JPS59199561A - Manufacture of cement formed body - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a cement molded body, and in detail,
The present invention relates to a method for producing a cement compact that is dense and strong and has excellent shape retention until it is fired and rehydrated.

Generally, it is well known that when a cement molded body is heated to a high temperature, its strength decreases. It is already known that by obtaining a molded product with a low water content and pre-hydrating it, a high-strength cement molded product can be obtained by subsequently performing calcination and rehydration. 56-4.8464). However, with this method, the shape retention of the molded product from firing to rehydration hardening is not good, and when producing a surface-finished cement molded product, pre-hydration After applying paint or glaze to the surface of the molded product and firing it as described above,
There is a tendency for fine cracks to occur in the cement base and coating film of the molded body during cooling and rehydration, or during this cooling.

The present invention was made in order to solve the above-mentioned problems, and after molding and firing a shichimeshite kneaded material, it has excellent shape retention until rehydration, and also forms a dense and high-strength cement. 1- To provide a method for producing a cement molded product which can obtain a molded product and which does not cause cracks in the molded product base or coated IKU even when the surface is finished by coating with paint or glaze and forming Vε. The purpose is to

The method for producing a cement molded body of the present invention involves molding a cement kneaded product containing Pol I to land cement, a silicate, a surfactant, and No. 1 into a desired shape. It is characterized by hydration.

In the method of the present invention, the cement mixture contains portolan 1-cemene 1- as well as a silicate and a surfactant. When a molded product made from a cement kneaded product is heated, this silicate undergoes dehydration condensation and solidifies, forming a skeleton in the molded product and improving shape retention after firing. The surfactant prevents this silicate from gelling rapidly at room temperature due to the calcium ions produced during hydration of the Portland cement. Therefore, when a surfactant is not used together with a silicate, when preparing a cement mixture, the silicate rapidly gels, making the composition of the mixture non-uniform;
In some cases, kneading may not be possible, and as a result, it becomes difficult to obtain a molded product with surface strength.

The silicate is blended in an amount of 5 to 70 parts by weight per 1 to 100 parts by weight of Portland cement, and the surfactant is blended in an amount of 0.5 to IO parts by weight per 100 parts by weight of Portland cement. When the silicate content is less than the above range,
When heated, the silicate forms a skeleton in the molded product, and the effect of maintaining its shape retention is not sufficient.On the other hand, when the amount exceeds the above range, Portland cement cannot be obtained. In addition, when the amount of surfactant is too small, rapid kelization of silicate cannot be prevented.
On the other hand, if the amount is too high, the kneaded product will not harden properly.

As the silicate, an alkali metal salt is usually used, and strium silicate, potassium silicate, and lithium silicate are particularly preferred. Further, the surfactant is not particularly limited, but for example, a nonionic surfactant such as polyoxyalkylene monoether is preferably used.

In the present invention, the cement mixture may contain fine particles such as fly ash and silica sand, and reinforcing fibers such as asbestos and glass fiber, as required.

In the method of the present invention, the Pol 1 to land cement mixture as described above is molded into a desired shape, but the molding method and molding pressure at this time are not limited at all, and the desired shape and required strength of the hardened product are A molded article is obtained by a pressing method, an extrusion method, etc., depending on the method. In addition, in the case of press molding, the molding pressure is, for example, 50 to 2000 kg/c+1! However, it is not limited to this.

The molded article thus obtained is then fired, and the firing temperature is usually in the range of 150 to 900°C.

The firing temperature is particularly determined when obtaining a molded body with a surface finish.
It is selected appropriately depending on the type of paint or glaze used. For example, when using a silicate paint, the firing temperature is 150 -
A temperature of 300°C is suitable, and if a glaze is used,
Temperatures of 300 to 900°C are preferred.

Next, this fired product is cooled and then rehydrated to obtain a cement molded body, but the rehydration method is not particularly limited as long as the necessary moisture is supplied, and for example,
It is carried out under pressure in water, steam or in an autoclave.

