JPH07187856A - Production of permanently embedded form for highly durable concrete - Google Patents

Abstract

PURPOSE:To easily obtain high durability, weatherability and high strength by molding a kneaded product of cement and fiber, etc., by extrusion and subjecting the obtained molding to steam curing so that it has a specified porosity and bending strength. CONSTITUTION:The kneaded product is obtained by compounding 80-99wt.% cement, 1-20wt.% fiber of one or more kinds selected from among inorganic natural fiber, organic natural fiber or synthetic fiber, water and sand. Next, this kneaded product is molded by extrusion to mold the embedded form having the protruding part 11 and the recessed part 12 having about 300mm width, about 25mm thickness (at the protruding part) and about 3000mm length on the rear. Subsequently, the obtained molding is charged into a steam curing room to be cured at about 60 deg.C for about 16 hours, thus the permanently embedded form for concrete, having 10-25% porosity and >=8PMa bending strength, is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a permanent buried formwork for concrete, and more specifically, it has high durability, that is, excellent weather resistance and high strength, which can be easily manufactured. The present invention relates to a method for manufacturing a permanent buried formwork for concrete.

[0002]

2. Description of the Related Art Conventionally, formwork materials generally used in the formwork construction method for buildings and the like have been used on the premise that they are demolded and reused. Plywood and steel lumber called is used. In recent years, molds made of various materials have been used or tried. For example, thin concrete boards, glass fiber reinforced cement boards and other forms, FRP (fiber reinforced plastic) products that are lightweight and aesthetically pleasing, and for the purpose of recycling hard paper waste forms and non-woven fabrics as new forms in recent years. There is also a water-permeable formwork that uses a wooden formwork.

[0003]

However, the formwork as described above has an inherent drawback due to the difference in the material, and in order to use it in a permanent formwork such as a wooden formwork or a resin formwork, etc. There is a problem that it is inferior in fire resistance, and a water-permeable mold that uses a non-woven fabric and a wooden mold together or a discard mold made of hard paper is preferable because it has water permeability, but there is a problem with durability that can be used semipermanently There is also steel material, resin and FR
There is a problem in that a good concrete structure cannot be obtained because the product made of P does not have properties such as water absorption and water permeability and therefore has no function of modifying the concrete to be placed. On the other hand, the use of wooden formwork has been a problem in recent years due to environmental problems, demand for reducing wood resources and shortening the construction method, etc.
Alternative formwork building materials, especially buried formwork, have been demanded.

Therefore, as a result of studying such a problem, the present inventor found that the condition of the formwork material containing cement is that the excess water of the placed concrete is absorbed and the water of the internal concrete is absorbed. It is necessary to reduce the cement ratio, and in order to have such an absorbing effect, it is necessary to make the porosity of the mold material 10% to 25%. In order to make the formwork maintenance-free (no need to hold or manage), excellent weather resistance is a prerequisite, and the bending strength of the formwork material is 8 MPa to 45 M.
There are two points that a strength of Pa is required.

Therefore, when the form material satisfying these two points was further investigated, the form obtained by kneading the mixture of cement and fiber with water, extruding, and further steam curing was obtained. It has been found that the embedded formwork has excellent performance, and the present invention has been completed here. Therefore, the problem to be solved by the present invention is 10
% To 25% porosity and a bending mold having a bending strength of 8 MPa or more can be easily manufactured, and further high durability, that is, excellent weather resistance, and high strength permanent burying mold for concrete. It is to provide a manufacturing method of.

[0006]

The problems to be solved by the present invention are achieved by the following inventions. (1) In a method for manufacturing a permanent buried formwork for concrete having a porosity of 10% to 25% and a bending strength of 8 MPa or more, a mixture of cement, fiber and water is kneaded, and the obtained kneaded product is extruded. Then, a method for producing a permanent buried formwork for concrete, which comprises subjecting the obtained molded product to steam curing.

