JP6568291B1 - Cement admixture, expansion material, and cement composition - Google Patents

Abstract

It is possible to impart large expansion to concrete over an initial age (for example, age 2 to 7 days) after placing concrete, to suppress drying shrinkage strain, and to suppress deterioration of long-term strength development. Provide cement admixtures. A cement admixture containing free lime, a hydraulic compound, and anhydrous gypsum and containing SrO as a chemical component. [Selection figure] None

Description

  The present invention relates to a cement admixture, an expansion material, and a cement composition used, for example, in the field of civil engineering and construction.

  Reduction of cracks in cement / concrete is important from the viewpoint of reliability, durability, aesthetics, etc. of concrete structures, and further progress in technology for cement admixtures that have the effect of improving these, that is, cement-based expansion materials. It is desired.

So far, a concrete expansion material (Patent Document 1) having excellent expansion characteristics with a small addition amount, a cement expansion material (Patent Document 2) in which the surface of free lime is coated with calcium carbonate, and the like have been proposed. In recent years, combined use of an expansion material and a shrinkage reducing agent has been proposed (Patent Document 3).
On the other hand, a digestion-resistant calcia clinker composed of a solid solution of calcia and strontium oxide has been proposed (Patent Document 4).

Japanese Patent No. 4244261 JP 54-93020 A JP 2003-12352 A JP-A-57-205363

Conventional expandable materials have the property of expanding up to 7 days of age. However, there is a problem that the drying shrinkage behavior is not much different from the case where the expansion material is not mixed. Moreover, although the combined use of the expansion material and the shrinkage reducing agent is effective in suppressing drying shrinkage, there is a problem that long-term strength development is reduced.
The digestion-resistant calcia clinker described in Patent Document 4 is intended to be used as a basic refractory raw material, and there is no description about using it as an expansion material for the purpose of suppressing cracks in cement and concrete.

  From the above, the present invention imparts large expansion to cement / concrete over the initial age after casting of cement / concrete (for example, 2 to 7 days of age), suppresses drying shrinkage strain, and develops long-term strength. An object of the present invention is to provide a cement admixture, an expansion material, and a cement composition that can suppress the decrease in the amount of the cement.

  As a result of intensive studies in view of the above problems, the present inventors have found that this problem can be solved by a cement admixture containing free lime, a hydraulic compound, and anhydrous gypsum and containing SrO as a chemical component. Completed the invention. That is, the present invention is as follows.

[1] A cement admixture containing free lime, a hydraulic compound, and anhydrous gypsum and containing SrO as a chemical component.
[2] The cement admixture according to [1], wherein the content of SrO is 0.001 to 5.0 parts by mass with respect to 100 parts by mass of the cement admixture.
[3] The cement admixture according to [1] or [2], further comprising ZrO ₂ as a chemical component.
[4] The cement admixture according to [3], wherein the content of ZrO ₂ is 0.0001 to 5.0 parts by mass with respect to 100 parts by mass of the cement admixture.
[5] The cement admixture according to any one of [1] to [4], wherein the specific surface area of branes is 2,000 to 6,000 cm ² / g.
[6] On a volume basis, the content ratio of particles of 10 μm or less is 30 to 60% by volume, and the ratio (A / B) of the content ratio A of 100 μm or less and the content ratio B of particles of 10 μm or less is 1.5. The cement admixture according to any one of [1] to [5], which is ˜4.0.
[7] as the hydraulic _{compound, 3CaO · 3Al 2 O 3 ·} CaSO 4, 3CaO · SiO 2, 2CaO · SiO 2, 4CaO · Al 2 O 3 · Fe 2 O 3, 6CaO · 2Al 2 O 3 · Fe 2 One or two or more types selected from the group consisting of O ₃ , 6CaO · Al ₂ O ₃ · Fe ₂ O ₃ , and 2CaO · Fe ₂ O ₃ are described in any one of [1] to [6] Cement admixture.
[8] An expansion material comprising the cement admixture according to any one of [1] to [7].
[9] A cement composition comprising the cement admixture according to any one of [1] to [7].

