JPH0472794B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a molten slag-resistant concrete material, and more particularly to a molten slag-resistant concrete material based on a cured calcium silicate heat-resistant cement having excellent heat resistance. (Prior Art) Conventionally, various materials with high heat resistance have been developed and used in various high-temperature devices, and metals, ceramics, cement, etc. have been used as inorganic materials. Among these, metals and ceramics are generally dense and have high mechanical strength, and are used for various purposes as heat-resistant materials, but there are problems such as the fact that they cannot be molded into containers or require high temperature treatment. Cement has the advantage that a molded product of a desired shape can be easily obtained by mixing aggregate and water to fluidize it and pouring it into a mold. However, the use of heat-resistant cement as a heat-resistant material is difficult because it cannot withstand high temperatures like ceramics and lacks mechanical strength.
It's not very popular. (Problems to be Solved by the Invention) Alumina cement is known as a typical heat-resistant cement. Although alumina cement has rapid hardening and high heat resistance, it suffers from a reduction in strength due to dislocations and a reduction in hot strength due to weakening of the bond at intermediate temperatures. Portland cement, which is the most common cement with a calcium silicate composition, has a large amount of Ca(OH) ₂ produced during hydration and hardening, so it undergoes the following reaction: Ca(OH) ₂ CaO+H _2O (slaking phenomenon), which causes structural deterioration, and has poor heat resistance. Therefore, by adding and mixing ultrafine particles of SiO ₂ to this, a product has been provided in which the above-mentioned slaking phenomenon is prevented by the following reaction. Ca(OH) ₂ +SiO ₂ →CxSyHz (However, in this formula, C: CaO, S: SiO ₂ ,
(H: H ₂ O, and it is thought that C ₂ S, C ₃ S ₂ and CS are mainly produced and mixed) However, the present inventor has found that there is a problem with this prevention method alone. I knew. In other words, the results of differential thermal analysis are 490℃, 730℃,
Deterioration of the structure has been confirmed at 905°C, and a residual compressive strength test with heating revealed that there is a rapid decrease in strength when the temperature exceeds 700°C. (Means for Solving the Problems) In view of the above, the present inventor has conducted research to prevent the occurrence of the slaking phenomenon in calcium silicate cement, render residual calcium hydroxide harmless, and significantly improve heat resistance. We have developed a concrete material with improved molten slag resistance. That is, the present invention provides a molten slag-resistant concrete material in which a slurry of a mixture containing calcium phosphate as a main component and an acidic aqueous solution is poured onto the surface of a hardened calcium silicate heat-resistant cement layer to form an integrated layer. This is a concrete material for molten slag that is resistant to molten slag. The molten slag-resistant concrete material of the present invention can be used in places where molten slag comes into contact, such as a waste slag receiving pan from a converter or a passage floor through which slag flows. For example, in converter operation, the slag remaining in the converter after steel tapping is discharged into a slag receiving pan directly or via a slag pan truck, and after being cooled, it is taken out by rotating the slag receiving pan. The structure of the slag receiving pan used during the slag discharge is an ark-shaped one with an open top, as shown in FIG. For example, the concrete material of the present invention is applied to the slag receiving pan. FIG. 1 is a partially cutaway perspective view of an example of a slag receiving pan for receiving molten slag discharged from a converter, using the molten slag-resistant concrete material of the present invention, and 1 is a frame body. , 2 is a calcium silicate-based heat-resistant cement hardened material layer, which is placed on the inner surface of the frame 1. 