(2) The method for producing a permanent buried formwork for concrete as described in the above item 1, wherein sand is added to the mixture.

(3) The method for manufacturing a permanent buried formwork for concrete according to any one of the above items 1 and 2, wherein the bending strength is 8 MPa to 45 MPa.

(4) Cement 80% to 99% by weight and fiber 20% to 1% by weight, the permanent buried formwork for concrete according to any one of the above items 1 to 3. Manufacturing method.

(5) For concrete according to any one of the above items 1 to 4, wherein the fiber is at least one kind selected from inorganic natural fibers, organic natural fibers and synthetic fibers. Manufacturing method for permanent buried formwork.

(6) The method for producing a permanent buried formwork for concrete according to any one of the above items 1 to 5, wherein the back surface of the formwork is formed in an uneven shape.

The present invention will be described in more detail below. The permanent buried formwork for concrete of the present invention is 10%.
A permanent embedding formwork for concrete having a porosity of -25% and a bending strength of 8 MPa or more is used. The permanent embedding formwork for concrete is composed of cement and fibers as a form material, Is added and kneaded, the resulting kneaded product is extruded and molded, and the resulting molded product is steam-cured to obtain a porosity of 10% to 25% and a pressure of 8 MPa.
Those having the above bending strength can be easily obtained, and therefore, an embedded formwork having further higher durability can be obtained, and the embedded formwork is further integrated with concrete after construction to further improve weather resistance. Also, a concrete structure having excellent bending strength can be obtained.

By the method for producing a permanent buried formwork for concrete of the present invention, excellent durability can be obtained. This durability includes bending strength, neutralization prevention, salt penetration prevention, frost damage prevention, etc. Weather resistance such as ultraviolet rays, wind and rain, and acid rain 2
It is a kind of effect. The material constituting the permanent buried formwork for concrete of the present invention, cement and fibers, as this cement, including ordinary Portland cement, early strength Portland cement, Portland cement such as ultra early strength Portland cement, blast furnace cement. Any mixture of silica cement, mixed cement such as fly ash cement, and alumina cement may be used.

Examples of the fibers include inorganic fibers such as wollastonite and asbestos, natural organic fibers such as pulp and synthetic fibers, and more specifically, the natural organic fibers include NB.
K pulp, LBK pulp, cotton pulp, hemp pulp and other pulp, wood powder, sawdust, cork powder, various fibers, and the like,
Examples of synthetic fibers include vinyl chloride, nylon, polyamide, polyester, polyurethane, vinylon, polyethylene, aramid fiber, and carbon fiber. These fibers may be used in any length, but preferably 1
mm to 20 mm long is preferable, and further 2 mm to 1
A length of 0 mm is preferable. The fiber diameter is 0.0
01 mm to 2 mm is preferable.

The ratio of cement to fiber used in the present invention is 80% to 99% by weight of cement and 20% of fiber.
Wt% to 1 wt%, preferably cement 85
% To 98% by weight and 15% to 2% by weight of fibers. If the amount of cement is less than 80% by weight, the strength is insufficient, which is not preferable. If the amount of cement exceeds 99% by weight, the strength is not increased and it is economically disadvantageous. If the fiber content is less than 1% by weight, the reinforcing effect is not so great, and if it exceeds 20% by weight, the strength is rather lowered.

The permanent buried formwork for concrete of the present invention is
It is produced by kneading a mixture of cement, fiber and water, extruding the obtained kneaded product, and then subjecting the obtained molded product to steam curing. The mixture of the cement, the fiber and the water may be prepared by adding the fiber to the cement and mixing the mixture, and then adding the water to the mixture, or kneading the cement, the fiber and the water at the same time. The kneading time may be relatively short, and a sufficiently uniform kneaded product can be obtained in 2 to 15 minutes. Further, sand may be added to this mixture or kneaded product, and the addition amount of sand is preferably 50% by weight to 300% by weight with respect to cement. Further, the amount of water used when forming the kneaded product of the cement and the fiber used in the present invention is preferably 10 parts by weight to 55 parts by weight of water with respect to 100 parts by weight of the kneaded product, and the obtained buried type The water-cement ratio of the frame may be an ordinary water-cement ratio, but is preferably 15% to 50% in water-cement ratio.
%.

