JPS646150B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an improvement in a method for manufacturing glazed cement products using thermal spraying technology. [Prior Art] Glazed cement products have beautiful surfaces. , and has the advantages of excellent surface strength and durability.

Conventionally, glazed cement products have been manufactured by kneading a raw material composition of cement, water and aggregate, and adding various additives and reinforcing fibers as necessary, and then using pressure molding or extrusion molding. Alternatively, it is formed by molding and curing using an appropriate method such as a casting method, and the resulting cured product is fired and glazed, and then subjected to a rehydration treatment.

However, the above method has the disadvantage that not only a large amount of energy is consumed since the entire hardened cement body is fired, but also that it is difficult to control the temperature during the firing process. There was also the problem that large cement products such as precast concrete plates could not be glazed due to restrictions on the size of firing kilns.

Therefore, a method has been proposed in which a glazed cement product is manufactured by welding a frit-like glaze component to a hardened cement body using a gas spraying method or a plasma spraying method.

[Problem to be solved by the invention]

Although the technique of glazing a hardened cement body using the above-mentioned thermal spraying technique has been studied in the past, it has not yet been put to practical use. This is because, compared to glazed cement products obtained by firing in a kiln, the glaze was not smooth and pinholes, cissing, foaming, blistering, etc. were extremely likely to occur.

[Means for Solving the Problems] As a result of repeated research into the causes of various defects on the glazed surface, the present inventors found that cement hydrates were formed on the surface layer of the hardened cement body due to the high heat of the sprayed coating. It was discovered that this is because the feed water evaporates and water vapor is released.

Until now, moisture such as free water and adsorbed water contained in cement, and components that are easily decomposed by heat in cement itself,
Alternatively, it is known that organic components in various additives evaporate and become gas when heated, and when this passes through the glaze layer it causes pinholes and repellency, and when it remains within the glaze layer it causes foaming and swelling.

However, it has not been clarified that the bound water in cement hydrate is the cause of the defects.

The present invention was created based on the above-mentioned knowledge, and its characteristics are that a raw material composition made by adding water and, if necessary, aggregates, fibers, various additives, etc. to cement, is kneaded and molded. , a hardened cement body is obtained by hydration hardening, the surface layer of the hardened cement body at least in the area to be glazed is heat-treated at a temperature higher than 600°C, and a glaze component is applied to the surface of the area to be glazed by gas spraying or plasma spraying. After welding, the heat-treated portion of the hardened cement body is rehydrated and hardened.

[Effect]

In the present invention, by heat-treating the surface layer of the portion to be glazed of the hardened cement body at a temperature higher than 600°C,
Not only moisture such as free water and adsorbed water contained in the surface layer, easily decomposed components of the cement itself, and organic components in various additives, but also bound water in the cement hydrate. removed in advance. Therefore,
When the glaze component is welded to the surface layer by gas spraying or plasma spraying, there is no possibility that gas will be generated therefrom and cause various defects in the glaze layer. Therefore, a beautiful glazed surface without defects is formed on the surface of the hardened cement body.

If the heat treatment temperature is below 600℃, the bound water from the cement hydrate will not evaporate sufficiently, and there is a risk that water vapor will be generated when the glaze components are thermally sprayed, resulting in pinholes, etc. in the glaze layer. There is. Therefore, the heat treatment temperature needs to be higher than 600°C.

In addition, the strength of the heat-treated portion decreases due to the loss of bound water. Therefore, by rehydrating and hardening the heat-treated portion of the hardened cement body, the strength can be restored.

〔Example〕

Hereinafter, the procedure for manufacturing a glazed cement product according to the present invention will be explained based on FIG. 1 showing an example.

First, the method for manufacturing the hardened cement body 1 will be described. The cement used in the present invention can be appropriately selected from commonly used types such as Portland cement and alumina cement. As the aggregate, those commonly used as aggregates for cement, such as river sand, silica sand, Schierben, and Shamotsu, can be used as needed. Furthermore, glass fibers, asbestos, steel fibers, etc. may be blended as reinforcing materials, and various additives such as water reducing agents, hardening accelerators, etc. may be added as desired.

Water is added to a raw material composition prepared by blending the above raw materials in an appropriate ratio, kneaded, molded into a desired shape using a molding method such as pour molding, pressure molding, or extrusion, and then cured. A hardened cement body 1 is obtained.

Next, the obtained hardened cement body 1 is heat-treated at a temperature higher than 600°C. Through this heat treatment,
In addition to free water and adsorbed water contained in hardened cement, water such as condensed water and interlayer water existing between particles of cement hydrate, components that are easily decomposed by heat contained in cement itself, Furthermore, not only the organic components in the additive but also the bound water of the cement hydrate is removed. However, it is known that when the heat treatment temperature reaches around 1000°C, the strength deteriorates significantly. Therefore, the heat treatment temperature is preferably 950°C or lower.

Note that the heat treatment is definitely performed in the furnace 2 as shown in FIG. 1, but is not limited thereto. for example,
Although not shown, bound water and the like may be removed in advance by heating the surface layer of the portion to be glazed with a torch or the like. In this case, there is an advantage that even buildings that have already been constructed can be repaired.

