JPH08319143A - Cement admixture and cement composition - Google Patents

Abstract

PURPOSE: To impart cement with high strength and improve resistance to penetration of chlorine ion (resistance to salt) and durability by mainly using a cement admixture mainly comprising II-type anhydrous gypsum, pozzolan material and blast furnace slag and cement. CONSTITUTION: This cement composition is mainly composed of 8-45 pts.wt. of cement admixture mainly comprising 100 pts. wt. of II-type anhydrous gypsum having >=3000 cm<2> /g Blaine number, 40-50 pts.wt. of pozzolan material such as silica fume and diatomaceous earth, etc. and 2-15 pts. wt. of blast furnace slag having >=1.4 basicity as (CaO+Al2 O3 +MgO)/SiO2 , >=50% vitrification ratio and >=4000cm<2> /g Blaine value and 100 pts.wt. of cement. The composition is used in an amount of 250-450kg/m<3> unit cement amount and mixed with sand, ballast and a suitable amount of water, and further, a water reducing agent, as necessary, blended with mortar or concrete to form a pole, then steam cured at 40-100 deg.C under normal pressure to obtain a pole having high strength, resistance to salt and durability.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a cement admixture and a cement composition suitable for salt-resistant poles.

[0002]

^2. Description of the Related Art Conventionally, the concrete used for manufacturing poles is designed and mixed so that the design strength on the 28th day exceeds the design strength of 500 kgf / cm ^2. Concrete with an amount of cement of 460 to 550 kg / m ³ and a water cement ratio of about 35% is used.

However, when a pole manufactured using such concrete is installed along the coast, the reinforcing bars rust or crack due to the splash of water, that is, the permeation of chlorine ions in seawater. However, there was a problem with durability, such as red rust blowing out.

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

However, although this method can reasonably obtain high strength, there is a problem that durability, particularly permeation resistance of chlorine ions (salt resistance), cannot be sufficiently obtained.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by using specific amounts of type II anhydrous gypsum, pozzolanic substances and blast furnace slag. Has been completed.

[0007]

Means for Solving the Problems That is, the present invention provides (1)
Cement admixture mainly composed of 100 parts by weight of type II anhydrous gypsum, 40 parts by weight of pozzolanic material and 500 parts by weight or less and 2 to 15 parts by weight of blast furnace slag, (2) Cement 1
A cement composition containing, as main components, 00 parts by weight and 8 to 45 parts by weight of the cement admixture described in (1).

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below.
The type II anhydrous gypsum in the present invention has an X-ray diffraction pattern of the form II-CaSO ₄ , and is obtained by firing dihydrate, semi-water, type III anhydrous gypsum, etc. It is also possible to use a natural byproduct or natural anhydrous gypsum. Further, the type II anhydrous gypsum is not limited to impurities contained naturally or industrially.

The type-II anhydrous gypsum preferably has a Blaine value of 3,000 cm ² / g or more, preferably 4,000 to 7,
500 cm ² / g is more preferable. Brain value is 3,000
If it is less than cm ² / g, it remains unreacted even after steam curing, and this tends to react for a long period of time and lose the stability of the hardened concrete, which is not preferable.

Although various types of pozzolanic substances in the present invention can be mentioned, silica fume and diatomaceous earth are preferable from the viewpoints of properties such as strength and salt resistance as well as handleability of concrete during pole production.

That is, since the pole is thinner than other centrifugally-molded products, when the concrete is put in the formwork divided into two parts, the concrete becomes a heap. 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.

The term "silica fume" as used herein refers to ultrafine powder containing as a main component amorphous SiO ₂ which is a by-product during the production of silicon alloys such as metallic silicon, ferrosilicon and calcium silicon.

[0013] The diatomaceous earth is a deposit of unicellular algae remains called diatom, which is characterized by its porosity.

