JPH08404U - Liner sheet for concrete formwork - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: As a lining sheet for a concrete formwork, water permeability, water permeability, and drainage are better than woven fabrics, and yarn deviation and misalignment do not easily occur, and durability and stability of the entire sheet It is provided with excellent properties and good compatibility with the form shape. SOLUTION: 2 woven integrally from synthetic fiber yarn
It is composed of a multi-layer knitted fabric of more than one layer, the constituent yarn of the front side layer in contact with concrete is a hydrophobic fiber, and the constituent yarn of the back side layer in contact with the form is made of a fiber having a hydrophobicity lower than that of the constituent yarn of the front side layer, It is assumed that the water that has permeated into the front layer can easily permeate into the back layer.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a lining sheet for a concrete formwork used when placing and constructing a concrete structure.

[0002]

[Problems to be solved by conventional techniques and devices]

 Concrete reacts water with cement to solidify it, and in order to obtain a durable concrete structure, it is important to make the mixed state of concrete uniform and to densify concrete.

Conventionally, crater-like depressions (pits) generated on the surface of concrete impair the surface strength and durability thereof, which are particularly important for concrete structures, and contribute to the deterioration of concrete. In particular, the area around the coast is exposed to salt damage, and the above deterioration is remarkable in areas with severe environmental conditions.

That is, air bubbles and excess water in the concrete float up to the surface as the concrete hardens, but in the conventional formwork, these remain without being discharged to the outside, and these become crater-like depressions on the surface. . In addition, since excess water gathers near the formwork, the water / cement ratio in the concrete surface layer tends to increase. As a result, the concrete surface layer is likely to deteriorate.

Therefore, in order to densify the surface layer of concrete in particular and increase its durability, it is necessary to efficiently discharge air bubbles and excess water in the concrete from the mold part to the outside. As a means for that, it is considered to improve drainage by using a form lined with a sheet made of a woven fabric having water permeability and cement filter properties, for example.

However, if the sheet lined in the formwork is made of a woven fabric as described above, the yarns are likely to slip and cause yarn deviation or uneven density, or deformation or yarn slippage at the peripheral edge. Easy to fray.

Particularly in the case of a mold made of plywood, a standard size one is often used by cutting it to an appropriate size, and it may be cut diagonally or a hole may be drilled. However, in this case, deformation or fraying due to the slip of the thread is likely to occur around the cut end of the lining sheet, and therefore, the cutting process in the state where the sheet is stuck is not easy, and the usability is improved. Is bad. In addition, since the woven fabric has almost no elasticity, it lacks flexibility and flexibility in the formwork, and tensioning the formwork is troublesome. In particular, it is difficult to use it on a curved form such as a circular formwork.

[0008] In view of the above, the present invention provides a sheet for lining concrete molds, which has better water permeability, water permeability, and drainage than woven fabric, and is less likely to cause yarn deviation or misalignment. It is intended to provide a product which is excellent in durability strength and stability as a whole and is suitable for use in a form shape, which is suitable for use.

[0009]

[Means for Solving the Problems]

 The present invention, which solves the above-mentioned problems, is an inner lining sheet stretched on the surface of a concrete formwork, which comprises a multi-layer knitted fabric of two or more layers integrally knitted with synthetic fiber yarns. It is characterized in that the constituent yarn of the front side layer contacting with is composed of a hydrophobic fiber, and the constituent yarn of the back side layer contacting with the mold is composed of a fiber which is inferior in hydrophobicity to the constituent yarn of the front side layer.

In the present invention, polyolefin fibers such as polypropylene fibers are preferably used as the hydrophobic fibers. As the constituent yarns of the back side layer, it is preferable to use fibers that are more hydrophilic than the constituent yarns of the front side layer, and mainly polyester fibers are preferably used. Further, it is desirable that the back side layer in contact with the mold has a lower density than the front side layer.

[0011]

[Action]

 According to the lining sheet of the present invention having the above-mentioned configuration, when concrete is poured using a formwork to which the lining sheet is attached, bubbles and surplus water that are semi-actively pushed out of the concrete by the lateral pressure are initially generated. The lining sheet is distributed and discharged. Then, as the concrete hardens, excess water, etc. floats out from the concrete and reaches the lining sheet part consisting of a multi-layer knitted fabric, and the fibers of the surface layer positively act on the surface layer due to the capillary phenomenon. It is absorbed by and permeates into and is further distributed to the backside layer where it is discharged.

Particularly in the case of the present invention, since the constituent yarns of the front layer are hydrophobic fibers and the constituent yarns of the back layer contacting the mold are fibers having a hydrophobicity lower than that of the constituent yarns of the front layer, The water that has penetrated into the front side layer due to the tube phenomenon easily moves to the back side layer, which has poor hydrophobicity, because the constituent yarns of the front side layer are hydrophobic fibers, so that there is a difference in density between the front and back layers. Even if it does not exist, it is immediately permeated to the back side layer, flows through this back side layer portion, and is efficiently discharged to the outside from the space of the mold and the like.

