JPH054951B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method of manufacturing a heat-resistant concrete member, and particularly to a method of manufacturing a heat-resistant concrete member with an excellent surface layer. (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 they have problems such as being difficult to mold or requiring high-temperature treatment. Cement has the advantage that it can be easily molded into a desired shape by mixing aggregate and water, fluidizing 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 has problems with a decrease in strength due to dislocations and a decrease in hot strength due to weakening of the bond at intermediate temperatures. And, Portland cement, which is the most common cement with calcium silicate-based compositions, has a large amount of Ca (OH) ₂ produced during hydration and hardening, which causes it to react less than Ca (OH) _2. It has the disadvantage of causing CaO+H ₂ O (slaking phenomenon), leading to structural deterioration, and has poor heat resistance. Therefore, by adding and mixing ultrafine particles of SiO ₂ to this, a heat-resistant cement is provided that prevents the occurrence of the slaking phenomenon through the following reaction. Ca(OH) ₂ +SiO ₂ →C×SyH _Z (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 inventor believes that there is a problem with such a prevention method alone. I learned. In other words, differential thermal analysis confirmed that the structure deteriorated at 490°C, 730°C, and 905°C, and a residual compressive strength test with heating showed that a rapid decrease in strength occurred when the temperature exceeded 700°C. I found out that there was. (Means for Solving the Problems) In view of the above, the present inventor has developed a method for manufacturing heat-resistant concrete members that has significantly improved heat resistance. After curing and curing to form a cement cured product molded product, a slurry of a mixture of calcium phosphate as a main component and an acidic aqueous solution is placed on the surface of the product and hardened.
This is a method for manufacturing heat-resistant concrete members characterized by lamination and integration, and as shown in Figure 1, heat-resistant concrete members are produced using cement or Portland cement mixed with ultrafine SiO ₂ particles. Heat-resistant concrete that is a cement hardened product 1
A slurry containing calcium phosphate as a main component is cast onto the surface of the slurry to form a slurry casting body 3, which is then hardened and laminated into an integrated structure. At this time, it is necessary to apply an acidic aqueous solution as a surface treatment agent to the surface of the concrete 1 to form a treatment layer 2, and furthermore, considering workability, an acidic aqueous solution adjusted to a pH of about 3 to 6 is applied. It is preferable to form the treatment layer 2 by coating. Further, in this case, it is more preferable to use a phosphoric acid aqueous solution as the acidic aqueous solution, especially for reasons explained later. To adjust the pH of the acidic aqueous solution, commonly used alkaline agents such as ammonia; organic amines such as ethanolamine; hydroxides of alkali or alkaline earth metals such as sodium, potassium, and calcium can be used. Incidentally, in the above configuration, Portland cement can be used to manufacture the cement cured product molded product, but as mentioned above, this is a commonly used cement, and is low in cost and easily available. Furthermore, when the calcium phosphate placed on the surface is heated to a high temperature, it forms apatite with a melting point of 1400 to 1800°C or higher, and this product exhibits excellent resistance to high temperatures. The acidic aqueous solution in the slurry is useful for hydrating and hardening calcium phosphate, but especially when using a phosphoric acid aqueous solution, as shown in the equation below, free calcium hydroxide ( Capturing Ca(OH) ₂ ),
Excellent advantages are exhibited due to the formation of a strong interface with the calcium phosphate slurry. 2H ₃ PO ₄ +3Ca(OH) ₂ →Ca ₃ (PO ₄ ) ₂ +6H ₂ O Concrete members obtained by combining and laminating the above component compositions are easy to form and manufacture, and cast calcium phosphate is Extremely heat resistant
Since it acts as a non-combustible fireproof coating material up to 1600℃, it has excellent properties such as excellent heat resistance and excellent mechanical strength at high temperatures. A specific example of the manufacturing method of the present invention is carried out, for example, as follows. First, add ultrafine particles to cement or
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 acidic aqueous solution is applied to the surface in advance to neutralize unneutralized residual calcium hydroxide. However, the neutralization step can be omitted if necessary. Next, a slurry prepared by mixing a powder containing calcium phosphate as a main component and an acidic aqueous solution as a hardening agent is cast onto the surface of the cured cured product molded body to a desired thickness to form an integral layer. 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. Calcium phosphate, which is the main component of the mixture slurry used in the present invention, has an atomic ratio of calcium to phosphorus (gram atom ratio, the same applies hereinafter).
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, an acidic aqueous solution is also used as a curing accelerator. Both organic acids and inorganic acids are effective as acids for creating such acidic aqueous solutions.
Naturally, mixtures thereof are also effective. These acids are necessary to obtain a shortened curing time and increased hardness. These acids,
When 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 their salts such as alkali metal, alkaline earth metal or ammonium salts, and derivatives of base organic acids which 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. Next, in the present invention, it is preferable to add fluoride as an accelerator for the hardening of calcium phosphate under the above conditions into apatite in water. Such fluorides may include ammonium or amine salts, alkali metal salts, alkaline earth metal salts, etc. of hydrofluoric acid, as long as the fluorine 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 the atomic ratio of calcium to fluorine. Furthermore, in order to increase the hardness of the cured product, soluble compounds containing metal atoms Me such as iron, cobalt, nickel, chromium, barium, and stroitium, which can become divalent or trivalent ions other than calcium, are added to the phosphate radicals (PO) in calcium phosphate. ₄ ), the molar ratio Me/PO ₄ of 2.5×10 ⁻⁴ or more can be added to the mixture slurry, or it 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. At this time, as mentioned above, if a dilute phosphoric acid aqueous solution is used as the acidic aqueous solution, the residual calcium hydroxide generated from the cured product molded article can be immobilized as a calcium salt of phosphoric acid, and this immobilized calcium phosphate Due to the interposition of the layer, the slurry hardened body containing chemically homogeneous calcium phosphate as a main component cast thereon becomes more firmly integrated. 