JPH02196051A - Production of fiber-cement board - Google Patents

Abstract

PURPOSE:To obtain a fiber-cement board having satisfactory strength without deteriorating the reinforcing fibers by adding coarse aggregate and reinforcing fibers other than asbestos to a blend of cement having a specified Blaine value with silica having a specified Blaine value, mixing and molding them and curing this molded body in water. CONSTITUTION:Coarse aggregate and reinforcing fibers other than asbestos are added to a blend of 35-45wt.% cement having 6,000-8,000cm<2>/g Blaine value with 30-40wt.% silica having 10,000-12,000cm<2>/g Blaine value so as to regulate the total amt. of them to 100wt.%. They are mixed, kneaded with water and molded. This molded body is naturally cured and further cured in water for >=2 weeks. Fibers of PP, PE or glass are preferably used as the reinforcing fibers other than asbestos.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a fiber cement board, and more particularly to a method for manufacturing a fiber cement board using fibers other than asbestos as reinforcing fibers.

[Conventional technology]

It has been well known that asbestos fiber is useful as a reinforcing fiber for cement products, but its use has been forced to be discontinued due to both the fact that it causes dust pollution and resource depletion, and various alternative fibers to asbestos are being explored. This is the current situation.

The use of organic synthetic fibers such as polypropylene fibers or glass fibers as substitute fibers for asbestos has been proposed and widely implemented.

By the way, when the above-mentioned organic synthetic fibers are cured at high temperature and high pressure for cement products, the fibers deteriorate or melt due to the heat during curing, so there is a problem that the reinforcing effect is not sufficient17), and in the case of glass fibers, There was a problem in that the corrosion caused by the alkali was accelerated by the heat, resulting in deterioration.

(Problem to be solved by the invention) In view of the above problems, this invention
Even if reinforcing fibers of m are used, there will be no deterioration of the fibers, etc. (
The purpose of this invention is to provide a method for manufacturing fiber cement boards that can develop sufficient strength.

(!It! The technology that led to solving the problem) That is, the method for manufacturing fiber cement board of this invention has a plain value of 6000 to 8.
000 cm3/g cement 35-45% by weight, plain value 10000-12000 cm3/g silica 30
Adding the remaining weight percent of coarse aggregate and reinforcing fibers other than asbestos to a cement and silica mixture consisting of ~40 weight percent, and mixing;
The method is characterized in that a water-added shaped body is molded, the shaped body is naturally cured, and then it is cured in water for two weeks or more.

[Function] In this invention, the plain values of cement and silica are limited by making the particles of both particles smaller than a certain level, thereby increasing the specific surface area, increasing the reactivity, and achieving high strength when cured in water as described below. This is to generate a cement matrix of
If it is less than 00cm3/g, the above-mentioned effect cannot be obtained, and if it is larger than 8000d/g, the permeability of added water will deteriorate, especially in the case of dry manufacturing, and cement particles will adhere to the compression roll. This is because the resulting shaped body cannot be molded.

The same applies to silica, and the plain value is set to 10,000 to 12,000 dlg as a range in which the above-mentioned disadvantages do not occur.

Any reinforcing fibers other than asbestos may be used as the reinforcing fibers added to these cement and silica formulations, but preferred examples include polypropylene, polyethylene, and glass fibers.

In this invention, underwater curing is used as a curing means for cement products in order to avoid the high heat caused by autoclaving, and in conjunction with strengthening the bonding strength of the cement matrix by limiting the plain values of cement and silica as described above. This is to obtain strength comparable to autoclave curing.

〔Example〕

Next, the present invention will be explained in detail.

Using cement with a plain value of 6,000 cm3/g and silica with a plain value of 10,000 cm3/g, the blended raw materials in Table 1 were mixed uniformly in a dry state, and a piece of 5 mm thick, 45 cm long and wide, with 90 cm ends was prepared using a dry method. A large number of plates were formed, and after being naturally cured in the air for two days, they were cured in water for two weeks.

After that, when we conducted a JIS No. 4 bending test, Table 1
The results are shown in the column below.

Table 1 Table 2 Next, as a comparative example, instead of the underwater curing in Examples 1 to 4, autoclave curing was performed at 178° C. for 10 hours.

When a JIS No. 4 bending test was conducted on the above-mentioned plate material, the results shown in Table 2 showed that the physical properties had deteriorated due to thermal deterioration of the reinforcing fibers.

Next, plates were formed by curing in water in the same manner as in the example except that cement with a plain value of 3000 aj/g and silica with a plain value of 4000 cd/g were used, and a JIS No. d bending test was performed on these plates. 3, and it was found that the strength was considerably inferior compared to the example.

Table 3 JIS J bending test Next, in Comparative Examples 2-1 to 2-4 above, instead of curing in water, autoclave curing was performed at 178°C for 10 hours, and a JIS J bending test was conducted. The results shown in Table 4 Therefore, it was found that the strength equivalent to that of the example could not be obtained.

Table 4 〔effect〕

Claims (1)

[Claims] (1) Plain value 6000-8000cm^3/g cement 35-45% by weight, plain value 10000-12
000cm^3/g of cement consisting of 30 to 40% by weight of silica, a silica blend, with the remaining weight% of reinforcing fibers other than coarse aggregate and asbestos added, mixed with water, and shaped into a shaped body. A method for manufacturing a fiber cement board, which comprises curing the shape naturally and then curing it in water for two weeks or more.