WO2021246288A1 - Cement admixture and cement composition - Google Patents

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

Cement admixture and cement composition

The present invention mainly relates to cement admixtures and cement compositions used in the fields of civil engineering and construction.

Conventionally, as a method of promoting the waterproofness of cement concrete, in order to make the water / cement ratio as small as possible, as specified in JIS A 6204 "Chemical admixture for concrete", a water reducing agent or a high-performance water reducing agent Is commonly used.

On the other hand, as a method of improving the waterproof property without reducing the water powder ratio, for example, an admixture made by mixing a calcium sulfoluminate compound and a calcined white clay product (see Patent Document 1) or a water repellent agent. A method of mixing a carbonated admixture with cement (see Patent Document 2), coating a filler (aggregate) with a water-repellent material (see Patent Document 3), and applying a water-repellent agent to the surface of a hardened cement concrete. What is done (see Patent Document 4).

However, cement concrete has a risk of cracking due to hardening shrinkage and drying shrinkage, and it has been difficult to impart waterproofness to cement concrete.

Japanese Unexamined Patent Publication No. 2006-219319 Japanese Unexamined Patent Publication No. 2012-11640 Japanese Unexamined Patent Publication No. 1-317140 Japanese Unexamined Patent Publication No. 2004-231488

An object of the present invention is to provide a cement admixture and a cement composition that enhance the waterproofness of concrete.

The present inventors have found that the problem can be solved by a combination of 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.

[1] One or more hydraulic compounds selected from the group consisting of (A) elimite, calcium silicate, and calcium aluminoferrite, (B) free lime, (C) anhydrous gypsum, and (D). A cement admixture containing alumina silica powder.
[2] The cement admixture according to [1], which has a specific surface area of 4,500 cm and ^{2 / g or more.}
[3] CaO is 40-65 parts by weight as a chemical component, _Al 2 _{O 3} 5 to 15 parts by weight, SiO ₂ of 5 to 30 parts by weight, SO ₃ is 20 to 30 parts by weight [1] or [2 ] The cement admixture described in.
[4] (A) Hydraulic compound is 15 to 20% by mass, (B) Free lime is 25 to 43% by mass, (C) Anhydrous gypsum is 25 to 35% by mass, and (D) Alumina silica powder is 17 to 28% by mass. The cement admixture according to any one of [1] to [3], which is by mass%.
[5] A cement composition comprising the cement admixture according to any one of [1] to [4] and cement.

According to the present invention, it is possible to provide a cement admixture and a cement composition that enhance the waterproofness of concrete.

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

[Cement admixture]
The cement admixture of the present embodiment contains one or more hydraulic compounds selected from the group consisting of (A) elimite, calcium silicate, and calcium aluminoferrite, (B) free lime, and (C) anhydrous. It contains gypsum and (D) alumina silica powder.
By containing the above four types, it is possible to improve the waterproofness of concrete, and in particular, the reaction of the cement admixture and the cement composition containing the cement admixture is activated at an appropriate time to activate the cement concrete. It can prevent cracks and impart waterproofness.
Hereinafter, each component will be described.

(A) Hydraulic compound:
The hydraulic compound of the present embodiment is one or more selected from the group consisting of elimite, calcium silicate, and calcium aluminoferrite.
According to these hydraulic compounds, ettringite, calcium silicate hydrate, calcium aluminosilicate hydrate, and calcium aluminate hydrate produced by hydration fill the voids to densify the structure and make it waterproof. Can be improved.

(Elimite)
Irimaito is also called calcium sulfoaluminate and Auin a mineral represented by the chemical formula _{3CaO · 3Al 2 O 3 · CaSO} 4.

Elimite is made from, for example, a lime raw material such as limestone, a sulfate raw material such as gypsum, and an alumina raw material such as bauxsite, and has _{a molar ratio of CaO: CaSO 4} : Al ₂ O ₃ of 3: 1: 3. It is manufactured by blending in a ratio, firing at about 1500 ° C. using kiln or the like, and crushing.

Irimaito is Blaine specific surface area (JIS R5201, hereinafter referred to as Blaine value) is 2,000 ~ 4,000cm ² / g one C1, mixing a C2 ones 5,000 ~ 8,000cm ² / g It is preferable to use it. The mixing ratio C1 / C2 of C1 and C2 is preferably 2 to 5, more preferably 2.5 to 3.5. When it is 2 or more, a good waterproof effect can be expected without reducing the reaction speed. When it is 5 or less, the bleeding water of the cement concrete is reduced, and the waterproof effect can be expected by reducing the cavities caused by the bleeding water.

(Calcium silicate)
Calcium silicate is a is not particularly limited as to collectively CaO-SiO ₂ system, generally, 2CaO · SiO ₂ or 3CaO · SiO ₂ is well known.

