Cement admixture and cement composition

Abstract

Provided are a cement admixture and a cement composition that enhance the waterproofness of concrete.　A cement admixture containing: (A) one or more hydraulic compounds selected from the group consisting of ye'elimite, calcium silicate, and calcium aluminoferrite; (B) free lime; (C) anhydrous gypsum; and (D) alumina-silica powder.

Description

[Technical field]

[0001] The present invention relates to a cement admixture and a cement composition that are used mainly in the fields of civil engineering and construction. [Background technology]

[0002] Conventionally, the most common method for promoting the waterproofing of cement concrete has been to use water-reducing agents or high-performance water-reducing agents to minimize the water-cement ratio, as specified in JIS A 6204 "Chemical admixtures for concrete."

[0003] On the other hand, methods for improving waterproofing without reducing the water-to-powder ratio include, for example, an admixture made by mixing a calcium sulfoaluminate compound with fired white clay (see Patent Document 1), a method of mixing a water repellent and a carbonated admixture with cement (see Patent Document 2), coating a filler (aggregate) with a water repellent (see Patent Document 3), and applying a water repellent to the surface of hardened cement concrete (see Patent Document 4).

[0004] However, there is a risk of cracks occurring in cement concrete due to hardening shrinkage, drying shrinkage, and the like, and it has been difficult to impart waterproofing to cement concrete. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2006-219319 A [Patent Document 2] JP 2012-111640 A [Patent Document 3] Japanese Patent Application Publication No. 1-317140 [Patent Document 4] JP 2004-231488 A Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention aims to provide a cement admixture and a cement composition which enhance the waterproofing properties of concrete. [Means for solving the problem]

[0007] The present inventors have found that the above-mentioned problems can be solved by combining a specific hydraulic compound, free lime, anhydrous gypsum, and alumina-silica powder, and have completed the present invention. That is, the present invention is as follows.

[0008] [1] A cement admixture comprising: (A) one or more hydraulic compounds selected from the group consisting of ielimite, calcium silicate, and calcium aluminoferrite; (B) free lime; (C) anhydrous gypsum; and (D) alumina-silica powder. [2] Blaine specific surface area is 4,500 cm 2 / g or more of the cement admixture according to [1]. [3] Chemical composition: CaO 40-65 mass parts, Al 2 O 3 5 to 15 parts by mass of SiO 2 5 to 30 parts by mass, SO 3 The cement admixture according to [1] or [2], wherein the amount is 20 to 30 parts by mass. [4] The cement admixture according to any one of [1] to [3], wherein (A) the hydraulic compound is 15 to 20 mass%, (B) the free lime is 25 to 43 mass%, (C) the anhydrous gypsum is 25 to 35 mass%, and (D) the alumina-silica powder is 17 to 28 mass%. [5] A cement composition comprising the cement admixture according to any one of [1] to [4] and cement. Effect of the Invention

[0009] According to the present invention, it is possible to provide a cement admixture and a cement composition that enhance the waterproofing properties of concrete. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention (the present embodiment) will be described in detail, but the present invention is not limited to this embodiment. In this specification, "parts" and "%" are based on mass unless otherwise specified. In addition, "cement concrete" is a general term for cement paste, mortar, and concrete.

[0011] [Cement admixture] The cement admixture of the present embodiment contains (A) one or more hydraulic compounds selected from the group consisting of ielimite, calcium silicate, and calcium aluminoferrite, (B) free lime, (C) anhydrous gypsum, and (D) alumina-silica powder. By containing the above four types, it is possible to improve the waterproofing properties of concrete, and in particular, it is possible to activate the reaction of cement admixtures and cement compositions containing the cement admixtures at the appropriate time, thereby preventing cracks in cement concrete and imparting waterproofing properties. Each component will be described below.

[0012] (A) Hydraulic compound: The hydraulic compound of this embodiment is one or more selected from the group consisting of eelimite, calcium silicate, and calcium aluminoferrite. These hydraulic compounds produce ettringite, calcium silicate hydrate, calcium aluminosilicate hydrate, and calcium aluminate hydrate through hydration, which fill voids and thereby densify the structure and improve waterproofing.

[0013] (Elimite) Elimite is also called calcium sulfoaluminate or auine, and is composed of 3CaO·3Al 2 O 3 ·CaSO 4 It is a mineral represented by the chemical formula:

[0014] Eelimite is produced by, for example, synthesizing CaO:CaSO using limestone and other lime raw materials, sulfate raw materials such as gypsum, and alumina raw materials such as bauxite. 4 :Al 2 O 3 The materials are mixed in a molar ratio of 3:1:3, fired at about 1500°C in a kiln or similar, and then crushed to produce the product.

[0015] Elimite has a Blaine specific surface area value (JIS R5201, hereafter referred to as the Blaine value) of 2,000 to 4,000 cm 2 / g C1 and 5,000~8,000cm 2 It is preferable to use a mixture of C1 and C2 with C1 / C2 having a mixing ratio of 2 to 5, and more preferably 2.5 to 3.5. When the mixing ratio is 2 or more, a good waterproofing effect can be expected without decreasing the reaction rate. When the mixing ratio is 5 or less, the bleeding water of the cement concrete is reduced, and the waterproofing effect can be expected by reducing the cavities caused by the bleeding water.

