Curing sheet and curing sheet for manufacturing precast concrete members

Abstract

To provide a curing sheet suitable for steam curing in manufacturing a precast concrete member.SOLUTION: A curing sheet 1 is provided with laminates 20 and 30 including respectively cloth sheets 21 and 31 on both sides of a foam material sheet 10. In one of the laminates, 20, the outermost layer is made of the cloth sheet 21 and in the other of the laminates, 30, the outermost layer is made of a non-breathable film 32. The laminates 20 and 30 include respectively an extruded film layers 22 and 34, and the foam material sheets 10 and the laminates 20 and 30 are integrated by the extruded film layers 22 and 34 being molten and bonded.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a curing sheet used for steam curing in the production of precast concrete members, and a curing sheet for precast concrete member production.

Background Art

[0002] In order to obtain high-quality concrete with sufficient strength, it is necessary to cure the placed concrete by maintaining it at the temperature and humidity required for hardening. For example, in the curing of concrete placed at a construction site, wet curing is performed by covering the surface with a water-retaining curing sheet for a certain period of time to supply moisture, thereby preventing the placed concrete from drying.

[0003] As a conventional concrete curing sheet, a sheet in which a film and a net are laminated on a fiber sheet such as a nonwoven fabric is known (see, for example, Patent Document 1). The concrete curing sheet of Patent Document 1 has a resin net disposed on the surface in contact with the concrete, so that when peeling from the concrete at the end of curing, the constituent fibers are suppressed from falling off from the fiber sheet and it is said that it can be used repeatedly.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The concrete curing sheet of Patent Document 1 is used for wet curing in which the sheet is adhered to the concrete placed at a construction site. However, there are various methods for curing concrete, and the performance required for the curing sheet varies depending on the curing method.

[0006] In a precast concrete member manufacturing plant, for the purpose of improving productivity, steam curing is carried out to promote the strength development of concrete by supplying steam generated by a boiler or the like. The curing sheet used for steam curing is required to have high heat retention to maintain the temperature of the steam and airtightness to prevent steam leakage. In addition, since a steel formwork is used in the manufacture of precast concrete members, the curing sheet used for the manufacture of precast concrete members is required to have sufficient strength so that it does not easily get damaged such as tearing or breaking even when hooked on the steel formwork. Furthermore, the curing period in steam curing is within several hours to one day, and compared with a construction site where curing for several days is required, the curing sheet will be frequently reused in the manufacturing plant. However, from an economic point of view, it is desired that it can be used over a long period of more than one year, so the curing sheet is required to have high durability.

[0007] Regarding this point, the concrete curing sheet of Patent Document 1 is for use in wet curing that retains water by a fiber sheet, so it does not have the heat retention and airtightness required for steam curing. Also, the strength and durability of the concrete curing sheet of Patent Document 1 only suppress the shedding of constituent fibers from the fiber sheet when peeling from the concrete, and do not satisfy the strength and durability required for use in a precast concrete member manufacturing plant.

[0008] The present invention has been made in view of the above problems, and an object thereof is to provide a curing sheet suitable for steam curing in the manufacture of precast concrete members and a curing sheet for manufacturing precast concrete members.

Means for Solving the Problems

[0009] The characteristic configuration of the curing sheet according to the present invention for solving the above problems is a curing sheet in which a laminate including a cross sheet is provided on both sides of a foam material sheet, the outermost layer of one laminate is made of a cross sheet, and the outermost layer of the other laminate is made of an airtight film.

[0010] The curing sheet of this configuration is a curing sheet provided with laminates including cross sheets on both sides of a foam material sheet. Since the outermost layer of one laminate consists of a cross sheet and the outermost layer of the other laminate consists of an airtight film, excellent heat retention and airtightness can be obtained in steam curing by the foam material sheet and the airtight film. Further, since the cross sheet is included in the laminates provided on both sides of the foam material sheet, excellent strength that does not easily break even when caught on a formwork and high durability that can withstand repeated use over a long period of one year or more can be obtained. As a result, the curing sheet of this configuration is suitable for steam curing in the manufacture of precast concrete members.

[0011] In the curing sheet according to the present invention, the laminate includes an extruded film layer, it is preferable that the foam material sheet and the laminate are integrated by the extrusion film layer being fused.

