JPH0681435A - Concrete staircase and corridor constituted of plate - Google Patents

Abstract

PURPOSE:To obtain high mechanical strength by molding concrete staircases and treads from an alumina cement composite material containing fly ash wool. CONSTITUTION:After fly ash wool is so properly cut that it has an appropriate length of fiber, if necessary, they are added into alumina cement paste. After they are sufficiently mixed with a hand-mixer, they are poured into a plastic form and are solidified and cured to manufacture fly ash wool reinforced alumina cement plates. Accordingly, particularly, excellent thermal shock efficiency and fire resistance suitable for staircase treads can be obtained.

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention can be used for stairs or corridors of low-rise and middle-high rise apartments, office buildings, apartments, condominiums, etc. of high strength, high fire resistance and light weight. The present invention relates to a concrete stairway and a corridor component plate, and is particularly used in the field of manufacturing a precast concrete tread plate.

[0002]

2. Description of the Related Art Performance required for stairs and corridor components of low-rise and medium-high-rise apartments such as prefabricated structures, such as stairs, footboards, waist boards, wallboards, corridor floorboards, wallboards, etc. Is non-combustible, lightweight, high mechanical strength, impact resistance, surface hardness, fire resistance, sound absorption, soundproofing, workability, etc. Various materials have been developed to satisfy these performances.
It is used. The materials are roughly classified into two types, metal type and concrete type.

Steel plates are used as metal-based components. However, especially in the case of treads and floorboards,
Since the footsteps easily echo, sound absorption and soundproofing are required.
Therefore, it is further necessary to attach a rubber to the surface of the iron plate or use a damping steel plate. Further, in the case of metal, rust prevention treatment is indispensable, and it is necessary to apply paint after construction. In addition, metals can melt in a fire. As described above, the metal component plate has many problems, particularly in terms of sound absorption / soundproofing property, corrosive property, workability, nonflammability, and the like.

Concrete-based stairs and corridor components are also used in large quantities. In this case, there is relatively little concern about noise and corrosion, but there is another major problem. Conventional concrete boards are generally made on-site, but they take a lot of time, such as formwork preparation, concrete placement, and formwork removal, which causes a delay in the construction period. is there. When producing industrial products, it is necessary to always give importance to work efficiency, but in the case of cementitious materials, long-term curing is required to develop strength. In general, it takes 28 days for underwater curing to reach practical strength, which requires a large amount of production equipment, curing equipment and the like. Whether or not strength can be developed early and shipped as a product is also important from the viewpoint of production efficiency.

Further, recently, since the prefabricated construction method has been adopted in the construction field, various building materials are manufactured as precast concrete products. Concrete boards such as treads are also made by this method, but if the shape of the concrete board is the same as that of the case of on-site casting, it will be remarkably large in size and will be heavy and difficult to handle. However, if the wall thickness is reduced to reduce the weight of the concrete plate, problems will occur in terms of strength.

[0006] In order to solve these problems, concrete boards reinforced with various reinforcing fibers have been developed and used in concrete tread boards, which have a problem of mechanical strength. The reinforcing fibers in that case include steel fibers, glass fibers, carbon fibers, asbestos fibers, synthetic fibers such as vinylon, and the like, but these conventional reinforcing fibers all have various problems.

Since steel fibers have a large specific gravity, it is difficult to uniformly distribute and arrange them in a product.
Further, since corrosion is unavoidable, long-term strength reduction cannot be avoided. Further, since the glass fiber is dissolved when dispersed in the cement paste, it cannot be used unless it is an alkali resistant glass fiber containing a large amount of zirconia component. At the same time, the cement used must also be a special grade with low alkalinity. Therefore, it is inevitable that the product price of concrete boards will increase.

[0008] Carbon fibers are beginning to be used in large quantities in curtain walls and the like because of their excellent chemical resistance and excellent mechanical strength. However, there are problems that the density of carbon fiber itself is as large as about 1.5 to 1.8 g / cm ³ , it is difficult to disperse in mortar or concrete, it is expensive, and there is no oxidation resistance. Therefore, the range of use is limited. Asbestos fibers have been used in large quantities in the cement secondary product field because of their fire resistance and low cost. However, asbestos fibers are carcinogenic and their use is beginning to be restricted, and they are about to be stopped. Synthetic fibers such as vinylon have recently begun to be used because the concrete products in which they are dispersed have a large deformability. However, the mechanical strength of vinylon itself is low, and addition of vinylon does not strengthen the strength. Further, as a matter of course, it is weak against heat and cannot be used as a refractory material.

