JPH07206493A - Cement admixture and cement composition - Google Patents

Abstract

PURPOSE:To obtain a cement admixture capable of imparting high expansibility without lowering the strength manifesting property by mixing an expandable material obtained by heat-treating a mixture of CaO material and CaF2 material with anhydrous gypsum. CONSTITUTION:This cement admixture is formed by heat-treating a mixture contg. CaO material and CaF2 material. The admixture consists of a mineral with CaO and CaF2 as the effective components and contains 10-30 pts.wt. of the expandable material and anhydrous gypsum in 100 pts.wt. of CaO plus CaF2. Amorphous calcium aluminate can be further incorporated into the composition. Limestone, slaked lime, etc., are exemplified as the CaO material of expandable material, and naturally occurring fluorite, CaF2 as the industrial by-product are exemplified as the CaF2 material. The calcination is preferably conducted at about 1000-1450 deg.C.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention mainly relates to a cement admixture and a cement composition used in the field of civil engineering and construction.

[0002]

2. Description of the Related Art Cement is a widely used material because it can produce large structures at low cost, but it has the problem of shrinking, and many cements are used to compensate for this shrinkage. Cement admixtures have been proposed (JP-A-53-13650, JP-A-53-31170, etc.).

These cement admixtures impart expandability and are excellent materials for supplementing the shrinkage of cement.

[0004] However, the hardened material using cement has a problem that the strength developing property decreases as it receives a large expansion force without receiving any restraining force. There has been an increasing demand for cement admixtures that can impart great expandability without being treated.

The present inventor has made diligent efforts to solve these problems, and as a result, by using a cement admixture in which a specific expansive substance and anhydrous gypsum are combined,
Furthermore, they have found that the problem can be solved by using an amorphous calcium aluminate together, and have completed the present invention.

[0006]

[Means for Solving the Problems] That is, the present invention provides a CaO source.
Fees and CaF₂Expanded material produced by heat-treating a mixture containing raw materials
Quality, CaO and CaF₂Made from minerals containing
And CaF in the mineral ₂But CaO and CaF₂Total 100 weight
10 to 30 parts by weight of the expansive substance, and anhydrous gypsum
A cement admixture containing, the expanding material,
Anhydrous gypsum and amorphous calcium aluminum
Is a cement admixture containing
A cement composition containing a Japanese material and cement.
It

The present invention will be described in more detail below.

The raw material of the expansive substance according to the present invention can be arbitrarily selected depending on the purity and cost and is not particularly limited. For example, the CaO raw material is CaCO ₃ such as limestone or slaked lime. Quality and Ca (OH) ₂ quality,
Examples of the CaF ₂ raw material include fluorite naturally produced and CaF ₂ as an industrial by-product. Si present in the raw material
The inclusion of impurities such as O ₂ , Fe ₂ O ₃ , CaSO ₄ , MgO, and TiO ₂ is
There is no particular limitation as long as it does not substantially impair the object of the present invention.

The blending ratio of the raw materials in the present invention is such that CaF ₂ is CaO and CaF ₂ as the chemical composition of the expanding substance as a product.
It is necessary to make it 10 to 30 parts by weight, and 15 to 25 parts by weight is preferable. If the amount of CaF ₂ is less than 10 parts by weight, for example, the expansiveness may be rapidly exhibited by the first day of age, and a cement hardened product using the expansive substance may be cracked or the strength development may be deteriorated. CaF ₂
If it exceeds 30 parts by weight, the expandability tends to decrease.

In the present invention, since the decomposition temperature of CaF ₂ largely changes depending on the blending ratio of the mixture of raw materials and the content of impurities, the firing temperature during firing is not particularly limited, but normally the firing temperature is Is preferably about 1,000 to 1,450 ° C.
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 expansive substance is not particularly limited, and may be, for example, a rotary type.
Any method such as firing with a kiln or melting with an electric furnace is possible.

The particle size of the expansive substance is not particularly limited, but a Blaine value of 1,500 to 8,000 cm ² / g is preferable.
If it is less than 1,500 cm ² / g, strength development tends to deteriorate,
If it exceeds 8,000 cm ² / g, the expandability may not be fully exhibited.