In the present invention, the amount of the pozzolanic substance used is
Type II anhydrous gypsum 100 parts by weight, pozzolanic substance 40
It is more than 500 parts by weight and more than 500 parts by weight. If the pozzolanic substance is 40 parts by weight or less, the effect of improving the durability is small, and if it exceeds 500 parts by weight, the unit water amount increases, the strength decreases, and the workability due to slump drop largely decreases.

The amount of type II anhydrous gypsum and pozzolan of the present invention used is 6 to 30 parts by weight per 100 parts by weight of cement. The amount of type II anhydrous gypsum and pozzolan used is 6
If it is less than 30 parts by weight, the effect of improving the 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 due to the slump drop becomes large.

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

Represents the degree of latent hydraulicity of blast furnace slag
Basicity (CaO + Al) ₂O₃＋ MgO) / SiO
₂Is preferably 1.4 or higher in the present invention, and 1.7 or higher.
Is more preferable.

The vitrification rate of the blast furnace slag powder is 50%.
The above is preferable, and 90% or more is more preferable.

The blast furnace slag powder preferably has a Blaine value of 4,000 cm ² / g or more obtained by crushing or crushing / classifying, and the finer the particle size, the better. Further, the minimum particle size of the blast furnace slag powder obtained by crushing or crushing / classifying industrially and economically is usually 10 μm or less,
The value of D50 is about 3 to 6 μ, and the Blaine value is about 10,000 cm ² / g. The use of such finely ground blast furnace slag powder is more preferred.

When the blast furnace slag powder is used in combination with type II anhydrous gypsum and a pozzolanic substance, it exhibits remarkably high strength, and salt resistance can be further improved.

The amount of blast furnace slag powder used is 100% cement.
2 to 15 parts by weight is preferable, and 4 to 10 parts by weight is more preferable. 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 extension of strength and salt resistance cannot be expected. Not only is it uneconomical, but depending on the amount of pozzolanic substances used, there is no portlandite in the hardened concrete at all, and there is concern that rusting of the reinforcing bars may occur due to a decrease in alkalinity, especially prestressing of poles, etc. The product is not preferable because it is also subjected to stress corrosion due to the tension of the steel rod.

Therefore, the cent admixture of the present invention, namely,
The amount of type II anhydrous gypsum, pozzolanic material and blast furnace slag used is 8 to 45 parts by weight per 100 parts by weight of cement.

In the present invention, the blast furnace slag powder is
The reason why such a synergistic effect is exhibited is unknown,
By pulverizing blast furnace slag, the dissolution rate of the Al component in a large amount in the blast furnace slag flour is faster, and dissolution rate and balance of type II anhydrous gypsum, efficiently ettringite (3CaO · Al ₂ O ₃ · 3CaSO ₄ · 32H ₂ O), fill the voids in the concrete, and solidify. At the same time, type II anhydrous gypsum increases the elution amount of the Al component in the blast furnace slag powder, makes the blast furnace slag particles porous, and enhances the hydration reaction amount of the entire blast furnace slag powder, which results in remarkable strength. It is believed that they show an increase and an improvement in salt resistance.

Further, in the present invention, the unit cement amount is preferably in the range of 250 to 450 kg / m ³ . 250 kg / m
^If it is less than ³ , the water-cement ratio will suddenly increase and the cement concentration will decrease, so design strength cannot be obtained and salt resistance cannot be expected. When the unit cement content exceeds 450 kg / m ³ , the strength increases, but the salt resistance tends to decrease, and the weather resistance tends to deteriorate. Tend to occur.

Although the reason why the salt resistance is reduced despite the increase in the strength is not clear, the water cement ratio also inevitably decreases when the unit cement amount increases, so the pozzolanic material and the blast furnace at this time are also reduced. This is probably because the reaction amount of slag powder decreased.

The cement used in the present invention includes various portland cements such as normal, early strength, super early 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, a chemical admixture 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, 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.

