JPH02164750A - Special cement composition - Google Patents

Abstract

PURPOSE:To improve the thermal stability and thermal shock resistance of a special cement compsn. by specifying the components such as CaO, SiO2, Al2O3 and F and the fineness of powder and incorporating a prescribed hydraulic component and a prescribed stable mineral. CONSTITUTION:This special cement compsn. has a compsn. consisting of, by weight, 28-62% CaO, 14-48% SiO2, 5-23% Al2O3, 1-11% F and <=20% other components and >=2,000cm<2>/g fineness of powder measured by the Blaine method and contains 11CaO.7Al2O3.CaF2 and/or beta-2CaO.SiO2 as a hydraulic component and one or more among 3CaO.2SiO2.CaF2, 2CaO.Al2O3.SiO2 and CaF2 as stable minerals recognized by a powder X-ray diffraction method.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a special cement composition with excellent thermal stability.

[Prior art] It is well known that steel slag has been effectively used in cement due to its latent hydraulic properties.
A typical example is cement using blast furnace slag.

On the other hand, the use of steelmaking slag is also known, and slag cement with a specific composition has been proposed (Japanese Patent Publication No. 57-342
Publication No. 27).

Furthermore, in Japanese Patent Application Laid-open No. 57-129849,
1 of aO・SiO2 and 3CaO4SiO□・CaFz
A cement is disclosed comprising a blend of steelmaking electric furnace reduction stage slag and gypsum in specific proportions of one or two species and a solid solution of 12CaO.7Al2O3 and CaF2.

There is also a proposal for a cement made by blending gypsum and slaked lime with steelmaking slag (Japanese Patent Publication No. 44536/1983).

Furthermore, Japanese Patent Application Laid-open No. 166739/1983 discloses that steelmaking slag powder containing alkali and boron components in a sunset scene can be used as cement.

[Problem to be solved by the invention] Cement based on steel slag does not pose a practical problem in terms of reproducibility if the slag composition is large and stable, such as blast furnace slag. In the case of furnace steel slag, the slag composition always changes slightly, as well as the cooling rate and atmosphere, so it is very problematic to seek reproducibility when using it for cement.

The above-mentioned Japanese Patent Application Laid-Open No. 63-166739 describes a steel-making slag cement developed by the present inventors, which was developed by the present inventors as a unique cement that has thermal stability, unlike ordinary cement. However, there are large variations and lack of reliability for industrial use.

This is problematic because the slag composition inevitably changes due to the nature of slag, and at the same time, the composition required for heat-resistant cement has not been analyzed.

On the other hand, all of these slag cements have a slower hydraulic reaction than Portland cement, and are often inferior in strength, so there are many problems before they can be put to practical use.

In view of the above problems, the present inventors have elucidated the composition of slag based on numerous experiments from various angles in order to develop a thermally stable cement by complete synthesis separately from slag. As a result, we succeeded in developing a special cement that can be used advantageously industrially.

[Means for Solving the Problems] That is, the special cement composition to be provided as an object of the present invention is a powder mainly composed of pulverized material after melting and cooling, and has the following properties: ■The chemical composition is CaO= 28.0-62.0% by weight, S
1oz = 14.0-48.0% by weight, A 1203
= 5.0 to 23.0% by weight, F = 1.0 to 11.0% by weight, and other components are in the range of 20% by weight or less; ■ Mineral composition determined by powder X-ray diffraction method: 11
CaO4^e20. 'CaFz and/or β-2C
a(hydraulic component of lsiOz and 3CaO4Si02
・CaF2.2CaO・＾12oz ・SiO□ and C
Contains at least one or two or more stable minerals selected from aF; ■ Fineness is at least 200 as measured by Blaine specific surface area measurement.
In the following, the special cement composition of the present invention will be further explained.

The special cement composition according to the present invention is a powder whose main component is a pulverized product after melting and cooling, and has the above three physicochemical properties. may be, for example, steelmaking reduction stage slag, or a synthetic product produced by melting and cooling a mixture of desired raw materials.The latter is more advantageous in terms of quality control, but The former is economically advantageous if it can be obtained in terms of quality.

Therefore, the three properties of the special cement composition according to the present invention depend primarily on the properties of the pulverized material after melting and cooling, which is the main component.

