JP2013245526A - Wet-curing sheet for concrete and concrete curing method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wet-curing sheet for concrete, which is lightweight when being wetted by water, has superior long-term water holding properties and can be repeatedly used, and to provide a concrete curing method using the same.SOLUTION: A wet-curing sheet (1) for concrete comprises: a fiber sheet layer (2) having a water holding part (4) formed therein; and a reinforcing film (3) integrally formed at a rear face of the fiber sheet layer (2). The water holding part (4) is formed by irradiating the fiber sheet layer (2) with electron beams to graft-polymerize acrylate. The concrete curing method is a concrete curing method using the wet-curing sheet (1) for concrete, and comprises putting the sheet on a concrete placing surface after the concrete is placed to cure the concrete, and then removing the sheet after curing.

Description

  The present invention relates to a wet curing sheet used when placing concrete and a concrete curing method using the same.

  The quality (denseness) of the concrete surface is affected by the concrete curing method. That is, it is important to promote the cement hydration reaction by keeping the concrete surface wet for as long as possible to form a concrete surface with high density. In other words, when the concrete surface dries during the necessary curing period, the quality of the concrete will deteriorate. The ideal curing method is underwater curing in which water is cured, but underwater curing with a real structure is not realistic. In addition, there is a curing method by watering such as constantly supplying water to the concrete surface, but there is also a problem that the flowing water exhibits alkalinity. Furthermore, it is relatively easy to keep the horizontal plane in a wet state, but it is difficult to maintain a wet state equivalent to the horizontal plane for the vertical plane.

  For example, Patent Documents 1 and 2 propose to prepare a sheet-like material such as a nonwoven fabric mixed with a water-absorbing material such as a highly water-absorbing polymer and use it on the surface of cast concrete to prevent drying. Has been. Further, it has been proposed to partially dispose a polymer water absorbent and a crosslinked polyethylene oxide on a non-woven fabric using rayon fibers. However, the conventional proposal has a problem that the cured curing sheet is very heavy and has a large burden when it is mounted on the concrete placing surface, and the water retaining material is not continuous in the form of the sheet surface, so it is difficult to perform uniform moisture curing. There is a problem.

JP-A-6-212799 JP-A-8-188486 JP 2002-81210 A

  In order to solve the above problems, the present invention provides a concrete wet curing sheet that is lightweight even in a water retention state, excellent in long-term water retention and can be used repeatedly, and a concrete curing method using the same.

  The concrete wet curing sheet of the present invention is a concrete wet curing sheet in which a water retention portion is formed on a fiber sheet and a film is integrated on the back surface, and the water retention portion irradiates the fiber sheet with an electron beam. The water-retaining compound is graft-polymerized.

  The concrete curing method of the present invention is a concrete curing method using the above-described concrete wet curing sheet, wherein the curing sheet is cured by attaching the curing sheet to concrete after placement, and is removed after curing. .

  In the present invention, the fiber sheet is irradiated with an electron beam, and the water retentive compound is graft polymerized, so that the water retentive compound is uniformly graft polymerized to the fiber sheet, and is lightweight and has good workability even during water retention. Even when used in a vertical portion, there is little drop of water, excellent long-term water retention, a concrete wet curing sheet that can be used repeatedly, and a concrete curing method using the same. Moreover, since this water curing sheet | seat has the water retention part uniformly formed in the fiber sheet surface, it can absorb water and retain water efficiently, and can maintain a concrete surface uniformly moist. In addition, the water retention period with a small amount of water absorption is longer than that of the conventional technology, the curing sheet itself can be made lighter, and the water retention performance is high. Drying can be suppressed. Furthermore, since the water retention compound is graft-polymerized to the fiber, the water retention compound does not fall off the fiber and can withstand repeated use.

FIG. 1 is a schematic cross-sectional view of a concrete wet curing sheet in one embodiment of the present invention. FIG. 2 is a schematic sectional view of a concrete wet curing sheet according to another embodiment of the present invention. FIG. 3 is a perspective view showing a concrete curing method using a concrete wet curing sheet in one embodiment of the present invention. FIG. 4 is a perspective view showing a concrete curing method using a concrete wet curing sheet according to another embodiment of the present invention. FIG. 5 is a plan view showing the concrete curing method of FIG. FIG. 6 is a graph showing the water supply amount measurement test results of the sheet of the example of the present invention and the comparative example. FIG. 7 is a graph showing the water supply amount measurement test results of the sheet of the example of the present invention and the comparative example. FIG. 8 is a graph showing the temperature and humidity during measurement of the amount of water supply of concrete cured using the sheets of Examples and Comparative Examples of the present invention. FIG. 9 is a graph showing changes in elapsed time of water permeability in the examples of the present invention and comparative examples.

