JPH02164749A - Special cement - Google Patents

Abstract

PURPOSE:To improve the thermal stability and thermal shock resistance of special cement by specifying the components such as CaO, SiO2, Al2O3 and F and the fineness of powder and by incorporating a prescribed hydraulic component and a prescribed stable mineral. CONSTITUTION:This special cement has a compsn. consisting of, by weight, 40-65% CaO, 10-32% SiO2, 7-24% Al2O3, 1.5-12% F and <=15% other components and 2,000-5,000cm<2>/g fineness of powder measured by the Blaine method, satisfies (CaO+MgO+1/3Al2O3)/(SiO2+F+2/3Al2O3)=1.2-2.8, CaO/SiO2=1.5-4.8 and Al2O3/ SiO2=0.25-2.2 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 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).

In addition, 7-2C
1 of aO・5iOz and 3Ca04SiOz・CaF2
Seed or two and IZCao・7^1203 and CaF 2
A cement is disclosed comprising a blend of steelmaking electric furnace reduction stage slag and gypsum in a specific proportion with a solid solution of gypsum.

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

Further, JP-A-63-166739 discloses the use of steelmaking slag powder containing a small amount of alkali and boron components 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 slag, the slag composition always changes slightly, and the cooling rate and atmosphere also vary, so it is very problematic to seek reproducibility when using it for cement.

The above-mentioned Japanese Unexamined Patent Publication No. 166739/1986 is a steelmaking 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.

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 to be provided as an object of the present invention has the following properties: ■Chemical composition is Ca0 = 40.0 to 65.0% by weight, S
i O2 = 10, 0-32, 0% by weight, A&, 0
3 = 7.0 to 24.0% by weight, F = 1.5 to 12.0% by weight, and other components within the range of 15% by weight or less; The chemical composition of ■■ is the following compositional formula ( Weight ratio) (A), (B)
and (C) must be satisfied; ■ Mineral composition determined by powder X-ray diffraction method: 11
Ca04^1z (1+'caF2 and 7 length or β-2C
The main hydraulic components of aO・SiO2 and 3Ca04SiO,
・CaF2.2CaO・^120.・5iOz and Ca
Grinding after melting and cooling, which has at least one or more stable minerals selected from F2; and (2) has a fineness in the range of 2000 to 5000 cm 2 / g by Blaine specific surface area measurement method. Characterized by being a thing.

The special cement of the present invention will be further explained below.

The special cement according to the present invention is a pulverized product after melting and cooling that has the above four physicochemical properties, but as long as it has these properties, even if it is steelmaking reduction stage slag, it can be blended with desired raw materials. Although the latter is more advantageous in terms of quality control, the former is economically advantageous if a predetermined quality can be obtained.

The special cement according to the present invention has the chemical composition as described above, but particularly preferably Ca0 = 42 to 60% by weight, Sio2 = 10 to 30% by weight, Al2O,
= 10 to 22% by weight, F = 4 to 12% by weight, and other components are 15% by weight or less.

Other components include unavoidable components that may be mixed in from corrosion of the raw material system and melting furnace refractories or intentionally mixed in to protect refractories from corrosion, and components that can be added arbitrarily. For example, unavoidable components include MgO component and Fe2O.

Ingredients include.

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

These are mainly necessary for modifying the γ type to the metastable β type when 2CaO・Sin is present as a hydraulic mineral, and 11Ca0・7Δ120
．． - When using only CaFz as a hydraulic mineral, it is not necessarily a necessary component, although in many cases it is preferable to contain appropriate amounts of these components, and the boron component is particularly preferred, with a content of at most 5% by weight as B2O3. It is preferable that the content is usually in the range of 0.2 to 3% by weight.

In addition, the chemical compositions are the above-mentioned compositional formulas (A), (B) and (
6 compositional formulas (A) with the necessary condition of satisfying C)
) and (B) are the so-called basicity formulas, and the composition formula (C)
This defines the permissible range for special cement, and all of them are necessary conditions established through numerous experiments along with the chemical composition.

