JP4918214B2 - Cement admixture and cement composition - Google Patents

Description

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

  Unless otherwise specified, parts and% in the present invention are shown on a mass basis.

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

  On the other hand, a cement admixture that improves the tensile strength of concrete has also been proposed (see Patent Document 5).

Recently, it has been clarified that the fine structure of the aggregate interface, so-called transition zone, is deeply related to the mass transfer of concrete and affects the durability of the concrete structure.
Normally, the transition zone of concrete is rough, which means that water tends to be unevenly distributed at the aggregate interface in composite concrete composed of cement, sand, gravel, water, and other materials. This is because material separation occurs at a microscopic level.
In modifying the transition zone of concrete, it is effective to prevent bleeding that can be said to be an indicator of material separation at a microscopic level.

  Therefore, the present inventor, as a result of various studies to solve the above problems, can prevent bleeding by using a specific cement admixture, even in a thin concrete structure such as a building structure, Further, the present inventors have found that a thick, massive concrete used in the field of civil engineering exhibits an excellent crack reduction effect, and has completed the present invention.

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 JP 2004-143030 A

  The present invention provides a cement admixture and a cement composition that can prevent bleeding and exhibit an excellent crack reduction effect even in a thin concrete structure such as a building structure or a massive concrete used in the civil engineering field.

The present invention comprises a mixed solidified product of alkali metal silicate, carboxylic acid, and water and a free lime-auin-anhydrous gypsum-based expanding material, and the blending ratio of the mixed solidified product and the expanding material is , mixture solidified 20-50 parts, a cement admixture is inflation material 80-50 parts, wherein the alkali metal silicate Ri said cement admixture der lithium silicate, free lime before Symbol inflation material The cement admixture having a content of 40 to 70%, a cement composition comprising cement and the cement admixture, wherein the cement admixture is 7 to 12 in 100 parts of the cement composition. Part of the cement composition.

The mixed solidified product of alkali metal silicate, carboxylic acid , and water (hereinafter referred to as the present solidified product) used in the present invention is a mixture of alkali metal silicate and carboxylic acid in an aqueous solution, and after mixing, It is obtained by dehydrating from an aqueous solution by drying or the like, or solidifying by cooling.

There is no particular limitation alkali metal silicate used in the present invention, typically, sodium silicate, potassium silicate, and lithium silicate, etc. can be mentioned, selecting among them lithium silicate It is preferable from the viewpoint of durability.

In the present invention , alkali metal silicate and carboxylic acid are used in combination from the viewpoint of stability .

  The carboxylic acid is not particularly limited, and specific examples thereof include, for example, citric acid, fumaric acid, malic acid, propionic acid, maleic acid, glycolic acid, gluconic acid, polyacrylic acid, lactic acid, formic acid, And acetic acid and the like. Among these, use of citric acid or fumaric acid is preferable from the viewpoint of stability.

The mixing ratio of alkali metal silicate and carboxylic acid in preparing this solidified product is not uniquely determined by the substance used, but it is mixed so that the pH after mixing is near neutral. There is a need to.

Te present invention smell, using A alkali metal silicate, mosquitoes when using the carboxylic acid, the ratio of the number of alkali metal atoms of the alkali metal silicate in salt, and the number of carboxyl groups in the carboxylic acid, metal / It is preferable to mix | blend so that a carboxyl group ratio may be 1-200, and it is more preferable to mix | blend so that it may become 2-100. If the metal / carboxyl ratio is less than 1, the silicate component is insoluble in water and may not be uniformly mixed. If the ratio exceeds 200, the water solubility of the silicate is too high and the fluidity of the concrete decreases. There is a case.

The amount of water to be mixed with the alkali metal silicate and a carboxylic acid, per 100 parts of the alkali metal silicate and a carboxylic acid, preferably at least 1 part, more preferably at least 10 parts. If it is less than 1 part, mixing may not be sufficient and the performance of the obtained solidified product may not be sufficient.

In the present invention, the alkali metal silicate and the carboxylic acid are mixed in an aqueous solution, and after mixing, the water is removed from the aqueous solution or cooled to produce the solidified product. It is preferable to solidify.
The method for removing moisture is not particularly limited, but it can be left to volatilize the water, or it can be heated to volatilize the water.

The expansion material has an expansion action, and is roughly classified into a gas foam material expansion material and a cement mineral expansion material. Specific examples thereof include, for example, a gas foam material expansion material, aluminum powder, Examples thereof include iron powder, a peroxide material, and a carbon material. Examples of the cement mineral-based expansion material include an ettringite-based expansion material, a lime-based expansion material, a lime-ettringite composite-type expansion material, and a magnesia-based expansion material. In the present invention, from the viewpoint of effective expansion properties can be imparted, Ru with cement mineral inflation material.

Examples of the cement mineral-based expansion material include those containing free lime and free magnesia. From the viewpoint of long-term stability, those containing free lime are used in the present invention .
As what contains free lime, a free lime-anhydrous gypsum-type expansion | swelling substance, a free lime-hydraulic compound-type expansion | swelling substance, a free lime-hydraulic compound-anhydrous gypsum-type expansion | swelling substance, etc. are mentioned, for example. In the present invention, free lime-hydraulic compound-anhydrous gypsum-based expansion material is used because of its good expansion performance. In particular, it is preferable to use an expanded 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 kinds selected from the group consisting of calcium aluminoferrite of ₂ O ₃ · 2Al ₂ O ₃ (C ₆ AF ₂ ) can be mentioned.In the present invention, Auin is used as the hydraulic compound, A free lime-auin-anhydrous gypsum-based expansion material (hereinafter simply referred to as expansion material) is used.