That is, the chemical composition of the pulverized material after melting and cooling is CaO = 40.0 to 65.0% by weight, S io 2 =
10-32.0% by weight, A1.0. =7.0~24.
0% by weight, F = 1.5 to 12% by weight, and other components are in the range of 15% by weight or less, particularly preferably CaO
=42-60% by weight, Sin2 = 10-30% by weight, A
l1zOp=10-22% by weight, F=4-12% by weight
and other components are 20% by weight or less.

In addition, other components include MgO components that may be mixed into the raw material system and melting furnace refractories due to corrosion, or may be intentionally mixed in to protect refractories from corrosion, and other unavoidable components such as Fe2O3 components. Can be mentioned.

Furthermore, in the present invention, one or more components such as boron, phosphorus, vanadium, sodium, potassium, barium, or strontium can be included in the other components in an amount of at most 5% by weight as an oxide. .

When 2CaO・SiO□ exists as a hydraulic mineral, these are mainly necessary to modify the γ type to the metastable β type, and 11CaO・7Al2O
3.When only CaF2 is used as a hydraulic mineral, it is not necessarily a necessary component; however, in most cases, it is preferable to contain appropriate amounts of these components.
Particularly preferred is a boron component, B20. The content is preferably at most 5% by weight, usually in the range of 0.2 to 3% by weight.

However, it is a necessary condition that the chemical composition of the pulverized product after melting and cooling satisfies the following compositional formulas (A), (B), and <C> as a weight ratio: Compositional formulas (A) and (B) is a so-called basicity formula, and the compositional formula (C) defines a kind of standard for the applicable range, and both of them were established through numerous experiments together with the chemical composition.

If a substance outside this range is used as a main component, the hydraulic properties and/or thermal stability will be insufficient, making it impossible to use a special cement composition that simultaneously has hydraulic strength and heat resistance up to around 1000°C. It is not possible to obtain something with good reproducibility.

Next, the pulverized product after melting and cooling is characterized by a crystalline fine powder whose mineral composition determined by powder X-ray diffraction shows a hydraulic mineral and a stable mineral having the above composition.

Therefore, the crystalline characteristics of the special cement composition according to the present invention depend solely on the crystalline fine powder as the main component.

In such a crystalline powder, the content of the hydraulic mineral component is in the range of 10 to 90% by weight, preferably 10 to 75% by weight, although it varies within the range of acceptable chemical composition.

The reason for this is that if the mineral content of any hydraulic component is less than about 10% by weight, practical hydraulic strength cannot be obtained; on the other hand, if it exceeds about 90% by weight, the cement-cured molded product will crack when heated. This is because thermal stability is lost due to phenomena such as (cracks) and distortion (warpage) occurring, as well as an increase in shrinkage rate and deterioration of strength.

In addition, in the above crystalline powder, 11CaO・7^f
The content ratio of the two hydraulic minerals =03.caF2 and β-2CaO.SiO is not particularly limited.

In addition, in the case of crystalline powder containing few hydraulic minerals, especially when 11CaO4^120 s ・Ca F 2 is small, gypsum must be converted into So, up to 5% by weight based on the total weight of the special cement composition. It is desirable to add and blend as needed.

The reason for this is that the addition of gypsum produces ettringite, a hydraulic component, and provides hydraulic strength at room temperature. However, increasing the amount of gypsum mixed will lead to dehydration of ettringite, change in volume, and weakening of the structure when the molded body is heated, impairing thermal stability, so as mentioned above, the amount added should be limited to 5% by weight. be.

The gypsum may be anhydrous, hemihydrous, or trihydric gypsum, or intermediates or mixtures thereof, and its production history is not particularly limited, but anhydrous or semiaqueous gypsum is preferably suitable.

Therefore, the limit for other components in the composition is 20% by weight, considering the addition of gypsum.

Next, in the crystalline powder, stable minerals are components that exhibit a crystalline phase that is substantially unrelated to hydraulic reactions, such as 3CaO.2SiOz.CaFz, 2CaO.
Refers to at least one or two or more crystal phases selected from Al2O3・SiO□ and CaF2, especially Ca
F2 is a component that is always included.

Furthermore, if an MgO component is unavoidably included, in addition to the above, 3CaO・MgO・2SiO
z, 5CaO・Mg0・3SiOz, 2CaO・MgO
- Contains one or more types of binary or ternary magnesium-based crystal phases such as 5i02 and MgO ^l, 03.