The amount of the expansive substance used is 5 in 100 parts by weight of the cement admixture consisting of the expansive substance and anhydrous gypsum described below.
0 to 90 parts by weight is preferable, and 60 to 80 parts by weight is more preferable. If it is less than 50 parts by weight, the expandability may decrease,
If it exceeds the weight part, the strength development effect may not be sufficiently obtained. Further, when using the below-mentioned amorphous calcium aluminate in combination, in the cement admixture 100 parts by weight of an expansive substance, amorphous calcium aluminate, and anhydrous gypsum, preferably 50 to 80 parts by weight, 55 ˜65 parts by weight is more preferred. If it is less than 50 parts by weight, the swelling property may decrease, and if it exceeds 80 parts by weight, the effect of developing strength may not be sufficiently obtained.

The anhydrous gypsum according to the present invention is not particularly limited, and in addition to naturally occurring anhydrous gypsum, it can be produced by heat-treating semi-aqueous gypsum or dihydrate gypsum or as an industrial by-product. Although it is possible to use such substances, it is preferable to use anhydrous gypsum having a high dissolution rate of 300 mg / l · min or more. Here, the dissolution rate of anhydrous gypsum is 50% in 1 liter of water at 20 ° C.
g of anhydrous gypsum was added, the mixture was stirred for 1 minute at 60 rpm, and the sulfate ion in the supernatant was analyzed by ion chromatography to show the value converted into the amount of CaSO ₄ .

The particle size of anhydrous gypsum is not particularly limited, but a Blaine value of 2,500 to 9,000 cm ² / g is preferable. If it is less than 2,500 cm ² / g, long-term durability may be deteriorated, and if it exceeds 9,000 cm ² / g, expandability may not be sufficiently exhibited.

The amount of anhydrous gypsum used is from 10 to 50 in 100 parts by weight of the cement admixture consisting of the expansive substance and anhydrous gypsum.
Weight part is preferable, and 20-40 weight part is more preferable. If it is less than 10 parts by weight, sufficient strength-producing effect may not be obtained, and if it exceeds 50 parts by weight, expandability may be insufficient. When the amorphous calcium aluminate is used in combination, 10 parts by weight of the cement admixture consisting of the expansive substance, the amorphous calcium aluminate, and anhydrous gypsum are used.
-40 parts by weight is preferable, and 20-30 parts by weight is more preferable.
If it is less than 10 parts by weight, sufficient strength-producing effect may not be obtained, and if it exceeds 40 parts by weight, expandability may be insufficient.

Amorphous calcium aluminum according to the present invention
It is preferable that the CaO content is 35 to 45% by weight. If the CaO content is less than 35% by weight, the expandability and strength development may be insufficient, and if it exceeds 45% by weight, the fluidity may decrease and the workability may deteriorate.

Amorphous calcium aluminate is a clinker obtained by melting a CaO raw material and an Al ₂ O ₃ raw material and quenching them.
Obtained by crushing.

The grain size of the amorphous calcium aluminate is not particularly limited, but it has a grain value of 1,500 to 6,0.
00 cm ² / g is preferred. If it is less than 1,500 cm ² / g, sufficient expandability may not be obtained, and if it exceeds 6,000 cm ² / g, workability may deteriorate.

The amount of the amorphous calcium aluminate used is 5 to 2 in 100 parts by weight of the cement admixture consisting of the expansive substance, the amorphous calcium aluminate, and anhydrous gypsum.
5 parts by weight is preferable, and 10 to 20 parts by weight is more preferable. 5
If it is less than part by weight, it may be difficult to obtain the strength development effect,
If the amount exceeds 25 parts by weight, the expandability may be reduced, or the fluidity of a cement kneaded mixture of cement, a cement admixture, water and the like may be reduced, resulting in poor workability.

The particle size of the cement admixture of the present invention depends on the purpose and application for which it is used and is not particularly limited, but it is usually used in a range of 1,500 to 8,000 cm ² / g in terms of brain value. It is preferable. If it is less than 1,500 cm ² / g, the strength development may be adversely affected, and if it exceeds 8,000 cm ² / g, the expandability may not be sufficiently exhibited.

