JPS61146503A - Manufacture of high-strength cement product - 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 [Industrial Field of Application] The present invention relates to a method for producing a high-strength cement product produced from a composition containing hydraulic cement and water.

[Prior Art and Problems to be Solved by the Present Invention] In cement products manufactured from hydraulic cement compositions, products having high strength, particularly high bending strength, are desired.

However, calcium silicate cement, calcium aluminate cement and il! A common characteristic of hydraulic cements, such as calcium acid cements, is that despite their different chemical compositions, curing reaction mechanisms, and varying degrees of hydration, their strengths are uniformly low, especially The bending strength usually remains at a level of about 30 to 100 kg/ay2.

Because of such low bending strength, reinforcing materials such as reinforcing bars and fibers are generally used.

On the other hand, according to Griffith's theory, the tensile strength of a brittle solid is determined by the size of defects in the material.
In accordance with this theory, it has been confirmed that extremely high strength can be achieved in products with limited pore size, as shown in Japanese Patent Publication No. 59-43431, for example. However, the manufacturing method exemplified in the above patent application is extremely complicated and unproductive; for example, methods such as repeatedly passing a sheet-like mixed material through a roll mill and then curing it under pressure in a press for 7 days are not practical. I can't say it's very accurate. In order to increase the production speed, it is possible to use rapidly hardening hydraulic cement, but this type of material has a narrow selection range and is expensive, making it suitable only for limited uses.

The reason why molding takes such a long time is that when the pressurizing operation during molding is stopped, the air bubbles contained in the mixed material become normal pressure and become coarse. Therefore, extrusion molding has been widely used in recent years as one of the molding methods for cement products due to its good production efficiency, but in this case as well, the molding pressure is released upon exiting the die, which inevitably causes the remaining air bubbles to become coarse. , Japanese Patent Publication No. 59-43431, it was inappropriate as a method for molding products.

In view of the above circumstances, the present inventor has developed a cement product that does not contain large air bubbles under normal pressure and has significantly improved strength, especially bending strength, using a general hydraulic cement as the main material. The present invention was completed as a result of intensive research to develop a method and method for manufacturing with high productivity by employing a cross-wire method and a molding method.

[Means for Solving the Problems] The gist of the present invention is to provide a method for manufacturing a cement product in which hydraulic cement and water are further mixed with aggregate, if necessary, and the mixture is hardened, and prior to the mixing, At least the hydraulic cement is degassed and then replaced with a gas that is water-soluble and reacts with an alkali or acid when dissolved in water, and the mixing is performed in the presence of the gas or under reduced pressure, and then under pressure. The present invention provides a method for manufacturing a high-strength cement product, in which the molding pressure is released before the setting and hardening reaction of the hydraulic cement starts.

Examples of the hydraulic cement used in the present invention include Portland cement, sucrose cement, silica cement, fly ash cement, high sulfate cement, alumina cement, magnesia cement, and various types of gypsum.

Also, examples of gases that are water-soluble and react with alkali or acid when dissolved in water that can be used in the present invention include carbon dioxide, sulfur dioxide, nitrous oxide, hydrogen chloride, and ammonia; Carbon dioxide is most suitable for the present invention in terms of ease of use. In the present invention, at least hydraulic cement, preferably water, aggregate, and other materials to be used are replaced with other special gas after depressurization treatment. To give an example of these treatments, hydraulic cement and aggregate is first put into a mixed material that can be depressurized, and it becomes easy to depressurize. From the viewpoint of the ultimate vacuum level, it is preferable to deaerate the crosstalk water separately. Both then introduce e.g. carbon dioxide,
The kneading in which all the materials are mixed in a carbon dioxide atmosphere may be carried out as is or, if necessary, may be carried out after reducing the pressure again.

In the present invention, methods for shaping the mixed material into a desired cement product include conventional pressure molding methods such as press molding, roll press molding, and vacuum extrusion molding.

In the present invention, it is not necessary to release the molding pressure until the hydraulic cement hardens in these molding methods, and the residual gas that is contained in the molding material and cannot be removed is replaced with a water-soluble gas. Because the solution reacts with the aqueous alkali or acid solution liberated from the mold, there is no bubble coarsening phenomenon even after the molding pressure is released, so no decrease in strength due to bubbles is observed.