These stable mineral components impart thermal stability to the special cement composition according to the present invention, and are contained in the crystalline powder in an amount of 10 to 90% by weight as described above.

As described above, the special cement composition according to the present invention contains 3CaO.5i in the crystalline powder after melting and cooling, which is the main component.
This cement is completely different from conventional Portland cement in that it does not contain any Oa, and it also contains free CaO.
One of its characteristics is that no ingredients are recognized.

In addition, in the present invention, the above mineral compositions and their proportions are all identified based on powder X-ray diffraction measurement method, and the proportion of each composition (R%) is determined by the following formula [where Hs is The height of the first peak of each mineral identified (
H represents the height (m) of the first peak of the target mineral, which is expressed in weight%.

Therefore, for example, 10 to 90% by weight of hydraulic minerals means [where Hss is the height of the first peak of each stable mineral (,
), H3 is the first of 11CaO4^12as ・CaFt
Peak height (m-), H2 is β-2CaO・SiO2
represents the height (am) of the first peak of .

Furthermore, the crystalline fine powder after melting and cooling has a Blaine specific surface area in the range of 2000 to 5000 cm2/g, and a special cement composition composed of this as a main component has a Blaine specific surface area of at least 2000 cI12/g. It is within the above range.

The reason for this is that if it is less than about 2000cI12/g, the hydraulic reaction and the pozzolanic reaction with activated silica described later are insufficient and initial strength cannot be obtained, making it impractical. It depends on the convenience of , and the blending amount of activated silica having a large specific surface area as described below.

In the special cement composition according to the present invention, the crystalline powder that is the main component can be prepared by modifying steelmaking slag, for example, but when producing in large quantities as a product with stable quality, it is necessary to prepare the crystalline powder as the main component. It is best to synthesize by blending raw materials.

That is, CaO raw material, Sin raw material, 120. Desired raw materials and F raw materials are blended so that the melt composition falls within the above range, and melted in a heating furnace such as an electric heating, arc or resistance type electric furnace, or a combustion type open hearth furnace.

In this case, the boron component may be mixed in advance or may be added directly to the melt.

Melting is carried out at a temperature of about 1300° C. or higher, and after complete melting, the material is tapped from the furnace and slowly cooled to crystallize, followed by coarse and fine grinding. During this fine pulverization, if necessary, a predetermined amount of gypsum is added and blended to produce a product.

In addition, in the powder after melting and cooling, the components and proportions of the crystal phase mainly depend on the composition of the raw material mixture,
Since it also depends on the cooling conditions, powder with the desired mineral composition can be obtained by adjusting the powder appropriately depending on the purpose of use.

The special cement composition according to the present invention is mainly composed of the above-mentioned crystalline fine powder after melting and cooling, and in particular, activated silica is blended to adjust the basicity.

Activated silica here refers to amorphous fine silica that causes a neutralization reaction of basic components such as CaO in cement in the presence of water and under heating conditions, such as ferrosilicon dust, fumed silica, silica sol, and Examples include activated clay, and ultrafine silica such as ferrosilicon dust and fumed silica are particularly suitable.

Although the amount of active silica blended varies depending on the crystalline fine powder after melting and cooling, the physical properties of the activated silica, the purpose of use of the special cement composition, etc., the special cement composition is used with a chemical composition within the above range, and in many cases, 5 to 35 parts by weight, especially 10 to 30 parts by weight of SiO□ based on the total weight of the composition
Parts by weight are preferred.

The special cement composition according to the present invention is made by blending activated silica into a fine powder that has been melted and cooled and has such specific physicochemical properties as its main component. The fine powder may be prepared in advance, or activated silica may be added at the time of use.

The special cement composition of the present invention differs from commonly used Portland cement in that it exhibits hydraulic properties in water with a low W/C, and has thermal stability and thermal shock resistance up to around 1000°C. are doing.

Therefore, when producing an inorganic molded body of a desired shape or size using this special cement composition as a binder, the aggregate used should be fire-resistant and heat-resistant, especially Those that have undergone a thermal history, such as chamotte, refractory brick scraps, ceramic layers, slowly cooled slags from various metal smelting processes, or igneous rocks are preferred.