On the other hand, in terms of fire resistance, the Portland cement type material, which is widely used as concrete or mortar in general, has no effect on the strength when the working temperature is 100 ° C. or lower, but when it is 110 ° C. or higher. As the shrinkage occurs, the hydrate interlayer water is also lost, and then the hydroxyl groups are dehydrated to further shrink, and the voids increase and the cement bond is lost, so that the strength decreases. 300
At temperatures above 0 ° C, the strength is reduced to about half the initial strength. At 600 ° C. or higher, the cement hardened product becomes so fragile that the prototype cannot be retained, and the mechanical strength is drastically reduced.

Alumina cement is known as a cement material that can be used under high temperature conditions. This is a cement produced by mixing bauxite and limestone, heating them until they are melted or a part thereof is melted and sintered, and then rapidly cooled and ground. This alumina cement has the characteristics of early strength and resistance to abrasion and impact. It is also stable in water containing sulfate ions. Alumina cement is a binder for castable refractories and plastic refractories that is not only used by being hardened with water, but also by adding refractory granules or powders and kneading with water to obtain the desired shape. Is also used as.

However, a construction body using alumina cement as a binding material for castable refractories or the like may explode when heated to a high temperature. This explosion is caused by desorption of free water in the matrix and rapid evaporation of water generated by dehydration of hydrate. As a countermeasure, select temperature rising conditions,
There is a method of adding an explosion proof material. As an explosion proof material,
Fibers, colloids such as basic aluminum lactate, metal aluminum, etc. are known, and such explosion-proof fibers include rock wool, glass fibers, ceramic fibers, alumina fibers, etc., and are appropriately selected depending on the required temperature range. Then used. However,
Rockwool and glass fiber melt at temperatures above 600 ° C, so the applicable temperature limit is low.
The product obtained must be alkali resistant. Also,
Ceramic fibers and alumina fibers are expensive and difficult to put into practical use.

[0012]

For these reasons, conventionally used concrete boards containing various fibers all have many problems. However, it is unavoidable that these concrete boards are lightweight,
In reality, it must be used as high-strength, fire-resistant concrete stairs and corridor components.

Therefore, the inventions described in claims 1 and 2 are made in view of the problems of the above-mentioned conventional techniques, and have high fire resistance and mechanical strength, are inexpensive, and are manufactured. It is an object of the present invention to provide a concrete stairway and a corridor component board, particularly a concrete tread board.

[0014]

It has been found that the above objects of the present invention can be achieved by a concrete stairway and corridor component plate, particularly a concrete tread plate, which comprises an alumina cement composite material containing fly ash wool. Was issued. As a result of various studies, fly ash wool reinforced alumina cement composites were prepared by using fly ash wool with high fire resistance obtained by melting fly ash at high temperature and forming into fibers, and using alumina cement with high fire resistance as a matrix. By using the material, it is possible to realize a concrete stairway and a corridor component plate, particularly a concrete tread plate, which satisfies the above-mentioned various purposes. Here, examples of the concrete stairs and corridor constituent plates of the present invention include a stairway tread, a communication board, a waist board, a wall board, and a corridor floor board, a wall board, and the like.

The fly ash wool used in the present invention can be obtained by melt-spinning coal ash (fly ash), which is a by-product of burning coal, at a high temperature of a few thousand and several hundred degrees to form fibers. Fly ash as a raw material is similar to the chemical composition of basalt, andesite, or blast furnace slag, which is the raw material for rock wool, but due to advances in manufacturing technology,
It has been found possible to produce high performance fibers with properties far superior to rock wool. Compared to rock wool, fly ash wool has a relatively long fiber length, which is advantageous in terms of heat insulation, and has a high melting temperature, and thus has excellent heat resistance. Furthermore, it meets the social demand for effective use of fly ash as described above and is excellent in economic efficiency.

The composition of fly ash as a raw material differs depending on the place of production of coal, but the main ones are silicon dioxide (silica) and alumina.
It accounts for 60 to 80% of the whole. In addition, it contains a small amount of ferric oxide, calcium oxide, magnesium oxide and the like. In order to maintain the quality of fly ash wool, it is preferable that the components of fly ash as a raw material are stable. Further, fly ash having a content of silicon dioxide as low as possible and a content of alumina as high as possible is preferable because it has a low viscosity at a high temperature and can be melted at a low temperature.
Further, in order to approximate the composition and solubility of fly ash wool to those of rock wool, auxiliary materials such as limestone can be added to fly ash.