3 is a layer treated with an acid aqueous solution, for example, a phosphoric acid aqueous solution, and the calcium silicate-based heat-resistant cement hardened material layer 2 A phosphoric acid aqueous solution is applied to the surface. And 4 is a calcium phosphate slurry cured material layer. In this example, a molten slag receiving pan structure is formed in which a slurry casting body 4 whose main component is calcium phosphate is laminated and integrated on the surface of a calcium silicate-based heat-resistant cement hardened material layer 2. At this time, it is necessary to apply an acid aqueous solution, especially a phosphoric acid aqueous solution, as a surface treatment agent to the surface of the calcium silicate-based heat-resistant cement cured material layer 2 to form a treated layer 3, and furthermore, at this time, workability is improved. Considering this, it is more preferable to form the treated layer 3 by applying a phosphoric acid aqueous solution adjusted to have a pH of about 3 to 6 for reasons described later. To adjust the pH of the phosphoric acid aqueous solution, commonly used alkaline agents such as ammonia, organic amines such as ethanolamine, alkali such as sodium and potassium, or alkaline earth metal hydroxides, etc. can be used. By the way, in the above configuration, the calcium silicate-based heat-resistant cement is, as mentioned above, a commonly used cement that is low in cost and easy to obtain. Furthermore, when the calcium phosphate placed on the surface is heated to high temperatures, it produces apatite with a melting point of 1,400 to 1,800 degrees Celsius or higher, and this product exhibits excellent resistance to high temperatures. The acidic aqueous solution in the slurry is useful for hydration-hardening of calcium phosphate, but especially when using a phosphoric acid aqueous solution, as shown in the formula below, it is continuously generated from a calcium silicate-based heat-resistant cement that is designed to prevent slaking. It captures free calcium hydroxide and forms a strong interface with calcium phosphate. 2H ₃ PO ₄ +3Ca(OH) ₂ →Ca ₂ (PO ₄ ) ₂ +6H ₂ O Calcium phosphate, which is the main component of the mixture slurry used in the present invention, has calcium and phosphorus in an atomic ratio (gram atom ratio, hereinafter referred to as same) as
Contains Ca/P at a ratio of 1.4 to 1.6, 700℃ to 1400℃
Preferably, the material is fired at a temperature of 900°C to 1300°C. In the present invention, acids may be used in addition to fluoride as a curing accelerator. The acid used in the practice of the present invention can be either an organic acid or an inorganic acid, and naturally a mixture thereof is also effective. These acids are necessary to shorten curing time and increase hardness. When these acids are used as a curing accelerator, the pH of the aqueous solution is preferably in the range of 2.5 to 6.0, more preferably 3.0 to 5.0, in view of the curing rate and physical properties of the cured product. Organic acids used in the practice of the present invention include formic acid,
Lower monobasic fatty acids such as acetic acid and propionic acid, hydroxycarboxylic acids such as malic acid, glycolic acid, lactic acid, citric acid, sugar acid, and ascorbic acid, acidic amino acids such as glutamic acid and aspartic acid, sialic acid, malonic acid, and succinic acid. , dibasic acids such as tardaric acid, adipic acid, maleic acid, fumaric acid, and muconic acid; keto acids such as pyruvic acid, acetoacetic acid, and levulinic acid; and aromatic carboxylic acids such as salicylic acid, benzoic acid, cinnamic acid, and phthalic acid. and its salts such as alkali metal, alkaline earth metal or ammonium salts, and derivatives of the above-mentioned organic acids that easily produce carboxylic acid groups by hydrolysis, such as acid anhydrides and acid chlorides. Inorganic acids include phosphoric acid, hydrochloric acid, sulfuric acid, nitric acid,
Examples include hydrofluoric acid and boric acid. When adjusting the pH of an aqueous solution containing these acids, ammonia, amines, alkali metal hydroxides, alkaline earth metal hydroxides, etc. can be used. Furthermore, in order to increase the hardness of the cured product, it is preferable to add fluoride to the mixture slurry containing calcium phosphate as a main component used in the present invention. Such a fluoride may be any ammonium or amine salt, alkali metal salt, or alkaline earth metal salt of hydrofluoric acid that can be incorporated into calcium phosphate to form fluoroapatite. In this case, the amount of fluoride added is preferably Ca/F 4.2 to 60 as an atomic ratio of calcium to fluorine. On the other hand, in order to increase the hardness of the cured product, it can be a divalent or trivalent ion other than calcium. The molar ratio Me/PO ₄ of soluble compounds containing metal atoms Me, e.g. iron, cobalt, nickel, chromium, barium, and strontium to the phosphate group (PO ₄ ) in calcium phosphate is 2.5×10 ^-4