Calcium silicate, from the viewpoint of the reaction rate is preferably 2000 ~ 4500cm ² / g in Blaine value, and more preferably 2500 ~ 4000cm ² / g.

(Calcium aluminoferrite)
Calcium aluminosilicate ferrite intended to generically compound mainly _CaO, the _{Al 2 O 3, Fe 2 O} 3, 4CaO · Al 2 O 3 · Fe 2 O 3 (C4AF), 6CaO · 2Al 2 O 3 · Fe _{2 O 3 (C6A2F), 6CaO} · Al 2 O 3 · 2Fe 2 O 3 (C6AF2) and the like are known.

The calcium aluminoferrite of the present embodiment is, for example, a kiln obtained by mixing a raw material containing calcia (CaO raw material), a raw material containing alumina (Al ₂ O ₃ raw material), a raw material containing ferrite (Fe ₂ O ₃ raw material), and the like. It is obtained by heat treatment such as firing in an electric furnace.

Calcium aluminosilicate ferrite, from the viewpoint of pot life, it is preferable that in the Blaine value is 2000 ~ 7000cm ² / g, and more preferably from 3000 ~ 6000cm ² / g.

Among the above hydraulic compounds, from the viewpoint of timing of hydration reaction and imparting expansion characteristics, it is preferable to contain 50% or more of elimite, and more preferably 70% or more.

(B) Free lime:
Free lime is usually called f-CaO (free lime). By containing free lime in the cement admixture according to the present embodiment, it is possible to supply the calcium content consumed in the reaction of the hydraulic substance. In addition, as a result of the expansion property being imparted by the free lime, drying shrinkage is suppressed.

Fineness of free lime, from the viewpoint of long-term strength and expansion, is preferably 2000 ~ 7000cm ² / g in Blaine value, and more preferably 3000 ~ 6000cm ² / g.

(C) Anhydrous gypsum:
The anhydrous gypsum may have any crystal structure. By containing anhydrous gypsum, the overall strength from the initial stage to the long term can be improved.

Fineness of anhydrite from the viewpoint of reactivity, is preferably 2000 ~ 5000cm ² / g in Blaine value, and more preferably 2500 ~ 4500cm ² / g.

(D) Alumina silica powder Alumina silica powder includes, for example, fly ash, blast furnace slag fine powder, metakaolin, silica fume, sewage sludge, volcanic ash, activated clay, and calcined clay.

Fineness of alumina silica powder from the viewpoint of the filling of the cured body tissue, is preferably 2500 cm ² / g or more in Blaine value, and more preferably 3500 cm ² / g or more.

The specific surface area of the cement admixture ^{is preferably 4,500 cm 2} / g or more in terms of brain value, and more preferably 4,500 to 5,500 cm ² / g. When it is 4,500 cm ² / g or more, a better waterproof effect can be expected.

The chemical composition of the cement admixture is 40 to 65 parts for CaO, 5 to 15 parts for _{Al 2} O ₃ , 5 to 30 parts for _{SiO 2} , and 20 to 30 parts for _{SO 3 from the viewpoint of good waterproof effect and strength development.} Is preferable. The content of the chemical component can be determined by fluorescent X-rays.

Further, from the viewpoint of better waterproof effect, (A) hydraulic compound is 15 to 20% by mass, (B) free lime is 25 to 43% by mass, and (C) anhydrous gypsum is 25 to 35% by mass in the cement admixture. %, The (D) alumina silica powder is preferably 17 to 28% by mass.
These contents are preferably determined by calculation based on the identification results of the chemical composition and the powder X-ray diffraction.

Since the cement admixture of the present embodiment as described above can improve the waterproofness of cement concrete, it is preferable to use it as a cement admixture for waterproofing. Further, since it also exhibits good expandability, it is more preferable to use it as an expansion material or a waterproof expansion material.

[Cement composition]
The cement composition according to the present 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 with respect to 100 parts of cement. When the amount used is 0.6 to 20 parts, a good waterproof effect and strength can be obtained.

Here, the cement is not particularly limited, and ordinary cement can be used. Specifically, various Portland cements such as ordinary, early strong, Zhao early strong, low heat, and moderate heat, these Portland cements. Various mixed cements mixed with blast furnace slag, fly ash, or silica, filler cement mixed with limestone fine powder and blast furnace slow cooling slag fine powder, waste utilization type cement, so-called eco-cement, etc. are mentioned. One or more of these can be used together.