The fly ash wool can be manufactured by a conventional mineral wool manufacturing method, for example, a batch system method (cupola method) by a cupola in which a powdery raw material is solidified and charged, or the raw material is a powder. An electric furnace method (for example, Geotech method by Geotech) using an electric furnace that is directly charged can be used. In particular, the electric furnace method is preferable because it has advantages such as a low power consumption rate, a high yield, a low shot sphere (non-fibrous particle) mixing ratio, and a long fiber length can be expected. The fly ash wool may optionally have the shot spheres at the ends of the fibers removed by a sprinkling operation. Fiberization of the high-temperature melt requires melting at a temperature at which an appropriate viscosity is obtained, and depending on the composition of the raw material coal ash, 1100-1
Temperatures of 900 ° C, especially 1400 to 1700 ° C, are suitable.

When the diameter and surface condition of fly ash wool are observed with a scanning electron microscope, the surface is smooth and most of them are glassy (amorphous). The diameter of fly ash wool has a distribution of about 1 to 10 μm, and the average diameter is almost 3
μm. The fiber length is about 20 to 300 mm. X
When the line diffraction analysis was performed, only the diffraction line of silicon dioxide (α-cristobalite) was observed, and the other diffraction lines were not found. The heat resistance of fly ash wool was examined by heating to 1300 ° C. in air using a thermal analyzer. As a result, there was no change in the thermogravimetric curve, and the weight did not increase or decrease. In the differential heat curve, there was no clear endotherm and exothermic peak at 1000 ° C or lower, but an exothermic peak near 1000 ° C and an endothermic peak near 1175 ° C were found. The former exotherm was due to the crystallization of vitreous fly ash wool, and the latter endotherm was due to the melting of fly ash wool. In fact, there is no fibrous fly ash wool in the platinum sample dish after analysis,
It was only melted and solidified. Therefore, the operating temperature of the composite material using the fly ash wool is preferably a temperature at which crystallization does not occur, that is, 1000 ° C. or less. However, if it is a short time, it can be used up to around the melting point of 1175 ° C. This temperature range is the same as that of various ceramic fibers conventionally provided.

Alumina cement is an inorganic hydraulic cement whose main component is calcium aluminate. The properties of alumina cement vary depending on the composition of CaO, Al ₂ O _3, etc., the particle size, and the like, and there are many types, from early-strength ones to fire-resistant ones. It is preferable to increase the proportion of CaO when the main purpose is to have early strength and mechanical strength, and to increase the proportion of Al ₂ O ₃ when aiming for fire resistance. The composition and particle size can be appropriately selected according to the purpose. If necessary, other additives such as aggregates, stabilizers,
A fluidizing agent or the like can be added.

The amount of fly ash wool that can be contained in the alumina cement composite material can be appropriately set depending on the properties of the alumina cement used, the water / cement ratio (W / C), and the like. Generally, it is advantageous that the higher the fly ash wool content, the higher the mechanical strength can be.However, if the content is too high, it becomes difficult to mix or disperse the fly ash wool into the cement, so the mechanical strength is high. descend. The fly ash wool content in the alumina cement composite can be controlled by the fly ash wool / cement ratio (FAW / C) during manufacturing. The FAW / C is usually about 0.01 to 0.4, and particularly preferably 0.1 to 0.25. The W / C is usually about 0.25 to 0.6, and particularly preferably 0.3 to 0.45.

The fly ash wool-containing alumina cement plate for stairs and corridor components according to the present invention has a mechanical strength depending on the amount of fly ash wool added, water / alumina cement ratio, type of alumina cement, curing method, shape and the like. Although it may be affected, the fire resistance and mechanical strength are remarkably improved as compared with the case where it is manufactured by the conventional precast concrete method. By appropriately selecting these manufacturing conditions, it is possible to easily manufacture a preferable stairway and corridor component board. The manufacturing conditions were studied in detail to produce a fly ash wool-containing cement board, which weighs 210 kg / cm.
The flexural strength and ^2, compression strength of 1450kg / cm ² was found to be achieved. These are more than cement alone
The bending strength is 3.5 times and the compressive strength is twice as large, which is presumed to be due to the reinforcing effect of fly ash wool.