[0012] According to the curing sheet of this configuration, since the laminate includes an extruded film layer and the foam material sheet and the laminate are integrated by the extrusion film layer being fused, it has flexibility and tear strength which are characteristics of extrusion lamination, and can be suitably used in the manufacture of precast concrete members.

[0013] In the curing sheet according to the present invention, the airtight film preferably has an air permeability of 1 cm 3 / (cm 2 ·s) or less as measured in accordance with the frazil method defined in JIS L 1096.

[0014] According to the curing sheet of this configuration, since the air permeability of the airtight film measured in accordance with the frazil method defined in JIS L 1096 is within the above range, steam leakage can be more reliably prevented in steam curing.

[0015] In the curing sheet according to the present invention, The airtight film is preferably a film with metal incorporated therein.

[0016] According to the curing sheet of this configuration, since the airtight film is a film with metal incorporated therein, excellent heat retention can be maintained over a long period of time.

[0017] In the curing sheet according to the present invention, The thickness is preferably 0.5 to 7 mm.

[0018] According to the curing sheet of this configuration, since the thickness is within the above range, workability and transportability are good, and appropriate heat retention can be obtained.

[0019] The characteristic configuration of the curing sheet for precast concrete member manufacturing according to the present invention for solving the above problems is It is formed by joining a plurality of long base cloth pieces made of any of the above curing sheets.

[0020] The curing sheet for precast concrete member manufacturing of this configuration is formed by joining a plurality of long base cloth pieces made of any of the above curing sheets. Therefore, in the manufacturing of precast concrete members such as large box culverts, it can be formed into a size that can cover the entire large formwork without gaps so that steam does not leak.

Brief Description of the Drawings

[0021]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0022] Hereinafter, the curing sheet of the present invention and the curing sheet for manufacturing precast concrete members will be described. However, the present invention is not intended to be limited to the configurations described in the embodiments and drawings below. In the drawings, although a plurality of layers constituting the curing sheet of the present invention are illustrated, the thickness relationship of each layer has been appropriately changed for ease of explanation and does not accurately reflect the size relationship (scale) of the thickness of each layer in the actual curing sheet.

[0023] <Curing sheet> FIG. 1 is a schematic cross-sectional view of a curing sheet 1 according to the present invention. The curing sheet 1 is a curing sheet suitable for steam curing in the manufacture of precast concrete members, and laminates 20 and 30 are provided on both sides of a foam material sheet 10.

[0024] The foam material sheet 10 is a member mainly responsible for the heat retention property of the curing sheet 1, and a resin foam sheet having bubbles formed therein can be used. Examples of the resin used for the resin foam sheet include polyolefin resins such as homopolymers or copolymers of ethylene, propylene, and butene, polyester resins such as polyethylene terephthalate and polyethylene 2,6-naphthalate, polyamide resins such as nylon 6, nylon 12, and copolymer nylon, polyvinyl alcohol resins, and polyvinyl alcohol resins such as ethylene-vinyl alcohol copolymers, and polyurethane resins such as polyurethane, polyurethane urea, and amine-urethane copolymers. In particular, polyolefin resins excellent in economy and productivity are preferable. These resins may be used alone or as a mixture of multiple types. Further, the resin foam sheet used for the foam material sheet 10 may contain a weathering agent, a hydrophilic agent, a metal filler, a pigment, and the like.

[0025] The thickness of the foam material sheet 10 is preferably 0.5 to 5 mm, and more preferably 2 to 4 mm. In the present invention, the thickness of each layer constituting the curing sheet 1 is measured by visually reading a cross section of the curing sheet 1 magnified at a magnification of 20 times using a magnifying glass or microscope with a scale. If the thickness of the foam material sheet 10 is within the above range, a sufficient heat insulating effect can be expected, and the curing sheet 1 will have the heat retention required for steam curing. In addition, it will be easy to transport and easy to install.

[0026] The laminates 20, 30 are components that are mainly responsible for the strength and durability of the curing sheet 1, and each includes a cross sheet 21, 31. The laminates 20, 30 provided on both sides of the foam material sheet 10 include the cross sheets 21, 31, which have high tear strength and excellent shape stability, so that the curing sheet 1 has excellent strength that does not easily break even if it gets caught on a formwork, and high durability that can withstand repeated use for a long period of time of more than one year. Since the laminates 20, 30 have different laminate structures, hereinafter the laminates 20, 30 will be referred to as the "first laminate 20" and the "second laminate 30", respectively.

