JP2002241160A - Cement admixture and cement composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a cement admixture capable of imparting excellent expansion characteristics to concrete even if a mixing rate is low, and to obtain a cement composition. SOLUTION: The cement admixture is obtained by heat treating a CaO raw material, SiO2 raw material and a CaF2 raw material and contains free calcium, calcium fluorosilicate and CaF2, and the cement composition contains cement and this cement admixture.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a cement admixture and a cement composition mainly used in the civil engineering and construction industries.

[0002]

2. Description of the Related Art It is important to reduce the cracks and improve the bending strength of cement and concrete from the viewpoints of reliability, durability, aesthetics, etc. of concrete structures. Further technological development of cement-based expanders is desired. Conventionally, as a cement admixture which gives expandability to cement / concrete, for example, a free lime-auin-anhydrous gypsum-based expanding material (Japanese Patent Publication No. 42-21840) and a free lime-calcium silicate-anhydrous gypsum-based expansion Lumber (JP-B 53-311)
No. 70). On the other hand, in recent years, development of high-fluidity concrete and high-strength concrete has been actively carried out for the purpose of improving the performance of concrete. Here, the concrete is a general term for cement paste, mortar and concrete.

[0003]

However, it has been pointed out that these high-performance concretes do not sufficiently exert the effect of the expanding material. At present, the development of an expandable material having excellent expandability, which can provide a large expandability even with a low mixing ratio of the expandable material, has been awaited.
In addition, recently, the transition from the conventional specification-based design system to a performance-based design system is under consideration, and it is expected that a clear performance specification will be established for durability, which has been neglected a bit. Can be In other words, the effect of cracking on durability is quantified, so reducing cracking is an important issue.However, in order to widely use cement-based intumescent materials that are effective in reducing cracking, the amount used must be reduced. Therefore, it is essential to reduce the economic burden. The present inventors have conducted various studies to solve these problems, and as a result, obtained the knowledge that the problems can be solved by using a specific cement admixture, and completed the present invention. Was.

[0004]

Means for Solving the Problems That is, a CaO raw material,
A substance obtained by heat-treating a SiO ₂ raw material and a CaF ₂ raw material, which is a cement admixture containing free lime, calcium fluorosilicate and CaF _2, and containing cement and the cement admixture. A cement composition.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail.

[0006] The cement admixture of the present invention, CaO raw material, a substance obtained by heat-treating the SiO ₂ raw material and CaF ₂ material, free lime, is one comprising a calcium fluorosilicone silicate and CaF ₂ . For the ratio is not particularly limited, free lime, clinker in 100 parts consisting of calcium fluorosilicone silicate and CaF _2, the free lime is preferably from 30 to 65 parts,
35 to 55 parts is more preferred. Further, the calcium fluorosilicate is preferably 20 to 55 parts, more preferably 30 to 50 parts. Further, CaF ₂ is preferably 5 to 30 parts,
10 to 25 parts is more preferred. If the composition ratio of each compound in the clinker is not in the above range, excellent expansion characteristics may not be obtained. In addition, the part and% which show the mixing ratio used by this invention are a mass unit.

[0007] calcium fluoroalkyl silicate of the present invention is to collectively CaO-SiO ₂ -CaF ₂ compounds, the CaO C, to represent the SiO ₂ and S, C ₁₁ S ₄ C
aF ₂ or C ₃ S ₂ is CaF _2, etc., the present invention hereinafter calcium fluorosilicone silicate, expressed as C ₁₁ S ₄ CaF _2.

When producing the cement admixture of the present invention, C
aO raw material, SiO_TwoRaw materials and CaF_TwoRaw material obtained by heat treatment
Free lime, C₁₁S_FourCaF_TwoAnd C
aF _TwoSynthesize a clinker consisting of
Manufactured. Free lime, C₁₁S_FourCaF_TwoAnd CaF_Twoof
Some or all were synthesized separately and mixed
However, such an effect cannot be obtained as in the present invention. CaO field
Material, SiO_TwoRaw materials and CaF_TwoHeating the mixture of raw materials
Free lime, C₁₁S_FourCaF_TwoAnd CaF_TwoAnd from
Clinker was synthesized and crushed to produce
As a method of confirming whether or not cement
Coarse particles of Japanese material, specifically particles larger than 100 μm
Is analyzed with a microscope or the like to analyze the composition.
Separated lime, C₁₁S_FourCaF_TwoAnd CaF_TwoIs mixed
Can be easily determined by confirming

The heat treatment temperature at the time of producing the cement admixture of the present invention is not particularly limited, since the decomposition temperature of CaF ₂ changes greatly depending on the mixing ratio of the raw material mixture and the content of impurities. However, the range of 1000 to 1350 ° C is preferable, and the range of 1050 to 1300 ° C is more preferable. If the temperature is lower than 1000 ° C., the expansion properties of the obtained cement admixture are not sufficient.
₂ may melt.