When the constituent yarn of the back side layer is made of a fiber having a relatively hydrophilic property, the permeated water is more likely to move to the back side layer. Also, if the back layer has a lower density than the front layer, water that has penetrated into the back layer can move more easily to the rough back layer, and the flowability in the back layer is also good, and the water flows along the mold. It is easy and exhibits excellent water permeability, water flow and drainage.

Moreover, since the lining sheet of the present invention is made of a multi-layer knitted fabric that is integrally knitted, it is excellent in the integrity of the entire sheet and causes yarn deviation and uneven density as compared with woven cloth. Instead, it has uniform permeability and drainage throughout. In addition, there is no fear that the thread will come off at the end. Furthermore, since it has elasticity peculiar to the knitted fabric, it is excellent in adaptability and flexibility to the formwork shape.

[0015]

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a concrete formwork in which the lining sheet (a) of the present invention is stretched, and FIG. 2 shows an enlarged part of the concrete formwork. (1) is a mold body made of wood such as plywood, or made of synthetic resin or metal such as steel plate, and the lining sheet (a) is attached to the surface of the form body (1), that is, the surface of the dam. .

The lining sheet (a) is composed of a knitted fabric having a multilayer structure of two or more layers integrally knitted from synthetic fiber yarn as shown in the figure, and is knitted by double-sided knitting of a circular knitting machine, for example. It has a relatively high density knitting structure, has a cement filter property that can block the outflow of cement particles, and has the effect of aeration and drainage of air and surplus water. It consists of a knitted fabric. To increase the water permeability a little, a small hole (mesh) surface may be used. The thickness of the knitted fabric is preferably within the range of 0.5 to 1.5 mm.

(2) shows a front side layer in contact with concrete (C), (3) shows a back side layer in contact with the formwork body (1), and (4) shows an intermediate layer connecting both front and back layers. As these constituent yarns, at least the constituent yarn (2a) of the front layer (2) is made of a hydrophobic fiber such as polypropylene fiber having a relatively high hydrophobicity.

The constituent yarns (3a) of the back side layer (3) and the constituent yarns of the intermediate layer (4) are made of fibers having a hydrophobicity lower than that of the constituent yarns (2a) of the front side layer (2). Among them, it is preferable to use polyester fiber or the like which is more hydrophilic than the constituent yarn (2a) of the surface layer (2).

In the illustrated embodiment, the back side layer (3) and the intermediate layer (4) have different densities by different thicknesses, so that the back side layer (3) is 3) It has a lower density. In some cases, both the front and back layers are configured to have the same density, but in the case of the figure, the back layer (3) has a coarser mesh than the front layer (2) due to the knitting structure. In particular, in order to improve running water and drainage, it is preferable to make rough streaks in the longitudinal direction. In this case, the size of the stitches can be appropriately set according to the usage, and the maximum void in this case is 100 μm or less in diameter, preferably less than about 50 μm. The thread thickness can be set appropriately within the range of 30 to 400 denier.

3 and 4 each illustrate a knitted fabric having a multilayer structure in which the front and back sides have different densities, and FIG. 3 shows the constituent yarn (2a) and the back side of the front side layer (2). A three-layer structure knitted fabric in which the constituent yarn (3a) of the layer (3) and the constituent yarn (4a) of the intermediate layer (4) are connected is schematically shown, and FIG. 2) and a back layer (3) composed of constituent yarns (3a) are schematically shown.

Reference numeral (5) is a water passage hole, which is provided as necessary, particularly when the form body (1) is made of a non-permeable material such as metal or synthetic resin.

As in the above-mentioned examples, hydrophobic fibers are used for the constituent yarns of the front side layer (2), and fibers with poor hydrophobicity such as polyester fibers are used for the constituent yarns (3a) of the back side layer (3). With the lining sheet (a) configured as above, once the surplus water rising from the concrete permeates the front side layer (2), the permeated water easily moves to the back side layer (3) with poor hydrophobicity. Even if the front side layer (2) and the back side layer (3) are not provided with a density difference, the back side layer (3) is circulated and efficiently discharged to the outside of the mold. When the constituent yarn of the back side layer (3) is made of a fiber having a relatively hydrophilic property, the permeated water is more likely to move to the back side layer.

In particular, in the case of the above examples, since the back layer (3) has a lower density than the front layer (2), the difference in the size of the pores due to this density difference and the above-mentioned hydrophobicity Due to this difference, the water that has penetrated into the front side layer (2) is more likely to permeate and move to the back side layer (3) with coarse mesh, and exhibits excellent water flow and drainage properties.