  According to the present invention, a large expansion is imparted to cement / concrete over the initial age after casting of cement / concrete (for example, 2 to 7 days of age), drying shrinkage strain is suppressed, and long-term strength development is achieved. It can be aimed at providing a cement admixture, an expansion material and a cement composition capable of suppressing the decrease.

Hereinafter, the cement admixture, the expansion material, and the cement composition according to the embodiment of the present invention will be described.
The parts and% used in this specification are based on mass unless otherwise specified. The term “cement / concrete” as used in the present invention is a general term for cement paste, mortar, and concrete.

[1. Cement admixture and expansion material]
The cement admixture according to the present embodiment contains free lime, a hydraulic compound, and anhydrous gypsum, and contains SrO as a chemical component.

(Free lime)
Free lime is usually called f-CaO (free lime). By including free lime in the cement admixture according to the present embodiment, expansion characteristics are imparted, and as a result, drying shrinkage is suppressed.
The content of free lime is preferably 10 to 95 parts and more preferably 40 to 90 parts with respect to 100 parts of the cement admixture. By containing 10 to 95 parts, the effect of suppressing drying shrinkage can be exhibited without causing deterioration in long-term strength development.
In firing when producing a cement admixture, the crystal particle size of free lime in the cement admixture is increased by increasing the firing temperature or by appropriately adjusting the blending amount and particle size of the input raw material other than the CaO raw material. Can be increased or the content can be increased.

(Hydraulic compound)
The hydraulic compound according to the present embodiment is an ehlmite represented by 3CaO.3Al ₂ O ₃ .CaSO ₄ , 3CaO.SiO ₂ (abbreviated as C ₃ S) or 2CaO · SiO ₂ (abbreviated as C ₂ S). Calcium silicate, 4CaO · Al ₂ O ₃ · Fe ₂ O ₃ (abbreviated as C ₄ AF), 6CaO · 2Al ₂ O ₃ · Fe ₂ O ₃ (abbreviated as C ₆ A ₂ F), 6CaO · Al ₂ Calcium aluminoferrite represented by O ₃ · Fe ₂ O ₃ (abbreviated as C ₆ AF), calcium ferrite such as 2CaO · Fe ₂ O ₃ (abbreviated as C ₂ F), etc., one of these or It is preferable that 2 or more types are included. Among _{them, 3CaO · 3Al 2 O 3 ·} CaSO 4, C 4 AF, it is preferred to include one or more of _{C 2} S.

  The content of the hydraulic compound is preferably 2 to 45 parts, more preferably 5 to 30 parts, and even more preferably 7 to 20 parts with respect to 100 parts of the cement admixture. By being 2-45 parts, a high expansion characteristic can be provided.

(Anhydrous gypsum)
The content of anhydrous gypsum is preferably 3 to 50 parts, more preferably 10 to 40 parts, and even more preferably 20 to 30 parts with respect to 100 parts of the cement admixture.
In addition, when there is little content of anhydrous gypsum in a cement admixture, the amount of anhydrous gypsum used as the range which is 3-50 parts with respect to 100 parts of cement admixtures can be added separately.

(SrO)
The cement admixture according to the present embodiment contains SrO as a chemical component. When a certain amount of SrO is solid-dissolved in the cement admixture (or expanding material), drying shrinkage (after 7 days of age) can be reduced. In addition, storage stability can be improved.

  The content of SrO is preferably 0.001 to 5.0 parts by mass, more preferably 0.001 to 0.5 parts by mass with respect to 100 parts by mass of the cement admixture, 0.005 More preferably, it is -0.5 mass part. In particular, when the amount is 0.001 to 0.5 parts by mass, the effect of reducing drying shrinkage becomes better.

(Other ingredients)
The cement admixture according to this embodiment preferably further contains ZrO ₂ as a chemical component. The content of ZrO ₂ is preferably 0.001 to 5.0 parts by mass, more preferably 0.0001 to 0.1 parts by mass with respect to 100 parts by mass of the cement admixture. More preferably, the content is 0003 to 0.05 parts by mass. In particular, the fluidity can be improved by being 0.0001 to 0.1 parts by mass.

