JPH02277859A - Lining sheet of framework for concrete - Google Patents

Abstract

PURPOSE:To obtain the title sheet having excellent endurance and stability and good property corresponding to framework by constructing a constituent yarn facing on the concrete side of multilayer knit fabric of synthetic fiber yarn from hydrophobic yarn and constructing a layer of framework side from the layer having density equivalent to the concrete side or layer having density lower than the concrete side. CONSTITUTION:Surface side layer 2 on the concrete side is constructed from a hydrophobic fiber yarn 2a such as a polyolefin based fiber and back side layer 3 facing on a framework 1 is constructed from a layer having density equivalent to the surface side layer or lower than the surface side layer to provide the lining sheet (a) having good water-permeable property, water passing-through property and water discharging property.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a lining sheet for concrete formwork used when pouring concrete structures.

[Conventional technology and issues to be solved] Concrete is made by reacting water with cement to solidify it.In order to obtain a durable concrete structure, it is necessary to make the mixing state of concrete uniform and make the concrete dense. It is important to

Conventionally, crater-like dents (pockets) that occur on concrete surfaces impair surface strength and durability, which are particularly important for comfort structures, and are a cause of concrete deterioration. This deterioration is particularly noticeable in areas near the coast that are exposed to salt damage or have severe weather conditions.

In other words, air bubbles and excess water in the concrete rise to the surface as the concrete hardens, but with conventional formwork, these are not drained to the outside and remain behind, creating crater-like depressions on the surface. Also, because excess water collects near the formwork, the water/cement ratio in the surface layer of concrete tends to increase. As a result, the concrete surface layer tends to deteriorate.

Therefore, in order to densify the concrete, especially the surface layer, and increase its durability, it is necessary to efficiently discharge air bubbles and excess water in the concrete from the formwork to the outside.

As a means of achieving this, it has been considered to improve drainage performance by using, for example, a mold lined with a sheet made of a woven fabric that has water permeability and cement filler properties.

However, if the sheet lined in the formwork is made of woven fabric as mentioned above, the threads tend to slip, causing thread misalignment and density unevenness, and deformation and fraying at the periphery due to thread slipping. Easy to wake up.

Particularly in the case of plywood wave formwork, it is often used by cutting the standard size to the appropriate size, and it may also be cut diagonally or drilled with a drill.
In this case, deformation and fraying due to thread slipping are likely to occur around the cut end of the lining sheet, making it difficult to cut the sheet while it is attached, making it inconvenient to use. It has become.

Furthermore, since the woven fabric has almost no elasticity, it has poor adaptability and flexibility to the shape of the mold, making it troublesome to attach it to the mold. In particular, it is difficult to apply it to circular molds with curved surfaces.

In view of the above, the present invention has been developed as a lining sheet for concrete formwork, which has better water permeability, water permeability, and drainage performance than woven fabrics, is less likely to cause thread slippage or mesh misalignment, and has a durable and durable sheet as a whole. It is also an object of the present invention to provide a material that is suitable for use, has excellent stability, and has good adaptability to mold shapes.

[Means for Solving the Problems] The present invention, which solves the above-mentioned problems, is an lining sheet stretched over the surface of a concrete formwork, comprising two or more layers integrally knitted from synthetic fiber yarns. At least the constituent threads of the front layer in contact with the concrete are made of hydrophobic fibers, and the back layer in contact with the formwork has a density equal to or lower than that of the front layer. do.

In addition, the second aspect of the present invention is as an lining sheet made of a multilayer knitted fabric of two or more layers knitted together from synthetic fiber yarn.
It is characterized in that the constituent threads of the front layer in contact with the concrete are made of hydrophobic fibers, and the constituent threads of the back layer in contact with the formwork are made of fibers having lower hydrophobicity than the constituent threads of the front layer.

In each of the above inventions, polyolefin fibers such as polypropylene fibers are preferably used as the hydrophobic fibers. Further, as the constituent threads of the back layer, it is preferable to use fibers that are relatively more hydrophilic than the constituent threads of the front side layer, and polyester fibers are preferably used mainly.

