JP2612071B2 - How to make salt-tolerant poles - Google Patents

Description

The present invention relates to a method for producing a salt-resistant pole.

<Conventional technology and its problems> Conventionally, concrete used in the production of poles has been designed and blended to exceed the design strength of 500 kgf / cm ² on the 28th of material age. 460
Concrete of up to 550 kg / m ³ and a water cement ratio of about 35% is used.

However, when a pole made using such concrete is installed along the coast, the seawater splashes, that is, the penetration of chlorine ions in the seawater causes rusting or cracking of the reinforcing steel, and red rust occurs. There was a problem in durability such as blowing out.

As a method of obtaining high strength by steam curing, 100 parts by weight of type II anhydrous gypsum and, for example, a silica admixture containing 5 to 40 parts by weight of a siliceous substance such as silica fume, silicate clay and fly ash. The method used is known (Japanese Patent Publication No. 57-49504).

However, although this method can provide a reasonably high strength, there is a problem that a sufficient effect cannot be obtained with respect to durability, particularly, resistance to permeation of chloride ions (salt resistance).

The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, by using a specific amount of type II anhydrous gypsum and pozzolan, and blast furnace slag, the present inventors have obtained the knowledge that can solve the above-mentioned problems, and completed the present invention. Reached.

<Means for Solving the Problems> That is, the present invention relates to (A) I based on 100 parts by weight of cement.
6 types of cement admixture containing more than 100 parts by weight of type I anhydrous gypsum and more than 40 parts by weight of pozzolanic substances and 500 parts by weight or less
A method for producing a salt-resistant pole, wherein a concrete produced by mixing 2 to 15 parts by weight of (B) blast furnace slag with (B) blast furnace slag is subjected to centrifugal force molding.

 Hereinafter, the present invention will be described in detail.

The type II anhydrous gypsum in the present invention is one whose X-ray diffraction pattern shows the form of II-CaSO ₄ and obtained by calcining dihydrate, hemihydrate, type III anhydrous gypsum, etc. Those produced as a by-product from the process and natural anhydrous gypsum can also be used. In addition, Type II anhydrous gypsum is not limited to naturally or industrially contained impurities.

The fineness of Type ^II anhydrous gypsum is 3,000 cm ² in Blaine value.
/ g or more is preferable, and 4,000 to 7,500 cm ² / g is more preferable. If the Blaine value is less than 3,000 cm ² / g, it is likely to remain unreacted even after steam curing, and this will react for a long time,
It is not preferable because the stability of the hardened concrete body tends to be lacking.

There are various types of pozzolanic materials in the present invention, and silica fume and diatomaceous earth are preferable in terms of properties such as strength and salt resistance, as well as handling properties of concrete during pole production.

That is, since the pole is thinner than other centrifugally molded products, when the concrete is put into the divided formwork, the concrete is piled up. Therefore, if concrete does not have plasticity, there is a tendency that the formwork cannot be assembled. Silica fume and diatomaceous earth are important factors that enhance the plasticity of this concrete and promote efficient production.

Here, the silica fume is an ultrafine powder mainly composed of amorphous SiO ₂ by-produced during the production of silicon alloys such as metallic silicon, ferrosilicon and calcium silicon.

Diatomaceous earth is a deposit of unicellular algae called diatomaceous earth, and is characterized by its porosity.

In the present invention, the used amount of the pozzolanic substance is more than 40 parts by weight of the pozzolanic substance with respect to 100 parts by weight of anhydrous type II gypsum, and 5
00 parts by weight or less. If the pozzolans content is less than 40 parts by weight,
The effect of improving the durability is small, and if it exceeds 500 parts by weight, the unit water volume increases, the strength decreases, and the decrease in workability due to slump drop increases.

The used amount of the cement admixture of the present invention is 6 to 30 parts by weight based on 100 parts by weight of cement. If the amount of the cement admixture is less than 6 parts by weight, the effect of improving durability is small, and if it exceeds 30 parts by weight, the strength tends to decrease with an increase in the unit water amount, and the workability decreases due to slump drop. growing.