Outside this range, the hydraulic properties and/or thermal stability will be insufficient, and it will not be possible to reproducibly obtain a special cement that simultaneously has hydraulic strength and heat resistance up to around 1000°C, which is impractical.

Furthermore, it is sufficient that the special cement according to the present invention is a crystal grain powder having a hydraulic mineral as a hydraulic crystalline phase and a stable mineral as a non-hydraulic crystalline phase as shown in (1) above.

Therefore, the crystalline material having the compositions (1) and (2) above can be obtained by cooling the raw material melt described below, and depending on the cooling conditions, it may be a mixed crystalline material including an amorphous material, but preferably only the crystalline material. is better.

In such crystal grain powder, the content of the hydraulic mineral component is within the range of 5 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 hydraulic mineral component is less than about 5% by weight, practical hydraulic strength cannot be obtained, whereas 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 cracking) and distortion (warping), as well as an increase in shrinkage rate and deterioration of strength.

In addition, in the above crystalline particle powder, 11CaO・7^
120. 'C*F2 and β-2CaO-SiO□2
The content ratio of the two hydraulic minerals is not particularly limited.

In addition, in the case of crystal grain powder with a small amount of hydraulic minerals, especially when 11Ca0.7^l, O, .CaFz is small, gypsum may be added as necessary up to 5% by weight based on the total weight in terms of SO5. It is desirable to add and blend, but
If the amount of gypsum added is too large, it will lead to dehydration of ettringite, change in volume, and weakening of the structure during heating of the molded body, impairing thermal stability, so as mentioned above, the amount added is limited to 5% by weight.

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.

Next, in the present invention, stable minerals refer to crystalline phase components that are substantially unrelated to hydraulic reactions, and are 3Ca0
4SiOz・CaFz, 2CaO・^ff120. '
5iOi and CaF.

CaF2 is preferably present.

Furthermore, if an MtrO component is unavoidably included, in addition to the above, 3CaO・Hgo・2Si
O2,5CaO・Mg0・3Si02.2CaO-Mg
One or more types of binary or ternary magnesium-based crystal phases such as O.5iOz and MgO-^1205 are included.

These stable mineral components provide thermal stability to the special cement according to the present invention, and as described above, 1.
It is contained in a range of 0 to 95% by weight.

In this way, this cement is a powder that has been melted and cooled, and no crystalline phase of 3CaO.SiO2 is observed, which is a cement that is completely different from conventional Portland cement, and is one of its characteristics.

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 (+am) of the first peak of the target mineral], which is expressed in weight %.

Therefore, for example, 5 to 90% by weight of hydraulic minerals means [where Hss is the height of the first peak of each stable mineral (am
), H2 is the first of 11CaO・7^N20)・CaFz
Peak height (lIIll), H2 is β-2CaO・5
represents the height (mm) of the first peak of iOz].

Furthermore, the cement according to the present invention has a Blaine specific surface area of 20
00 to 5000cm2/y, the reason for this is that if it is less than about 2000c+i2/g,
This is because the hydraulic reaction is insufficient and initial strength cannot be obtained, making it impractical. On the other hand, the upper limit is set practically for convenience of pulverization.

The special cement according to the present invention can be prepared by modifying steelmaking slag, for example, but if it is to be produced in large quantities with stable quality, it is better to synthesize it by blending desired raw materials. .

That is, the CaO raw material, the 5in2 raw material, the A I 203 raw material, and the F raw material are blended with desired raw materials so that the melt composition falls within the above range, and then melted in a heating furnace. As a heating furnace,
Examples include electric heating, arc or resistance type electric furnaces, and combustion type open hearth furnaces.

Note that components such as boron may be mixed in advance or may be directly added and blended into 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 can be added and blended to produce a product.

Note that although the components and proportions of the crystalline phase in the product mainly depend on the composition of the raw material mixture, they are also affected by the cooling conditions, so they should be adjusted appropriately depending on the purpose of use to obtain cement with the desired mineral composition. Can be done.