The amount of the cement admixture of the present invention to be used varies depending on the purpose of use, but when the cement admixture comprises an expansive substance and anhydrous gypsum, it is 3 per 100 parts by weight of the cement and the cement admixture in total. -15 parts by weight is preferable, and 5-12 parts by weight is more preferable. If it is less than 3 parts by weight, the expandability is not sufficient, and if it exceeds 15 parts by weight, abnormal expansion may occur. When the cement admixture is composed of expansive substances, amorphous calcium aluminate, and anhydrous gypsum, it is preferably 3 to 20 parts by weight, more preferably 5 to 15 parts by weight. If it is less than 3 parts by weight, the expandability is not sufficient,
If it is used in excess of the weight part, abnormal expansion may occur.

As the cement according to the present invention, various portland cements such as normal, early strength, super early strength, and moderate heat, various mixed cements obtained by mixing these portland cements with pozzolanic substances such as blast furnace slag and silica, and Alumina cement etc. are mentioned. The cement admixture of the present invention is particularly effective when used in combination with mixed cement.

In the present invention, in addition to cement and cement admixture, a setting regulator, a water reducing agent, a high-performance water reducing agent, an AE agent, A
E water reducing agent, high performance AE water reducing agent, thickening agent, aggregate such as sand and gravel, cement rapid hardening material, rust inhibitor, antifreezing agent, polymer emulsion, clay mineral such as bentonite, zeolite, hydrotalcite, And one or more of ion exchangers such as hydrocalumite, inorganic sulfates such as aluminum sulfate and sodium sulfate, inorganic phosphates, and boric acid do not substantially inhibit the object of the present invention. It can be used in combination within a range.

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 some or all of them may be mixed in advance. . As the mixing device, any existing stirring device can be used, for example, a tilting barrel mixer, an omni mixer, a V-type mixer, a Henschel mixer, a Nauta mixer, or the like can be used.

The method for curing the concrete of the present invention is not particularly limited, and any conventional curing method such as normal temperature / normal pressure curing, steam curing, high temperature / high pressure steam curing, and pressure curing is performed. However, the effect of the present invention is more remarkable when steam curing is performed. When performing steam curing, it is more preferable to perform pre-curing for about 3 to 8 hours at room temperature and atmospheric pressure.

[0026]

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

Example 1 Limestone powder was used as a CaO raw material, and fluorspar was used as a CaF ₂ raw material, and the mixture was heated at a maximum firing temperature of 1,300 ° C.
Clinker obtained by firing using a rotary kiln
Was crushed and adjusted to a brain value of 3,000 ± 200 cm ² / g to obtain an expanded material. Unit amount is 500 kg / m ^{3 of} cement and coarse aggregate
960 kg / m ^3, fine aggregates 713kg / m ^3, and concrete formulation of water 200 kg / m ³ - Doo, a cement admixture composed of 70 parts by weight of expanded material are shown in Table 1 and anhydrous gypsum 30 parts by weight of cement And 100 parts by weight of the cement admixture in total, were mixed in an amount of 7 parts by weight to prepare a concrete kneaded product, and a test piece of φ100 mm and L200 mm was prepared. The prepared specimen was heated for 4 hours at a heating rate of 16 ° C./h, steam-cured at 65 ° C. for 5 hours, and then naturally cooled. After that, the compressive strength of each material was measured. Further, the expansion coefficient was measured according to JIS A 6202 B method. After the 1-day age measurement, underwater curing was performed. The results are also shown in Table 1.

<Materials used> CaO raw material: Limestone powder produced by Aoki Mine, Denki Kagaku Kogyo Co., Ltd.
4,230 cm²/ g CaF₂Raw materials: Natural fluorspar powder made by Matsushita Minsan Co., Ltd. Anhydrous gypsum: Natural gypsum, solubility 352mg / l ・ min Cement α: Ordinary Portland semé manufactured by Denki Kagaku Kogyo
Coarse aggregate: Himekawa, Niigata Prefecture, Gmax = 15mm, specific gravity 2.67 Fine aggregate: Himekawa, Niigata prefecture, specific gravity 2.63 Water: Tap water The composition of the expansive substances is CaO and F according to JIS R 5202.
₂Quantify the quantity and then F ₂Amount of CaF₂Converted to.

[0029]

[Table 1]

Example 2 Using 100 parts by weight of the expanding material, 20 parts by weight of CaF ₂ was used to change the compounding amount of the cement admixture with respect to 100 parts by weight of the cement and the cement admixture as shown in Table 2. The same procedure as in Example 1 was carried out except the above. The results are also shown in Table 2.