[0027] The first laminate 20 has a laminated structure in which a cross sheet 21 is arranged as the outermost layer opposite the side facing the foam sheet 10, and an extruded film layer 22 is laminated on the foam sheet 10 side of this cross sheet 21.

[0028] The cross sheet 21 is a net-like or woven sheet in which split, tape-like film is crossed in a polygonal shape such as a lattice or in a spider web shape, and for example, Sof (registered trademark) (manufactured by Sumika Sekisui Film Co., Ltd.) or Warif (registered trademark) (manufactured by JX ANCI Co., Ltd.) can be used. Such a cross sheet 21 not only has high tear strength, but also has excellent shape stability.

[0029] The extruded film layer 22 is a member for adhering the first laminate 20 to the foam material sheet 10. The extruded film layer 22 is preferably a resin film extruded onto the cross sheet 21 using, for example, a T-die. By extruding the extruded film layer 22, the foam material sheet 10 and the first laminate 20 are firmly integrated by extrusion lamination, and as a result, the curing sheet 1 exhibits the tear strength which is a characteristic obtained by extrusion lamination. By uniformly forming the extruded film layer 22 as a resin film on the cross sheet 21, the air permeability of the entire curing sheet 1 can be further reduced, and the occurrence of steam leakage in steam curing can be surely prevented. Further, a resin film to be the extruded film layer 22 is formed as a precoat on the cross sheet 21, and the foam material sheet 10 and the first laminate 20 are adhered by methods such as thermal lamination or ultrasonic welding, or instead of the extruded film layer 22, a resin film is formed by applying an adhesive resin to the entire surface of the cross sheet 21 in dry lamination or wet lamination, and the foam material sheet 10 and the first laminate 20 may be adhered. Examples of the resin used for the resin film include polyolefin resins such as homopolymers or copolymers of ethylene, propylene, and butene, polyester resins such as polyethylene terephthalate and polyethylene 2,6-naphthalate, polyamide resins such as nylon 6, nylon 12, and copolymer nylon, polyvinyl alcohol resins and polyvinyl alcohol resins such as ethylene-vinyl alcohol copolymer, polyimide resins, polyetherimide resins, polysulfone resins, polyethersulfone resins, polyetheretherketone resins, polycarbonate resins, polyvinyl butyrate resins, polyacrylate resins, and fluorine-based resins such as ethylene-tetrafluoroethylene copolymer, chlorotrifluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, vinylidene fluoride, and perfluoroethylene-perfluoropropylene-perfluorovinyl ether copolymer. In particular, polyolefin resins excellent in economy and productivity are preferable. These resins may be used alone or as a mixture of plural kinds.The thickness of the extrusion film layer 22 is preferably 3 to 50 μm, more preferably 10 to 30 μm. If the thickness of the extrusion film layer 22 is within the above range, the adhesion by the extrusion lamination of the foam material sheet 10 and the first laminate 20 has sufficient strength, and the curing sheet 1 has excellent durability. Further, the hardness of the resin film that becomes the extrusion film layer 22 is suppressed, the curing sheet 1 is flexible and easy to handle, and since the followability to the mold is good when covering the mold, steam leakage is less likely to occur.

[0030] The second laminate 30 has a laminated structure in which an airtight film 32 is disposed on the outermost layer on the side opposite to the side facing the foam material sheet 10, and an extrusion film layer 33, a cross sheet 31, and an extrusion film layer 34 are laminated in this order on the foam material sheet 10 side of the airtight film 32. The cross sheet 31 in the second laminate 30 has the same configuration as the cross sheet 21 in the first laminate 20, and the extrusion film layers 33 and 34 in the second laminate 30 have the same configuration as the extrusion film layer 22 in the first laminate 20.