As described above, according to the present invention, the mechanical strength is improved as compared with the conventional cement board. Therefore, particularly in the case of a tread that requires a sufficient strength, the amount of cement required to achieve the same mechanical strength is small, so that the weight and cost of the cement plate can be reduced. . Furthermore, the manufacturing conditions of the composite material were examined in detail, and for example, the production of fly ash wool reinforced alumina cement board having a mechanical strength that was satisfactory as a tread, was found to have a density of about 1.9 to 2.4 g / cm ^3. was gotten. This is compared with, for example, a known extruded cement hollow board "Mace" (manufactured by Mitsubishi Materials; length 1 m, width 1 m and thickness 60 mm) known as a step board for stairs. In contrast to 50 kg, when the material of the present invention having the same size is manufactured, the weight is only about 30 to 35 kg. It can be seen that the tread of the present invention is much lighter.

Furthermore, the surface of the cement board according to the present invention was extremely hard, and even if it was strongly rubbed at the corner of a coin (10 yen), it was not scratched and no cement powder was produced. The surface of this cement board was also excellent in abrasion resistance.

Further, the fly ash wool-containing cement board of the present invention has high fire resistance. For example, when the cement board of the present invention was directly put into an electric furnace heated to 900 ° C. from room temperature, it did not burst or shatter. Furthermore, even after being kept in the electric furnace for 120 minutes, no change in shape such as expansion and contraction was observed. Further, the fly ash wool-containing alumina cement plate having excellent mechanical strength according to the present invention was put in an electric furnace at 900 ° C.
When the mechanical strength (bending strength and compressive strength) of the cement board was determined after heat treatment for a minute and cooling, the mechanical strength of this cement board was lowered by heat treatment at an extremely high temperature of 900 ° C. It was found that it has much higher mechanical strength than the cement board and is excellent in fire resistance and heat resistance. Further, the fly ash wool-containing alumina cement plate which was heated to 900 ° C. and was in a red hot state was taken out from the electric furnace and directly put into water, but it was not cracked or cracked and has excellent thermal shock resistance. I knew that.

The fly ash wool reinforced alumina cement board used in the present invention is prepared by appropriately finely dividing fly ash wool so as to have a suitable fiber length, and then adding it to the alumina cement paste according to a usual method. By mixing and dispersing, an alumina cement composite material can be prepared, which can be easily cured and cured if necessary.

The mechanical strength of the alumina cement board according to the present invention can be further improved by curing the steel in an autoclave after the initial solidification.
As described above, in the production of concrete boards, it is important from the viewpoint of production efficiency whether or not the strength of concrete boards can be developed early and shipped as products. One of the methods of developing early strength is steam curing and autoclave curing. The former is a method of curing by leaving it in water vapor, in which the temperature is relatively low and the pressure is atmospheric pressure. The latter autoclave method puts concrete condensate in the autoclave and heats it under pressure for several hours,
It accelerates the hardening reaction of cement. The pressure curing conditions specified by JIS are 180 ° C, 10 atm,
6 hours (1 cycle).

In the present invention, a simple autoclave (121 ° C,
An attempt was made to cure using 1.5 atm). Generally, the simple autoclave (pressurized steam curing) method has a larger curing effect than the steam curing method, but is less effective than the autoclave curing method. However, according to the present invention, it has been found that a cement board having sufficient strength can be obtained by pressure steam curing for a short time after one day of casting. For example, as a result of various examinations, a specimen having a bending strength of 300 kg / cm ² and a compressive strength of 470 kg / cm ² was obtained one day after casting. This shows that the strength is equivalent to that of the 7-day underwater curing, and can greatly contribute to the improvement of production efficiency.

From the above, the fly ash wool reinforced alumina cement board according to the present invention is a material that is lightweight and has high mechanical strength, fire resistance, and thermal shock resistance, and is suitable for low-rise and middle-high rise prefabricated houses. It was found that the properties of concrete stairs and corridor components, particularly stair treads, were sufficiently satisfied. Further, fly ash wool is economical because it uses fly ash, which is a waste, as a raw material. Further, pressure steam curing can be applied to the production of the concrete plate of the present invention, whereby a tread plate having high mechanical strength can be simply and quickly produced.

[0029]

EXAMPLES The present invention will be illustrated below with reference to examples, but the present invention is not limited thereto. Example 1 Alumina cement No. 1 (manufactured by Denki Kagaku Kogyo) having high mechanical strength and manufactured for construction was used as the alumina cement. Fly ash wool (made in China; see Reference Example 1 below for characteristics) was finely divided by hand to a length of 0.5 cm to 1 cm, and then a predetermined water / cement ratio (W /
A predetermined amount of fly ash wool was added to an alumina cement paste with a C ratio of 0.3 or 0.4) and thoroughly mixed with a hand mixer, followed by a plastic mold (length 6.4 cm, width 3.4 cm). , Height 0.8 cm). After 1 day, the mold was removed and cured in water for 7 days. After air drying,
The bulk density, bending strength and compressive strength of the obtained cement board were determined. The results are shown in Table-1. Where FAW
/ C indicates the weight ratio of fly ash wool / cement.

