JPH08188486A - Curing of concrete and curing sheet using the same - Google Patents

Abstract

PURPOSE: To provide a method to promote effective and uniform curing even in the cases of vertical, slant and downward surfaces of concrete and to enable early removal of formwork by putting a specific curing sheet on the placed surface of concrete to retain the water content of the concrete. CONSTITUTION: This concrete curing sheet consists of a nonwoven fabric of 0.1-5mm thickness containing 10-60wt.% of a highly water-absorbing polymeric nonbulky formed product consisting of surface-hydrolyzed acrylic fibers or sodium polyacrylate crosslinked product capable of absorbing 800-2000wt.% of physiological saline, having such a compensable vertical length as to have <200wt.% in the water content difference between the upper and lower ends thereof in such a state that physiological saline of a proper quantity is saturated and held therein in a vertically suspended posture. This sheet is put on the placed surface of concrete in a wet state that, after removing a concrete formwork, the concrete is sprinkled with water once or twice per two days, to firmly attach the sheet to the concrete surface and retain an appropriate water content of the concrete.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a concrete curing method for obtaining high strength and durability of cast concrete during construction and civil engineering, and a curing sheet used therefor.

[0002]

2. Description of the Related Art Conventionally, it has been known that when concrete cast in construction or civil engineering works is rapidly dried, its strength may be lower than expected. In addition, in concrete construction methods that use formwork, in order to increase the rotation rate of the formwork and reduce costs, the formwork is often removed and re-installed 1-2 days after concrete is placed. used. However, if the formwork is removed quickly, the concrete surface tends to dry out, impairing its strength and durability. Therefore, to prevent drying, sprinkle water after placing concrete at the construction site. However, the applied water will dry quickly, especially on the walls, ceiling, etc.
Even after it is hung, it has the drawback that the water drips and is washed away. On the other hand, it is well known that underwater curing is the best for improving the strength of concrete.

Therefore, it is possible to prevent the concrete surface from drying,
There is an attempt to coat the concrete surface with a heavy cloth or a simple non-woven fabric to keep it always wet, but with such a method, the concrete surface actually dries relatively quickly and the drying prevention effect is small. . So, for example, about 5
A curable sheet having a three-layer structure in which a nonwoven fabric is laminated on both sides of a foamed polyurethane sheet having a thickness of mm in a sandwich shape is commercially available. However, such a thick curing sheet has a drawback of being heavy and difficult to handle, so that it is mainly laid on a floor surface and is not suitable for being attached to a vertical or inclined wall surface or a downward bottom surface. In such places such as the wall surface and the bottom surface where it is difficult to attach, a normal heavy cloth, which is unavoidably dried and is relatively fast, is often used. But,
The vertical or downward surface of normal heavy cloth and concrete does not adhere unless it is constantly pressed, so the effect of moisturizing and retaining water is further reduced by simply attaching them. Therefore, even if the economy is sacrificed, the removal of the formwork must be delayed.

On the other hand, in order to prevent drying, it is known that a sheet-like material such as a non-woven fabric mixed with a water-absorbing material such as a super-water-absorbing polymer is attached to a cast concrete surface, as disclosed in, for example, JP-A-60-51263. It is proposed in Japanese Patent Laid-Open No. 63-70765 or Japanese Patent Laid-Open No. 6-1212799. However, the water-absorbent sheet described in JP-A-60-51263 is used when placing a concrete slab without using a formwork, and the breathing water is spread while the concrete is not set after it has set. After removing and once removing it, the concrete surface is finished. Then, subsequently, a sheet containing breathing water is placed on the slab again to prevent drying. Therefore, when this sheet is attached to the finishing slab, it is heavy and difficult to handle because it already absorbs enough water, and it can be placed on the slab, but under the slab, pillar surface, beam surface,
It is extremely difficult to mount it on a vertical surface or an inclined or downward surface such as a wall surface. Further, even if the sheet that has already swollen in this way is attached to the concrete surface and further water is sprinkled on it, it is extremely unlikely that the gap between the sheet and the concrete surface will be filled with further water swelling of the sheet, The two cannot be in close contact. Therefore, this water absorbing sheet is not suitable for exhibiting a sufficient drying preventing effect as a curing sheet.