In the present invention, blast furnace slag powder is further used.

Blast furnace slag powder is a fine powder obtained by crushing or pulverizing and classifying vitrified molten slag produced as a by-product from a blast furnace, and other powders usually used for blast furnace cement can also be used. .

Basicity represented as representing a degree of latent hydraulic blast furnace slag _{(CaO + Al 2 O 3 +} MgO) / SiO 2 , in the present invention, preferably 1.4 or more, more preferably 1.7 or more.

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

Blast furnace slag powder is obtained by crushing or crushing and classification,
A Blaine value of 4,000 cm ² / g or more is preferable, and the finer the particle size, the better. In addition, the minimum particle size of blast furnace slag powder obtained by industrially and economically pulverizing or pulverizing / classifying is usually 10μ or less, and the value of D50 is 3 to 6μ.
And a Blaine value of about 10,000 cm ² / g. Use of such a fine blast furnace slag powder is more preferable.

When blast furnace slag powder is used in combination with type II anhydrous gypsum and pozzolan, it is possible to develop remarkably high strength and further improve salt resistance.

The amount of blast furnace slag powder used is preferably 2 to 15 parts by weight, more preferably 4 to 10 parts by weight, based on 100 parts by weight of cement. If the amount of blast furnace slag powder is less than 2 parts by weight, the effect of promoting the strength development and salt resistance of type II anhydrous gypsum and pozzolan is small, and if it exceeds 15 parts by weight, the strength and salt resistance effects cannot be expected to increase. In addition to being uneconomical, depending on the amount of pozzolanic material used, portlandite in the concrete hardened body is completely eliminated, and there is a concern that rusting of reinforcing steel due to a decrease in alkalinity may occur. The product is not preferable because stress corrosion due to the tension of the steel rod is also added.

In the present invention, the blast furnace slag powder has a large amount of blast furnace slag powder by pulverizing the blast furnace slag, although the reason for exhibiting such a synergistic effect is unknown.
The dissolution rate of the Al component is increased, and the ettringite (3CaO.
Al ₂ O ₃・ 3CaSO ₄・ 32H ₂ O) to fill the voids in concrete and make it more dense. At the same time, type II anhydrous gypsum increases the elution amount of Al component in blast furnace slag powder,
It is considered that the blast furnace slag particles are made porous to increase the hydration reaction amount of the whole blast furnace slag powder, thereby showing a remarkable increase in strength and improvement in salt resistance.

Further, in the present invention, the unit cement amount is 250 to 450
A range of kg / m ³ is preferred. If it is less than 250 kg / m ³ , the water-cement ratio suddenly increases and the cement concentration decreases, so that the design strength cannot be obtained and the salt resistance cannot be expected. When the amount of the unit cement exceeds 450 kg / m ^3, the strength is increased, salt tolerance, tend to decrease rather and tend to weather resistance deteriorate when exposed cured extended period outdoors, cracked Tends to occur.

Although the strength is increased, the reason why the salt resistance is reduced is not clear, but when the unit cement amount is increased, the water-cement ratio is inevitably reduced, so that the pozzolanic substance and the blast furnace slag powder at this time are not removed. This is probably due to the decrease in the reaction amount.

The cement used in the present invention includes various Portland cements such as ordinary, early-strength, ultra-high-strength, moderate heat, and white. Further, blast furnace cement is difficult to use because of problems such as neutralization, oxidation and discoloration, but silica cement and fly ash cement can be used. As the cement has a larger hydraulic coefficient and a higher fineness, the salt resistance is improved.

In producing a salt-resistant pole using the cement admixture of the present invention, if necessary, a chemical admixture such as a water reducing agent, an AE water reducing agent, an accelerator and a retarder can be used in combination.

Particularly, 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.