[Function] The special cement composition according to the present invention is mainly composed of a pulverized product after melting and cooling having the above-mentioned specific chemical composition, and contains 11CaO, 7Al2O3, CaF2 and/or β- 2 Hydraulic mineral components of CaO/SiO □ and 3
CaO4SiO, ・CaF2.2CaO・Al2O3・
The details of the reaction mechanism are unknown, but the details of the reaction mechanism are unknown, 11CaO・7Al2O3・C
aF 2 generates a calcium aluminate hydrate through a hydraulic reaction at room temperature and imparts initial strength. Also,
Most of β-2CaO.SiO□ exists as an unhydrated crystalline phase, but the hydration reaction gradually progresses to improve long-term strength. Furthermore, when obtaining a fire-resistant and heat-resistant inorganic molded body using this cement composition as a binder, ILCao4Al2O3, -CaF2 is hydraulically hardened by the same hydration reaction as described above, although it also depends on the amount. In the presence of activated silica, calcium aluminate hydrate is heated to 2C
CaO-^12 (:h
In 5if2 minerals, β-2CaO・SiO, is 3C
CaOSiOz C such as aO4SiO, ・CaF2
It changes into an aFt-based mineral, imparting thermal stability.

In this way, the cement composition according to the present invention exhibits a bonding effect for various aggregates as a unique cement composition that simultaneously has hydraulic properties and heat resistance.

[Example] (B203”31.8% by weight, CaO=29.2% by weight
, Sio2=25.7% by weight, Na20=8.3
% by weight) was added to the melt in an amount of 1.5% by weight.

Next, this molten metal was poured into a carbon slugbot lined with refractory bricks and equipped with a heat-insulating lid, and slowly cooled overnight.

Next, these slowly cooled lumps were coarsely crushed using a show crusher, and then further finely crushed using a ball mill to obtain a fine powder after melting and cooling. When the physical properties of this fine powder were measured, the results shown in Tables 1 and 2 were obtained.

After melting various mixtures prepared using quicklime, quartzite, blast furnace slag, fluorite, alumina sand, and industrial chemicals as raw materials in a 100 KVA resistance electric furnace, sand-like borosilicate alkali glass was then obtained. 85% by weight of fine powder and silica flower [manufactured by Japan Heavy Chemical Industry Co., Ltd.]
A special cement composition as shown in Table 3 was obtained by blending 115 parts by weight of S + 02 = 90% by weight.

1 a. Preparation of molded bodies (specimen) Using the special cement composition obtained in each example as a binder, add aggregate chamotte powder (hereinafter referred to as The composition and particle size are shown in Table 5), a water reducing agent and water were kneaded in an ASTM standard mortar mixer with a ball capacity of 51 to give a flow value of about 200 mm.

Strategy --- First - J round - 5th! Then, 150 + * + * X 450 mm X 10IIs
It was poured into a mold, vibration-molded, kept in a constant temperature and humidity chamber at 20°C and 80% RH for 18 hours, and then removed from the mold.
After air-drying for 120 hours in a constant temperature and humidity room at 0°C and 50% RH, each molded body after air-drying was cut with a cutter to give a thickness of 160m+@X40+*mX 10m+* (thickness). Nine specimens were prepared for each sample, and three sets of three specimens were prepared.

b. Curing conditions for specimens 1 Test Two of the three specimens were dried at 150° C. for 5 hours, placed in an electric furnace that had been heated to 850° C., and heated for 10 minutes. After taking out one set of samples, they are allowed to cool naturally and used as specimens for measuring physical properties.

After the other set of samples was taken out, they were immediately put into water at 20°C, immersed for 1 hour, taken out, and air-dried for 7 days to be used as measurement specimens.

The remaining set was air-dried for 6 days without heat treatment and used as a measurement specimen.

Evaluation method for C6 specimen (1) "Bending strength" is measured with a span of 1001, center load, and constant displacement load -0.5+ua/min. The numerical value is the average value of one set of three specimens.

(2) "Shrinkage rate" is the longitudinal dimension of the same specimen (160 mm - x 40 mm x 1011 m thickness) after air-drying and 8
After being rapidly heated to 50°C and left to cool, it was measured using a caliper, and the dimensional change was expressed as a percentage, with the dimension after air-drying being 100.The numerical value is the average value of 3 pieces per set, as in item (1) above. be.