[0031] As the airtight film 32, for example, a metal kneaded film in which metal particles are kneaded into a resin as a base material, a metal vapor deposition film in which metal is vapor deposited on a resin film as a base material, etc. can be used. In particular, it is preferable to use a metal kneaded film having excellent durability. As the resin serving as the base material of the metal kneaded film, the same one as the extrusion film layer 22 can be used. Examples of the metal kneaded into the metal kneaded film include aluminum, nickel, stainless steel, chromium, silver, tin, titanium, iron, zinc, copper, silicon, and magnesium. In particular, aluminum or stainless steel having excellent economic efficiency and productivity is preferable. These metals may be used alone or as an alloy. The airtight film 32 is measured by a frigid form tester in accordance with Method A (frigid form method) specified in "8.26 Air permeability" of "JIS L 1096 Test methods for fabrics and knitted fabrics" (hereinafter simply referred to as "air permeability"). The air permeability is 1 cm 3 / (cm 2·s) is preferably as follows. If the air permeability of the airtight film 32 is 1 cm 3 / (cm 2 ·s) or less, steam leakage can be prevented and the heat retention property of the curing sheet 1 can be improved.

[0032] To the extrusion film layers 22, 33, 34, and the airtight film 32, an ultraviolet absorber, a light stabilizer, an antioxidant, a flame retardant, a heat stabilizer, a rust preventive agent, a copper poisoning resistant stabilizer, an antistatic agent, a plasticizer, a terminal blocking agent, a lubricant, an organic lubricant, a chlorine scavenger, a blocking agent, a viscosity modifier, etc. may be added as necessary. Examples of the ultraviolet absorber include drugs such as benzophenone-based, salicylate-based, cyanoacrylate-based, benzoate-based, benzotriazole-based, triazine-based, and nickel-based drugs. Examples of the light stabilizer include drugs such as benzotriazole-based, triazine-based, benzophenone-based, organic nickel-based, hindered piperidine-based, and hindered amine-based drugs. Examples of the antioxidant include drugs such as phenol-based, phosphorus-based, sulfur-based, blend-based, and phosphite-based drugs.

[0033] The thickness of the curing sheet 1 is preferably 0.5 to 7 mm, and more preferably 2 to 5 mm. In the present invention, the thickness of the curing sheet 1 is a measured value obtained by measuring in accordance with the method specified in "5.6 Measurement with Vernier Calipers" of "JIS K 7153 Plastics - Method for Obtaining Linear Dimensions of Test Specimens" so as not to compress or damage the surface of the test specimen by bringing the outer jaws of the vernier calipers into contact. If the thickness of the curing sheet 1 is within the above range, a foam material sheet 10 with appropriate heat retention can be obtained, and appropriate stiffness and firmness and good followability to the shape of the mold can be obtained, resulting in excellent workability and transportability.

[0034] The weight per unit area of the curing sheet 1 is preferably 100 to 700 g / m 2 . If the weight per unit area is within the above range, it will have excellent workability and transportability, and in particular, it can reduce fluttering and the like caused by the influence of wind during construction.

[0035] The curing sheet 1 preferably has a tearing strength (hereinafter simply referred to as "tearing strength") measured by a tensile testing machine in accordance with Method A (single tongue method) specified in "8.17 Tear strength" of "JIS L 1096 Test methods for fabric and knitted fabric fabrics" of 100 to 300 N, and more preferably 120 to 250 N. Since a steel formwork is used in the manufacture of precast concrete members in the manufacturing factory, it is easy to catch on the formwork when covering or removing the curing sheet 1 during steam curing. However, if the tearing strength of the curing sheet 1 is within the above range, it will have sufficient strength that damage such as tearing or breaking will not easily occur even if it is caught on the steel formwork.

[0036] As the product form of the curing sheet 1, a roll is preferable. Its size preferably has a width of 0.8 to 2 m and a length of 1 roll of 10 to 400 m, more preferably a width of 1 to 1.5 m and a length of 1 roll of 20 to 200 m. With such a product form, the workability and transportability of the curing sheet 1 will be excellent.

[0037] In addition, the curing sheet 1 may have other layers added to the first laminate 20 and the second laminate 30 as long as the flexibility to follow the shape of the formwork during steam curing is not impaired. For example, a metal-embedded film may be added to the first laminate 20 as an airtight film. However, since the outermost layer in the first laminate 20 is the cross sheet 21, it is preferable that the airtight film in the first laminate 20 is laminated on the foam material sheet 10 side rather than the cross sheet 21.

