JPH0137346B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing an alkali-resistant glass fiber reinforced colored cement board. Conventionally, when alumina is produced from bauxite by the Bayer process, the red mud that is produced as a by-product as an extraction residue has little utility value, and its emission amount is 0.5 to 0.8 in the dry state per ton of alumina (Al ₂ O ₃ ). In Japan, it is approximately 1 to 1.5 million tons/year. For this reason, alumina manufacturing plants are having trouble disposing of it, and various research has been done in the past, such as using it as artificial lightweight aggregate, but even now, there is no example of using it in large quantities, and it is not possible to dispose of it in land landfills, ocean dumping, etc. The reality is that waste is disposed of at great expense, such as by storing it in red mud ponds. On the other hand, when coloring various secondary cement products such as slate and blocks, if the product is subjected to tertiary processing and surface painting, the tertiary processing process will increase costs and cause damage to the surface, resulting in damage to the paint film. It is preferable to mix a coloring agent in the cement board manufacturing process to color the entire product. When coloring the entire product, adding coloring agents such as pigments increases the cost and reduces the strength of the product, making it difficult to commercialize the product. In addition, many fiber-reinforced cement boards with improved tensile strength, bending strength, impact strength, etc. have been commercialized by mixing various inorganic or organic fibers with cement to produce a hydraulically hardened body. Asbestos fiber is the predominant reinforcing fiber. This asbestos fiber is a natural resource, and there are problems such as rising prices and difficulty in obtaining it due to resource depletion.In addition, regulations have been added from an occupational health perspective regarding asbestos dust generated during product manufacturing and processing. Due to the increasing number of constraints such as aging, there is a growing interest in reinforcing fibers to replace asbestos. Under these circumstances, alkali-resistant glass fiber has attracted attention as a reinforcing material to replace asbestos, and has been put into practical use in some products. However, this alkali-resistant glass fiber cannot be said to have sufficient alkali resistance, and Ca
Due to the strong alkalinity of (OH) ₂ , it is gradually eroded and there is concern about long-term strength loss.
The uses of alkali-resistant glass fiber reinforced cement boards are naturally limited. Therefore, in order to improve the long-term durability of alkali-resistant glass fibers, it has been considered to use alumina cement as a hardening agent or to mix activated silica powder, but when using alumina cement,
The effect of temperature is large; at curing temperatures of 23 to 25°C or higher, the strength decreases significantly, making it unusable for practical use. Also, when curing at normal pressure, the reaction with Ca(OH) ₂ does not occur as expected when activated silica powder is mixed in. Since the process does not progress and the pH of the cured product decreases only to about 12, it has not yet reached the point where it contributes to improving the long-term durability of the alkali-resistant glass fiber. The inventors of the present invention have conducted extensive research in consideration of the current situation described above, and have discovered that by adding red mud to alkali-resistant glass fiber reinforced cement boards, the long-term strength of the product is less likely to deteriorate and that an inexpensive colored cement board can be created. It has been discovered that it can be manufactured, and the present invention has been achieved based on this knowledge. That is, when manufacturing a fiber-reinforced cement board, the present invention mixes alkali-resistant glass fibers into some or all of the reinforcing fibers in an amount of 0.5 to 5% by weight of the cement,
The method for producing an alkali-resistant glass fiber reinforced colored cement board is characterized by adding 5 to 30% by weight of red mud (in terms of solid content) based on cement. If the alkali-resistant glass fiber content is less than 0.5%, the reinforcing effect will not be sufficient, and if it exceeds 5%, the fibers will not be uniformly dispersed in the papermaking process. Furthermore, if the red mud content is less than 5%, effective coloring cannot be achieved, and if it exceeds 30%, the strength of the product will be significantly reduced. As the cement used in the present invention, in addition to Portland cement, general cements such as blast furnace cement, fly ash cement, silica cement, and ultra-fast hardening cement are used. Tables 1, 2, and 3 show the physical properties of red mud. By adding this red mud at 5 to 30% by weight (in terms of solid content) of cement, cement board formation based on the dilution effect can be achieved.
Decrease in PH and Fe ₂ O ₃ , Al ₂ O ₃ , SiO ₂ ,
The alkalinity of the cement board decreases due to a chemical reaction between multiple components such as R ₂ O, TiO ₂ and Ca(OH) ₂ generated by hydration of cement, and the surface of glass fibers due to the above chemical reaction products. It is thought that the long-term strength decline of the alkali-resistant glass fiber-reinforced cement board is reduced due to the protective effect of the alkali-resistant glass fibers.

【table】

【table】

[Table] Next, the present invention will be explained in more detail with reference to Examples. Example 1 180 g of ordinary Portland cement, 20 g of red mud (dry) with the composition shown in Table 1, and 2 g of alkali-resistant glass fiber.
(Cem-filtrated strand length 25 mm), 10 g of asbestos and 4 g of pulp were added, 400 ml of water was added to this, and after kneading with a mixer, a mold covered with cloth (150
mm x 200 mm) and dehydrated for 1 minute at a pressure of 100 Kg/cm ² . Fifteen colored cement boards were made using the same procedure. Curing was carried out for 28 days at 20°C and 80% R and H, and then it was cured indoors. Table 4 shows the bending strength of the obtained cement boards for each material age and the pH of the crushed cement boards. (Bending strength test is based on JIS A-1408)

[Table] *Average value of 5 sheets each Example 2 To 160 g of ordinary Portland cement board and 40 g of red mud (dry) with the composition shown in Table 1, add 10 g of alkali-resistant glass fiber and 4 g of pulp, which are the same as in Example 1, and add water.
After adding 400 ml and kneading with a mixer, 15 colored cement boards were obtained in the same manner as in Example 1. Table 5 shows the bending strength of the obtained cement boards for each material age and the pH of the crushed cement boards.

[Table] * Comparison example of average value of each 5 sheets 1 For comparison, without using red mud, add 10 g of alkali-resistant glass fiber and 4 g of pulp to 200 g of ordinary Portland cement, add 400 ml of water to this, and mix with a mixer. Cement board was made in the same manner as in Example 1.
I got 15 pieces. Table 6 shows the bending strength of the obtained cement boards for each material age and the pH of the crushed cement boards.

[Table] * Comparison example of average values of 5 sheets each 2 For comparison, red mud was not used, and 200 g of ordinary Portland cement, 2 g of alkali-resistant glass fiber, and asbestos were used.
10 g of pulp and 4 g of pulp were added thereto, 400 ml of water was added thereto, and after kneading with a mixer, 15 cement boards were obtained in the same manner as in Example 1. Table 7 shows the bending strength of the obtained cement boards for each material age and the pH of the crushed cement boards.

[Table] * Average value of 5 sheets each

Claims (1)

[Claims] 1. When manufacturing fiber-reinforced cement boards, alkali-resistant glass fibers are added to some or all of the reinforcing fibers.
A method for producing an alkali-resistant glass fiber-reinforced colored cement board, which comprises mixing 0.5 to 5% by weight of cement and adding 5 to 30% by weight of red mud (calculated as solid content).