The above can be added to the mixture slurry, or can be used in combination with the above-mentioned fluoride. In this case, as shown in Examples below, the metal atoms (Me) can also be introduced into the calcium phosphate by adding a compound containing these metal atoms (Me) at the time of baking the calcium phosphate. The powder component of the slurry containing calcium phosphate as a main component used in the present invention and the liquid component consisting of an acidic aqueous solution are preferably mixed at a weight ratio of 10:2 to 10:5. If the liquid component is less than this, the fluidity of the composition will be insufficient, and if it is more than this, the fluidity of the composition will be excessive, which is not preferable. Although the slurry containing calcium phosphate as a main component of the present invention can be used alone, the following advantages can be expected when it is used with the addition of aggregate. (a) By using inexpensive aggregates, it is possible to reduce the manufacturing cost of the product, molten slag-resistant concrete material. (b) Heat resistance and dimensional stability can be improved by using aggregate with good thermal stability. (c) It is possible to reduce weight by using aggregate with low specific gravity. Aggregates that are generally used for concrete can be used, but igneous rock phosphate rock, aqueous rock phosphate rock, and their calcined products are preferable because they are apatite of the same quality as the hardened material obtained. It can be said to be a material. The molten slag-resistant concrete materials obtained by combining the plasticity of each of the above components and laminating them can all be molded by pouring and are easy to manufacture, and the hardened cast calcium phosphate slurry has very high heat resistance. It has excellent properties such as excellent heat resistance and excellent mechanical strength at high temperatures, as it acts as a non-combustible fire-resistant coating material up to 1600°C. The production of the molten slag-resistant concrete material of the present invention is carried out as follows. First, ultra-fine grains were added to calcium silicate-based heat-resistant cement.
A mixture of SiO ₂ (for example, silica hume) is mixed with high-quality shamots, brick scraps, etc., water is added and the mixture is uniformly mixed, and then poured into a mold. After leaving it for a certain period of time to cure and harden,
Next, an acid aqueous solution, preferably a phosphoric acid aqueous solution, is applied to the surface in advance to neutralize the unneutralized residual calcium hydroxide. However, the neutralization step can be omitted if necessary. Next, a slurry of a mixture sufficiently mixed with a powder component mainly composed of calcium phosphate and a liquid component consisting of an acidic aqueous solution as a hardening agent is used alone or after mixing with aggregate as necessary, and then the cured and cured product is prepared. It is poured onto the surface to the desired thickness and laminated into one piece. In this case, the desired thickness is usually considered to be from several millimeters to several tens of centimeters, but it varies depending on the type of the cured material. That is, the thickness is determined so that the temperature transmitted through the cured product of calcium phosphate and its hardening agent is below the heat resistance temperature (usage limit temperature) of the cured cured product. At this time, if a phosphoric acid aqueous solution is used as the acidic water, residual calcium hydroxide generated from the cured product can be immobilized as a calcium salt of phosphoric acid, and due to the presence of this immobilized calcium phosphate layer, In addition, a slurry containing chemically homogeneous calcium phosphate as a main component, which is poured on top of the slurry, becomes more firmly integrated. As a result, the molten slag-resistant concrete material is resistant to corrosion even when it comes into contact with relatively high-temperature molten slag, and its mechanical strength decreases less, making it easier to manufacture and more durable than conventional materials. is also considerably improved. As shown in FIG. 2, the layered structure of the above-mentioned molten slag-resistant concrete material includes a layer 2 of cured calcium silicate-based heat-resistant cement, a layer 3 treated with acid, and a layer 3 of cured calcium phosphate slurry on top of the layer 2 of cured calcium silicate-based heat-resistant cement. The layers 4 are stacked one after another. (Example) Next, an example of the present invention will be described. As shown below, for each type of molten slag-resistant concrete material of Examples 1 to 3 of the present invention, heat-resistant cement material of Comparative Example 1, and ordinary Portland cement material of Comparative Example 2, a 4 cm x 4 cm x 12 cm A test specimen was created and its residual compressive strength, fire resistance, and thermal spalling resistance were confirmed. As shown in Table 1, the molten slag-resistant concrete material of the example exhibited superior properties compared to other cement materials, and the results were good. Example 1: Ordinary Portland cement mixed with 44.1% (weight ratio) of ultrafine SiO ₂ was kneaded at 35% W/C, hardened, and a 1M citric acid solution was applied to the surface. Next, a calcium phosphate slurry having the composition shown below was placed thereon and laminated and integrated to obtain a test specimen. A mixed powder of 97.5% calcium phosphate (Ca ₃ (PO ₄ ) ₂ ) and 2.5% calcium fluoride.