[0038] The curing sheet 1 configured as described above is preferably used in steam curing with the first laminate 20 having the cross sheet 21 on the outermost layer facing the concrete side to which steam is supplied and the second laminate 30 having the airtight film 32 on the outermost layer facing the outside air side. In such a usage method, since the cross sheet 21, which is excellent in tear strength on the concrete side, of the curing sheet 1 comes into contact with the formwork, it will not be easily damaged even if it gets caught on the formwork when covering or removing the curing sheet 1. Also, since the airtight film 32 comes into contact with the outside air, the heat retention of the steam in steam curing is further improved. However, even when the curing sheet 1 of the present invention is used with the second laminate 30 having the airtight film 32 on the outermost layer facing the concrete side to which steam is supplied and the first laminate 20 having the cross sheet 21 on the outermost layer facing the outside air side, in steam curing, it has heat retention, airtightness, and strength and durability that pose no practical problems.

[0039] <Curing Sheet for Manufacturing Precast Concrete Members> Figure 2 is a perspective view of the curing sheet 100 for manufacturing precast concrete members according to the present invention. For example, in the case of a curing sheet with a width of 0.8 to 2 m and a length of 1 roll of 10 to 400 m, when manufacturing precast concrete members such as large box culverts, it cannot cover the entire formwork as it is. Therefore, when manufacturing large precast concrete members, it is preferable to join a plurality of curing sheets 1 and use them as the curing sheet 100 for manufacturing large precast concrete members.

[0040] The curing sheet 100 for manufacturing precast concrete members is obtained, for example, by arranging a plurality of long curing sheets 1 as base fabric pieces in the width direction and joining the long sides of two adjacent curing sheets 1. Further, when the formwork to be covered is longer than the curing sheet 1 serving as the base fabric piece, a plurality of curing sheets 1 are arranged in the longitudinal direction as base fabric pieces, and the short sides of two adjacent curing sheets 1 are joined to form the curing sheet 100 for manufacturing precast concrete members that can cover the entire formwork. The shape and size of the curing sheet 100 for manufacturing precast concrete members may be selected according to the shape, size, etc. of the formwork to be covered.

[0041] In the curing sheet 100 for manufacturing precast concrete members, examples of the joining method of the curing sheet 1 serving as the base fabric piece include sewing, fusion bonding, adhesion, etc. In particular, it is preferable to join by sewing, which provides excellent joining strength at the joint 1a. Further, in addition to sewing, the joining strength of the joint 1a can be further increased by combining fusion bonding and adhesion.

[0042] When joining the base fabric pieces by sewing, it can be carried out by commonly applied sewing methods such as straight stitch, double chain stitch, flat fell seam, catch stitch, safety stitch, zigzag stitch, and flat lock stitch. The thickness of the sewing thread is preferably 700 dtex (equivalent to size 20) to 2800 dtex (equivalent to size 0), and the number of stitches per centimeter is preferably 2 to 10 stitches / cm. From the perspective of joint strength, it is preferable that a plurality of rows of stitch lines are formed at the joint part 1a where the curing sheet 1 serving as the base fabric piece is joined. The plurality of rows of stitch lines can be formed, for example, using a multi-needle type sewing machine with the distance between the stitch needles being about 2 to 30 mm. However, when the joint part 1a is short, it may be sewn multiple times with a single-needle sewing machine. The sewing thread used for sewing can be appropriately selected from those generally called chemical fiber sewing threads and those used as industrial sewing threads. Examples of the material of the sewing thread include nylon 6, nylon 66, nylon 46, polyester, high molecular polyolefin, fluorine-containing, vinylon, aramid, carbon, glass, and steel. Also, the form of the sewing thread can be a spun yarn, a filament twisted yarn, a filament resin processed yarn, etc. When joining the base fabric pieces by fusion, it can be carried out by heat fusion, high-frequency welding, etc. When joining the base fabric pieces by adhesion, it can be carried out using an adhesive.

[0043] For the curing sheet 100 for manufacturing precast concrete members, it is preferable that two adjacent curing sheets 1 overlap at the joint part 1a. Thereby, the leakage of steam from the joint part 1a can be more reliably suppressed.

[0044] The curing sheet 100 for manufacturing precast concrete members may be provided with hemming at the ends or corners according to the construction method. The material of the hemming is not limited, and brass, aluminum, iron, etc. can be used.

[0045] The curing sheet 100 for manufacturing precast concrete members configured as described above Since it is formed by joining a plurality of long base fabric pieces made of the curing sheet 1, in the manufacture of precast concrete members such as large box culverts, it can be formed into a size that can cover the entire large formwork without gaps so that steam does not leak. Further, when the joint portion 1a is joined by sewing, it has a strength that is not easily damaged even if the joint portion 1a is caught on the formwork when covering or removing the curing sheet.

