JP4607150B2 - 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.

In recent years, in the field of civil engineering and architecture, there has been an increasing demand for improving the durability of concrete structures.
One of the deterioration factors of concrete structures is cracking. Cracks impair the reliability of concrete.
There are various causes of cracks, such as cracks caused by drying shrinkage or self-shrinkage, and temperature cracks peculiar to massive concrete or rich concrete.
The temperature cracks typical of massive concrete and rich concrete are due to hydration exotherm.

As one of the important technologies for suppressing cracks, an expanded material has been attracting attention.
This is because cracks can be reduced by using the expandable material and play a certain role in extending the life of the concrete structure.

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).
However, cracks could not be completely controlled by using only the expansion material.

As a technique for suppressing thermal cracking of massive concrete, so-called mascon, a method of applying a hydration heat inhibitor has been proposed (see Patent Documents 5 to 8).
However, in reality, sufficient performance has not yet been realized, and there is a strong demand for the development of a cement admixture that can effectively suppress temperature cracking in a wide temperature environment from room temperature to high temperature.
In addition, there is a strong demand for the development of cement admixtures that can effectively suppress cracks in thin concrete, such as soil concrete and slab concrete, and also in massive concrete.

On the other hand, humic acid and nitrohumic acid are widely used in the agricultural field such as soil conditioners for the purpose of root activation and maintenance / improvement of geopower.
Nitrohumic acid is obtained, for example, by reacting a pulverized product of young charcoal containing a corrosive substance such as lignite and grass charcoal with nitric acid.
As a soil conditioner, this nitrohumic acid, or magnesium nitrohumate that is reacted with one or more of dolomite, magnesite, magnesia, serpentinite, magnesium silicate, magnesium hydroxide and the like are proposed. (See Patent Document 9).
However, what effect is produced when this is used as a cement admixture is not known at all.

  The nitrohumic acid and magnesium nitrohumate are mainly composed of humic acid, but the effect of the present invention cannot be obtained simply by mixing humic acid or humic acid salt with cement.

Japanese Patent Publication No.42-021840 Japanese Examined Patent Publication No. 53-031170 Japanese Patent Application Laid-Open No. 07-232944 JP 2001-064054 A Japanese Patent Laid-Open No. 06-305799 JP 2002-137951 A JP 2002-241167 A JP 2003-034564 A Japanese Patent Publication No. 40-014122

  The present invention provides a cement admixture and a cement composition used in civil engineering and building applications.

The present invention, humic acid produced from lignite and nitric acid, light magnesia, and a reaction product obtained from siliceous material, Ri Na contain an expansion agent, the chemical components of the reaction product, 45 humic acid 58%, Ku-soluble _{MgO2~13%, SiO 2 4~12%,} Fe 2 O 3 2~9%, Al 2 O 3 2~8%, and 0 to 20% moisture, the expansion material, free lime And a hydraulic compound and / or anhydrous gypsum, and the hydraulic compound is one or more selected from the group consisting of Auin, calcium silicate, calcium aluminoferrite, and calcium ferrite, and 100 parts of cement admixture Among them, a cement admixture which is 1 to 50 parts of a reaction product and 50 to 99 parts of an expanded substance, and the cement admixture whose siliceous substance is sandstone, and the particle size of the reaction product is 600 μm or less a cement admixture, cement and Ri Na contain the cement admixture, in 100 parts of cement composition, cement admixture is a cement composition is 1-12 parts.

  By using the cement admixture of the present invention, an excellent crack suppression effect can be imparted, and the medium to long-term strength development is good, even in thin concrete such as soil concrete and slab concrete. Further, a cement composition capable of remarkably reducing cracks can be obtained even in concrete in which temperature cracks are manifested in massive concrete or prestressed concrete.

Unless otherwise specified, parts and% in the present invention are shown on a mass basis.
The concrete in the present invention is a general term for cement paste, cement mortar, and concrete.

  In the present invention, a cement admixture containing a reaction product obtained from humic acid generated from lignite and nitric acid, light magnesia, and a siliceous material, and an expansion material is used.

Although the present invention uses lignite, young coals such as grass coal, lignite, and peat from which humic acid can be obtained by reaction with nitric acid can also be used.
Further, as nitric acid, one having a concentration of 20 to 50% is usually used.
Light magnesia neutralizes the produced humic acid. In the present invention, dolomite, magnesite, magnesium hydroxide, and the like can also be used.
Examples of siliceous substances include silica and sandstone, but sandstone is usually used.