As the above-mentioned hydrophobic fiber, a polyolefin-based fiber made of polypropylene, polyethylene, and a copolymer thereof, and among them, 100% hydrophobic polypropylene fiber is particularly preferably used. That is, polypropylene fiber is light and strong among fibers, has excellent water resistance, quick drying property, chemical resistance, etc., and is suitable for lining concrete formwork. Of course, other relatively hydrophobic synthetic fibers can also be used.

Needless to say, the fibers having a hydrophobicity lower than that of the surface layer (2) and being relatively hydrophilic may be synthetic fibers other than the polyester fibers.

Means for tensioning the lining sheet (a) having the above-mentioned configuration on the surface of the mold body (1) is, for example, a desired location such as a peripheral edge, etc. Secure with rivets and other parts so that they will not easily peel off. Of course, it is also possible to adhere to the surface of the form body (1).

In particular, since the lining sheet (a) is a multi-layer knitted fabric integrally knitted by double-sided knitting of a circular knitting machine in which stitch loops are continuous in history, In addition to being more stable than woven cloth, it has elasticity that is peculiar to the knitted fabric, and it is easy to adapt it to the shape of the formwork. You can also In addition, since the structure of the multi-layered knitted fabric is stable, the misalignment does not easily occur even when another object such as concrete comes into contact with it. In addition, the slip and detachment of the thread are unlikely to occur even at the end portion, and in the case of a plywood formwork, it is possible to easily perform cutting processing depending on the place of use.

Usage test 100% hydrophobic polypropylene fiber was woven into the front layer and polyester fiber was used in the back layer and the intermediate layer, and the back layer was made lower in density than the front layer by density difference between the front and back layers. The formwork using the lining sheet of the present invention was tested for use by placing concrete.

At the same time, as a comparative example, a usage test was also performed on a mold using a double-woven woven fabric as a lining sheet. The concrete of the test specimen was cast in four layers, with a vibrator for 60 seconds per layer. The patter ratio and surface strength were measured at four points evenly in the longitudinal direction of the central portion of the test concrete body. Surface strength depends on Schmidt hammer.

[0031]

[Table 1] As described above, the lining sheet of the present invention has more dehydration amount, less puddle ratio of the concrete surface, and more excellent surface strength than the woven sheet. This indicates that the concrete surface layer was drained smoothly and the concrete structure of the surface was densified.

[0032]

[Effect of device]

 As described above, according to the concrete type lining sheet of the present invention, it is superior in water permeability, water flow and drainage property to the woven fabric sheet, and bubbles and surplus water floating on the concrete surface are discharged. Once the excess water permeates the front layer, it moves immediately to the back layer due to the difference in hydrophobicity between the front layer and the back layer or the combination of this and the density difference. Since water is quickly and efficiently discharged to the outside, crater-like depressions due to air bubbles and water are less likely to occur on the concrete surface, and the water / cement ratio of the surface layer is also low. Therefore, it is possible to obtain a durable concrete structure which has a beautiful surface and whose surface strength is developed early and greatly increased. Furthermore, since the drainage performance is excellent as described above, it is possible to shorten the construction period from concrete pouring to demolding.

Moreover, the lining sheet of the present invention is made of a multi-layer knitted fabric, has excellent integrity and stability of the entire sheet, and has good drainage property in which thread deviation and uneven density are less likely to occur as compared with woven cloth. Can hold. In addition, it is adaptable to the shape of the mold and has flexibility, so it can be easily attached to the mold. Further, when it is used for a plywood mold, it is easy to cut the mold diagonally and perform punching, which is easy to handle.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view of a concrete formwork provided with a lining sheet according to the present invention.

FIG. 2 is an enlarged perspective view of a part of the above.

FIG. 3 is a schematic cross-sectional view illustrating a multi-layer structure knitted fabric used for the seat of the present invention.

FIG. 4 is a schematic plan enlarged view illustrating the knitting structure of the multilayer structure knitted fabric used for the sheet of the present invention.

FIG. 5 is a partial sectional view of a concrete pouring state.

[Explanation of symbols]

 (a) Liner sheet (1) Formwork body (2) Front side layer (2a) Front side layer constituent thread (3) Back side layer (3a) Back side layer constituent thread (4) Middle layer (c) Concrete

Claims (1)

[Scope of utility model registration request] 1. A lining sheet stretched on the surface of a concrete formwork, comprising a multi-layer knitted fabric of two or more layers integrally knitted from synthetic fiber yarns, and comprising a front side layer in contact with concrete. A liner sheet for concrete formwork, wherein the yarn is a hydrophobic fiber, and the constituent yarn of the back side layer in contact with the form is a fiber having a hydrophobicity lower than that of the constituent yarn of the front side layer.