JP2006069831A - Cement admixture and cement composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cement admixture, which is excellent in the keeping quality of flowability, exhibits excellent expanding property or hydration heat reducing effect and can obtain a long-term rust preventive effect, and to provide a cement composition. <P>SOLUTION: The cement admixture contains complex salt of tungstic acid and citric acid and/or molybdic acid and citric acid, and an expandable substance. The expandable substance contains one or more kinds of hydraulic compound selected from a group comprising free lime, hauynite, calcium silicate, calcium ferrite and calcium aluminoferrite and further contains gypsum anhydride. The cement composition contains cement and the cement admixture. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention mainly relates to a cement admixture and a cement composition used in the civil engineering and construction industries.

  In the present invention, “parts” and “%” are based on mass unless otherwise specified.

In recent years, establishment of technology for improving the durability of concrete structures has been desired, and one of the important technologies for achieving this is the expansion of cracks that can play a certain role in extending the life of concrete structures. The material is drawing attention.
There have been many proposals for the expansion material from the old days, and new proposals have been made even recently (see, for example, Patent Documents 1 to 4).

However, at present, it is difficult to realize a long life of the concrete structure only with the expansion material.
This is because the concrete is a porous body, and even if cracking is prevented, carbon dioxide and chloride ions, which are degradation factors, penetrate for a long time and corrode the reinforcing bars. Therefore, depending on the expansion material, it is necessary to take measures against long-term deterioration after reducing construction defects and preventing early deterioration.

  On the other hand, as an effective means for corrosion prevention of reinforcing bars, a method of adding nitrite (see Patent Document 5 and Patent Document 6) and a method of adding a complex salt of tungstic acid or molybdic acid and citric acid (see Patent Document 7) Etc. are known.

  Moreover, the fluidity of concrete plays an important role in reducing initial defects such as construction defects. For this reason, establishment of a technique capable of imparting fluidity retention is also required, and further effective measures against cracks due to hydration heat that are manifested in massive concrete are required.

  Therefore, the present inventor has made various efforts to solve the above problems, and as a result, by using a specific cement admixture, the fluidity retention is good and the hydration calorific value can be reduced, Since it can also impart expansibility, it can effectively reduce initial defects, prevent premature deterioration, and can also provide a rust prevention effect, so that measures against long-term deterioration can be taken. As a result, the present invention has been completed.

Japanese Patent Publication No.42-021840 Japanese Examined Patent Publication No. 53-031170 Japanese Patent Application Laid-Open No. 07-232944 Japanese Patent Laid-Open No. 13-064054 Japanese Patent Publication No.33-000940 Japanese Patent Publication No.42-022957 JP 2002-012458 A

  The present invention provides a cement admixture and a cement composition that can reduce construction defects, prevent early deterioration, and can also take measures against long-term deterioration.

  The present invention is a cement admixture comprising a complex salt of tungstic acid and citric acid and / or a complex salt of molybdic acid and citric acid and an expansion material, the expansion material comprising free lime, Auin, calcium silicate, The cement admixture containing one or two or more hydraulic compounds selected from the group consisting of calcium ferrite and calcium aluminoferrite, and the expansion material is free lime, Auin, calcium silicate, calcium ferrite And a cement admixture comprising one or more hydraulic compounds selected from the group consisting of calcium aluminoferrite and anhydrous gypsum, and further comprising cement and the cement admixture. A cement composition.

  The complex salt of tungstic acid and citric acid and / or the complex salt of molybdic acid and citric acid used in the present invention (hereinafter referred to as this complex salt) is a substance capable of supplying tungstate ion or molybdate ion, and a citric acid component. It is obtained by mixing a substance that can be supplied in water.

  The substance capable of supplying tungstate ion or molybdate ion is not particularly limited, and specific examples thereof include, for example, potassium tungstate, sodium tungstate, lithium tungstate, potassium molybdate, sodium molybdate, And alkaline metal salts such as lithium molybdate, and alkaline earth metal salts such as calcium tungstate, magnesium tungstate, calcium molybdate, and magnesium molybdate. Among them, the use of lithium salt or calcium salt is preferable from the viewpoint of preventing alkali-aggregate reaction and because it has a large effect of preventing rebar corrosion, but in terms of economy, potassium salt and sodium salt are selected. However, it is not uniquely determined.

  The substance capable of supplying the citric acid component is not particularly limited, and specific examples thereof include citric acid, sodium citrate, potassium citrate, calcium citrate, and magnesium citrate. . Among these, use of sodium citrate, particularly trisodium citrate is preferable from the viewpoint of high complex salt forming ability with a tungstic acid component and the like.

  In preparing the complex salt used in the present invention, the mixing ratio of tungstic acid or molybdic acid and citric acid is usually such that the molar ratio of tungstic acid or molybdic acid to citric acid is 1: 1.5 to 1.5: 1. Preferably, the vicinity of 1: 1 is more preferable. Outside this range, the tungstic acid component, the molybdic acid component, or the citric acid component may be redundant and may not be efficient.