First, lignite is oxidized and decomposed with nitric acid to produce humic acid, and light magnesia and siliceous substances are added to neutralize it to produce a neutralized product.
The use ratio of lignite and nitric acid is not particularly limited, but usually 40 to 70 parts of nitric acid in terms of anhydrous matter is preferable to 100 parts of lignite in terms of dry matter.
The use ratio of light magnesia and siliceous material is not particularly limited, but when sandstone is used as siliceous material, it is usually 5-30 parts of light magnesia against 100 parts of lignite in terms of dry matter. 10 to 25 parts are preferred.
The neutralized product is granulated and then dried to form a reaction product using water or the like.

  In the present invention, the reaction product obtained from humic acid, light magnesia, and siliceous substance produced from lignite and nitric acid (hereinafter simply referred to as reaction product) is used after adjusting the particle size by classification and grinding treatment, etc. Is possible. Among these, it is preferable to use a fine particle portion of 600 μm or less. Further, it is possible to use a humic acid bitter fertilizer produced in the same manner as it is or after adjusting the particle size by sieving, classification, pulverization or the like.

Chemical components of the reaction product of the present invention is usually humic acid 45-58%, Ku-soluble MgO is 2 to 13% SiO ₂ is 4 to 12% Fe ₂ O ₃ is 2 to 9% Al ₂ O ₃ is 2 to 8% and moisture is 0 to 20%. In addition, water-soluble MgO is 1 to 5% among soluble MgO.
Here, the highly soluble MgO means MgO dissolved in a 2% aqueous citric acid solution, and the water-soluble MgO is included in the soluble MgO.

The reaction product of the present invention is mainly composed of humic acid on the chemical component, but the effect of the present invention cannot be obtained by simply using humic acid or a salt thereof.
This has been found through numerous experiments. The cause is not clear, but it is presumed that a unique composite material is formed by the interaction with light silicic substances such as light magnesia and sandstone added in the process of producing the reaction product.
It is also possible that the solubility of chemical components varies depending on the combination with these silicic substances such as light magnesia and sandstone.

  The MgO component contained in the reaction product contains a mixture that is soluble in water and a component that is sparingly soluble. This is also considered to be one factor that produces the effects of the present invention.

  The particle size of the reaction product is not particularly limited, but it is usually preferable to use a fine particle having a particle size of 600 μm or less. When coarse particles are contained, there is a possibility that a sufficient effect of suppressing heat of hydration may not be obtained, and strength development may be deteriorated.

The expansion material of the present invention is not particularly limited, and is roughly classified into a gas foam material expansion material and a cement mineral expansion material. Specific examples thereof include, for example, aluminum powder, iron powder, a peroxide material, and a carbon material in the case of a gas foam material expansion material. Examples of the cement mineral expansion material include ettringite expansion material, lime expansion material, lime-ettringite composite expansion material, and magnesia expansion material.
In the present invention, it is preferable to use a cement mineral-based expansion material from the viewpoint of imparting effective expansibility.

  Examples of the cement mineral expansion material include expansion materials including free lime such as ettringite expansion material, lime expansion material, and lime-ettringite composite expansion material, and expansion materials including free magnesia such as magnesia expansion material. However, from the viewpoint of long-term stability, an expanded material containing free lime is preferable.

Examples of the expansion material containing free lime include an expansion material including a free lime-anhydrous gypsum system, an expansion material including a free lime-hydraulic compound system, and an expansion including a free lime-hydraulic compound-anhydrogypsum system. Substances and the like.
In the present invention, since the expansion performance is good, it is preferable to use an expansion material containing a free lime-hydraulic compound-anhydrous gypsum system, and in particular, a free lime content exceeding 40% is preferable.

  Here, examples of the hydraulic compound include one or more selected from the group consisting of Auin, calcium ferrite, calcium aluminoferrite, calcium silicate, and calcium aluminate.

As such an expanding material, a commercially available expanding material or a static crushing material can be used.
Commercially available expandable materials and statically crushed materials are sold by various companies, and representative examples thereof include, for example, “Denka CSA” and “Denka Power CSA” manufactured by Denki Kagaku Kogyo Co., Ltd. Examples include “Pacific Gypcal”, “Expan”, “N-EX”, and “Bleister” manufactured by Taiheiyo Materials.