In the method of manufacturing a permanent buried formwork for concrete of the present invention, the kneaded product kneaded as described above is extruded. This extrusion molding may be a molding method usually used in this technical field, and for example, an extruder is used to extrude the kneaded product from an extrusion die to form a desired shape.
The extrusion of this kneaded material is a method of continuously extruding it by a screw in a cylinder. The extruded buried formwork is then placed in a curing chamber and steam cured. This steam curing is performed by sending high temperature steam to a curing chamber under atmospheric pressure at a temperature of 40 ° C. to 85 ° C. and a curing time of 2 hours to 36 hours. At this time, the temperature rising rate is 12 ° C / h to 33 ° C / h.
Therefore, the maximum temperature of 60 ° C to 75 ° C is preferable. The pre-positioning time before steam curing is preferably 1 to 12 hours. This regimen can also be repeated as needed.

In the present invention, this steam curing promotes the porosity and the bending strength so that the porosity becomes 10% to 25% and the bending strength becomes 8 MPa or more. However, when concrete is poured by having a porosity in this range, the components of the concrete flow into the pores, the formwork and the poured concrete are integrated, and excess water is absorbed to obtain high strength. Therefore, a product having excellent weather resistance can be obtained. Therefore, when the porosity is less than 10%, the components of the concrete containing water do not sufficiently flow in, so that the performance of the form becomes insufficient, and when the porosity exceeds 25%, the component material of the form becomes small. Therefore, sufficient durability cannot be obtained. The size of pores or pores formed in the present invention is preferably 10Å to 2,500Å in diameter. Furthermore, according to the method for producing a permanent buried formwork for concrete of the present invention, a preferable buried formwork having a bending strength of 8 MPa or more, preferably 8 MPa to 45 MPa can be obtained.

The permanent buried formwork for concrete used in the present invention is produced in any shape, and the surface in contact with the cast concrete may be flat or uneven, but is preferably. It is good to have unevenness. When the formwork has irregularities, it is preferable to place the reinforcing bars for the cast concrete in the depressions. Examples of the shape of the unevenness include a corrugated shape, a zigzag shape, a Mt. Fuji shape, and a U-shape.
The concave portion and the convex portion may be symmetrical or asymmetrical, or may be a combination of these shapes. Aggregates such as sand and gravel can be added to the mold material used in the present invention, and if necessary, additives or admixtures well known in the art can be added.

[0020]

In the present invention, the mixture of cement, fiber and water is kneaded, extruded and then steam-cured, so that the porosity is easily 10% to 25% and the bending strength is 8%.
An embedded formwork that satisfies the condition of MPa or more can be easily obtained, and by using this embedded formwork, after placing concrete, a high-strength concrete structure is integrated between the formwork and the concrete. Obtainable.

[0021]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 The buried form shown in the partial perspective view of FIG. 1 was manufactured by the manufacturing method of the present invention, and concrete was poured using this to form a concrete structure. In FIG. 1, the buried formwork 1
Has a convex portion 11 and a concave portion 12 on the back surface of the embedded formwork 1. The kneaded product for formwork is 77% by weight of cement, fiber (carbon fiber (pitch type), diameter 0.0145 m)
m, length 10 mm, aspect ratio 690) 2.7% by weight, water 27% by weight and methylcellulose (thickener) 1.
3 wt% was prepared and kneaded for 6 minutes to obtain a uniform kneaded product. Then, a material for a mold made of this kneaded product is extruded and molded to have a width of 300 mm, a thickness (convex portion) of 25 mm, and a length of 3,
A 000 mm embedded formwork 1 was molded. The molded product was carried into a steam curing chamber and cured under atmospheric pressure at a preheating time of 4 hours at a temperature rising rate of 15 ° C / hour at a temperature of 60 ° C for a curing time of 16 hours. The buried formwork 1 thus obtained was excellent in weather resistance and strength and had high durability.