When using the special cement according to the present invention, it is of course possible to use it by itself, but in many cases, it can be used in combination with activated silica to better exhibit its characteristic bonding function.

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

In addition, when producing an inorganic molded body of a desired shape or size using this cement as a binder, the aggregate to be used is not particularly limited, but if one is desired to have fire resistance and heat resistance, In particular, materials that have undergone a thermal history, such as chamotte, refractory brick scraps, various ceramic layers, slowly cooled slags or igneous rocks from various metal smelting processes, are preferable.

[Function] The special cement according to the present invention is a pulverized product after melting and cooling having the above-mentioned specific chemical composition, 11Ca04
＾t20. 'CaF2 and/or β-2CaO・Si
Hydraulic mineral components of O2 and 3Ca04SiO2・CaFz
, 2CaO.^1203.5iOz, and CaF2. However, 11CaO・7^e20
3.CaF 2 generates a calcium aluminate hydrate through a hydraulic reaction at room temperature and imparts initial strength. Furthermore, although most of β-2CaO.5iOz exists as an unhydrated crystalline phase, the hydration reaction gradually progresses to improve long-term strength.

Furthermore, if activated silica is added for the purpose of obtaining a fire-resistant and heat-resistant inorganic molded body using this cement as a binder, 11CaO・7＾120°・Ca
F2 is hydraulically hardened by the same hydration reaction as described above.

In the presence of activated silica, calcium aluminate hydrate is heated to form 2CaO.^i'20.・C like SiO2
aO-^1zO* 5102 minerals, β-2CaO
-SiO2 changes into a CaO-5ift-CaFz mineral such as 3CaO.2Si02.CaFz, which imparts thermal stability.

As described above, the cement according to the present invention is a unique cement that has both hydraulic properties and heat resistance, and exhibits the binding effect of various aggregates.

[Example] When the physical properties were measured, the results shown in Tables 1 and 2 were obtained.

After melting various mixtures prepared using quicklime, silica stone, blast furnace slag, fluorite, alumina sand, and industrial chemicals as raw materials in a 100 KVA resistance electric furnace, borosilicate alkali glass powder (8203 = 31.8% by weight) ) was added in an amount of 1.5% by weight based on the melt.

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

Next, these slowly cooled lumps were coarsely crushed using a Joe crusher, and then further finely crushed using a ball mill to obtain special cement. Regarding this special cement, the special cement obtained in each example was used as a binder, and the aggregate chamotte powder (chamotte powder) was added to it in the proportions shown in Table 3.
The composition and particle size are listed in Table 4 below), silica flour [5iOz = 90% by weight, manufactured by Japan Heavy Chemical Industry Co., Ltd.], a water reducing agent, and water were prepared so that the flow value was approximately 2001. ASTM standard ball capacity J151
It was mixed with a mortar mixer.

Next, it was poured into a mold of 160 wo + X 450 + am
, 50% RH constant temperature, air-drying in a constant temperature room for 120 hours. Next, each molded body after air-drying was cut with a cutter to a size of 160m + * x 40mm x 10mm (thickness).
Nine specimens were made for each sample, and three sets of three specimens were made.

Composition and particle size of chamotte, curing conditions for specimens 1 Out of 3 specimens, 2 specimens were dried at 150°C for 5 hours and heated in an electric furnace that had been heated to 850°C in advance. Put it in, 10
Heat for a minute. 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 one set was used as a measurement specimen without being heat-treated.

Evaluation method for C1 specimen (1) "Bending strength" is measured at a span of 100I, center load, and constant displacement load = 0.5 mm/min. Values are for 1 sample 1
This is the average value of three sets of specimens.

(2) “Shrinkage rate” is for the same specimen (16011RIX 4
The longitudinal dimensions (0 mm The numerical values shown are the average values of one set of three, similar to the above-mentioned item (1).

(3) "Warpage" was determined by measuring "curvature" and "curvature" due to heating in accordance with JIS^-5209r Ceramic Tile, using the plane in contact with the mold as the measurement surface for the heated specimen.