The cement admixture according to the present embodiment preferably has a brane specific surface area of 2,000 to 6,000 cm ² / g, and more preferably 2,500 to 5,000. When the specific surface area of the brain is 2,000 to 6,000 cm ² / g, the concrete structure can be prevented from being broken by the long-term expansion, and the expansion performance can be favorably maintained.
In addition, the Blaine specific surface area value in this specification can be calculated | required based on JISR5201 (physical test method of cement).

In addition, from the viewpoint of reducing slump loss, securing the expansion amount with a small amount of addition, and preventing pop-out, the content of particles of 10 μm or less is 30 to 60% by volume, and the content of particles of 100 μm or less. It is preferable that the ratio (A / B) of A and the content ratio B of particles of 10 μm or less is 1.5 to 4.0. The content rate of particles of 10 μm or less is 20 to 60% by volume, and the ratio (A / B) of the content rate A of particles of 100 μm or less and the content rate B of particles of 10 μm or less is 1.8 to 3.0. More preferably.
In the present invention, the particle content is determined by dispersing the cement admixture in ethanol for 1 minute with an ultrasonic wave using a laser diffraction / scattering particle size distribution measuring apparatus, then setting the sample refractive index to 1.770, the dispersion medium. It is calculated based on the particle size distribution measured on a volume basis under the condition of a refractive index of 1.360.
The cement admixture of the present invention is obtained by appropriately mixing and firing CaO raw material, Al ₂ O ₃ raw material, Fe ₂ O ₃ raw material, SiO ₂ raw material, CaSO ₄ raw material, SrO raw material, and ZrO ₂ raw material.

Examples of the CaO raw material include limestone and slaked lime. Examples of the Al ₂ O ₃ raw material include bauxite and aluminum residual ash. Examples of the Fe ₂ O ₃ raw material include copper calami and commercially available iron oxide. Examples of the SiO ₂ raw material include silica stone. However, examples of the CaSO ₄ raw material include dihydrate gypsum, hemihydrate gypsum, and anhydrous gypsum.

The SrO raw material is not particularly limited, and examples thereof include celestite, strontium stone, strontium oxide, and strontium carbonate.
The ZrO ₂ raw material is not particularly limited, and examples thereof include zirconium oxide, zirconium hydroxide, zirconium carbonate, zirconium oxychloride, zirconium sulfate, zirconium acetate, organic acid zirconium and zircon sand.
In addition, when SrO and ZrO ₂ are contained in the CaO raw material, the Al ₂ O ₃ raw material, the SiO ₂ raw material, and the CaSO ₄ raw material, it is not necessary to newly add the SrO raw material or the ZrO ₂ raw material.

These raw materials may contain impurities, but this is not a problem as long as the effects of the present invention are not impaired. Examples of impurities include MgO, TiO ₂ , MnO, P ₂ O ₅ , Na ₂ O, K ₂ O, Li ₂ O, sulfur, fluorine, and chlorine.

The cement admixture can be produced by blending the above raw materials so that a desired mineral composition and SrO have a desired chemical composition, appropriately pulverizing, etc., and firing.
The firing method is not particularly limited, but firing is preferably performed at a temperature of 1,100 to 1,600 ° C. using an electric furnace or kiln, and more preferably 1,200 to 1,500 ° C. If it is less than 1,100 ° C., the expansion performance is not sufficient, and if it exceeds 1,600 ° C., anhydrous gypsum may decompose.
Moreover, when grind | pulverizing, it is preferable to carry out by a well-known method so that a brane specific surface area may be 2,000-6,000 cm < ² > / g.

