulfate (V) were added in different amounts φ20 × 5 × 30 cm
Centrifugal molded specimens are molded, and the amount of sludge generated, the solid content of dried sludge, the thickness of the non-tightened inner surface of the centrifugal molded specimens, and the 1-day compressive strength after steam curing are measured. did. The results are shown in Table-4.

In addition, centrifugal force molding was performed for 2 minutes with 3G, 4 minutes with 9G, and 3 minutes with 30G, and a constant amount of 18 kg of concrete was added, and the hollow portion was covered with a lid to prevent the sludge coming off from getting wet.

As can be seen from Table-4, it is effective to use an inorganic substance together in order to improve the moldability of the centrifugal force molded product of the concrete using this admixture.

It should be noted that the inorganic substance does not have the remarkable effect as in the case of the present invention even when used in combination with Experiment Nos. 3-1 to 2 as Comparative Examples.

Example 4 Using the concrete of Experiment Nos. 2-4 to 6 of Example 2, an outer diameter of 30
PC piles having a length of 0 mm × a thickness of 60 mm, a length of 4 m (for bending moment) and a length of 1 m (for compression) were formed by an ordinary method and cured under the same curing conditions as in Example 2. After that, a bending test and a compression test were performed on the 7th day. The results are shown in Table-5.

In addition, the reinforcement of the PC pile is a high-frequency heat kneading Co., Ltd. PC steel bar φ13 mm ×
4 pieces and φ11mm × 4 pieces (straight reinforcement), spiral reinforcement was inserted φ3mm iron wire at 10cm intervals so that the initial tensile stress of PC steel bar was 160kgf / cm ² against the pile cross section.

Example 5 Using the same concrete as in Example 4, centrifugal curing was performed by a conventional method under the same curing conditions to prepare a fume tube, and an external pressure strength test was conducted for 7 days. The results are shown in Table-6.

The fume tube has an inner diameter of 100 mm, a thickness of 82 mm, and a length of 2,430 mm.
With the dimensions, the rebar is a type A tube with a straight bar ratio of 0.2% and a spiral bar of double 1.49%.

<Effect of the invention> As shown in the examples, by using the cement admixture of the present invention, it is possible to produce a concrete having high strength and high durability, and further, the admixture of the present invention. The cement molded product using is significantly improved in performance as a molded product.

Claims (2)

[Claims] 1. A cement admixture mainly comprising 100 parts by weight of blast furnace slag fine powder having a particle size of 12 μ or less and 60% or more and 10 to 750 parts by weight of II type anhydrous gypsum. 2. A cement composition comprising 100 parts by weight of cement and 4 to 35 parts by weight of the cement admixture according to claim 1.