Example 2 In Example 1, cement 51 was used as a kneaded material for formwork.
Wt%, sand 26 wt%, fiber (carbon fiber (pitch type), diameter 0.0145 mm, length 10 mm, aspect ratio 690) 2.0 wt%, water 20 wt% and methylcellulose (thickener) 1 wt% Except that the kneaded product of
Similar to Example 1, width 300 mm, thickness (convex portion) 25
An embedded mold 1 having a length of 3,000 mm and a length of 3,000 mm was manufactured and steam-cured under the same conditions as in Example 1.

As shown in the partial perspective view of FIG. 2, using the buried formwork 1 thus obtained, concrete 2
Was cast to prepare a sample of a concrete structure. At this time, the reinforcing bars 3 were arranged on the concave portion 12 of the buried form 1 and on the outer surface side of the concrete 2. A durability test was conducted using this sample, and the results are shown in Table 1. As a comparative example, a concrete mold was used, and concrete was cast into this mold to form a concrete structure. The strength was calculated from the coefficient of restitution of the Schmidt hammer.

[0025]

[Table 1]

As is clear from Table 1, the embedded formwork obtained by the manufacturing method of the present invention is excellent in bending strength,
The strength of the cocrete structure is superior to that of the comparative example and the weather resistance is also good.

[0027]

The method for producing a buried form according to the present invention has a porosity of 10% to 25% by kneading a mixture of cement, fiber and water, extruding, and steam curing. In addition, an embedded formwork that satisfies the condition that the bending strength is 8 MPa or more can be easily manufactured, and thus a permanent embedded formwork for concrete having further excellent weather resistance can be obtained, and concrete can be cast using this embedded formwork. The provided concrete structure has a particularly remarkable effect that the mold and the concrete are integrated to obtain a high-strength and highly durable concrete structure having excellent weather resistance.

[Brief description of drawings]

FIG. 1 is a partial perspective view showing a permanent buried formwork for concrete of the present invention.

FIG. 2 is a partial perspective view showing a concrete structure using the permanent buried formwork for concrete of the present invention.

[Explanation of symbols]

 1 Embedded formwork 2 Casting concrete 11 Recessed portion 3 Reinforcing bar 12 Convex portion

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location E04B 1/16 C 7121-2E 2/86 FA / (C04B 28/02 14:38 Z 16 : 02 Z 16:06) Z (72) Inventor Yukinori Kawahara 1-297 Kitabukuro-cho, Omiya-shi, Saitama Mitsubishi Materials Corporation Cement Research Institute

Claims (6)

[Claims] 1. A method for producing a permanent buried formwork for concrete having a porosity of 10% to 25% and a bending strength of 8 MPa or more, wherein a mixture of cement, fiber and water is kneaded to obtain a kneaded product. A method for producing a permanent buried formwork for concrete, which comprises subjecting to extrusion molding and then subjecting the obtained molded product to steam curing. 2. The method for producing a permanent buried formwork for concrete according to claim 1, wherein sand is added to the mixture. 3. The method for producing a permanent buried formwork for concrete according to claim 1, wherein the bending strength is 8 MPa to 45 MPa. 4. The production of a permanent buried formwork for concrete according to claim 1, which comprises 80% by weight to 99% by weight of cement and 20% by weight to 1% by weight of fibers. Method. 5. The permanent embedding for concrete according to claim 1, wherein the fiber is at least one selected from inorganic natural fiber, organic natural fiber and synthetic fiber. Formwork manufacturing method. 6. The method for manufacturing a permanent buried formwork for concrete according to claim 1, wherein the backside of the formwork is formed in an uneven shape.