Is not particularly limited particle size of the expansion material of the present invention, usually, the Blaine specific surface area value (hereinafter, referred to as Blaine value) is preferably 2,000~6,000cm ² / g, the about 2,500~4,000cm ² / g Those are more preferred. If it is less than 2,000 cm ² / g, the long-term stability may be deteriorated, and if it exceeds 6,000 cm ² / g, the expandability may not be sufficiently obtained.

  The cement admixture of the present invention contains a reaction product and an expansion material, but when used together with the reaction product, the expansion performance is good due to the synergistic effect compared to the case where the expansion material is used alone. become.

  The ratio of the reaction product and the expansion material in the cement admixture is not particularly limited, but usually 1 to 50 parts of the reaction product is preferable in 100 parts of the cement admixture composed of the reaction product and the expansion material. 5 to 40 parts, more preferably 50 to 99 parts, more preferably 60 to 95 parts. If the blending ratio of the reaction product and the expansion material is not within the above range, the effects of the present invention may not be sufficiently exhibited.

  Although the usage-amount of the cement admixture of this invention is not specifically limited, Usually, 1-12 parts are preferable in 100 parts of cement compositions which consist of a cement and a cement admixture, and 3-9 parts are more preferable. If the amount of the cement admixture used is small, there is a possibility that a sufficient crack-inhibiting effect cannot be obtained, and if it is used excessively, strength development may be deteriorated.

  Here, as the cement, various portland cements such as normal, early strength, super early strength, low heat, and moderate heat, various mixed cements in which blast furnace slag, fly ash, or silica is mixed with these portland cements, these portland cements are used. Examples include filler cement mixed with limestone powder, blast furnace slow-cooled slag fine powder, etc., and environmentally friendly cement (eco-cement) manufactured using municipal waste incineration ash and sewage sludge incineration ash as raw materials. One or more of them can be used.

    The cement admixture and cement composition of the present invention may be mixed at the time of construction, or may be partially or wholly mixed in advance.

  In the present invention, fine aggregates such as sand, coarse aggregates such as gravel, expanded materials, quick hard materials, water reducing agents, AE water reducing agents, high performance water reducing agents, high performance AE water reducing agents, antifoaming agents, Various additives such as sticky agent, rust preventive agent, antifreeze agent, shrinkage reducing agent, polymer emulsion, setting modifier, clay mineral such as bentonite, anion exchanger such as hydrotalcite, etc., ground granulated blast furnace slag , One or more selected from the group consisting of admixed materials such as blast furnace slow-cooled slag fine powder, limestone fine powder, fly ash, and silica fume, etc. are used in a range that does not substantially impair the object of the present invention. It is possible.

  Hereinafter, the present invention will be described in more detail based on experimental examples, but the present invention is not limited thereto.

Experimental example 1
Using a cement admixture containing 25 parts of the reaction product shown in Table 1 and 75 parts of the expansive substance A, the cracking suppression effect of soil concrete and mass concrete was investigated.
7 parts of 100 parts of cement composition consisting of cement α and cement admixture is used as cement admixture, unit cement composition amount 300kg / m ³ , unit water amount 170kg / m ³ , s / a = 47%, slump 18cm Concrete with a design strength of 21 N / mm ² was prepared, and the compressive strength and the rate of change in length were measured.
We also confirmed the occurrence of cracks when using concrete with the same composition and placing it between soils and when creating mass concrete walls. The results are also shown in Table 1.
In addition, it carried out similarly about the case where a commercially available humic acid is used instead of the reaction product for the comparison.

<Materials used>
Cement α: Commercially available ordinary Portland cement, specific gravity 3.15
Expansion material A: free lime-hydraulic compound-anhydrous gypsum-based expansion material, hydraulic compound is Auin, free lime content 50%, Auin content 20%, and anhydrous gypsum content 30%, Blaine value 3,000 cm ² / g, specific gravity 3.15
Fine aggregate: Himekawa, Niigata prefecture, specific gravity 2.62, maximum aggregate size 5mm
Coarse aggregate: Himekawa, Niigata prefecture, specific gravity 2.64, maximum aggregate size 25mm
Water: Tap water Commercially available humic acid: Reagent, Humic acid

<Measurement method>
Compressive strength: Measured length change rate according to JIS A 1108: Measured length change rate at 7 days of age according to JIS A 6202 (B) Crack condition / Soil: Crack occurrence condition of soil concrete, length 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. Not acceptable when 3 or more cracks occurred, acceptable when 2 cracks occurred, good when 1 crack occurred, and excellent when no cracks occurred.
Cracks / Mascon: Cracking condition of mass concrete, formwork is kept up to 7 days of age, and a wall with a thickness of 1m, height of 2.5m, length of 10m is created, and two or more cracks are generated. Or, the number of cracks is one, but it is not possible if the crack width is 0.2mm or more, but the number of cracks is one, but if the crack width is 0.1mm or more and less than 0.2mm, it is possible, the number of cracks is one. In addition, when the crack width was less than 0.05 mm, it was good, and when there was no crack that could be visually observed, it was excellent.