[0031]

[Table 2]

[0032] The blast furnace cement is used as in Example 3 Cement, amount units, each cement 500 kg / m ^3, coarse aggregate 953kg / m ^3, fine aggregates 708kg / m ^3, and concrete formulation of water 193 kg / m ³ Was performed in the same manner as in Example 1 except that 1 part by weight of the water reducing agent was added to 100 parts by weight of the cement and the cement admixture in total. The results are shown in Table 3.

<Materials used> Cement β: Blast furnace cement type B water reducing agent manufactured by Denki Kagaku Kogyo Co., Ltd .: Denka FT-500G manufactured by Denki Kagaku Kogyo Co., Ltd. Main component naphthalenesulfonic acid formalin condensate

[0034]

[Table 3]

Example 4 A cement admixture 10 was prepared using the expanding material used in Example 2.
Example 3 was repeated except that the amount of anhydrous gypsum in 0 part by weight was changed as shown in Table 4. The results are also shown in Table 4.

[0036]

[Table 4]

Example 5 A cement admixture consisting of 60 parts by weight of the expansive substance shown in Table 5, 15 parts by weight of amorphous calcium aluminate (A-CA), and 25 parts by weight of anhydrous gypsum was used as the cement and the cement admixture. Was carried out in the same manner as in Example 1 except that 10 parts by weight was added to 100 parts by weight in total. The results are also shown in Table 5.

<Materials to be used> A-CAi: A clinker obtained by crushing a clinker obtained by melting a mixture of reagent grade 1 calcium carbonate and aluminum oxide in a molar ratio of 10: 8 at 1,650 ° C. and quenching. Brain value
It was set to 3,410 cm ² / g. CaO content 40%

[0039]

[Table 5]

Example 6 Example 5 was repeated except that the expansive substance used in Example 2 was used and the compounding amount of the cement admixture was changed as shown in Table 6 with respect to 100 parts by weight of the total amount of the cement and the cement admixture. I went the same way. The results are also shown in Table 6.

[0041]

[Table 6]

Example 7 Example 5 except that cement β was used as the cement.
I went the same way. The results are shown in Table 7.

[0043]

[Table 7]

Example 8 A cement admixture 10 was prepared using the expanding substance used in Example 2.
By changing the amount of anhydrous gypsum in 0 parts by weight, the swelling substance and A-
Example 7 was carried out in the same manner as in Example 7, except that the amount of CA was increased / decreased in equal amounts to keep the amount of cement admixture constant. The results are shown in Table 8
Shown in.

[0045]

[Table 8]

Example 9 A cement admixture 10 was prepared using the expanding substance used in Example 2.
Example 7 was carried out in the same manner as in Example 7, except that the type and amount of A-CA in 0 part by weight was changed, and the amounts of the expanding substance and anhydrous gypsum were increased / decreased in equal amounts to make the amount of the cement admixture constant. The results are shown in Table 9.

<Materials used> A-CA: A clinker obtained by melting a mixture of first-grade reagent calcium carbonate and aluminum oxide in a molar ratio of 10:10 at 1,650 ° C. and quenching the resulting clinker. Brain value
It was set to 3,150 cm ² / g. CaO content 35% A-CA Ha: A mixture of calcium carbonate of the reagent first grade and aluminum oxide having a molar ratio of 10: 7 was melted at 1,650 ° C. and rapidly cooled. Value
It was set to 3,090 cm ² / g. CaO content 44%

[0048]

[Table 9]

[0049]

EFFECTS OF THE INVENTION By using the cement admixture of the present invention, in particular, an expansive property is imparted to the mixed cement, and a cement composition exhibiting high strength development is obtained.

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Claims (3)

[Claims] 1. CaO raw material and CaF₂Heat treatment of mixture containing raw materials
CaO and CaF₂Effective
CaF contained in the mineral ₂But CaO
And CaF₂Of 10 to 30 parts by weight in total 100 parts by weight of
A cement admixture containing quality and anhydrous gypsum. 2. CaO raw material and CaF₂Heat treatment of mixture containing raw materials
CaO and CaF₂Effective
CaF contained in the mineral ₂But CaO
And CaF₂Of 10 to 30 parts by weight in total 100 parts by weight of
Quality, amorphous calcium aluminate, anhydrous gypsum
A cement admixture containing and. 3. A cement composition containing cement and the cement admixture according to claim 1 or 2.