Example

[0046] Hereinafter, an example of the curing sheet for manufacturing a precast concrete member of the present invention will be described. In this example, curing sheets for manufacturing precast concrete members (Examples 1 to 5) having the configuration of the present invention were produced. Further, for comparison, a curing sheet for manufacturing a precast concrete member (Comparative Example 1) was produced in which a laminate including a cross sheet was provided on one side of a foam material sheet, but a layer other than the laminate was provided on the other side.

[0047] <Example 1> An uncrosslinked polyethylene foam sheet (foam material sheet) with a thickness of 3 mm was prepared. An aluminum kneaded polyethylene film and a flat yarn fabric (cross sheet) woven flat with 8 yarns / 2.54 cm both warp and weft were prepared, and these were laminated and adhered by extrusion lamination through a polyethylene extrusion film layer formed by T-die extrusion molding. A polyethylene extrusion film layer was laminated on the surface of this laminate on the cross sheet side by extrusion molding, and further an uncrosslinked polyethylene foam sheet was laminated by extrusion lamination to produce an intermediate body in which a second laminate was laminated on one side of the foam material sheet.

[0048] Next, a flat yarn fabric (cross sheet) was prepared by plain weaving polyethylene flat yarns both warp and weft at 8 yarns / 2.54 cm, and a polyethylene extruded film layer was laminated on this cross sheet by extrusion molding to form a first laminate. The surface of this first laminate on the side of the polyethylene extruded film layer and the surface of the previously prepared intermediate on the side of the foam material sheet were opposed to each other and laminated by heat lamination to obtain a curing sheet with a width of 2 m and a length of 20 m.

[0049] Using 10 of these curing sheets, the long sides of adjacent curing sheets were joined by sewing at a pitch of 5 mm with a double-loop sewing machine using polyester No. 5 sewing thread, and a curing sheet for manufacturing a precast concrete member with a square shape of approximately 20 m in the vertical direction and approximately 20 m in the horizontal direction was obtained (Example 1). The air permeability of the aluminum-incorporated polyethylene film used in the preparation of the curing sheet was 0 cm 3 / (cm 2 ·s) as measured in accordance with the frazil method specified in JIS L 1096.

[0050] <Example 2> As the foam material sheet, an uncrosslinked polyethylene foam sheet with a thickness of more than 1 mm was used. Otherwise, in accordance with Example 1, a curing sheet for manufacturing a precast concrete member of Example 2 was obtained.

[0051] <Example 3> As the foam material sheet, an uncrosslinked polyethylene foam sheet with a thickness of more than 5 mm was used. Otherwise, in accordance with Example 1, a curing sheet for manufacturing a precast concrete member of Example 3 was obtained.

[0052] <Example 4> The laminated structure of the curing sheet is the same as that of the curing sheet for manufacturing a precast concrete member of Example 1, but the curing sheet for manufacturing a precast concrete member of Example 4 was turned inside out compared to the curing sheet for manufacturing a precast concrete member of Example 1 in steam curing and each of the evaluations described later.

[0053] <Example 5> Ten curing sheets identical to those used in Example 1 were used, and the long sides of adjacent curing sheets were partially overlapped and joined by heat fusion to obtain a curing sheet for manufacturing a precast concrete member of Example 5.

[0054] <Comparative Example 1> Only a polyethylene extrusion film layer was laminated by extrusion molding on the surface of the foam material sheet of the intermediate body prepared in Example 1. Otherwise, a curing sheet for manufacturing a precast concrete member of Comparative Example 1 was obtained according to Example 1.

[0055] Ten curing sheets for manufacturing a precast concrete member of each of Examples 1 to 5 and ten curing sheets for manufacturing a precast concrete member of Comparative Example 1 were used respectively, and various measurements and evaluations were carried out.

[0056] <Measurement Method> 1.1 Thickness [mm] The thickness of the curing sheet for manufacturing a precast concrete member was measured in accordance with the method specified in "5.6 Measurement with Vernier Calipers" of "JIS K 7153 Plastics - Method for Determining Linear Dimensions of Test Specimens".

[0057] 1.2 Mass per unit area [g / m 2 The mass per unit area of the curing sheet for manufacturing a precast concrete member was measured in accordance with Method A (JIS method) specified in "8.3 Mass per Unit Area" of "JIS L 1096 Test Methods for Fabrics and Knitted Fabrics".