Further, the method proposed in Japanese Patent Laid-Open No. 63-70765 discloses that a water absorbent sheet is brought into contact with a concrete surface to absorb and remove breathing water on the surface quickly, and then the sheet is removed so that the exposed concrete surface is self-cleaned. The purpose is to spread the leveling material to achieve effective self-leveling, and it is not intended to keep the surface of the placed concrete moisturized and water during the curing period.
Nor does it suggest it.

Further, Japanese Patent Laid-Open No. 6-212799 has been proposed by the present inventors, in which a water-absorption curing sheet is attached to a concrete placing surface in a wet state after removing the concrete formwork. Then, a construction method is disclosed in which the sheet is swollen in water by absorbing water so that the sheet is brought into close contact with the concrete surface and the concrete surface is kept in a wet state during curing, and then the sheet is peeled off. This method is effective in achieving good concrete curing, but subsequent studies have shown that when it is applied to a vertical or inclined concrete placing surface, the desired effect is not always obtained and the wet state is maintained for a long time. It has been found that unpredictable care and effort are required to maintain good and uniform curing, and still leave much room for improvement. Therefore, there is a long-awaited demand in the industry for a concrete curing sheet that adheres well to concrete placing surfaces of various configurations, has an excellent moisturizing effect, and is easy to handle.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to promote effective and uniform easy curing of cast concrete, particularly in vertical or inclined or downward planes, in construction and civil engineering, and formwork The purpose is to provide a concrete curing method that enables the early removal of concrete.
Another object is to provide a concrete curing sheet which is used in such a concrete construction method and is easy to handle and has an excellent curing effect.

[0008]

Means for Solving the Problems As a result of research on the shape, composition, structure and mounting method of the water-absorbing sheet, the present inventors have found that when a curing sheet (water-absorbing sheet) attached to a wall surface is sprayed with water and left as it is. It was found that the water content in the sheet, that is, the water content, changes vertically with time as it dries, and gradually inclines from a lower water content in the upper part to a higher water content in the lower part. Is different,
Depending on it, the drying condition of the concrete also differs, and there is a big difference in the curing effect.Therefore, at the time of construction, the curing sheet with various vertical lengths was held vertically and the difference in moisture content between the top and bottom and the curing effect were kept. As a result of researching the relationship between the above, the present invention has been completed.

In the concrete curing method of the present invention, the difference in water content between the upper end portion and the lower end portion is less than 200% by weight in a state in which the physiological saline is fully saturated and held in a vertically suspended posture. A curing sheet with a vertical length commensurate with the above is attached to the vertical or inclined or downwardly wet concrete placing surface in a wet state after removing the concrete formwork, and then water is sprinkled on it. By doing so, the curing sheet is brought into close contact with the concrete surface and is also maintained at an appropriate water content.

In the present invention, the reason why the physiological saline solution is used to define the water content is that the water discharged from concrete contains salts, and the water absorption rate of fibers and chemical substances is generally fresh water and salt-containing water. Therefore, physiological saline is used as a substitute for the salt-containing water discharged from the concrete in the measurement of the water absorption rate.

Here, the "state in which the physiological saline solution is fully and fully retained in a vertically suspended posture" (hereinafter referred to as "vertical saturated state") is immersed in the physiological saline solution for about 30 minutes, for example. Thus, the sheet is sufficiently impregnated with physiological saline, and then immediately suspended vertically, so that the state where water drops no longer drip from the lower end of the sheet. This state varies to some extent depending on the structure of the sheet, the type of matrix fibers, and the temperature and humidity conditions of the atmosphere, but is usually achieved within about 2 hours at the longest after suspension, and in some cases within tens of minutes in some cases.

Further, "the vertical length corresponding to the difference in water content between the upper end and the lower end of the sheet (hereinafter referred to as" upper and lower water content difference ") is less than 200% by weight" means the above "vertical saturated state". The water content (% by weight) of a horizontally long piece of cloth, which is divided into about 2 cm lengths from the upper edge to the lower edge of the sheet material in ", is measured, and the difference between the water content of the uppermost piece and the lowermost piece is 200. The vertical length of a sheet commensurate with being less than wt%.