[0030]

[Table 1]

The rate of increase in strength due to the addition of fly ash wool was different depending on the W / C ratio, but it was 3.5 to 4 times the bending strength and the compressive strength was higher than that without fly ash wool. It was 1.7 to 2.5 times larger. Further, although the strength tends to decrease as the amount of fly ash wool added increases, this is probably because mixing and dispersion become difficult as the amount of fibers increases.

Further, in order to verify the fire resistance, the fly ash wool-containing alumina cement plate was heated to 900 ° C. to examine the thermal change and mechanical strength. The fly ash wool-containing alumina cement plate produced by the above method was placed in a square electric furnace, heated to 900 ° C. at a temperature rising rate of 300 ° C./hour, and held for 120 minutes. The cement board in the red hot state was taken out of the electric furnace and immediately put into water. It made a loud noise, but the cement board did not crack or crack. For comparison, when the same experiment was attempted on an alumina cement board containing no fly ash wool, many cracks were formed on the surface. By containing the fly ash wool, a remarkable effect is observed, and it can be seen that the cement plate containing the fly ash wool has extremely excellent thermal shock resistance.

Next, the fly ash wool-containing cement plate was taken out from the electric furnace at 900 ° C. and naturally cooled.
The shape of the cement plate did not change even after the heat treatment, and the shrinkage ratio was almost zero. The weight change was about 20% lighter. No cracks or swelling was observed on the surface of the cement board. The bending strength and the compression strength of the heat-treated cement board were determined.
Cement board containing fly ash wool before heat treatment,
Bending strength 210 kg / cm ^2, it was compression strength 1350 kg / cm ^2. Bending strength 100kg / after heat treatment at 900 ℃
cm ² and compressive strength decreased to 540 kg / cm ² , but even with these values, the mechanical strength is sufficiently high and is a practical value.

Example 2 In order to improve the efficiency of manufacturing conditions, the influence of pressure curing on mechanical strength was examined. Finely crush the fly ash wool by hand to a length of 0.5 cm to 1 cm, and then add a prescribed amount of fly ash wool to an alumina cement paste with a prescribed water / cement ratio (W / C = 0.3). Was added and thoroughly mixed with a hand mixer, and then a plastic form (length 14.3 cm, width 7.9 cm, height 2.1).
(cm) and the mold was removed after 1 day. To improve work efficiency, put the sample in a simple autoclave,
Curing was carried out at 0 ° C (1.5 atm) for 1 hour. The bulk density, bending strength and compressive strength of the obtained cement board were determined. For the purpose of comparison, an attempt was made to produce only a cement condensate containing no fly ash wool, but the mechanical strength could not be measured because the cement hardened immediately and was broken into pieces. The results are shown in Table-2.

[0035]

[Table 2]

By performing pressure curing, FAW / C
Of 0.20, bending strength of 300 kg / cm ² and 470 k
It showed a compressive strength of g / cm ² . On the other hand, when it was cured in water for 1 week after demolding under the same conditions, the bending strength was 250 kg / cm ² ,
The compression strength was 540 kg / cm ² . Therefore, it can be seen that even with such a simple pressure curing, a strength one day after casting can be as high as that of the water curing for 7 days or more. These things mean that underwater curing equipment such as a large water tank is not required and contributes to the improvement of production efficiency.

Reference Example 1 The chemical composition of the fly ash wool raw material (fly ash) used in Examples 1 and 2 and the characteristics of the fibers of the fly ash wool were compared with those of glass wool and rock wool, respectively. It shows in Table-4.

[0038]

[Table 3]

[0039]

[Table 4]

[0040]

Industrial Applicability According to the present invention, a stairway and a corridor constituting plate made of a cement plate in which fly ash wool is dispersed in alumina cement is lighter than a conventional precast concrete cement plate and has high mechanical strength. It is suitable for stair treads. Furthermore, it has excellent thermal shock strength and fire resistance, and it was proved that it is highly safe even in the event of a fire. In addition, it is excellent in economic efficiency and can effectively utilize the conventional problem of coal ash. Further, by carrying out pressure steam curing, early strength development is possible.

Claims (2)

[Claims] 1. A concrete stairway and corridor component board comprising an alumina cement composite material containing fly ash wool. 2. A concrete tread comprising an alumina cement composite material containing fly ash wool.