  The expanding material of the present invention is not particularly limited, and any material that expands can be used. Broadly speaking, there are gas foaming material type expansion materials and cement mineral type expansion materials. Specific examples thereof include, for example, an aluminum powder, an iron powder, a peroxide material, and a carbon material in a gas foaming material-based expansion material, and an ettringite-based expansion material, a lime-based expansion material in a cement mineral-based expansion material. , And lime-etringite composite system expansion material. In the present invention, it is preferable to use a cement mineral-based expansion material from the viewpoint of imparting effective expansibility.

The cement mineral expansion material will be described in more detail.
Examples of the cement mineral-based expanding material include those containing free lime and free magnesia, but those containing free lime are preferred from the viewpoint of long-term stability.

  Examples of the expanding material containing free lime include free lime-anhydrous gypsum-based expanding material, free lime-hydraulic compound-based expanding material, and free lime-hydraulic compound-anhydrous gypsum-based expanding material. In the present invention, since the expansion performance is good, it is preferable to use a free lime-hydraulic compound-anhydrous gypsum-based expansion material, and it is particularly preferable to use an expansion material having a free lime content of 40 to 70%. If the free lime content is outside this range, a sufficient crack reduction effect may not be obtained.

The hydraulic compound, for example, _{Auin, 2CaO · SiO 2 (C 2} S) and 3CaO · SiO ₂ Calcium silicate _{(C 3 S), CaO ·} Fe 2 O 3 (CF) and 2CaO · Fe ₂ O ₃ ( C ₂ F) calcium ferrite, 6CaO · 2Al ₂ O ₃ · Fe ₂ O ₃ (C ₆ A ₂ F), 4CaO · Al ₂ O ₃ · Fe ₂ O ₃ (C ₄ AF), and 6CaO · Al _One or two or more types selected from the group consisting of calcium aluminoferrite of ₂ O ₃ · 2Al ₂ O ₃ (C ₆ AF ₂ ) can be mentioned.
As such an expanding material, a commercially available expanding material or a static crushing material can be used.
Expandable materials and static crushed materials are commercially available from various companies, and representative examples thereof include, for example, trade name “DENKA CSA”, trade name “DENKA POWER CSA” manufactured by Denki Kagaku Kogyo Co., Ltd. “Sachs”, trade name “Pacific Gypcal” manufactured by Taiheiyo Materials Co., Ltd., trade name “Expan”, trade name “N-EX”, trade name “Breister”, and the like.

The particle size of the expansion material of the present invention is not particularly limited, but is usually 2,000 to 6,000 cm ² / g in terms of the specific surface area of brain (hereinafter referred to as “brain value”), more preferably 2,500 to 4,000 cm ² / g. preferable. If it is less than 2,000 cm ² / g, long-term stability may be deteriorated, and if it exceeds 6,000 cm ² / g, expandability may not be sufficiently obtained.

  The blending ratio of the complex salt and the expansion material in the cement admixture according to the present invention is not particularly limited, but usually 5 to 50 parts of the complex salt in 100 parts of the cement admixture composed of the complex salt and the expansion material. Thus, 95 to 50 parts of the expanding material is preferable, 10 to 40 parts of the complex salt, and 90 to 60 parts of the expanding material is more preferable. If the complex salt is less than 5 parts and the swelling material exceeds 95 parts, the fluidity retention effect, hydration heat reduction effect, and rust prevention effect may not be sufficiently obtained. Conversely, the complex salt is 50 parts. If the expansion material is less than 50 parts, crack resistance may not be sufficient.

  The amount of the cement admixture used in the present invention is preferably 1 to 12 parts, more preferably 3 to 9 parts, in 100 parts of a cement composition composed of cement and cement admixture. If it is less than 1 part, the effects of the present invention, that is, the fluidity can be maintained, the hydration calorific value can be reduced, the excellent expansibility can be obtained, and the effective rust prevention effect can be obtained sufficiently. May not be possible, and if it exceeds 12 parts, it may overexpand.

  As the Portland cement used in the present invention, various portland cements such as normal, early strength, very early strength, low heat, and moderate heat, various mixed cements obtained by mixing these portland cements with blast furnace slag, fly ash, or silica, In addition, examples include filler cement mixed with limestone powder and blast furnace slow-cooled slag fine powder, environmentally friendly cement manufactured using various industrial wastes as the main raw material, so-called eco-cement, and so on. More than one species can be used together.

  In the present invention, in addition to the cement admixture and cement of the present invention, limestone fine powder, fly ash, silica fume, metakaolin, diatomaceous earth, blast furnace annealed slag fine powder, sewage sludge incineration ash and its molten slag, municipal waste incineration ash, Additive materials such as molten slag and pulp sludge incineration ash, rapid hardening materials, dampening heat inhibitors such as dextrin, antifoaming agents, thickeners, antifreeze agents, shrinkage reducing agents, steel fibers, vinylon fibers, carbon One or more of fiber and fiber materials such as wollastonite fiber, clay minerals such as polymer and bentonite, and anion exchangers such as hydrotalcite, etc. are substantially inhibited. It is possible to use in the range which does not.