  In the concrete wet curing sheet of the present invention, the water retention compound is fixed to the fiber sheet, and a film for suppressing water evaporation is integrated on the back surface. For example, the electron beam irradiation is performed from the front side of the fiber sheet. Then, a water retention compound such as acrylic acid or acrylate is graft polymerized. As shown in (Chemical Formula 1), for example, to graft polymerize acrylic acid by irradiating the cellulose fiber with an electron beam, acrylic acid is grafted to cellulose as shown in (Chemical Formula 2) and / or (Chemical Formula 3) below. Then, it is presumed that a carboxylate is formed by neutralization as shown in the following (Chemical Formula 4) and / or (Chemical Formula 5). The solution used for the neutralization treatment is preferably an aqueous solution of an alkali metal hydroxide such as NaOH, KOH, or LiOH. An example of neutralization with NaOH aqueous solution is shown below. Cell refers to cellulose. In addition, it is possible to directly graft polymerize an acrylate such as sodium acrylate without depending on the neutralization step.

  In the present invention, when the concrete wet curing sheet is 100% by weight, the weight ratio of the water retaining part is 5 to 35% by weight, more preferably 6 to 20% by weight. If it is the said range, it has sufficient water absorption and water retention.

  The water retaining part is formed on the surface of the fiber of the fiber sheet layer and does not exist as a clear layer. However, the thickness is preferably in the range of 10 to 1000 μm, more preferably 100 to 500 μm. . If it is the said range, it has sufficient water absorption and water retention.

  The water retention compound used in the present invention may be any compound that can be graft-polymerized by electron beam irradiation. For example, acrylic acid, sodium acrylate, polyethylene glycol dimethacrylate (acrylate), ethylene oxide-modified pentaerythritol tetraacrylate, acryloyl Morpholine, hydroxyethyl methacrylate (acrylate), vinyl pyrrolidone, dimethylacrylamide, polyvinyl alcohol and the like are used. Acrylic acid or sodium acrylate is preferred.

  Although the fiber which can be used by this invention is not specifically limited, The cellulose fiber, polyethylene fiber, polypropylene fiber, nylon fiber, polyvinyl alcohol fiber, etc. which can use an electron beam graft polymerization method are preferable. In particular, it is preferable to have cellulose fibers. The cellulose fiber may be any material such as cotton, hemp, rayon, and cupra. The ratio of the cellulose fiber to the fabric can be used in the range of 10 to 100% by weight.

  Although a fiber sheet will not be restrict | limited especially if it is a sheet form, A nonwoven fabric or a textile fabric is preferable. This is because it excels in properties such as thickness, weight per unit area (weight per unit area), and dimensional stability. As the nonwoven fabric, a nonwoven fabric starting from a card web, a nonwoven fabric starting from an air lay web, a wet nonwoven fabric, a spunbond nonwoven fabric, a melt blown nonwoven fabric, a needle punched nonwoven fabric, a thermal bond nonwoven fabric, a chemical bond nonwoven fabric, a hydroentangled nonwoven fabric and the like can be used. Among these, a thermal bond nonwoven fabric and a needle punch nonwoven fabric are preferable. In the case of a woven fabric, any structure such as plain weave and twill weave can be used.

The weight (unit weight) per unit area of the fiber sheet layer is preferably 80 to 250 g / m ² , more preferably 90 to 200 g / m ² . If it is the said range, it has sufficient hydrophilic property, water absorption, and water retention.

  The water absorption rate of the concrete wet curing sheet is preferably 50 to 500% by weight, more preferably 100 to 450% by weight. If it is the said range, it has sufficient hydrophilic property, water absorption, and water retention.

  A film or the like having a net or a hole may be further integrated on the water retention layer side (surface side) of the fiber sheet layer. When the net is integrated, the dimensional stability is further enhanced. In particular, when a nonwoven fabric is used as the fiber sheet, it can be easily peeled off from the concrete contact surface at the end of curing, and the constituent fibers can be further prevented from falling off. In addition, water retention can be provided also to a net | network by performing electron beam processing from the surface side (net | network provision side) in the state which integrated the net | network.