High-performance water reducing agents are surfactants with a large dispersing ability that do not accompany excessive delay in coagulation or excessive air entrainment even when added in large amounts, and include salts of naphthalenesulfonic acid formaldehyde condensate and melaminesulfonic acid formaldehyde. Examples thereof include salts of condensates, high molecular weight lignin sulfonates and polycarboxylates as main components. Specifically, for example, Kao Corporation's trade name “Mighty 150”; Trade name "FT-500" manufactured by Pozoris Bussan Co., Ltd. and "NL-4000" manufactured by Pozoris Bussan Co., Ltd.

The amount of the high-performance water reducing agent 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.

Then, it is preferable to select the amount to be used within this range so that the concrete retains plasticity in accordance with the change in the type and brand of cement and the aggregate such as sand.

Cement admixture of the present invention and cement, sand, gravel and an appropriate amount of water, further, if necessary, blending a water reducing agent, etc., kneading mortar or concrete, and producing a pole, the cement admixture of the present invention is May be mixed with cement in advance to form a cement composition, or each component may be separately or premixed directly into a mixer during kneading, and further dispersed in water and added in a slurry form. Is also good.

The kneading method, the molding method, the method of arranging the poles, the method of introducing the prestress, and the like are not particularly limited, and a method usually used for manufacturing a pole can be used.

The normal pressure steam curing of the pole using the cement admixture of the present invention is performed at a temperature in the range of 40 to 100 ° C, and more preferably in the range of 50 to 80 ° C.

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

Example 1 Using the concrete mixing symbol C shown in Table 1, Table 2
As in 100 parts by weight of anhydrous type II gypsum, changing the amount of pozzolanic matter, changing the amount of cement admixture added to cement, kneading concrete by a conventional method, φ10 × 20
A cm test piece was molded.

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

The water-cement ratio is the weight ratio of the amount of water to the amount of cement, and the cement admixture is replaced by the fine aggregate and the volume in parts by weight based on 100 parts by weight of cement. If the amount of cement admixture used was outside the target slump, the amount of water was adjusted to adjust the slump.

<Materials> Cement: Made by Denki Kagaku Kogyo Co., Ltd., ordinary Portland cement (specific gravity 3.16) Sand: River sand from Himekawa, Niigata Prefecture (specific gravity 2.65) Gravel: 〃 Crushed stone (specific gravity 2.68) Water: groundwater water reducing agent: high-performance water reducing agent "FT-500" (specific gravity: 1.20), manufactured by Denki Kagaku Kogyo Co., Ltd. Main component: naphthalenesulfonic acid formaldehyde condensate type II Anhydrite: Shin-Akita Chemical Co., Ltd., hydrofluoric acid generation by-product gypsum, Brain value 6,000 cm ² / g (porosity 0.5),
Specific gravity 2.96 Silica: Silica fume, manufactured by Nippon Heavy Chemical Industry Co., Ltd., specific gravity 2.20 Diatomaceous earth: Diatomaceous earth, Showa Chemical Co., Ltd. product name “Radiolite SPF”, specific gravity 2.10 <Test method> (1) Measurement of strength Compression The strength was measured using a cylindrical specimen of φ10 × 20 cm packed with vibration in accordance with JIS A 1108, with a material age of 1 day.

(2) Measurement of salt resistance A cylindrical specimen of φ10 × 20cm was removed from the mold in one day, and then
After curing in a curing box controlled at 20 ± 3 ° C and RH60 ± 5% for 28 days, immersed in a 3% NaCl aqueous solution, taken out at 6 months of age, cut out the center of the specimen to a size of φ10 × 1cm, The whole dried at 300 ° C. for 24 hours was pulverized, and the amount of permeated chlorine ions was measured by X-ray fluorescence analysis.

(3) Measurement of workability Immediately after concrete kneading, slump was measured in accordance with JIS A 1101, and after 20 minutes, slump was measured again.

As is clear from Table 2, the examples using an appropriate amount of type II anhydrous gypsum and silica fume or diatomaceous earth pozzolanic material have a significantly reduced amount of permeated chloride ions and improve salt resistance. The effect is recognized.

If the amount is not proper, salt resistance will not be improved, and workability such as slump drop will be deteriorated.