Although the particle size of the expanded material is not particularly limited, usually, the Blaine specific surface area value (hereinafter, referred to as Blaine value) is preferably 2,000~6,000cm ² / g in, 2,500~4,000cm ² / g is more 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 present solidified product and the expanding material in the cement admixture in the present invention is 20 to 50 parts of the present solidified product in 100 parts of the cement admixture composed of the present solidified product and the expanding material, and the expanded material 80 to 50 When this solidified material be part expansion material is less than 5 parts exceeds 95 parts, may not be obtained sufficiently effect of preventing bleeding, massive sufficiently obtained crack resistance of concrete, such as civil engineering structures It may not be possible. On the contrary, if the solidified product exceeds 50 parts and the expanded material is less than 50 parts, crack resistance in a thin concrete structure such as a building structure may not be sufficiently obtained.

  Although the usage-amount of a cement admixture is not specifically limited, Usually, 1-12 parts are preferable in a cement composition which consists of a cement and a cement admixture, and 3-9 parts are more preferable. If it is less than 1 part, the effect of the present invention, that is, bleeding can be prevented, and even in a thin concrete structure such as a building structure, or in a massive concrete used in the civil engineering field, an excellent crack reduction effect is exhibited. In some cases, sufficient performance may not be obtained, and when it exceeds 12 parts, it may over-expand.

  As the 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 blast furnace slag, fly ash, or silica with these portland cements, and , Filler cement mixed with limestone powder, blast furnace slow-cooled slag fine powder, etc., environmentally friendly cement manufactured using various industrial waste as the main raw material, so-called eco-cement, etc., one or two of these The above 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, Its molten slag, and admixture materials such as pulp sludge incineration ash, rapid hardening materials, dextrin and other hydration heat inhibitors, antifoaming agents, thickeners, rust inhibitors, antifreeze agents, shrinkage reducing agents, steel fibers, One or more of fiber materials such as vinylon fiber, carbon fiber, and wollastonite fiber, polymers, clay minerals such as bentonite, and anion exchangers such as hydrotalcite, etc. It is possible to use in the range which does not inhibit substantially.

  In the present invention, the mixing method of each material is not particularly limited, and the respective materials 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, bleeding can be prevented, and an excellent crack reduction effect is exhibited even in a thin concrete structure such as a building structure or a massive concrete used in the civil engineering field.

A cement admixture was prepared by blending the solidified product and the expanding material shown in Table 1.
The prepared cement admixture, a cement composition 100 parts consisting of cement and a cement admixture, and 9 parts of the unit cement amount of composition 315 kg / m ^3, unit water ^{180kg / m 3, s / a41} %, air amount 4.5 ± Concrete with 1.5% and slump 18 ± 2.5 cm was prepared.
In addition to measuring the bleeding rate and length change rate of the prepared concrete, we confirmed the occurrence of cracks when placed in soil. The results are also shown in Table 1.

<Materials used>
Cement: Ordinary Portland cement, brain value 3,300cm ² / g
The present solidified product A: Lithium silicate and fumaric acid were mixed in water so that the pH was 7.0 and dried at 50 ° C. Solidified expanded material A: free lime-anhydrous gypsum-based expanded material, free lime content 50% , Anhydrous gypsum content 50%, brain value 3,000cm ² / g
Expansion material B: Free lime-auin-anhydrous gypsum-based expansion material, free lime content 50%, auin content 20%, 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%, 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 of 20% 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 3,000cm 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>
Bleeding rate: Measured according to JIS A 1123, calculated at 6 hours of age. Rate of change in length: Measured expansion rate at 7 days of age according to JIS A 6202 (B) Cracking status: Vertical 5 m × Concrete with a width of 5 m and a thickness of 10 cm was placed, and the occurrence of cracks was observed after 6 months. X when multiple cracks occur, △ when one crack occurs, ○ when no cracks are observed

  The same operation as in Example 1 was performed except that the solidified product and the expanded material shown in Table 2 were used. The results are also shown in Table 2.

<Materials used>
This solidified product B: Sodium silicate and fumaric acid are mixed in water so that the pH is 7.0, and dried at 50 ° C. This solidified product C: Sodium silicate and citric acid are adjusted so that the pH is 7.0 Solidified product mixed in water and dried at 50 ° C

  The same procedure as in Example 1 was carried out except that the cement admixture in the amount shown in Table 3 consisting of 20 parts of the present solidified product A and 80 parts of the expanded substance B was used. The results are also shown in Table 3.

  Using a cement admixture composed of the present solidified material and an expanded material shown in Table 4, a wall of 2 m in height, 10 m in length and 60 cm in thickness was formed, and its crack reduction effect was confirmed. The results are also shown in Table 4.

<Measurement method>
Crack occurrence status: Observe the crack occurrence status one month after the construction of the wall. X when multiple cracks occur, △ when one crack occurs, ○ when no cracks are observed

  By using the cement admixture of the present invention, bleeding can be prevented, and even in a thin concrete structure such as a building structure or in a massive concrete used in the civil engineering field, it exhibits an excellent crack reduction effect. Can be used extensively for civil engineering and architectural purposes.

Claims (4)

It contains a mixed solidified product of alkali metal silicate, carboxylic acid, and water, and a free lime-auin-anhydrous gypsum-based expanding material, and the mixing ratio of the mixed solidified product and the expanding material is a mixed solidified product. Cement admixture characterized in that it is 20 to 50 parts and expandable substance 80 to 50 parts.   The cement admixture according to claim 1, wherein the alkali metal silicate is lithium silicate. The cement admixture according to claim 1 or 2 , wherein a free lime content of the expansion material is 40 to 70%. And cement, a cement composition comprising the cement admixture according to any one of claims 1 to claim 3, wherein the cement admixture is a cement composition 100 parts, 7 ~ Cement composition characterized by being 12 parts.