  The material for the evaporation-suppressing film to be lined is not particularly limited. For example, a polypropylene (PP) film, a polyethylene terephthalate (PET) film, a nylon film, a polyvinyl chloride film, or the like can be used. Moreover, the film for suppressing evaporation is applied to the back side of the fiber sheet. In the present invention, the surface side of the fiber sheet refers to the surface in contact with the concrete, and the back surface refers to the opposite surface.

  In the concrete curing method of the present invention, the sheet is mounted on the concrete casting surface after the concrete is cast, and is removed after curing. At the time of mounting, the seat may be wetted with water. During curing, for example, water is added once a day so that the sheet does not dry. The concrete construction may be construction at a construction site, but may be construction produced in a factory. Both are suitable for natural curing. In addition, concrete placement generally encloses four sides with a formwork and pours concrete from above. Since the surface into which the concrete is poured is in an open state, the curing sheet can be used in a state in which the concrete has hardened to some extent. In addition, the mold surface side (usually the vertical surface side) is demolded after a certain period of time has passed (after the concrete has developed a strength that does not interfere with the mold being removed), and then the concrete surface (form frame) Use a curing sheet so that the surface does not dry.

  This will be described below with reference to the drawings. FIG. 1 is a schematic cross-sectional view of a concrete wet curing sheet in one embodiment of the present invention. In this concrete wet curing sheet 1, a water retaining portion 4 is formed on the surface of the fiber sheet layer 2, and a reinforcing film 3 is integrated on the back surface. The water retaining part 4 is irradiated with an electron beam on the surface of the fiber sheet layer, sodium acrylate is graft-polymerized, and exists as a sodium acrylate graft fiber.

  FIG. 2 is a schematic sectional view of a concrete wet curing sheet according to another embodiment of the present invention. In the concrete wet curing sheet 5, a net 6 is integrated on the surface of the fiber sheet layer 2, a water retaining layer 4 is formed thereon, and a reinforcing film 3 is integrated on the back surface.

  Hereinafter, the present invention will be described more specifically with reference to examples. The present invention is not limited to the following examples.

<Measurement method>
Measurement was performed by the method shown in Table 1.

<Fiber sheet>
A card web nonwoven fabric composed of 80% by weight of rayon fibers and 20% by weight of polyolefin thermal bonding fibers was used as a needle punched nonwoven fabric (manufactured by Kurashiki Textile Processing Co., Ltd .: “KBP120”). Since the basis weight and thickness differ depending on each embodiment, they are described in each embodiment.
<Evaporation suppression film>
A polyethylene resin film was used. The film and the nonwoven fabric sheet were integrated by extrusion lamination.

(Examples 1-2)
In this example, the nonwoven fabric was irradiated with an electron beam, and then sodium acrylate was bonded to cellulose fibers by the Pad method. Electrons are applied to one surface of the nonwoven fabric under the conditions of an acceleration voltage of 200 kV and an irradiation dose of 40 kGy in a nitrogen gas atmosphere by an electro curtain type electron beam irradiation apparatus (EC250 / 30 / 90L; manufactured by I. Electron Beam Co., Ltd.). Irradiated with rays. The dough irradiated with the electron beam was immersed in an aqueous solution of 20% by weight sodium acrylate (manufactured by Nacalai Tesque), squeezed with a mangle until the squeezing rate was about 70% by weight, and then left at 35 ° C. overnight. After leaving overnight, the electron beam is irradiated again under the same conditions. Thereafter, in order to remove the unreacted monomer adhering to the nonwoven fabric, it was washed with hot water, washed with water, then squeezed with a mangle and dried at 100 ° C. for 180 seconds with a drier to prepare an evaluation sample. The conditions and results are shown in Table 2.

(Example 3)
This was carried out in the same manner as in Examples 1 and 2, except that a net made of a polyethylene material (15 g / m ² basis weight) was heat-sealed on the surface of the needle punched nonwoven fabric, and then an evaporation suppression film was laminated on the back surface. The conditions and results are shown in Table 2.

(Experiment 1)
Next, the time-dependent change of the water absorption of the fiber sheet (curing sheet) of Examples 1-3 and a commercial product curing sheet as a comparative example was measured. The sample size was 250 mm in length and 250 mm in width. After being immersed in water for 1 hour, the sample was pulled up, and the weight after 1 minute was measured. Thereafter, the sample was hung in a room at 20 ° C. and dried, and the change in weight over time was measured. FIG. 6 is a graph showing changes in water absorption over time, FIG. 7 is a comparison graph of FIG. 6, and FIG. 8 is a temperature and humidity condition during measurement. 6 and 7, sample A shows the product of Example 1, sample B shows the product of Example 2, and sample C shows the product of Example 3. 6 and 7, it can be seen that the fiber sheets of Examples 1 to 3 have equivalent or higher water retention amounts than the comparative example products. In addition, the value of elapsed time (minute) 0 in FIG. 6 shows an initial weight, and it turns out that the initial weight is lighter than the comparative example goods of the fiber sheet of Examples 1-3.