After the heat treatment is completed in this way, the glaze component, which has been shaped into a frit, is then welded to the surface of the hardened cement body 1 using a gas spraying device or a plasma spraying device 3 to form a glaze layer. . In conventional technology, when thermal spraying glaze components, the bound water of cement hydrates (e.g. calcium hydroxide, calcium silicate hydrates) on the surface layer of the hardened cement body dehydrates and generates water vapor. Components that are easily thermally decomposed and organic components in additives evaporate and generate gas. Therefore,
Welding of the glaze was inhibited, and pinholes, cissing, foaming, blistering, etc. occurred. In contrast, in the method of the present invention, the surface layer of the area to be glazed is heat-treated in advance, thereby removing the components that evaporate from the surface layer during thermal spraying of the glaze components. Therefore, the welding of the glaze components is not inhibited, and a defect-free, smooth and beautiful glazed surface can be formed on the surface of the hardened cement body.

Note that gas spraying or plasma spraying herein refers to a method in which a molten glaze component is sprayed onto the hardened cement body 1 using gas or plasma to form a glazed surface on the surface thereof, as well as a method described in Japanese Patent Application Laid-Open No. 1973- It is also possible to use the method described in Japanese Patent No. 103413, in which a glaze component is applied in advance to the surface of a hardened cement body, and the glaze is melted using gas or plasma to weld the glaze. The frit-like glaze component used in this example is, for example, glass powder to which commonly used auxiliary agents such as zinc white and zircon and inorganic pigments are added. The particle size of the fritted glaze component is preferably adjusted to a range of 40 to 160 μm. Further, although the properties of the frit-like glaze component are by no means limited, it is preferable that the frit-like glaze component has characteristics such as being softened at as low a temperature as possible and having high wettability.

Once a glazed surface is formed on the surface of the hardened cement body 1, the heated portion is rehydrated and hardened. The heat treatment reduces the strength of that part, but as previously disclosed by the applicant in Japanese Patent Application No. 52-87196, the strength is restored by rehydration and hardening later, making it practically usable. There is no problem at all. In addition,
As a means for rehydrating and hardening, in addition to underwater curing, steam curing, etc., natural curing using moisture in the air may be used depending on the implementation situation.

Next, a specific example of manufacturing a glazed cement product based on the present invention will be described.

(Manufacturing Example) A cement hardened body was obtained by kneading, molding, and hydration hardening a raw material composition having the following blending ratio.

Raw material composition of hardened cement: Cement: 100 parts by weight Aggregate (Shyamatsuto) 100 parts by weight Asbestos 5 parts by weight Water 35 parts by weight The obtained hardened cement was heated in a furnace at 800℃ for 2 hours.
Heat treatment was performed for an hour.

The following frit glaze was thermally sprayed onto the surface of the hardened cement body after the heat treatment.

Fritz: Made by Nichito Sangyo Co., Ltd. M25 particle size 60~
Adjusted to 100μm Thermal spraying equipment: Metco 5P gun After glazing, the cement hardened body was heated at 60℃, 100%RH,
It was steam cured for 48 hours and rehydrated to harden.

The glazed surface of the glazed cement product thus produced had a uniform and smooth surface with no foaming or repellency.

The embodiments of the present invention are not limited to those described above. The specific composition, such as the type and blending ratio of the raw materials used, the components of the glaze, etc., can be changed as appropriate depending on the implementation mode.

〔Effect of the invention〕

The method for producing glazed cement according to the present invention provides excellent effects as listed below.

When welding glaze components by gas spraying or plasma spraying, the components that evaporate from the surface layer of the area to be glazed in the hardened cement body are removed in advance, so there are no defects such as pinholes, cissing, foaming, or blistering. A smooth and beautiful glazed surface can be obtained.

Since gas spraying or plasma spraying can be used as a means of applying glaze to the hardened cement body, it is possible to easily apply glaze to very large cement products such as precast concrete plates. Furthermore, it is possible to apply glaze to objects that have already been applied to buildings and the like.

Compared to the temperature control of conventional firing glazing methods, thermal spraying makes it easier to control the glaze state, resulting in fewer uneven finishes and more uniform quality. Furthermore, it is more energy efficient than firing the entire hardened cement body. Therefore, a significant improvement in yield is achieved.

In short, the present invention provides an extremely effective means for putting into practical use a method of manufacturing cement products with a beautiful glazed surface using gas spraying or plasma spraying, which was previously thought to be difficult. It is something to do.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of the present invention. 1...Cement hardened body, 2...Furnace, 3...Thermal spraying device.

Claims (1)

[Claims] 1. A raw material composition prepared by adding water and, if necessary, aggregates, fibers, various additives, etc. to cement is kneaded, molded, and hydrated to obtain a hardened cement body, and at least the surface layer of the part to be glazed is coated with the hardened cement body. It is characterized by heat treating at a temperature higher than 600°C, welding the glaze component to the surface of the part to be glazed by gas spraying or plasma spraying, and then rehydrating and hardening the heat-treated part of the cement hardened body. A method for manufacturing glazed cement products.