Experimental example 2
The reaction product was used in the same manner as in Experimental Example 1 except that the reaction product used in Experiment No. 1-1 was used and the expanded material shown in Table 2 was used. The results are also shown in Table 2.

<Materials used>
Expansion material B: free lime-anhydrous gypsum-based expansion material, free lime content 50%, anhydrous gypsum content 50%, brain value 3,000 cm ² / g, specific gravity 3.10
Inflation material C: free lime - hydraulic compound - anhydrous gypsum-based, hydraulic compound calcium ferrite (C ₂ F), free lime content 50% C ₂ F content of 20% anhydrous gypsum content of 30% Blaine Value 3,000cm ² / g, specific gravity 3.30
Expansion material D: free lime-hydraulic compound-anhydrous gypsum system, hydraulic compound is calcium aluminoferrite (C ₄ AF), free lime content 50%, C ₄ AF content 20%, anhydrous gypsum content 30%, Brain value 3,000cm ² / g, specific gravity 3.20
Expansion material E: Free lime-hydraulic compound system, free lime content 60%, hydraulic compound is calcium silicate (C ₃ S) and calcium aluminoferrite (C ₄ AF), C ₃ S content 30%, C ₄ AF content 10%, Brain value 3,000cm ² / g, Specific gravity 3.18
Expansion material F: free lime-hydraulic compound-anhydrous gypsum system, hydraulic compounds are calcium silicate (C ₃ S), calcium aluminoferrite (C ₄ AF), calcium aluminate (C ₃ A), 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, specific gravity 3.17

Experimental example 3
Experimental Example 1 except that the maximum particle size shown in Table 3 and the chemical composition used was a cement admixture containing 25 parts of the same reaction product and 75 parts of the expanded material A used in Experiment No. 1-1. The same was done. The results are also shown in Table 3.

Experimental Example 4
The experiment was conducted in the same manner as in Experimental Example 1 except that the cement admixture containing 25 parts of the reaction product and 75 parts of the expanded substance A used in Experiment No. 1-1 was used in the amounts shown in Table 4. The results are also shown in Table 4.

Experimental Example 5
Table 5 shows 7 parts of a cement admixture containing 25 parts of the reaction product and 75 parts of the expansion material A used in Experiment No. 1-1 in 100 parts of a cement composition composed of cement and a cement admixture. The same operation as in Experimental Example 1 was performed except that cement and a cement admixture were used. The results are also shown in Table 5.

<Materials used>
Cement β: Commercial blast furnace cement type B, specific gravity 3.06

  By using the cement admixture of the present invention, an excellent crack suppression effect can be imparted, and the influence on the strength development is small, the medium- to long-term strength development is good, such as soil concrete and slab concrete. Even in a thin concrete, there is an effect that a cement composition capable of remarkably reducing cracks can be obtained even in massive concrete or concrete in which temperature cracks are manifested in prestressed concrete.

Claims (4)

Humic acid produced from lignite and nitric acid, light magnesia, and a reaction product obtained from siliceous material, Ri Na contain an expansion agent, the chemical components of the reaction product, 45-58% by weight humic acid, Ku-soluble MgO2~13 wt%, SiO ₂ 4 to 12 wt%, Fe ₂ O ₃ 2 to 9 wt%, Al ₂ O ₃ 2 to 8 wt%, and 0 to 20 wt% water, the expansion material, Cement admixture containing free lime, hydraulic compound and / or anhydrous gypsum, wherein the hydraulic compound is one or more selected from the group consisting of Auin, calcium silicate, calcium aluminoferrite, and calcium ferrite The cement admixture which is 1-50 mass parts of reaction products and 50-99 mass parts of expansion | swelling substances in 100 mass parts .   The cement admixture according to claim 1, wherein the siliceous substance is sandstone.   The cement admixture according to claim 1 or 2, wherein the particle size of the reaction product is 600 µm or less. Cement, in 100 parts by mass-than, cement compositions containing the cement admixture according to any one of claims 1 to 3, cement cement admixture is 1-12 parts by weight Composition.