(3) "Warpage" was determined by measuring "bumpy warpage" and "dented warpage" of the heated specimen according to JIS 8-5209r Ceramic Tile, using the plane in contact with the mold as the measuring surface.

It should be noted that the measured values are marked with a (+) sign for "bumpy warpage", and the sign (-) is given for "dented warp".

The numerical values are the average values of one set of three, similar to items (1) and (2) above.

(4) "Cracks" are determined visually using a loupe with a magnification of 16 times.

(5) In the abuse test, changes in the specimen are visually observed after curing under pressure in an autoclave at 180°C for 3 hours.

d. Results of evaluation When the physical properties of each specimen obtained above were measured, the results shown in Tables 6 and 7 were obtained.

As can be seen from the above results, all of the air-dried cured specimens, except for Example 7, had a bending strength of approximately 100 kg/c-2 or more, and all of the specimens after heating and quenching at 850°C had a bending strength of approximately 100 kg/c-2 or more. It exceeds dry curing products.

What's more, even with severe thermal changes from room temperature to 850℃, virtually no cracking is observed, and the shrinkage rate is 0.2%.
The warpage is also extremely small.

Furthermore, even if the test specimen heated to red-hot temperature of 850°C was rapidly cooled, no hair cracks occurred and the bending strength did not change.
There was even a slight tendency for the strength to increase, and when this was air-dried for 7 days, the strength again exceeded that of the heating hole.

A special cement composition was obtained by blending silicon flour in the amount shown in Table 9 to the melted and cooled fine powder prepared in Example 1. Its composition is shown in Table 8.

Test specimens were prepared using this composition in the proportions shown in Table 9 and evaluated.
The results in the table were obtained. Note that the operating conditions for preparing the specimen and the evaluation method were exactly the same as in Example 1.

A fixed amount of gypsum hemihydrate was added to the melted and cooled fine powder prepared in Example 7.

A test specimen was prepared using a mixture of this fine powder in the proportions shown in Table 11, and the test specimen was evaluated.
The results shown in Table 12 were obtained. Note that the operating conditions for preparing the specimen and the evaluation method were exactly the same as in Example 1. Also,
The composition of the special cement composition is shown in Table 13.

[Effects of the Invention] The special cement composition according to the present invention has remarkable thermal stability and thermal shock resistance, unlike conventional Portland cement.

Therefore, an inorganic molded article using this as a binder will not have its bonding properties deteriorated by heat, so its use will expand to fields that require heat resistance and fire resistance.

Patent applicant Nihon Kagaku Kogyo Co., Ltd.

Claims (1)

[Claims] 1. A powder whose main component is a pulverized product after melting and cooling,
The powder has the following properties: [1] Chemical composition is CaO = 28.0 to 62.0% by weight,
SiO_2=14.0-48.0% by weight, Al_2O_
3 = 5.0 to 23.0% by weight, F = 1.0 to 11.0% by weight, and other components are in the range of 20% by weight or less; [2] Mineral composition determined by powder X-ray diffraction method As a hydraulic component of 11CaO・7Al_2O_3・CaF_2 and/or β-2CaO・SiO_2 and 3CaO
・2SiO_2・CaF_2, CaO・Al_2O_3
・At least one selected from SiO_2 and CaF_2
Contains a species or two or more stable minerals; [3] Fineness is at least 2 by Blaine specific surface area measurement
000 cm^2/g or more; A special cement composition characterized by having: 2. The special cement composition according to claim 1, wherein the powder whose main component is the pulverized product after melting and cooling is a mixture of the pulverized product after melting and cooling and activated silica. 3. The special cement composition according to claim 1, wherein the powder whose main component is the pulverized product after melting and cooling is a mixture of the pulverized product after melting and cooling, gypsum, and activated silica. 4. Powder whose main component is the pulverized material after melting and cooling is such that the pulverized material is 65 to 95% by weight and the activated silica is S, based on the total weight.
The special cement composition according to claim 2 or 3, wherein the content of iO_2 is 5 to 35% by weight and the gypsum content is 0 to 5% by weight as SO_3. 5. The special cement composition according to any one of claims 1 to 4, wherein the pulverized product after melting and cooling contains a boron component of 0.1 to 5% by weight as B_2O_3.