JPS6042178B2 - alumina cement - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to alumina cement, and in particular aims to propose a new hydraulic composition with improved fire resistance and resistance to alkalis.

Normal alumina cement is generally 12CaO・7A
12O3 (hereinafter referred to as C).

A), CaO-A1.03 (also CA) and CaO-2A1.

O. The main component is hydraulic calcium aluminate such as (CA0), which has high fire resistance and excellent short-term strength, so it is used for furnace linings, various ceramic products, emergency construction, cold construction, etc. be done. Among them, CA
-CA2-based alumina cement has the advantage of greater fire resistance than those whose main component is CA.

In an attempt to further improve the fire resistance of such alumina cement, α-N.

O. (hereinafter abbreviated as α-A) has been attempted to be mixed with fine powder. O) Na. In applications where it comes into contact with alkali vapors, solutions, or alkaline slag containing O, etc., α-A is attacked by these alkalis and becomes β-A.
Al. O. Since it transfers to (β-A) and causes a decrease in strength, its uses are limited. The inventor has proposed that an advantageous solution to such drawbacks is to add Ca to the alumina cement made of the above-mentioned hydraulic calcium aluminate.
This invention was completed by discovering the excellent effect of the presence of O-6Al2O3 (hereinafter abbreviated as CA6) powder.

However, regarding CA6, it has been used as an aggregate in alumina cement at a high ratio of 1 x 4 or more by weight to the cement, and has been used in part because it contributes to improving the high-temperature performance of refractories. Although it is known, the hydraulic properties of such aggregates are not a particular problem, especially when powdered C.
A.

Therefore, attempts to use it as a cement component have not been considered, and even more so, its contribution to increasing resistance to alkali is something that the inventor himself could not have predicted. , the inventors described above α-A
In order to resolve the inconvenience of increasing fire resistance due to α-A, which is sometimes accompanied by strength deterioration, we have carried out extensive experiments on various substances to find additives to alumina cement that can replace α-A. This is the first time it has been investigated. This invention basically consists of Al2O3/C
It is an alumina cement made of a mixed powder of 10 parts by volume of hydraulic calcium aluminate with an aO molar ratio of less than 3 and 10 to 35 parts by volume of hardly hydraulic calcium aluminate whose main component is CA6, and The Al2O3 content in the total composition of the mixed powder is 55 to 85% by weight, and Ca
O archer. 03/CaO●Al2O3 weight ratio is 0.05~
3 is alumina cement.

In this invention, the hydraulic calcium aluminate is
It consists of one or more of Cl2A7, CA and CA2, and the reason why the Al2O3/CaO molar ratio is limited to less than 3 is that if this value is 3 or more, the hydraulic properties are insufficient for use as the main component of cement. This is because the strength is so low that it is impossible to achieve the strength required for the intended use of the cement. Hydraulic-resistant calcium aluminate mainly composed of CA6 is an essential component of the present invention in accordance with the above-mentioned findings regarding improved resistance to alkali, and in particular, its component ratio is limited to Al2O3/CaO as described above. 1 part by weight of hydraulic calcium aluminate
A range of 0 to 35 parts is suitable for the purpose of the present invention.

As the amount of the compound increases, the resistance to alkali becomes stronger, but when the amount exceeds 35 parts, the hydraulic properties of the cement decrease to the point where it is unsuitable for use. When the amount is less than 1 part by weight, no significant effect on increasing resistance to alkali can be expected. Calcium aluminate is generally made of quicklime,
Calcareous raw materials such as slaked lime and carbonated lime and alumina raw materials such as bauxite, diamond bore or high purity Al2O3 powder are mixed almost stoichiometrically and fired or melted at a high temperature of 1600°C or higher. The high-temperature processing equipment produced, especially for CA6, is preferably a rotary kiln, which presents less difficulty in removing the product.

The processed product obtained from the above raw material composition at a nearly S stoichiometric ratio to the CA6 composition usually has a CA6 content of 8% or more by volume.
It contains a small amount of CA2, but almost no α-A is observed, so it can be used without any problems.

The processed product, ie, the calcium aluminate mainly composed of CA6, and the above-mentioned hydraulic calcium aluminate may be mixed by pulverizing the mixture of the two, or by mixing pre-pulverized mixtures.