[Function] 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, air bubbles and the like are initially pushed out semi-actively from the concrete by lateral pressure. Excess water flows through the lining sheet and is discharged. As the concrete hardens, excess water rises to the surface and reaches the lining sheet made of multilayer knitted fabric, where it is actively absorbed into the front layer by capillary action caused by the fibers in the front layer. penetrate,
Further, it circulates to the back layer and is discharged.

In particular, in the case of the first invention, since the back layer has a density equal to or lower than that of the front layer, the water that has penetrated into the front layer may be affected by the fact that the constituent fibers of the front layer are made of hydrophobic fibers. It is easy to move onto the front layer JJ to the coarse back layer,
It immediately permeates to the back layer without staying in this front layer,
In addition, the flowability in this back layer is good, and it flows easily along the formwork, so it exhibits extremely excellent water permeability, water permeability, and drainage performance.

In addition, as in the second invention, the constituent threads of the front layer are hydrophobic.
Even when the constituent fibers of the back layer in contact with the formwork are made of fibers that are less hydrophobic than the constituent threads of the front layer, the water that has permeated into the front layer by capillary action as described above will penetrate into the less hydrophobic back layer. Therefore, even if there is no difference in density between the front and back layers, it immediately permeates to the back layer, circulates through this back layer, and is efficiently released outside through gaps in the formwork. It is discharged. When the constituent threads of the back layer are made of relatively hydrophilic fibers, the permeated water moves more easily to the back layer.

Moreover, since the lining sheet of the present invention is made of an integrally knitted multilayer fabric, the entire sheet has excellent integrity, and compared to woven fabrics, there is no yarn shift or density unevenness, and the overall Possesses uniform water permeability and drainage properties. Furthermore, there is no risk of the thread being pulled out at the end. Furthermore, since it has elasticity unique to knitted fabrics, it has excellent adaptability and flexibility to formwork shapes.

[Example] Next, embodiments of the present invention will be described based on the drawings.

Figure 1 shows a concrete formwork on which the lining sheet (a) of the present invention is stretched, and (1) is the formwork body made of wood such as plywood, synthetic resin, or metal such as steel plate, and the lining sheet (a) is Sheet (
a) is attached to the surface of the form body (1), that is, the surface of the weir plate.

As shown in the figure, the lining sheet (a) consists of a knitted fabric with a multilayer structure of two or more layers knitted together from synthetic fiber yarns, for example, by double-sided knitting on a circular knitting machine, and is relatively easy to use. It is a high-density knitted structure that has cement filter properties that can block the outflow of cement particles, and has the effect of ventilating and draining air and excess water. Become. If you want to slightly increase water permeability, use small holes (
(metshu) sometimes on the surface.

The thickness of the knitted fabric is preferably within the range of 0.5 to 1.5 +w.

(2) shows the front layer in contact with the concrete (C), (3) shows the back layer in contact with the form body (1), and 4) shows the middle layer connecting both the front and back layers. As these constituent threads, hydrophobic fibers such as relatively highly hydrophobic polypropylene fibers are used at least as constituent threads (2a) of the front layer (2).

The density difference between the back layer (3) and the front layer (2) is usually made by changing the knitting structure or the thickness of the yarn, so that the back layer (3) is different from the front layer (3). ) composed of lower density. In some cases, both layers are made to have the same degree of individuality, but in the case shown in the figure, the texture of the back layer (3) is made coarser than that of the front layer (2) due to the knitting structure. In particular, in order to improve water flow and drainage, it is preferable to create rough streaks in the longitudinal direction. The size of the stitches in this case can be appropriately set depending on the mode of use, and the maximum void in this case is set to a diameter of 100 μm or less, preferably less than about 50 μm.

The thickness of the thread can also be set appropriately within the range of 30 to 400 deniers.