As described above, according to the method of the present invention, the Portland cement kneaded material contains a silicate and a surfactant, and the silicate does not undergo rapid gelation when the molded product of the kneaded product is heated. , forms a former layer in the molded product, so the molded product has poor shape retention from firing to rehydration, and therefore,
It is possible to obtain a molded product with excellent dimensional accuracy, and
When obtaining a surface-finished molded body, no minute cracks occur in the molded body or the coating film even after firing, and in this way, a surface-finished cement molded body with a tough coating film can be obtained.

Examples of the present invention are listed below. In each case, the bending strength of the obtained seams and molded bodies was determined according to JIS A1408.
Measurements were made in accordance with the bending test method for architectural boards.

Example 1 A kneaded product was prepared by mixing 100 parts by weight of Portland cement, 20 parts by weight of 1-lium silicate (water glass No. 3), 2 parts by weight of a surfactant, and 20 parts by weight of water.
Press molding was performed at a pressure of 0 kg/crA to obtain a sheet measuring 20 cm in length and width and 1 cm in thickness.

Pre-order this sheet at 100'C! ! ? i After drying, hold and bake at 4111 degrees (300 degrees Celsius) for 30 minutes,
Next, 411. The name was rejected. Thereafter, it was rehydrated in water for 2 weeks to obtain a molded body. This molded body has
There is no abnormality in the coating film or the base J (and the bending strength is 230k)
g/CIl! Met.

Example 2 A kneaded product was prepared by mixing 100 parts by weight of Portolan I cement, 30 parts by weight of potassium silicate, 1 part by weight of a surfactant, and 15 parts by weight of water.
It was molded into. After pre-drying this sheet at 100°C, a silicate-based paint was applied to its surface, heated to 290°C, held at this temperature for 30 minutes for firing, and then cooled to room temperature.

Next, it was rehydrated in water for two weeks to obtain a molded body. There were no abnormalities in the coating film or the substrate of this molded product, and the bending strength was 250 kg/cA.

Example 3 A kneaded product was prepared by mixing 50 parts by weight of Portland cement thorium, 2 parts by weight of a surfactant and 18 parts by weight of water, and molded into a sheet 1- in the same manner as in Example 1. Glaze glass was applied to the surface of this Sea I-, dried at 100 °C, sawed, heated to 650 °C in an electric furnace, held for 40 minutes, fired, and then cooled to room temperature. . Next, 1] After being rehydrated in saturated steam at 0°C for 1 day, the molded product was further rehydrated in water for 1 week. Moreover, the bending strength was 180 kg/c.

Example 4 1 part by weight of Portland cement 100 ff, 15 parts by weight of sodium silicate, 1 part by weight of surfactant, 0.75 parts by weight of methyl cellulose, 5 parts by weight of asbestos and 19 parts by weight of water were mixed and the mixture was split. This kneaded product was molded into a sheet using an extrusion molding machine. The obtained sheet was dried at 100°C, a silicate-based paint was applied to its surface, and the sheet was dried at 270°C for 6
After heating for 0 minutes to bake the paint, it was cooled to room temperature. Next, the molded product was obtained by rehydration in water for two weeks. This molded product had no abnormalities in the coating film or the base, and
The bending strength was 320 kg/cd.

Comparative Example 1 100 parts by weight of Portland cement, 50 parts by weight of sodium silicate, and 25 parts by weight of water were mixed.
During kneading, some of the cement powder became agglomerated, resulting in uneven mixing. The thus obtained kneaded product was molded into a sheet in the same manner as in Example 1, but the surface of Sheet 1 had many pores and an uneven surface texture. After cooling, it was rehydrated in water for one week to obtain a molded body. The bending strength of this molded body was 85 kg/crA.

Comparative Example 2 A kneaded product was prepared by mixing 100 parts by weight of Pol I land cement with 25 parts by weight of water.
After molding into a shape and drying at 100°C, glaze glass was applied to the surface, heated to 650°C, held for 40 minutes, fired, and then cooled to room temperature. During cooling, cracks occurred in the cement molded body base and some parts were damaged. After cooling, the molded body was rehydrated in water for one week. The bending strength is 130kg/c+lI.

Claims (1)

[Claims] (1) A method for producing a cement molded body, which comprises molding a cement mixture containing Portland cement, a silicate, a surfactant, and water into a desired shape, heating and baking it, and then rehydrating it. .