The content of mineral in the cement admixture produced as described above can be confirmed by a conventional general analysis method. For example, the pulverized sample can be applied to a powder X-ray diffractometer to confirm the produced mineral and analyze the data by the Rietveld method to quantify the mineral. Further, based on the identification result of chemical components and powder X-ray diffraction, the amount of minerals can also be obtained by calculation. In the present embodiment, it is preferable to obtain the mineral amount by calculation based on the identification result of the chemical component and the powder X-ray diffraction.
In addition, content of a chemical component can be calculated | required with a fluorescent X ray.

The cement admixture according to this embodiment preferably contains particles in which free lime, hydraulic compound, anhydrous gypsum, and SrO are present in the same particle. Further, when ZrO ₂ is contained, it is preferable that this is also present in the same particle.
Whether free lime, hydraulic compound, anhydrous gypsum, SrO, and ZrO ₂ are present in the same particle can be confirmed by an electron microscope or the like. Specifically, the cement admixture is embedded with resin, surface treatment is performed with an argon ion beam, the structure of the cross section of the particle is observed, and elemental analysis is performed to perform free lime, hydraulic compound, anhydrous gypsum, and It can be confirmed whether SrO and ZrO ₂ are present in the same particle.

  The cement admixture according to this embodiment as described above is preferably used as, for example, an expansion material. That is, the expansion material according to this embodiment is made of the cement admixture described above. Thereby, a big expansion | swelling can be provided to concrete over the initial age (for example, age 2-7 days) after concrete placement, a drying shrinkage | contraction distortion can be suppressed, and the fall of long-term strength expressability can be suppressed.

[3. Cement composition]
The cement composition according to the present embodiment contains the cement admixture described above. Here, as the cement used in the cement composition, various portland cements such as normal, early strength, super early strength, low heat, and moderate heat, and blast furnace slag, fly ash, or silica were mixed with these portland cements. Portland cements such as various mixed cements, filler cements mixed with limestone powder and blast furnace slow-cooled slag fine powders, and environmentally friendly cements (eco-cements) manufactured from municipal waste incineration ash and sewage sludge incineration ash One or two or more of these can be used. The cement admixture may be an expansion material according to this embodiment.

  In this embodiment, in addition to cement, cement admixture, and fine aggregates such as sand and coarse aggregates such as gravel, early strengthening agent, rapid hardening material, water reducing agent, AE water reducing agent, high performance water reducing agent, high Performance AE water reducing agent, fluidizing agent, antifoaming agent, thickener, rust preventive agent, antifreeze agent, shrinkage reducing agent, condensation reducing agent, hydration heat inhibitor, polymer emulsion, clay mineral such as bentonite, hydrotal One or two of the group consisting of admixtures such as anion exchangers such as slag, slag such as granulated blast furnace granulated slag and blast furnace annealed slag, limestone fine powder, siliceous fine powder, gypsum, calcium silicate More than one species can be used in combination as long as the object of the present invention is not substantially inhibited. In addition, organic materials can be used in combination with fibrous materials such as vinylon fibers, acrylic fibers, and carbon fibers.

  The amount of the cement admixture (or expansion material) used (mixing amount) is not particularly limited because it varies depending on the mixing of concrete, but usually a cement composition containing cement and cement admixture (or expansion material). 3-100 mass parts is preferable in 100 mass parts, and 4-7 mass parts is more preferable. Sufficient expansion | swelling performance is obtained because it is 3 mass parts or more. Moreover, since it is 12 mass parts or less, it does not become an overexpansion and it can prevent that an expansion crack arises in concrete.

"Experiment 1"
After blending and pulverizing CaO raw material, Al ₂ O ₃ raw material, Fe ₂ O ₃ raw material, SiO ₂ raw material, CaSO ₄ raw material, and SrO raw material so as to have the proportions of minerals and chemical components shown in Table 1. A clinker was synthesized by firing at 1,350 ° C., and pulverized to 3,000 cm ² / g in terms of Blaine specific surface area using a ball mill to prepare a cement admixture.
Using this cement admixture, 7 parts by mass of cement admixture is used in 100 parts by mass of cement composition consisting of cement and cement admixture, water / cement composition ratio = 50 mass%, cement composition / sand. A mortar with a ratio = 1/3 (mass ratio) was prepared in a room at 20 ° C., and the length change rate and the compressive strength were measured.
Moreover, about the cement admixture, the ratio (A / B) of the content rate A of the particle | grains of 100 micrometers or less and the content rate B of the particle | grains of 10 micrometers or less was calculated | required.