Hereinafter, the present invention will be described in detail with reference to Examples.
(Experimental Example 1)
A cement admixture (waterproof expansion material) was prepared by mixing (A) hydraulic compound, (B) free lime, (C) anhydrous gypsum, and (D) alumina silica powder so as to have the ratio shown in Table 1. .. 3.5 parts of this admixture is blended with 100 parts of cement, and a concrete blend of slump 12 ± 2.5 cm, air volume 4.5 ± 1.5%, W / C 60%, s / a 48% is used. And kneaded to obtain concrete.
Incidentally, the cement 288 kg / ^{m 3,} fine aggregate is 865kg / ^{m 3,} coarse aggregate is 987kg / ^{m 3,} the water was 173 kg / ^{m 3.}
The permeability ratio and compressive strength of the obtained concrete were measured. Further, 10 parts of the cement admixture was mixed with 100 parts of cement, and the length change rate of the concrete produced in the same manner was measured. The results are shown in Table 1.

<Material used>
Water: Tap water cement: Ordinary Portland cement, specific density 3.16
(A) a hydraulic compound: Irimaito (crystalline _{3CaO · 3Al 2 O 3 · CaSO} 4 , and ignition loss 1.0%, Blaine 5500cm ² / g)
(B) Free lime: Limestone powder calcined at 1300 ° C. using an electric furnace and crushed (brain value 4500 cm ² / g).
(C) Anhydrous gypsum: Commercial product (brain value 4000 cm ² / g)
(D) Alumina silica powder: Fly ash (Fly ash type II specified in JIS A 6201 "Fly ash for concrete", brain value 3,500 cm ² / g)
Fine aggregate Natural sand from Himekawa, Niigata Prefecture, specific density 2.62
Coarse aggregate: Crushed stone from Himekawa, Niigata Prefecture, maximum size 25 mm, specific density 2.64

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

Permeability ratio: After concrete was poured, a cylindrical specimen of φ100 mm × 100 mm was used and cured in water at 20 ° C. for 7 days, and a permeability test was performed. The test method was an output method, and a water pressure of 1.0 MPa was applied from the outer surface of the test piece for 500 hours, and the amount of bleeding water was measured and used as the water permeability. The water permeability without the cement admixture was used as the denominator, and the divided value was used as the water permeability ratio.

Compressive strength: Measured at 28 days of age according to JIS A 1108.
Length change rate: The length change rate at 7 days of age was measured according to JIS A 6202. In the evaluation, a length change rate of 200 × ^10-6 or more was good, 150 × ^10-6 or more, ^{less than 200 × 10-6} was acceptable, ^{and less than 150 × 10-6} was not acceptable.

 

(Experimental Example 2)
A cement admixture in which (A) hydraulic compound, (B) free lime, (C) anhydrous gypsum, and (D) alumina silica powder were mixed at the ratios shown in Table 2 was used to prepare concrete, and various evaluations were performed. Was performed in the same manner as in Example 1. The results are also shown in Table 2.

 

(Experimental Example 3)
Experiment No. Elimite, which is the 1-6 (A) hydraulic compound, was changed to calcium silicate (Experiment No. 3-1) and calcium aluminoferrite (Experiment No. 3-2) to form a cement admixture to prepare concrete. However, it was carried out in the same manner as in Example 1 except that various evaluations were made. The results are shown in Table 3.

　
 

(Experimental Example 4)
Experiment No. Fly ash, which is 1-6 (D) alumina silica powder, was mixed with blast furnace slag fine powder (Experiment No. 4-1), white clay calcined product (Experiment No. 4-2), and silica fume (Experiment No. 4-3). ) Was used as a cement admixture, concrete was prepared, and various evaluations were carried out in the same manner as in Example 1. The results are shown in Table 4.

 

The cement admixture of the present invention can improve the waterproofness of cement concrete, for example, and prevent cracks.

INDUSTRIAL APPLICABILITY The present invention is mainly effective as a cement admixture and a cement composition that promotes waterproofness of cement concrete used in the fields of civil engineering and construction.

Claims (5)

1. (A) One or more hydraulic compounds selected from the group consisting of elimite, calcium silicate, and calcium aluminoferrite, (B) free lime, (C) anhydrous gypsum, and (D) alumina silica powder. And, a cement admixture containing.
2. The cement admixture according to claim 1, wherein the brain specific surface area is 4,500 cm ^{2 / g or more.}
3. The cement according to claim 1 or 2, wherein CaO is 40 to 65 parts by mass, Al ₂ O ₃ is 5 to 15 parts by mass, SiO ₂ is 5 to 30 parts by mass, and SO _{3 is 20 to 30 parts by mass as chemical components.} Admixture.
4. (A) Hydraulic compound is 15 to 20% by mass, (B) Free lime is 25 to 43% by mass, (C) Anhydrous gypsum is 25 to 35% by mass, and (D) Alumina silica powder is 17 to 28% by mass. The cement admixture according to any one of claims 1 to 3.
5. A cement composition comprising the cement admixture according to any one of claims 1 to 4 and cement.