In the present invention, the strength is significantly improved, but it is also possible to use reinforcing materials such as fibers and various admixtures in combination.

The present invention is particularly effective in producing dense composites when used with fibers that tend to entrain air.

[Function] In the method as exemplified in Japanese Patent Publication No. 59-43431, the residual air bubbles become coarser as the press pressure is released. In addition, even if the cross-wire composition is vacuum-pushed during cross-wiring, the removal of air bubbles is incomplete, and handling such as molding under vacuum is complicated, and when the press pressure is released, the hydraulic reaction progresses and the strength deteriorates. It is still impossible until you reach a certain level.

This situation is the same in vacuum extrusion molding, and even a small amount of residual air turns into coarse bubbles at the tip of the die, deteriorating the strength.

In the present invention, the residual gas in the structure is removed after a certain period of time during pressure molding because it is temporarily replaced with a gas that is water-soluble and reacts with the alkali or acid added or liberated from the cement when dissolved in water. The bubbles almost disappear, and even if the molding pressure is removed before the hydraulic cement sets and hardens, the bubbles will not become coarser and there is no risk of a decrease in strength.

[Effects] As described above, according to the present invention, it is possible to obtain cement products with high strength, especially significantly improved bending strength, using ordinary hydraulic cement and a generally known molding method with high productivity. Because it can do this, its practicality is extremely high.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

[Example] Example 1 100 parts of Portland cement, 20 parts of silica powder, 2 parts of hydroxypropyl methylcellulose, and 2.5 parts of Tsukura asbestos were placed in an omnimixer capable of vacuum treatment, and the mixture was placed in a vacuum for about 10 minutes while stirring gently. Then, carbon dioxide was pressurized until the pressure returned to normal pressure, and 20 parts of kneading water that had been heated and degassed in advance was added, followed by stirring at high speed for about 3 minutes.

This mixture was then charged to a twin roll mill and formed into sheets. Next, the sheet was taken out and placed between two polyethylene terephthalate sheets and pressed for 20 k.
The sheet was left for 10 minutes under a pressure of 2 g/ax, and then taken out and placed in an atmosphere of 20° C. and 90% RH for one week, and then dried.

Dimensions: 50 x 17 x 3 by making cuts in this cement sheet.
A large number of test pieces of No. 11 were cut out and subjected to a three-point bending test using an Instron testing machine. The average bending strength of the test pieces was 415 kQ/ax2.

The surface of the test piece was polished with a fine abrasive to make it flat, and when this surface was observed with an optical microscope, the maximum diameter of the pores was 1.
There were no pores larger than 0.00 microns, and only extremely fine pores were included.

Example 2 The mixed wire material of Example 1 was molded into a plate shape using a vacuum extrusion molding machine, and the same test pieces as in Example 1 were cut out and the bending strength was measured, and the average was 365 k (+/ay2).

Further, even when observed using an optical microscope, no coarse bubbles with a maximum diameter of more than 100 microns were observed, indicating a dense structure.

Comparative Example 1 A mixture having the same composition as Example 1 was obtained by simply performing vacuum treatment using a mixer, adding kneading water, and stirring.

This product was pressed in exactly the same manner as in Example 1 to obtain a sheet. The average bending strength of this item is 185 kg/
It was cII2. Furthermore, the bending strength of the product extruded using the same procedure as in Example 2 was 148 klJ/at.
It was 2.

Many coarse pores exceeding 100 microns were observed under an optical microscope in both the pressed and extruded materials.

Claims (1)

[Claims] A method for manufacturing a cement product in which hydraulic cement and water are further mixed with aggregate as necessary and then cured, in which at least the hydraulic cement is deaerated prior to said mixing, and then water-soluble and When dissolved in water, a substitution treatment is performed with a gas that reacts with alkali or acid, and the mixing is performed in the presence of the gas or under reduced pressure, and then molded under pressure, and the molding pressure is applied before the setting and hardening reaction of the hydraulic cement starts. A method for manufacturing a high-strength cement product characterized by releasing the