The high-performance water-reducing agent is a surfactant having a large dispersibility, which does not cause excessive delay of coagulation or excessive air entrainment even when added in a large amount, and is a salt of a naphthalenesulfonic acid formaldehyde condensate, melamine. Examples thereof include salts of sulfonic acid-formaldehyde condensate, high molecular weight lignin sulfonates, polycarboxylates and the like as main components. Specifically, for example, product name "Mighty 15 manufactured by Kao Corporation" is used.
0 ", product name" FT-500 "manufactured by Denki Kagaku Kogyo Co., Ltd.,
The product name "NL-4000" manufactured by Pozoris Bussan Co., Ltd. and the like can be mentioned.

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

The cement admixture of the present invention and cement, sand,
Gravel and an appropriate amount of water, further, if necessary, a water reducing agent and the like are blended, kneading mortar or concrete, in producing a pole, the cement admixture of the present invention, as a cement composition by mixing it with cement in advance. Alternatively, the respective components may be added to the mixer directly or separately in advance during kneading, or may be added in the form of a slurry by dispersing in water.

The kneading method, the molding method, the method for arranging the poles, the method for introducing the prestress, etc. are not particularly limited, and the methods generally used when manufacturing the poles can be used.

Further, the atmospheric pressure steam curing of the pole using the cement admixture of the present invention is carried out in the range of 40 to 100 ° C, more preferably in the range of 50 to 80 ° C.

[0033]

EXAMPLES The present invention will be described below with reference to examples. Example 1 Concrete mixing code C shown in Table 1 was used, and as shown in Table 2, the amount of pozzolanic material was changed with respect to 100 parts by weight of II type anhydrous gypsum, and the addition amount of cement admixture to cement was changed. , Kneading concrete by the usual method, φ10 × 20
A cm test piece was molded. The specimen was pre-cured for 4 hours and then heated up to 65 ° C at a heating rate of 15 ° C / h,
After steam curing at normal pressure and holding for 4 hours as it was, it was naturally cooled, taken out from the steam curing tank the next morning, and subjected to various tests. The results are also 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 was parts by weight with respect to 100 parts by weight of cement, and was replaced by fine aggregate and volume. If the amount of cement admixture used was outside the target slump, the amount of water was adjusted to adjust the slump.

[0034]

[Table 1]

<Materials used> Cement: ordinary Portland cement manufactured by Denki Kagaku Kogyo Co., Ltd. (specific gravity 3.16) Sand: Niigata Prefecture Himekawa produced river sand (specific gravity 2.65) Gravel: 〃 Crushed stone (specific gravity 2.68) Water: Groundwater water reducing agent: High Performance water reducing agent, trade name "FT-500" manufactured by Denki Kagaku Kogyo Co., Ltd. (specific gravity 1.20) Main component naphthalene sulfonic acid formaldehyde condensate type II anhydrous gypsum: manufactured by Shin-Akita Kasei Co., Ltd., hydrofluoric acid by-product gypsum, Blaine 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 diatom: diatomaceous earth, product name "Radiolite SPF" manufactured by Showa Chemical Industry Co., Ltd., specific gravity 2.10

<Test Method> (1) Measurement of Strength The compressive strength was measured using a vibration-filled cylindrical test piece of φ10 × 20 cm in accordance with JIS A 1108, and was measured for one day. (2) Measurement of salt resistance A cylindrical specimen of φ10 × 20 cm was demolded in 1 day of age, then cured in a curing box controlled at 20 ± 3 ° C and RH60 ± 5% for 28 days, and then 3% NaCl. Immerse in the aqueous solution, take out after 6 months of age, cut out the central part of the sample with a size of φ 10 × 1 cm, dry it at 300 ° C for 24 hours, crush all the amount, and infiltrate by fluorescent X-ray analysis Was measured. (3) Measurement of workability Immediately after concrete mixing, slump was measured according to JIS A 1101, and 20 minutes later, slump was measured again in the same manner.

[0037]

[Table 2]

As is clear from Table 2, the examples in which an appropriate amount of type II anhydrous gypsum and a pozzolanic substance of silica fume or diatomaceous earth were used, the amount of permeated chlorine ions was significantly reduced, and salt resistance was improved. The improving effect is recognized. If the amount used is not proper, salt resistance will not be improved and workability such as slump drop will be deteriorated.