[0058] 1.3 Tear strength of the curing sheet [N] The tear strength of the curing sheet used for the curing sheet for manufacturing a precast concrete member was measured in accordance with Method A (Single Tongue Method) specified in "8.17 Tear Strength" of "JIS L 1096 Test Methods for Fabrics and Knitted Fabrics".

[0059] 1.4 Strength of the joint part [N] Hook the tip of the J-shaped hook of a spring scale onto the joint of the curing sheet for manufacturing precast concrete members supported horizontally. Then, apply a horizontal force to the curing sheet for manufacturing precast concrete members and measure the load at the moment when the joint breaks, which is taken as the strength of the joint.

[0060] <Evaluation method> 2.1 Durability (resistance to tearing) In the steam curing during the manufacture of precast concrete members, the curing sheet for manufacturing precast concrete members was used 20 times a month for 2 years. Then, the surface condition of the curing sheet for manufacturing precast concrete members was visually observed. The evaluation criteria were as follows. (Evaluation criteria) A: There are 0 to 5 tears of 10 mm or more per 100 m 2 and there are no tears at the joints. B: There are 6 to 10 tears of 10 mm or more per 100 m 2 and there are no tears at the joints. C: There are 0 to 5 tears of 10 mm or more per 100 m 2 but there are many tears at the joints. D: There are 10 or more tears of 10 mm or more per 100 m 2 and there are also tears at the joints.

[0061] 2.2 Durability (tearing strength of the curing sheet [N]) In the steam curing during the manufacture of precast concrete members, the curing sheet for manufacturing precast concrete members was used 20 times a month for 2 years. Then, in accordance with Method A (Single Tongue Method) specified in "8.17 Tearing Strength" of "JIS L 1096 Test Methods for Fabrics and Knitted Fabrics", the tearing strength was measured at a position not including the joint of the curing sheet for manufacturing precast concrete members.

[0062] 2.3 Durability (strength of the joint [N]) In steam curing in the production of precast concrete members, a curing sheet for precast concrete member production was used 20 times a month for two years, and then the durability (strength of the joint part) was measured by the method described in "1.4 Strength [N] of the joint part" above.

[0063] 2.4 Resilience in bending [g] A test piece of 200 mm × 50 mm was taken from the curing sheet for precast concrete member production before use, and the test piece was bent 180 degrees at the center of the long side. This test piece was placed on a weighing scale that could measure from 0 to 1 kg, and while holding the state of being bent 180 degrees by pressing from above with a finger, the value indicated by the weighing scale was read. The value obtained by subtracting the weight of the test piece from the read value was defined as the resilience in bending.

[0064] 2.5 Heat retention rate [%] Based on Method A (constant temperature method) specified in "8.27 Heat retention property" of "JIS L 1096 Test methods for fabrics and knitted fabrics", the heat retention rate was determined in a test environment of 20°C and 65% RH using an ASTM-type heat retention tester. For the curing sheets for precast concrete member production in Examples 1 to 3 and 5, and the curing sheet for precast concrete member production in Comparative Example 1, in the ASTM-type heat retention tester, the first laminate side was brought into contact with the constant temperature heating body, and for the curing sheet for precast concrete member production in Example 4, in the ASTM-type heat retention tester, the second laminate side was brought into contact with the constant temperature heating body to measure the heat retention rate.

[0065] 2.6 Workability In steam curing in the production of a box culvert (width 7.0 m, height 5.5 m, depth 2.0 m), the curing sheet for precast concrete member production was constructed from above the formwork, and its workability was evaluated. The evaluation criteria are as follows. (Evaluation criteria) A: It is familiar from the beginning. B: It is bulky at first but becomes familiar after being used for 5 steam curings. C: It is bulky at first but becomes familiar after being used for 20 steam curings. D: It bulges even after being used for 200 times of steam curing.

[0066] Table 1 shows the details, measurement results, and evaluations of the curing sheets for precast concrete member manufacturing in Examples 1 to 5 and the curing sheet for precast concrete member manufacturing in Comparative Example 1. In Table 1, the thickness of each layer constituting the curing sheet for precast concrete member manufacturing is the measured value read visually after magnifying the cross-section of the curing sheet for precast concrete member manufacturing 20 times with a magnifying glass with a scale.