In either case, the degree of pulverization is such that as alumina cement, it is necessary to provide good fluidity with a low amount of water, so the fineness of 10 μm or less should be 15% by weight or more, and more preferably 3% by weight or more. It's amazing.

A ball mill, a vibration mill, or the like can be used for pulverization, and an air blender, a mixer with blades, or the like can be used for mixing.

As a result of further experiments on the above-mentioned alumina cement, the inventors further found that the hydraulic composition mainly composed of lucium aluminate minerals, which is composed of CA1CA2 and CA6, as obtained as described above, was particularly developed. It was confirmed that a more significant improvement in fire resistance as well as strength is brought about when the Al2O3 content in the total composition is 55-85% by weight and the C.A2/CA weight ratio is 0.05-3. In other words, the basic components of the alumina cement of this invention are CA.l5CA2, of which CA is mainly used to develop strength, and CA2
mainly contributes to imparting fire resistance, and in order to combine both of these characteristics, the weight ratio of CA2/CA should be adjusted to 0.05 to 3, particularly preferably 0.1, depending on manufacturing considerations. ~1.
It is set to 0.

If the Al2O3 content is less than 55% by weight, the resistance to alkali will be unsatisfactory, while if it exceeds 85% by weight, the strength development may deteriorate.

Furthermore, when the CA2/CA ratio is less than 0.05, even if it is advantageous for developing strength, it is accompanied by a decrease in fire resistance.On the other hand, when the above ratio exceeds the above ratio, the development of strength is not possible at best in terms of fire resistance. It will be enough.

In addition, as mentioned above, the A of alumina cement obtained through the above-mentioned treatment is obtained by mixing the raw materials of hydraulic calcium aluminate such that the CA2/CA ratio is 0.05 to 3.
The 12O3 content is approximately 50 to 75% by weight of S, and under such conditions Cl.

Since almost no A7 is generated, processing efficiency is not hindered and firing becomes easy. The method of mixing the CA-CA2 type hydraulic calcium aluminate obtained in this manner with the non-hydraulic calcium aluminate whose main component is CA6 as described above is the same as described above. As a result, Al in the entire composition. An alumina cement with an O3 content of 55-85% by weight and a CA2/CA ratio of 0.05-3 is obtained. When any of the alumina cements mentioned above is mixed for use, the following retarder is added to the cement in order to suppress the drop in flow value and extend the workable time, that is, the pot life. It is advantageous to pre-contain from 0.01 to 2% by weight.

Retarder, carboxylic acids such as citric acid, tartaric acid, salicylic acid, malic acid, and their salts such as potassium or sodium, NaHCO3, KHCO3, Na2cO
3 and other inorganic carbonates, the former being 1 and the latter being 0.03
Advantageously, mixtures such as a mixture with a weight ratio of 1 to 3 can be used.

Next, embodiments of this invention will be described.

Example 1 85 parts by weight of a hydraulic calcium aluminate having the composition shown in Table 1 and 15 parts by weight of a non-hydraulic calcium aluminate mainly composed of CA6 having the composition shown in Table 2 were blended and ground in a ball mill. A] 203 content is 60
An alumina cement having a particle size of 10 μm or less in 40% by weight was obtained.

This alumina cement was mixed with 4=shimo-shyamotsu as an aggregate at a weight ratio of 1:4, and kneaded at a water-cement ratio of 0.55 to form a 4 x 4 x 16 c1n specimen.

After immersing this in a slag melt containing 1300°C K2O4 weight percent for 10 CHI, the bending strength was measured to be 63.5k9'd, which is significantly higher than 10.7k91d with commercially available alumina cement. It was possible to improve low resistance to alkali. Example 2 7 parts of CA-CA2 type alumina cement clinker having the composition shown in Table 3 and 3 parts of low-hydraulic calcium aluminate mainly composed of CA6 and having the composition shown in Table 4 were blended. , ground and mixed in a ball mill, CA2/CA weight ratio 0.35, Al.