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) It is possible to reduce the manufacturing cost of heat-resistant concrete products by using inexpensive aggregates. (b) Heat resistance or 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 commonly used for concrete can be used, but igneous rock phosphate ore or aqueous rock phosphate ore and their calcined products are preferred because they are apatite of the same quality as the hardened material obtained. It can be said to be aggregate. Therefore, the concrete member obtained by the production method of the present invention can be used as a structural member that is exposed to relatively high temperatures and does not allow a decrease in mechanical strength, and some examples thereof are as follows. (a) Regarding coke ovens, concrete inner walls of digestion towers, coke transport platform and rail flooring, concrete flue walls, exhaust gas ducts, etc. (b) Blast furnace-related items such as casthouses, casthouse gutter covers, slag pit walls, casthouse supports, slab cooling field surrounding walls, and receiving hole aprons. (c) Regarding converters and electric furnaces, pouring pit side walls, converter working floors, electric furnace preheating and exhaust gas ducts, electric furnace tapping and slag removal pit side walls, slaging yard floors, and peripheral side walls of continuous casting equipment. etc. (d) Regarding heating furnaces and drying furnaces, drying furnace side walls, drying furnace cover floor, heating furnace underground flue, etc. (e) Heat-resistant and fire-resistant partition materials, curtain wall materials, etc. for various buildings as heat-resistant and healthy materials. (Example) Next, an example of the present invention will be described. As shown below, test specimens of 4 cm x 4 cm x 12 cm were prepared for each type of concrete members according to the examples of the present invention in Examples 1 to 3, the heat-resistant cement material in Comparative Example 1, and the ordinary Portland cement material in Comparative Example 2. The remaining compressive strength, fire resistance, and thermal spalling properties were confirmed. As shown in Table 1, the results were good, with the heat-resistant concrete members of the examples exhibiting superior properties compared to other cement materials. Example 1: Ordinary Portland cement mixed with 44.1% (weight ratio) of ultrafine SiO ₂ particles was kneaded at 35% W/C, hardened, and a 1 mol 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 mixing 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 mixed and kneaded with (adjusted to) 21.4%. Example 3: Same as Example 1 except that the following calcium phosphate slurry 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 ), and 0.3% calcium fluoride (CaF ₂ ), and a 0.5 molar 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 can be seen from the above results, the concrete members obtained in Examples (1, 2, and 3) of the present invention all had good physical properties such as residual compressive strength, fire resistance, and thermal spalling resistance. It was hot. On the other hand, in the case of Comparative Examples (1, 2), the same physical properties were normal or poor. (Effects of the Invention) From the above, according to the method for producing heat-resistant concrete members according to the method of the present invention, (1) In the concrete members obtained, the hydrated and self-hardening material of calcium phosphate slurry is thermally stable even in an oxidizing atmosphere. It is stable at 1600℃
Acts as a non-combustible fireproof cladding material up to 1000℃
Furthermore, if a calcium silicate-based heat-resistant cement cured product molded product is used as the concrete base material, there will be little decrease in hot strength (compressive and bending strength) up to 800℃, and Therefore, the laminated and integrated heat-resistant concrete obtained by the present invention is a laminated and integrated heat-resistant concrete member that has an excellent heat-resistant protective layer and has excellent mechanical strength at high temperatures; (2) The concrete obtained In the component, the surface layer of the cement hardened material molded body and the cast calcium phosphate layer are in a microscopically complicated state (anchor-like bond) at the interface between the two, and the structure is a transition layer, so that they are laminated and integrated. (3) Both the cement and the calcium phosphate slurry, which are the raw materials for the concrete member according to the present invention, are hydrated.・Since it is a self-hardening material, it can be easily manufactured into any shape, that is, it can be molded using the same method as conventional cement or concrete molding. The slurry can form a thick, strong layer and is therefore essentially different from conventional fireproofing sprays, and can be easily applied to any thickness, such as a structural material. (5) The hydrated and hardened material layer of the slurry mainly composed of calcium phosphate not only inherently eliminates the need to consider the problem of carbonation that occurs with conventional cement-based hardened products; In addition, the present invention has the advantage that it is useful as a neutralizing treatment agent for the cement cured product molded body of the base material, and has excellent water resistance and air resistance, so it has an effective protective effect on the base material. Heat-resistant concrete members that are laminated and integrated have a very favorable combination structure, and exhibit many excellent functions and effects.

[Brief explanation of the drawing]

FIG. 1 shows a partial sectional view of the heat-resistant concrete member of the present invention. 1...Heat-resistant concrete, 2...Treatment layer, 3
...Cured mixture slurry.

Claims (1)

[Claims] 1. After hydrating and hardening the cement mixture to form a cured cement molded product, a slurry containing calcium phosphate as a main component and a mixture of calcium phosphate and an acidic aqueous solution is placed on the surface of the molded product and hardened. A method for manufacturing a heat-resistant concrete member, characterized by laminating and integrating the members. 2. The method for producing a heat-resistant concrete member according to claim 1, characterized in that the surface of the cement cured product molded body is previously treated with an acidic aqueous phosphoric acid solution. 3. Production of a heat-resistant concrete member according to claim 1 or 2, wherein the cement is Portland cement, a mixture of Portland cement with ultrafine particles of SiO ₂ added, or alumina cement. Method.