Figures 3 and 4 each illustrate a knitted fabric with a multilayer structure in which the front and back layers have different densities as described above. A three-layer structure knitted fabric in which the constituent yarns (3a) of the layer (3) are connected by the constituent yarns (4a) of the intermediate layer (4) is schematically shown, and FIG.
A two-layer knitted fabric consisting of a front layer (2) made of 2a) and a back layer (3) made of constituent yarns (3a) is schematically shown.

(5) is a water passage hole, which is provided as necessary, especially when the formwork body 1) is made of a water-impermeable material such as metal or synthetic resin.

In this example, since the back layer (3) has a lower density than the front layer (2), once the excess water floating out from the concrete penetrates into the front layer (2), the constituent fibers of the front layer (2) Because (2a) is made of hydrophobic fibers, penetrating water easily moves to the coarse back layer (3) and immediately permeates to the back layer (3) without staying in the front layer (2). At the same time, the flowability in this back layer (3) is also good due to its void-holding properties, and therefore it flows easily along the formwork, exhibiting excellent water permeability, water permeability, and drainage performance.

Furthermore, in this embodiment, the constituent yarns (
The constituent threads of 3a) and the middle layer (4) include the front layer (
Although it is possible to use a fiber having the same hydrophobicity as the constituent thread (2a) of 2), in practice, it is preferable to use a fiber that is less hydrophobic than the constituent thread (2a) of the front layer (2) and is relatively hydrophilic. It is preferable to use certain polyester fibers.

In other words, this difference in hydrophobicity and the difference in pore size due to the density difference combine to make it easier for permeated water to move through the layer from the front layer (2) to the back layer (3). , excellent drainage and dehydration effects.

In addition, when hydrophobic fibers are used for the constituent threads of the front layer (2), and fibers having lower hydrophobicity than the above-mentioned front layer, such as polyester fibers, are used for the constituent threads of the intermediate layer (4) and the back layer (3), As described above, even if there is no difference in density between the front layer (2) and the back layer (3), excellent water permeability and drainage performance can be achieved.

That is, in this case as well, the water that has permeated into the front layer (2) by capillary action as described above flows into the back layer (3), which is less hydrophobic.
), and therefore both the front and back layers (2)
Even if there is no density difference in (3) as mentioned above, it immediately permeates to the back layer (3), circulates through this back layer (3), and is efficiently released to the outside through the gaps between the formworks (A). It is discharged.

When the constituent threads of the back layer (3) are made of relatively hydrophilic fibers, the permeated water moves more easily to the back layer.

In addition, as the above-mentioned hydrophobic fibers, polyolein fibers made of polypropylene, polyethylene, and copolymers thereof, among which polypropylene fibers with 100% hydrophobicity are particularly preferably used. That is, polypropylene fibers are light and strong among fibers, and have excellent water resistance, quick drying properties, chemical resistance, etc., and are suitable for lining concrete formwork. Of course, other relatively highly hydrophobic synthetic fibers can also be used.

It goes without saying that the fibers that are less hydrophobic and relatively hydrophilic than the front layer (2) may be synthetic fibers other than polyester fibers.

The lining sheet (a) having the above structure can be stretched over the surface of the formwork body (1) by placing adhesive, rivets, etc. on the side or back surface of the formwork body at required points such as the periphery, for example. It is fixed so that it does not peel off easily. Of course, it is also possible to glue the seeds to the surface of the form body (1).

In particular, since the lining sheet (a) is made of a multilayer knitted fabric integrally knitted by double-sided knitting, etc., it is structurally more stable than woven fabric, and has good elasticity when knitted. This makes it easy to match the shape of the formwork, and it is also possible to adhere to the formwork body using the stretchability, even if there is a slight difference in size. In addition, since the multilayer knitted fabric has a stable structure, it does not easily become misaligned even when other objects, such as concrete, come into contact with each other. In addition, the thread is less likely to slip or come off at the ends,
In the case of plywood formwork, it is also possible to easily cut the formwork according to the place of use.