In addition, a (+) sign was attached to the measured value for "bumpy curvature", and a (-) sign was attached to the measured value for "dented curvature".

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 5 and 6 were obtained.

As can be seen from the above results, the air-dried cured specimen was the test No.
, except for 10, the bending strength is 70 kgf/c wheel 2
It has the following.

For test Nos. 1.2 and 3 in which activated silica was not added, a decrease in strength was observed due to heating, but it was found that by air-drying for 7 days after being placed in water, the strength recovered to almost the strength before heating. .

In particular, when used in combination with activated silica, the bending strength of all specimens heated to 850° C. exceeded that of the air-drying products, and the strength was further increased by air-drying.

Furthermore, even under severe thermal changes from room temperature to 850° C., virtually no cracking is observed, the shrinkage rate is within 0.2%, and warpage is extremely small.

Each of the special cements of Examples 1 to 7 was manufactured in a 100 KVA resistance electric furnace in the same manner as in Example 1 without adding borosilicate alkali glass.

After getting out of the bath, it was slowly cooled down.

The melts of Comparative Examples 1.2 and 4 completely collapsed when slowly cooled,
The product of Comparative Example 3 was partially collapsed, but the product of Example 8
．． The molten and cooled products of Nos. 9 and 10 did not disintegrate into powder, but solidified as a lump.

Each of these molten and cooled materials was pulverized in the same manner as in Example 1 to prepare special cement.

When the physical properties of this special cement were measured, the results shown in Tables 7 and 8 were obtained.

"Y Review" L Hi-5-1 A set of three test specimens were prepared using the formulations having the proportions shown in Table 9 under the same operating conditions as in Example 1.

After curing this specimen under the same operating conditions as in Example 1,
When the physical properties were evaluated, the results shown in Tables 10 and 11 were obtained.

11-14 The special cement prepared in Example 7 was mixed with predetermined amounts of silica flour and gypsum hemihydrate as a binder.

Test specimens were prepared using a formulation in which this binder was blended in the proportions shown in Table 12 and evaluated, and the results shown in Table 13 were obtained. Note that the operating conditions for preparing the specimen and the evaluation method were exactly the same as in Example 1.

[Effect of the invention] Unlike conventional Portland cement, the special cement of the present invention is an inorganic binder that has both remarkable thermal stability and thermal shock resistance, and these properties are particularly good when used in combination with activated silica. Demonstrated.

Patent applicant Nihon Kagaku Kogyo Co., Ltd.

Claims (1)

[Claims] 1. The following characteristics [1] Chemical composition: CaO = 40.0 to 65.0% by weight,
SiO_2=10.0-32.0% by weight, Al_2O_
3 = 7.0 to 24.0% by weight, F = 1.5 to 12.0% by weight, and other components are within the range of 15% by weight or less; [2] The chemical composition of [1] is as follows. Composition formula (weight ratio) (A)
, (B) and (C); 1.2≦(CaO+MgO+1/3Al_2O_3)/
(SiO_2+F+2/3Al_2O_3)2.8(A
)1.5≦(CaO)/(SiO_2)≦4.8(B)
0.25≦(Al_2O_3)/(SiO_2)≦2.
2(C)[3] Hydraulic components of 11CaO・7Al_2O_3・CaF_2 and/or β-2CaO・SiO_2 and 3 as mineral composition determined by powder X-ray diffraction method
CaO・2SiO_2・CaF_2, 2CaO・Al_
Contains at least one or two or more stable minerals selected from 2O_3・SiO_2 and CaF_2; and [4] Fineness is 2000 to 5 by Blaine specific surface area measurement method.
000 cm^2/g; A special cement consisting of a pulverized product after melting and cooling, characterized by: 2. Other components of the pulverized material after melting and cooling contain boron components.
The special cement according to claim 1, containing up to 5% by weight of _2O_3. 3. The special cement according to claim 1 or 2, which contains gypsum in an amount of at most 5% by weight, calculated as SO_3, based on the pulverized material after melting and cooling.