[0016] (Calcium Silicate) Calcium silicate is CaO-SiO 2 This is a general term for the system and is not particularly limited, but generally, 2CaO SiO 2 3CaO SiO 2 is well known.

[0017] From the viewpoint of reaction rate, calcium silicate has a Blaine value of 2000 to 4500 cm 2 / g, and 2500 to 4000 cm 2 It is more preferable that the molecular weight is / g.

[0018] (Calcium Aluminoferrite) Calcium aluminoferrite is made of CaO, Al 2 O 3 , Fe 2 O 3 It is a general term for compounds whose main component is 4CaO·Al 2 O 3 Fe2 O 3 (C4AF), 6CaO 2Al 2 O 3 Fe 2 O 3 (C6A2F), 6CaO·Al 2 O 3 2Fe 2 O 3 (C6AF2) and others are known.

[0019] The calcium aluminoferrite of the present embodiment can be produced by, for example, using a raw material containing calcia (CaO raw material) or a raw material containing alumina (Al 2 O 3 raw material), raw material containing ferrite (Fe 2 O 3 It is obtained by mixing the above ingredients and subjecting them to heat treatment such as firing in a kiln or electric furnace.

[0020] From the viewpoint of pot life, calcium aluminoferrite has a Blaine value of 2000 to 7000 cm 2 / g, and 3000 to 6000 cm 2 It is more preferable that the molecular weight is / g.

[0021] Of the above hydraulic compounds, from the viewpoints of the timing of the hydration reaction and imparting expansion properties, it is preferable that the composition contains 50% or more of eelimite, and more preferably 70% or more of eelimite.

[0022] (B) Free lime: Free lime is usually called f-CaO (free lime). By including free lime in the cement admixture according to the present embodiment, it is possible to supply calcium consumed in the reaction of hydraulic substances. In addition, the free lime provides expansion properties, thereby suppressing drying shrinkage.

[0023] The fineness of free lime should be 2000-7000 cm3 in Blaine value from the viewpoint of long-term strength and expansiveness. 2 / g, and 3000 to 6000 cm 2 It is more preferable that the molecular weight is / g.

[0024] (C) Anhydrite: The anhydrite may be of any crystal structure, and the inclusion of anhydrite can improve the overall strength from the initial stage to the long term.

[0025] From the viewpoint of reactivity, the fineness of anhydrous gypsum is 2000 to 5000 cm in Blaine value. 2 / g, and 2500 to 4500 cm 2 It is more preferable that the molecular weight is / g.

[0026] (D) Alumina-silica powder Examples of the alumina-silica powder include fly ash, ground granulated blast furnace slag, metakaolin, silica fume, sewage sludge, volcanic ash, activated clay, and calcined clay.

[0027] The fineness of the alumina silica powder is set to 2500 cm in Blaine value from the viewpoint of filling into the hardened body structure. 2 / g or more, and 2 It is more preferable that the molecular weight is 1 / g or more.

[0028] The specific surface area of ​​the cement admixture is 4,500 cm in Blaine value. 2 / g or more, and 4,500 to 5,500 cm 2 / g is more preferable. 2 / g or more, better waterproofing effect can be expected.

[0029] The chemical composition of the cement admixture is 40-65 parts CaO, 100% Al, and 100% Cr, which is good for waterproofing and strength development. 2 O 3 5 to 15 parts, SiO 2 5-30 copies, SO 3 The content of each chemical component is preferably 20 to 30 parts. The content of each chemical component can be determined by fluorescent X-ray analysis.

[0030] From the viewpoint of a better waterproofing effect, it is preferable that the cement admixture contains (A) 15 to 20 mass% hydraulic compound, (B) 25 to 43 mass% free lime, (C) 25 to 35 mass% anhydrous gypsum, and (D) 17 to 28 mass% alumina-silica powder. These contents are preferably determined by calculation based on the identification results of the chemical components and powder X-ray diffraction.

[0031] The cement admixture of the present embodiment as described above can improve the waterproofing of cement concrete, and is therefore preferably used as a waterproof cement admixture. In addition, since it also exhibits good expansion properties, it is more preferably used as an expanding material or a waterproof expanding material.

[0032] [Cement composition] The cement composition according to this embodiment contains the cement admixture of the present invention and cement. The amount of the cement admixture used is preferably 0.6 to 20 parts, more preferably 1.0 to 10 parts, per 100 parts of cement. When the amount is 0.6 to 20 parts, good waterproofing effect and strength can be obtained.