Example 2 A blast furnace slag powder was used in combination with the concrete having the composition shown in Example 1 and Experiment Nos. 1-11, as shown in Table 3, and specimens were prepared in the same manner as in Example 1, and various tests and concrete hardening were performed. Portlandite in the body was measured. The results are shown in Table-3.

The unit water volume of Experiment Nos. 2-1 and 2-2 was 140 kg /
m ^3, otherwise comparable slump was obtained at 145 kg / m ³ before and after.

<Materials> Slag powder a: Blast furnace slag powder, manufactured by Kawatetsu Reverment Co., Ltd., without water gypsum, crushed / classified product Blaine 6,000 cm ² / g 〃 b: 〃 10,500 cm ² / g <Test method> (4) Porto Measurement of landite The cylindrical specimen of φ10 × 20cm was removed from the mold in 1 day, the central part of the specimen was cut out in dimensions of φ10 × 1cm, and the whole dried at 300 ℃ for 24 hours was pulverized and subjected to chemical analysis. Was done. In addition,
Portlandite is shown in terms of f-CaO.

As is clear from Table 3, when blast furnace slag powder is used in combination with the cement admixture, the strength and the salt resistance are significantly improved.
If the amount of blast furnace slag powder is less than 2 parts by weight, the effect of addition is small.
Even when used in excess of parts by weight, the strength and salt resistance elongation are small, the portlandite in the hardened concrete is reduced, and rusting of the reinforcing steel is feared.

Example 3 As shown in Table 4, a cement admixture was added by using a concrete composition of the composition symbols A to F shown in Table 1,
Concrete poles were manufactured.

The pole is 13m long, 190mm in diameter, design crack load
Using a 350 kgf A-type pole, centrifugal molding was performed by a conventional method, steam curing was performed under the same conditions as in Example 1, and the next day, demolding was performed to introduce prestress, and outdoor curing was performed as it was. Thereafter, a bending strength test was performed on the 21st of the material age, and the initial crack load and the breaking load (design value: 700 kgf) were measured.

In addition, PC steel rods made by Induction Heating Co., Ltd. are used, and the reinforcement is PC steel rods φ7.4mm × 8 for reinforcement and reinforcement steel rods φ7.4mm × 4 (straight bars), spiral bars are φ3mm Were placed at 10 cm intervals so that the initial tensile stress of the PC steel rod was 10,150 kgf / cm ² .

In addition, concrete collected at the time of pole production was used to measure the compressive strength and the amount of permeated chlorine ions, φ20 × thickness 5 × length 30cm, and φ10 × for weatherability testing.
A 20 cm specimen was formed by centrifugal molding in the same manner as a pole. The results are shown in Table-4.

The compressive strength was measured at 21 days of material age, and the permeation amount of chloride ion was adhered at both ends with a PVC plate at 21 days of age to prevent a 3% NaCl aqueous solution from entering the hollow part, and immersed in the aqueous solution. A 6-month old material was cut into a slice of 1 cm thick and measured in the same manner as in Example 1.

<Test method> (5) Weather resistance After removing the specimen of φ10 × 20cm, it was cured by exposure to the outdoors.
Years later cracks were observed.

As is evident from Table 4, the concrete pole using the cement admixture of the present invention and having a unit cement amount of 250 to 450 kg / m ³ has remarkably improved strength, effect on salt resistance and weather resistance. .

<Effect of the Invention> As described above, the salt-resistant pole of the present invention has a high strength,
It has good weather resistance and high salt resistance.

Continuation of the front page (56) References JP-A-57-67057 (JP, A) Kasai, Kobayashi, ed. 3 and p. 101-102

Claims (1)

(57) [Claims] (1) 100 parts by weight of cement and (A) 100 parts by weight of anhydrous gypsum of type II and more than 40 parts by weight of pozzolan,
A salt resistant pole characterized in that concrete produced by mixing 6 to 30 parts by weight of a cement admixture whose main component is not more than 5 parts by weight and (B) 2 to 15 parts by weight of blast furnace slag is centrifugally molded. Recipe.