[0067]

Table 1

[0068] The curing sheets for precast concrete member manufacturing in Examples 1 to 5 all have a tear strength of 150 N or more for the curing sheet before use, so they have a strength suitable for steam curing in the manufacture of precast concrete members. Also, in the evaluation of durability after 2 years of use, the tear strength of the curing sheet does not drop below 100 N, so it is confirmed that they have excellent durability that can withstand frequent repeated use in the manufacturing factory. In addition, in the visual observation of durability (resistance to tearing) after 2 years of use, there were few places torn by 10 mm or more, and the durability was maintained.

[0069] For the curing sheets for precast concrete members in Examples 1 to 4 where the joining method is sewing, the strength of the joint before use is 300 N or more in each case, and in the evaluation of durability after 2 years of use, the strength of the joint is maintained at 300 N or more. Therefore, in frequent repeated use in the manufacturing factory, when covering or removing the formwork, it was confirmed that the joint has a strength that is not easily damaged even if it catches on the formwork. In particular, the curing sheet for precast concrete members in Example 1 is made by joining the same curing sheet as the curing sheet for precast concrete members in Example 5 where the joining method is heat fusion, but both the strength of the joint before use and the strength of the joint after 2 years of use are greater than those of the curing sheet for precast concrete members in Example 5. Therefore, it can be said that the joining method of the joint of the curing sheet for precast concrete members is more preferably by sewing.

[0070] Also, for the curing sheets for precast concrete members in Examples 1 to 5, the heat retention rate is 36% or more in each case, and it was confirmed that they have sufficient heat retention for steam curing. Note that the curing sheet for precast concrete members in Example 1 and the curing sheet for precast concrete members in Example 4 have the same structure. However, in the measurement of the heat retention rate, when the cross sheet of the first laminate was brought into contact with the constant temperature heating element and the airtight film of the second laminate was brought into contact with the outside air for the curing sheet for precast concrete members in Example 1, the heat retention rate was higher than that of the curing sheet for precast concrete members in Example 4 where the airtight film of the second laminate was brought into contact with the constant temperature heating element and the cross sheet of the first laminate was brought into contact with the outside air. From this, it can be said that it is desirable to use the curing sheet for precast concrete members according to the present invention with the side of the second laminate whose outermost layer is made of an airtight film in contact with the outside air.

[0071] On the other hand, the curing sheet for manufacturing precast concrete members in Comparative Example 1 without a cross sheet in the first laminate had low tear strength of the curing sheet before use at 80 N and joint strength at 127 N. Moreover, in the evaluation of durability after two years of use, the tear strength of the curing sheet significantly decreased to 30 N, and the joint strength also significantly decreased to 83 N. Therefore, it did not have the strength and durability required for steam curing in the manufacture of precast concrete members. In the visual observation of durability (resistance to tearing) after two years of use, more than 10 mm tears were observed at 100 pieces / 100 m 2 or more, and tears were confirmed at the joints.

Industrial Applicability

[0072] The curing sheet of the present invention and the curing sheet for manufacturing precast concrete members can be used for steam curing in the manufacture of precast concrete members such as box culverts in a manufacturing factory.

Explanation of Reference Numerals

[0073] 1 Curing sheet 10 Foam material sheet 20, 30 Laminate 21, 31 Cross sheet 22, 33, 34 Extruded film layer 32 Airtight film 100 Curing sheet for manufacturing precast concrete members

Claims

1. A curing sheet in which laminates including cross sheets are provided on both sides of a foam material sheet, wherein the outermost layer of one laminate is made of a cross sheet, the outermost layer of the other laminate is made of an airtight film, and the airtight film is a metal-embedded film curing sheet.

2. The laminate includes an extruded film layer, and the curing sheet according to claim 1, wherein the foam material sheet and the laminate are integrated by the fusion of the extruded film layer.

3. The airtight film has an air permeability measured in accordance with the frazil method defined in JIS L 1096 of 1 cm ３ / (cm ２ ·s) or less. The curing sheet according to claim 1 or 2

4. The curing sheet according to any one of claims 1 to 3, having a thickness of 0.5 to 7 mm.

5. A curing sheet for manufacturing a precast concrete member, formed by joining a plurality of long base fabric pieces made of the curing sheet according to any one of claims 1 to 4.

Images