[0010] The method of mixing the raw materials is not particularly limited, and an ordinary method can be used. The heat treatment method for producing the expanding material is not particularly limited, and can be performed by using a rotary kiln, an electric furnace, or the like.

Examples of the CaO raw material include limestone and slaked lime. Examples of the SiO ₂ raw material include silica stone, silica sand, and clay. Examples of the CaF ₂ raw material include naturally occurring fluorite and industrial by-products. CaF _{2 and the} like.

[0012] The particle size of the cement admixture of the present invention is not particularly limited.
00 to 6000 cm ² / g is preferable, and 2500 to 40
00 cm ² / g is more preferred. The particle size of the cement admixture is 1500cm less than ² / g, sometimes long-term durability is deteriorated, in some cases 6000 cm ² / g by weight, a sufficient expansion properties are not obtained.

The amount of the cement admixture of the present invention is not particularly limited, but is usually 3 to 11 parts, preferably 5 to 9 parts in 100 parts of a cement composition comprising cement and the cement admixture. Is more preferred. In less than 3 parts,
In some cases, sufficient expansion characteristics cannot be obtained, and when used in excess of 11 parts, overexpansion may occur.

As the cement of the present invention, there are various portland cements such as ordinary cement, high-strength, ultra-high-strength, low heat and moderate heat, various cements obtained by mixing blast furnace slag, fly ash and silica with these cements, and limestone. There is a filler cement mixed with fine powder and the like.

In the present invention, a water reducing agent, a high-performance water reducing agent, AE
Water reducing agent, high-performance AE water reducing agent, superplasticizer, defoamer, thickener, rust inhibitor, anti-freezing agent, shrinkage reducing agent, polymer emulsion and setting accelerator, setting retarder, and cement hardening agent,
It is possible to use one or more of clay minerals such as bentonite and anion exchangers such as hydrotalcite, boric acid and salts thereof within a range that does not substantially inhibit the object of the present invention. .

In the present invention, the method of mixing the respective materials 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. . As the mixing device, any existing device can be used, and examples thereof include a tilting mixer, an omni mixer, a Henschel mixer, a V-type mixer, and a Nauta mixer.

[0017]

The present invention will be described below in detail with reference to examples.

Example 1 A CaO raw material, a SiO ₂ raw material and a CaF ₂ raw material were blended, mixed and pulverized, and then heat-treated at 1200 ° C. for 3 hours using an electric furnace to synthesize clinker having the composition shown in Table 1, and pulverized. Thus, a cement admixture having a brane specific surface area of 3300 ± 200 cm ² / g was produced. The compound was identified by X-ray diffraction, and the ratio was calculated from the composition determined by chemical analysis.

For 100 parts of a cement composition composed of cement and a cement admixture, 7 parts of a cement admixture is used, and a water / cement composition ratio = 50%, a cement composition /
A mortar having a sand ratio of 1/3 was prepared, and the length change rate of a material age of 7 days was measured. For comparison, free lime, C
₁₁ S ₄ CaF ₂ and a mixture of CaF ₂ separately synthesized and mixed (Experiment No. 1-20: cement admixture T) were similarly tested. The results are also shown in Table 1.

<Materials> Cement: Commercial ordinary Portland cement Water: Tap water Sand: Himekawa, Niigata Prefecture, specific gravity 2.62 CaO raw material: Reagent primary calcium carbonate SiO ₂ raw material: Reagent primary silicon dioxide CaF ₂ raw material: Reagent First grade calcium fluoride

<Measurement method> Length change rate: Measured according to JIS A 6202.

[0022]

[Table 1]

Table 1 shows that the mortar using the cement admixture of the present invention has excellent expansion characteristics. In addition, it can be seen that the effect of the present invention cannot be obtained when free lime, C ₁₁ S ₄ CaF ₂ , and CaF ₂ are separately synthesized and mixed.

Except that the cement admixture C of Example 1 was used, the amount of the cement admixture in 100 parts of the cement composition was changed as shown in Table 2, and the compressive strength was measured.
Performed in the same manner as in Example 1. The results are also shown in Table 2.

<Measurement method> Compressive strength: Measured according to JIS R5201.

[0026]

[Table 2]

From Table 2, it can be seen that the mortar to which the cement admixture of the present invention is added has a greater rate of change in length as the amount thereof is increased, and exhibits excellent expansion characteristics.

[0028]

By using the cement admixture of the present invention, it is possible to impart excellent expansion characteristics to concrete even if the mixing ratio is small.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takayuki Higuchi 2209 Aomi, Aomi-cho, Nishikubiki-gun, Niigata Inside the Aomi Plant of Denki Kagaku Kogyo Co., Ltd. Chemical industry Co., Ltd. Aomi factory F term (reference) 4G012 MB08

Claims (2)

[Claims] 1. A cement admixture which is obtained by heat-treating a CaO raw material, a SiO ₂ raw material and a CaF ₂ raw material and which comprises free lime, calcium fluorosilicate and CaF ₂ . 2. A cement composition comprising a cement and the cement admixture according to claim 1.