(Experiment 2)
Next, a fiber sheet was pasted as a curing sheet on the circumferential surface (vertical surface) 10 of the concrete shown in FIG. 3 (cylindrical shape having a diameter of 100 mm and a height of 200 mm), and the upper and lower ends of the curing sheet protruded 1 cm from the specimen. It was in a state. Aluminum tape was applied to the upper and lower surfaces 11. Table 3 shows the concrete content.

  After the concrete was placed, the seal was cured, and after 2 days of age, the mold was removed and the curing sheet was immediately attached and cured. Water was added from the top of the curing sheet once a day, and the concrete surface was kept moist until the age of 28 days. The temperature was kept in a room at 20 ° C. The compressive strength was measured at a material age of 28 days. Table 4 shows the compressive strength and unit volume weight of each specimen. In addition, as a comparative example, a commercial product curing sheet, an example using a commercially available film curing agent, underwater curing (water temperature 20 ° C.), and air curing (room temperature 20 ° C. × humidity 50%) were added.

  From Table 4, it can be seen that the compressive strength and the unit volume weight when using the curing sheets of Examples 1 to 3 were the same level as the underwater curing, and were larger than the air curing.

(Experiments 3-6)
Surface observation was conducted as Experiment 3, an air permeability test as Experiment 4, a water permeability test as Experiment 5, and a chloride ion penetration depth test as Experiment 6. A specimen was prepared and cured in the same manner as in Experiment 2 except that the concrete molded body was changed to FIGS. The dimensional unit in each figure is mm. 4 in FIG. 4 is a concrete placing surface, and the test surface 13 and two side surfaces (vertical surfaces) of the back side surface are curing surfaces. The upper and lower ends of the curing sheet were protruded 1 cm from the specimen. Aluminum tape was applied to the four surfaces of the non-test surface 14 to suppress drying from other than the test surface. The air permeability test was performed on two test surfaces on the front and back sides. The water permeability test was conducted on only one surface with the curing surface up and down. After the water permeability test, the specimen was immersed in a 10% NaCl aqueous solution for 28 days, and the chloride ion penetration depth was measured. 5 of FIG. 5 is a position of an air permeability test and a water permeability test. The results are shown in Table 5. As for the air permeability coefficient and water permeability, the smaller the value, the denser the concrete. Moreover, the graph which shows the elapsed time change of water permeability is shown in FIG.

  From Table 5, when the curing sheets of Examples 1 to 3 are used, the density of the concrete surface layer and the resistance to penetration of chloride ions are the same as the commercial product curing sheet, slightly lower than the underwater curing, It can be seen that it has improved significantly.

  As described above, the curing sheet of this example was lightweight and good in workability even when wetted with water, and even when used in a vertical part, the water did not drop and was excellent in long-term water retention. Moreover, when the repeated use test was carried out, it was able to be used up to 10 times.

DESCRIPTION OF SYMBOLS 1 Sheet | seat for concrete wet curing 2 Fiber sheet layer 3 Film 4 Water retention layer 6 Net 10 Circumferential surface 11 of test body Upper and lower surfaces of test body 12 Concrete placement surface 13 Test surface 14 Non-test surface 15 Air permeability test, water permeability test position

Claims (5)

A concrete wet curing sheet in which a water retention part is formed on a fiber sheet and a film is integrated on the back surface,
The water retention part is a concrete wet curing sheet, wherein the fiber sheet is graft polymerized with a water retention compound by electron beam irradiation. The concrete fiber curing sheet according to claim 1, wherein the fiber sheet has an initial weight of 0.5 to 2.0 kg / m ² . 3. The concrete wet curing sheet according to claim 1, wherein the fiber sheet has a weight (unit weight) per unit area of 80 to 250 g / m ² .   The concrete wet curing sheet according to any one of claims 1 to 3, wherein a net is further integrated on the surface side of the fiber sheet. A concrete curing method using the concrete wet curing sheet according to any one of claims 1 to 4,
A concrete curing method, wherein after the concrete is placed, the sheet is mounted on the concrete placement surface and cured, and then removed after curing.

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