Example 2 Example 1, Experiment No. Blast furnace slag powder was used in combination with concrete having the composition shown in 1-11 as shown in Table 3, and a test piece was prepared in the same manner as in Example 1, and various tests and measurements of portlandite in the hardened concrete were performed. . The results are also shown in Table 3. In addition, the experiment No. A similar amount of slump was obtained at a unit water amount of 140 kg / m ^{3 in} the 2-1 and 2-2 blends and around 145 kg / m ^{3 in} other cases.

<Materials used> Slag powder a: blast furnace slag powder, manufactured by Kawatetsu Riverment Co., without gypsum dihydrate, crushed / classified product Brain 6,000 cm ² / g 〃 b: 〃 10,500 cm ² / g <Test method> ( 4) Measurement of portlandite A cylindrical specimen of φ10 × 20 cm was demolded in 1 day of age, a central portion of the specimen was cut out with a dimension of φ10 × 1 cm, and dried at 300 ° C. for 24 hours. , Chemical analysis was performed. The portlandite was converted to f-CaO.

[0041]

[Table 3]

As is clear from Table 3, when the type II anhydrous gypsum and the pozzolanic substance are used in combination with blast furnace slag powder, the strength and salt resistance are remarkably improved. If the amount of blast furnace slag powder is less than 2 parts by weight, the effect of addition is small.
The strength and salt resistance are low, the amount of portlandite in the hardened concrete is small, and there is concern that the reinforcing bars will rust.

Example 3 Using concrete mixes of mix symbols A to F shown in Table 1,
As shown in Table 4, cement admixtures were added to produce concrete poles. The pole is an A-type pole having a length of 13 m, an uncaliber of 190 mm, and a designed crack load of 350 kgf, which is centrifugally molded by a conventional method, steam-cured under the same conditions as in Example 1, and then demolded the next day to be prestressed. Was introduced and the outdoor curing was performed as it was. After that, a bending strength test was performed on the 21st day of the material age, and the initial crack load and the breaking load (design value 700 kgf) were measured. The PC steel rod used was manufactured by Induction Heat Kneading Co., Ltd., and the reinforcing bar was a PC steel rod φ7.4 mm x 8 for tensioning.
Books and reinforced steel rods φ7.4 mm × 4 (straight muscle), spiral wires were φ3 mm iron wires arranged at 10 cm intervals, and the initial tensile stress level of the PC steel rod was set to 10,150 kgf / cm ² . In addition, the concrete collected at the time of pole production is φ20 x for measuring compressive strength and the amount of permeated chlorine ions.
A specimen having a thickness of 5 cm and a length of 30 cm and a specimen having a diameter of 10 cm for a weather resistance test were prepared by centrifugal molding in the same manner as the pole. The results are also shown in Table 4. Compressive strength is age 2
The permeation amount of chloride ion is 21 days after the measurement.
Both ends were adhered with a vinyl chloride plate so as not to allow the 3% NaCl aqueous solution to enter the hollow portion, dipped in the aqueous solution, and sliced into 1 cm-thick sections for 6 months, and the same measurement as in Example 1 was performed. .

<Test Method> (5) Weather resistance A test piece of φ10 × 20 cm was subjected to outdoor exposure curing after demolding,
I observed the crack one year later.

[0045]

[Table 4]

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

[0047]

Industrial Applicability As described above, the salt-resistant pole made of the cement admixture of the present invention has high strength, good weather resistance, and high salt resistance.

Claims (2)

[Claims] 1. A cement admixture mainly comprising 100 parts by weight of type II anhydrous gypsum, more than 40 parts by weight of pozzolanic material and not more than 500 parts by weight, and 2 to 15 parts by weight of blast furnace slag. 2. A cement composition comprising 100 parts by weight of cement and 8 to 45 parts by weight of the cement admixture according to claim 1 as a main component.