A slurry made by blending and kneading 68.55% and 31.45% of a 1M citric acid solution (adjusted to pH 3 with aqueous ammonia). Example 2: Same as Example 1 except that a calcium phosphate slurry having the following composition was used. Dicalcium phosphate (CaHPO ₄ ) 99.8%,
0.2% of iron pyrophosphate (Fe ₄ (P ₂ O ₇ ) ₃ ) was mixed and ground, fired in an electric furnace at 500° C. for 2 hours, and then cooled to room temperature. 62% of this calcined powder and 38% of calcium carbonate CaCO ₃ are thoroughly mixed, calcined again in an electric furnace at 1200° C. for 2.5 hours, and then cooled to obtain Fe-containing calcium phosphate. This Fe-containing calcium phosphate 78.6% and 1M citric acid solution (however, PH4.5 with ammonia water)
Slurry prepared by mixing and kneading 21.4%. Example 3: Same as Example 1 except that a calcium phosphate slurry having the following composition was used. 73.5% powder mixed by pulverization at a ratio of 99.3% calcium phosphate (Ca ₃ (PO ₄ ) ₂ ), 0.4% acidic ammonium fluoride (NH ₄ HF ₂ ), 0.3% calcium fluoride (CaF ₂ ), and 0.5 mole phosphoric acid. Aqueous solution 26.5
Slurry mixed and kneaded with %. Comparative Example 1: (Heat-resistant cement material) 44.1% of ultrafine SiO ₂ added to ordinary Portland cement
% (weight ratio) of heat-resistant cement was mixed and kneaded at a water-cement ratio W/C of 35%, and a cured product was used as a test specimen. Comparative Example 2: (Ordinary Portland cement material) Ordinary Portland cement to water-cement ratio W/
A cured product mixed and kneaded with 35% C was used as a test specimen.

[Table] As is clear from the above results, Example 1,
In the cases of Nos. 2 and 3, all physical properties such as residual compressive strength, fire resistance, and thermal spalling properties were good, and they were preferable as materials for molten slag resistance. On the other hand, in the case of Comparative Examples 1 and 2, the same physical properties were normal or poor. (Effects of the Invention) As described above, the present invention is constructed by pouring a slurry of a mixture of calcium phosphate as a main component and an acidic aqueous solution onto the surface of a calcium silicate-based heat-resistant cement molded product and laminating it into an integrated structure. Since it is a molten slag-resistant concrete material, it has better physical properties such as residual compressive strength, fire resistance, and thermal spalling resistance than conventional concrete materials, and also has good corrosion resistance against molten slag. Since it is easy to manufacture and maintains sufficient hot mechanical strength, it is a novel and excellent molten slag-resistant concrete material at low cost.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway perspective view of an example of a slag receiving pan using the molten slag-resistant concrete material of the present invention, and Fig. 2 is a partial cross-section of the molten slag-resistant concrete material of the present invention. Show the diagram. DESCRIPTION OF SYMBOLS 1... Frame body, 2... Calcium silicate-based heat-resistant cement cured material layer, 3... Treatment layer, 4... Calcium phosphate slurry cured material layer.

Claims (1)

[Scope of Claims] 1. A concrete material for molten slag, which is constructed by pouring a slurry of a mixture of calcium phosphate as a main component and an acidic aqueous solution on the surface of a hardened calcium silicate heat-resistant cement layer and integrating the layers. A concrete material for use in molten slag that is resistant to molten slag. 2. The molten slag-resistant concrete material according to claim 1, wherein the surface of the calcium silicate-based heat-resistant cement hardened material layer is treated with an aqueous phosphoric acid solution. 3. Claim 1, characterized in that the calcium silicate-based heat-resistant cement is a mixture of Portland cement and ultrafine SiO ₂ particles.
The molten slag-resistant concrete material according to item 1 or 2.