(Materials used)
CaO raw material: Limestone Al ₂ O ₃ raw material: Bauxite Fe ₂ O ₃ raw material: Iron oxide SiO ₂ raw material: Silica CaSO ₄ raw material: Dihydrate gypsum SrO raw material: Strotian stone ZrO ₂ raw material: Zircon sand sand: JIS standard sand cement: Normal Portland cement, commercial product

(Test method)
Chemical composition: determined from fluorescent X-rays.
Ratio (A / B) of content A of particles of 100 μm or less and content B of particles of 10 μm or less: Laser diffraction / scattering type particle size distribution analyzer LA-920 manufactured by HORIBA was used. The cement admixture was dispersed in ethanol for 1 minute with ultrasound, and the volume-based particle size distribution was measured under the conditions of a sample refractive index of 1.770 and a dispersion medium refractive index of 1.360. From this particle size distribution, the content A of particles of 100 μm or less and the content B of particles of 10 μm or less were determined, and A / B was calculated. Mineral composition: Obtained by calculation based on the chemical composition and the identification result of powder X-ray diffraction.
Compressive strength: 4 × 4 × 16 cm specimens were prepared according to JIS R 5201, and the compressive strengths at 7 days (7d) and 28 days (28d) were measured.

"Experimental example 2"
Experiment No. In Example 1-5, except that the ZrO ₂ raw material was further used or the amount of SrO was adjusted to change the amounts of SrO and ZrO ₂ in the clinker as shown in Table 2 below. A similar experiment was conducted. The results are shown in Table 2.
(Test method)
Flow test: Mortar was kneaded according to JIS R 5201-2015 “Physical test method for cement”, and the 15-point flow value immediately after kneading was measured. The composition of temperature, humidity, and mortar was the same as in the compressive strength test. Standard sand was used in the test.

  The cement admixture of the present invention can impart large expansion and drying shrinkage strain suppression to concrete from the 2nd to 7th days after concrete placement, and there is no decrease in long-term strength development. Can be used widely.

Claims (8)

Free lime, hydraulic compound, and contains anhydrite, seen including a SrO as chemical components,
The SrO content is 0.001 to 5.0 parts by mass with respect to 100 parts by mass of the cement admixture ,
Cement admixture whose content of the said free lime is 10-95 parts with respect to 100 parts of cement admixtures. The cement admixture according to claim 1 , further comprising ZrO ₂ as a chemical component. The cement admixture according to claim 2 , wherein the content of ZrO ₂ is 0.0001 to 5.0 parts by mass with respect to 100 parts by mass of the cement admixture. Blaine specific surface area, a cement admixture according to any one of claims 1 to 3 which is 2,000~6,000cm ² / g. The content ratio of particles of 10 μm or less on a volume basis is 30 to 60% by mass, and the ratio (A / B) of the content ratio A of particles of 100 μm or less and the content ratio B of particles of 10 μm or less is 1.5 to The cement admixture according to any one of claims 1 to 4 , which is 4.0. The water as a hydraulic _{compound, 3CaO · 3Al 2 O 3 ·} CaSO 4, 3CaO · SiO 2, 2CaO · SiO 2, 4CaO · Al 2 O 3 · Fe 2 O 3, 6CaO · 2Al 2 O 3 · Fe 2 O 3, The cement admixture according to any one of claims 1 to 5 , comprising one or more selected from the group consisting of 6CaO · Al ₂ O ₃ · Fe ₂ O ₃ and 2CaO · Fe ₂ O _3. . The expansion material which consists of a cement admixture of any one of Claims 1-6 . A cement composition comprising the cement admixture according to any one of claims 1 to 6 .