  In the present invention, the mixing method of each material is not particularly limited, and each material may be mixed at the time of construction, or a part or all of them may be mixed in advance.

  Any existing apparatus can be used as the mixing apparatus, and for example, a tilting cylinder mixer, an omni mixer, a Henschel mixer, a V-type mixer, and a Nauta mixer can be used.

  By using the cement admixture of the present invention, the fluidity can be maintained, the hydration calorific value can be reduced, the excellent expansibility can be obtained, and the effective antirust effect can be obtained.

A cement admixture was prepared by blending the complex salt a and the expanding material shown in Table 1 and used to be 9 parts in 100 parts of a cement composition composed of cement and a cement admixture.
Unit cement composition amount 315 kg / m ^3, unit water ^{180kg / m 3, s / a41} %, air amount 4.5 ± 1.5%, and the concrete slump 18 ± 2.5 cm was prepared.
The time-dependent change of the slump of the prepared concrete, the adiabatic temperature rise, and the length change rate were measured, an accelerated corrosion test was performed, and the rusting state of the reinforcing bars was observed. The results are also shown in Table 1.

<Materials used>
Cement: Ordinary Portland cement, brain value 3,300cm ² / g
This complex salt A: Reagent primary potassium tungstate and reagent primary trisodium citrate are mixed in equimolar amounts. Synthetic swelling material A: Free lime-anhydrous gypsum-based swelling material, free lime content 50%, anhydrous gypsum 50% content, brain value 3,000cm ² / g
Expansion material B: free lime-auin-anhydrous gypsum-based expansion material, free lime content 50%, auin content 20%, and anhydrous gypsum content 30%, brain value 3,000 cm ² / g
Expansion material C: free lime-C ₂ F-anhydrous gypsum-based expansion material, free lime content 50%, C ₂ F content 20%, and anhydrous gypsum content 30%, brain value 3,000 cm ² / g
Inflation material D: free lime -C ₄ AF- anhydrous gypsum-based inflation material, free lime content 50% C ₄ AF content 20%, and anhydrous gypsum content of 30% Blaine 3,000 cm ² / g
Expansion material E: Free lime-C ₃ S-C ₄ AF system expansion material, free lime content 60%, C ₃ S content 30%, C ₄ AF content 10%, brain value 3,000 cm ² / g
Expansion material F: Free lime-C ₃ S-C ₄ AF-C ₃ A-Anhydrous gypsum-based expansion material, free lime content 55%, C ₃ S content 25%, C ₄ AF content 5%, C ₃ A content 5%, anhydrous gypsum content 10%, brain value 3,000cm ² / g
Water: Tap water fine aggregate: Himekawa, Niigata Prefecture, specific gravity 2.62
Coarse aggregate: Himekawa, Niigata Prefecture, specific gravity 2.64

<Measurement method>
Slump: Measures changes over time according to JIS A 1101. Adiabatic temperature rise amount: 10 liters of concrete with a kneading temperature of 20 ± 2 ° C is placed in a steel container, and the temperature at the center of the concrete is measured with a thermocouple in a completely insulated state . Calculate the heat insulation temperature rise by subtracting the kneading temperature from the maximum reached temperature Length change rate: Measure the expansion rate of 7 days of age according to JIS A 6202 (B) Accelerated corrosion test: Temperature 30 ° C, relative humidity 60 %, CO ₂ concentration was 10%, and accelerated neutralization was performed until the cover thickness was completely neutralized, and the corrosion of the reinforcing bars was observed. X when corrosion is 20% or more in area ratio, △ if corrosion is less than 20% in area ratio, ○ if corrosion is not observed

  The same procedure as in Example 1 was performed except that the complex salt shown in Table 2 and the expanding material B were used. The results are also shown in Table 2.

<Materials used>
This complex salt: synthesized by mixing equimolar amounts of reagent grade 1 potassium molybdate and reagent grade 1 trisodium citrate C: this mixture of equivalent amount of this complex salt and this complex salt Ingredient sodium nitrite

  A cement admixture consisting of 20 parts of this complex salt and 80 parts of expansive substance B was prepared, and the prepared cement admixture was used as shown in Table 3 in 100 parts of cement composition consisting of cement and cement admixture. Was carried out in the same manner as in Example 1. The results are also shown in Table 3.

  By using the cement admixture of the present invention, a cement composition having good fluidity retention, exhibiting excellent expansibility and hydration heat reduction effect, and obtaining long-term rust prevention effect Since it is obtained, it can be widely used for civil engineering and architectural purposes.

Claims (4)

  A cement admixture comprising a complex salt of tungstic acid and citric acid and / or a complex salt of molybdic acid and citric acid and an expansion material.   The expansion material contains free lime and one or more hydraulic compounds selected from the group consisting of Auin, calcium silicate, calcium ferrite, and calcium aluminoferrite. The cement admixture described.   The swelling substance contains free lime, one or more hydraulic compounds selected from the group consisting of auin, calcium silicate, calcium ferrite, and calcium aluminoferrite, and anhydrous gypsum. The cement admixture according to claim 1 or 2.   A cement composition comprising cement and the cement admixture according to claim 1.