Use test Knitted using 100% hydrophobic polypropylene fiber for the front layer and polyester fiber for the back layer and middle layer.
A use test was conducted by pouring concrete into a formwork using the lining sheet of the present invention, in which the density of the front and back layers was different and the density of the back layer was lower than that of the front layer.

At the same time, as a comparative example, a use test was also conducted on a formwork using a double-woven fabric as the lining sheet. The concrete for the test specimen was cast in four layers, and each layer was placed for 60 seconds using a vibrator.

The pock rate and surface strength were measured at four equal locations in the longitudinal direction of the central part of the test concrete body. Surface strength is determined by Schmidt hammer.

Results As described above, when the lining sheet of the present invention is used, the amount of water removed is larger, the pock rate on the concrete surface is lower, and the surface strength is also superior than when using the woven fabric sheet. This indicates that the concrete surface layer was drained smoothly and the concrete structure at the surface was densified.

[Effects of the Invention] As described above, the lining sheet for concrete molds of the present invention has superior water permeability, water permeability, and drainage performance compared to woven fabric sheets, and prevents air bubbles from rising on the concrete surface. Excess water is easily drained out, especially once it permeates into the front layer, it immediately moves to the back layer due to the density difference or hydrophobicity difference between the front and back layers, or a combination of these. Since the water is circulated and drained quickly and efficiently to the outside of the formwork, there are fewer bubbles and crater-like depressions caused by water on the concrete surface, and the water/cement ratio in the surface layer is also lowered. Therefore, it is possible to obtain a concrete structure with a beautiful surface, surface strength that develops quickly and increases significantly, and is durable.

Furthermore, as mentioned above, since it has excellent drainage performance, it is possible to shorten the construction period from concrete pouring to demolding.

In addition, the lining sheet of the present invention is made of a multilayer knitted fabric, and has excellent integrity and stability as a whole, and is less likely to cause yarn displacement or density unevenness than a woven fabric, and can have good drainage properties. It is also adaptable and flexible to formwork shapes.
Easy to attach to formwork. Furthermore, when used in a plywood formwork, it is easy to cut the formwork diagonally and to drill holes, making it easy to handle.

[Brief explanation of drawings]

The figures show embodiments of the present invention, in which Figure 1 is a partially cutaway perspective view of a concrete formwork on which the lining sheet of the present invention is stretched, Figure 2 is an enlarged perspective view of the same part, and Figure 3 is an enlarged perspective view of the same part. Figures and a schematic cross-sectional view illustrating a multilayer structure knitted fabric used in the sheet of the present invention,
FIG. 4 is a schematic enlarged plan view illustrating the knitted structure of the multilayer knitted fabric used in the sheet of the present invention, and FIG. 5 is a cross-sectional view of a portion of the knitted fabric in a state of concrete placement. (a)... Lining sheet, (1)... Form body, (2
) ... Front layer, (2a) ... Constituent yarn of the front layer, (3
)... Back side layer, (3a)... Constituent yarn of back side layer, <4
)...middle layer, (c)...concrete. Patent applicant: Atago Co., Ltd. Figure 2 3α Figure 5

Claims (1)

[Claims] 1. An lining sheet stretched over the surface of a concrete formwork, comprising two or more multilayer knitted fabrics integrally knitted from synthetic fiber yarn, and at least in contact with the concrete. A lining sheet for concrete formwork, characterized in that the constituent threads of the front layer are made of hydrophobic fibers, and the back layer in contact with the formwork has a density equal to or lower than that of the front layer. 2. An inner lining sheet stretched over the surface of concrete formwork, consisting of two or more layers of multilayer knitted fabric integrally knitted from synthetic fiber yarn, with the constituent yarns of the front layer in contact with the concrete being hydrophobic. 1. A lining sheet for concrete formwork, characterized in that the constituent fibers of the back layer in contact with the formwork are made of fibers that are less hydrophobic than the constituent threads of the front layer.