[0033] Here, the cement is not particularly limited, and ordinary cements can be used. Specific examples include various Portland cements such as normal, early strength, low early strength, low heat, and medium heat, various mixed cements in which Portland cement is mixed with blast furnace slag, fly ash, or silica, filler cements in which limestone powder or ground powder of slowly cooled blast furnace slag is mixed, waste-recycling cement, so-called ecocement, and the like. One or more of these can be used in combination. EXAMPLES

[0034] The present invention will now be described in detail with reference to examples. (Experimental Example 1) A cement admixture (expansive waterproofing agent) was prepared by mixing (A) hydraulic compound, (B) free lime, (C) anhydrous gypsum, and (D) alumina-silica powder in the proportions shown in Table 1. 3.5 parts of this admixture was mixed with 100 parts of cement, and concrete was obtained by kneading the mixture with a slump of 12±2.5cm, air content of 4.5±1.5%, W / C of 60%, and s / a of 48%. The cement is 288 kg / m 3 , fine aggregate is 865kg / m 3 , coarse aggregate is 987 kg / m 3 , 173 kg / m for water 3 It was decided. The water permeability and compressive strength of the concrete were measured. In addition, 10 parts of cement admixture was mixed with 100 parts of cement, and the length change rate of the concrete was measured. The results are shown in Table 1.

[0035] <Materials used> Water: Tap water Cement: Ordinary Portland cement, specific gravity 3.16 (A) Hydraulic compound: Eelimite (crystalline 3CaO 3Al 2 O 3 ·CaSO 4 , Ignition loss 1.0%, Blaine value 5500cm 2 / g) (B) Free lime: Limestone powder was fired at 1300°C in an electric furnace and crushed (Blaine value 4500 cm 2 / g) (C) Anhydrous gypsum: Commercially available (Blaine value 4000 cm 2 / g) (D) Alumina-silica powder: Fly ash (Type II fly ash as specified in JIS A 6201 "Fly ash for concrete", Blaine value 3,500 cm 2 / g) Fine aggregate: Natural sand from Himekawa River, Niigata Prefecture, specific gravity 2.62 Coarse aggregate: Crushed stone from Himekawa, Niigata Prefecture, maximum size 25mm, specific gravity 2.64

[0036] <Evaluation method> Slump: Measured according to JIS A 1101 Air volume: Measured according to JIS A 1128

[0037] Permeability ratio: After pouring the concrete, a cylindrical specimen of φ100mm x 100mm was used, cured in water at 20℃ for 7 days, and a permeability test was conducted. The test method was the output method, and a water pressure of 1.0MPa was applied to the outer surface of the specimen for 500 hours, and the amount of water that oozed out was measured and used as the permeability. The permeability without cement admixture was used as the denominator, and the value obtained by dividing the value was used as the permeability ratio.

[0038] Compressive strength: Measured according to JIS A 1108 at 28 days of age. Length change rate: The length change rate at 7 days was measured according to JIS A 6202. The evaluation was performed when the length change rate was 200×10 ―6 Above is good, 150 x 10 ―6 That's it, 200 x 10 ―6 Less than 150×10 ―6 Less than this is not acceptable.

[0039] [Table 1]

[0040] (Experimental Example 2) The same procedure as in Example 1 was repeated except that concrete was prepared using a cement admixture prepared by mixing (A) hydraulic compound, (B) free lime, (C) anhydrous gypsum, and (D) alumina-silica powder in the ratios shown in Table 2, and various evaluations were carried out. The results are also shown in Table 2.

[0041] [Table 2]

[0042] (Experimental Example 3) The same procedure as in Example 1 was carried out except that the hydraulic compound (A) in Experiment No. 1-6, ie, ie, eirimite, was replaced with calcium silicate (Experiment No. 3-1) and calcium aluminoferrite (Experiment No. 3-2) as cement admixtures, concrete was prepared, and various evaluations were carried out. The results are shown in Table 3.

[0043] [Table 3]

[0044] (Experimental Example 4) The same procedure as in Example 1 was carried out except that the fly ash, which is the alumina-silica powder (D) in Experiment No. 1-6, was replaced with ground granulated blast furnace slag (Experiment No. 4-1), burned white clay (Experiment No. 4-2), and silica fume (Experiment No. 4-3) as cement admixtures, concrete was prepared, and various evaluations were performed. The results are shown in Table 4.

[0045] [Table 4]

[0046] The cement admixture of the present invention can improve the waterproofing of cement concrete and prevent cracks, for example. [Industrial Applicability]

[0047] INDUSTRIAL APPLICABILITY The present invention is effective mainly as a cement admixture and a cement composition that promote the waterproofing of cement concrete used in the fields of civil engineering and construction.

Claims

1. (A) one or more hydraulic compounds selected from the group consisting of eelimite, calcium silicate, and calcium aluminoferrite, (B) free lime, (C) anhydrous gypsum, and (D) alumina-silica powder; (A) a cement admixture comprising 15 to 20 mass% of a hydraulic compound, (B) 25 to 43 mass% of free lime, (C) 25 to 35 mass% of anhydrous gypsum, and (D) 17 to 28 mass% of an alumina-silica powder.

2. Blaine specific surface area is 4,500 cm ２ 2. The cement admixture according to claim 1, wherein the viscosity is 1 / g or more.

3. Chemical components include 40 to 65 parts by mass of CaO, Al ２ O ３ 5 to 15 parts by mass of SiO ２ 5 to 30 parts by mass of SO ３ The cement admixture according to claim 1 or 2, wherein the amount is 20 to 30 parts by mass.

4. A cement composition comprising the cement admixture according to any one of claims 1 to 3 and cement.

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