An alumina cement having an O3 content of 73% by weight and a grain size of 10 PWL or less and a heel weight of 3% was obtained. In this alumina cement,
4wn fused alumina was mixed as an aggregate at a weight ratio of 1:4, kneaded at a water-cement ratio of 0.57, molded into a specimen, and cured at 20°C for 2 hours to obtain JIS-K- 221
Hot bending strength was measured according to 3.

The results are shown in Table 5. A comparative example is a commercially available refractory alumina cement. Next, aggregate consisting of four gourds was mixed with this alumina cement at a weight ratio of 1:4, and kneaded at a water-cement ratio of 0.57.
A test piece of ×1 size was molded.

After this was immersed in a slag melt containing % K2O3 nominal amount for 5C@, the bending strength was measured, and the bending strength was 53.9kIcF1f for the alumina cement of the present invention and 9.1kgIcF1f for the commercially available alumina cement.
Example 3 The blending ratio of alumina cement clinker and CA6 was changed to 6th.
Hot bending strength and resistance to alkali were measured for test specimens obtained in the same manner as in Example 2, except for the changes shown in the table.

The results are shown in Table 6. Regarding the composition of alumina cement clinker 70 and CA63O, the results of Example 2 were again listed for comparison.

Example 4 Next, 5 parts of C-Cl2A7-based alumina cement clinker having the composition shown in Table 7 and 5 parts of CA6-based calcium aluminate having the composition shown in Table 8 were mixed, and the mixture was heated in a ball mill. Grind and mix, Al2O3 content 76. An alumina cement was obtained in which 55% by weight of powder was 10 μm or less.

This formulation contains 4Tn! Fused alumina was mixed as an aggregate at a weight ratio of 1:4, and the water-cement ratio was 0.
57 to form a specimen, and after curing at 20° C. for 24 hours, hot bending strength was measured according to JISK-2213.

The results are shown in Table 9. The comparative example is a commercially available refractory alumina cement. Next, the aggregate was replaced with 4TSn siyamoto, which was mixed at a weight ratio of 1:4, and kneaded at a water-cement ratio of 0.564 to prepare a 40 x 40 x 160 size specimen. Slag melt containing % K2O3 saliva (1
When the bending strength was measured after being immersed in water (300°C) for 3 (2) days, the results shown in the first example were obtained.
Example 6 Example 5 Cement 10 according to the invention used in Example 4
Sodium citrate 5% saliva and soda carbonate 5% based on saliva volume
Additives consisting of 0.0% by weight. The weighing part was blended and mixed.

Regarding this formulation, hot bending strength, similar to Example 4,
When an alkali slag corrosion test was conducted, results similar to those of Example 4 were obtained. Furthermore, when the setting time, flow value and strength were measured, the results shown in Table 11 were obtained, and it was recognized that the strength was greater than that of commercially available refractory alumina cement.

Next, the aggregate was replaced with 4Twt calcined bauxite, which was mixed at a weight ratio of 1:4, and this was kneaded at a water-cement ratio of 0.6, and the flow value over time was measured after kneading. The results were as shown in Method 1.

A retarder was added to the internal weight of the alumina cement obtained in Example 1, and the flow value over time of the mortar was measured in accordance with JIS R 2521. The results are shown in Table 13.

Claims (1)

[Claims] 1 100 parts by weight of hydraulic calcium aluminate with an Al_2O_3/CaO molar ratio of less than 3, and CaO.6A.
Alumina cement made of a mixed powder with 10 to 350 parts by weight of poorly hydraulic calcium aluminate mainly composed of l_2O_3. 2 Al_2O_3 content in the total composition is 55 to 85% by weight, and CaO・2Al_2O_3/CaO・Al_
The alumina cement according to 1, wherein the 2O_3 weight ratio is 0.05 to 3. 3 100 parts by weight of hydraulic calcium aluminate with an Al_2O_3/CaO molar ratio of less than 3 and CaO.6A
The main component is a mixed powder with 10 to 350 parts by weight of poorly hydraulic calcium aluminate mainly composed of l_2O_3,
A retarder containing carbonic acid or its potassium or sodium salt and an inorganic carbonate in a weight ratio of 1:0.03 to 3 was added to the cement at an inner weight of 0.01%.
Alumina cement with a composition containing ~2%.