A method of fixing such a curing sheet for attaching to a concrete surface in a wet state is to use a tape such as a double-sided adhesive tape or a velcro tape,
There is a method of using a buried bolt. Among them, according to the method of using the embedded bolt and partially using the holding plate, the curing sheet can be stably attached even to the downward wall surface and can be prevented from dropping due to the action of wind or other external force. .

After being attached to the concrete surface, the curing sheet is sprinkled with water so that the sheet swells and fills the gap with the concrete surface to adhere to the concrete surface, and is kept at an appropriate water content to be vertical or inclined. Even when it is attached to the wall surface, the descent of the contained water is well suppressed, and the difference between the upper and lower water content in the single curing sheet is kept at a small value for a long time in cooperation with the water retention capacity of the concrete itself. By appropriately and intermittently repeating watering while observing the time when the difference between the upper and lower water contents increases due to drying, uniform and good concrete curing can be performed with a small watering frequency. The watering frequency required for uniform curing depends on the composition of the curing sheet, the type of matrix fiber, the inclination of the attached concrete surface, and the environmental conditions such as temperature and humidity, but at least once / two days, The purpose can be achieved preferably once or about once a day.

The curing sheet does not necessarily have to cover the entire surface of the concrete. This is because, since concrete is hydrophilic in nature, even a portion not covered with the curing sheet has a curing effect by allowing water to permeate and migrate from the portion covered with the surrounding curing sheet. Also, although it depends on the conditions such as the thickness of the curing sheet and the water retention amount, there is no substantial difference in the curing effect between the covered part and the exposed part even if the laying intervals of a plurality of curing sheets are separated by about 5 cm. .

When the length in the vertical direction increases to such an extent that the difference in water content between the upper and lower sides of the curing sheet in the vertically saturated state becomes 200% by weight or more, when the curing sheet is attached to a vertical or slanted wall surface, the water content decreases due to the fall of the water content. The slope of the rate becomes large,
As the moisture content of the curing sheet decreases, the curing effect of concrete such as strength improvement tends to decrease or become uneven. The difference between the upper and lower water contents depends on the water content, the water absorption rate, the length in the longitudinal direction, etc. of the curing sheet, and becomes smaller as the water content or the water absorption rate becomes larger or the length in the longitudinal direction becomes smaller. Furthermore, it depends on the installation conditions such as the installation angle of the curing sheet with respect to the vertical direction, the frequency of watering, or the drying speed that is affected by the installation location or installation time. As the installation angle approaches the vertical direction, the difference in water content between the top and bottom increases. If the frequency of watering increases, the difference in water content between the upper and lower sides will always be kept small. If the installation place is a place that is fast-drying and has good ventilation, the difference in water content between the top and bottom will be large, and the drying speed of the curing sheet will differ depending on the weather and season.

The curing sheet applied to the above-mentioned method of the present invention comprises a fiber cloth containing 10 to 60% by weight of a non-bulky super absorbent polymer capable of absorbing 800 to 2000% by weight of physiological saline. Provided a vertical length corresponding to the difference in water content between the upper end portion and the lower end portion being less than 200% by weight in a state in which the physiological saline is fully filled and held in a vertically suspended posture. Is characterized by.

It is preferable that the curing sheet has a water absorption capacity capable of retaining at least 1000% by weight of physiological saline. The water absorption capacity generally increases as the hydrophilicity of the constituent matrix fibers, the content of the non-bulky molded article of the superabsorbent polymer mixed therein, the bulk density and the basis weight of the sheet increase, but the water absorption capacity is 1000. If the amount is less than 5% by weight, the drying time will be shorter and the frequency of watering will increase, so the construction may be limited in terms of the season, place, etc. where drying is actually slow. When the water absorption capacity exceeds 1200% by weight, the drying time becomes longer, which is more preferable.
Since there is a dislike for the manufacturing cost to increase, it should be selected as appropriate in consideration of economic efficiency.

The curing sheet of the present invention basically comprises a non-woven fabric, a woven fabric, containing a matrix fiber and a non-bulky molded article of a super absorbent polymer in an amount of 10 to 60% by weight based on the weight of the sheet.
It is a sheet-shaped molded product such as a knitted fabric, and among them, a non-woven fabric is most suitable. The thickness of the sheet is about 0.5 to 5 mm, preferably about 1 to 2 mm. If it is less than 0.5 mm, the amount of water retention is small and a sufficient effect of preventing drying cannot be obtained.
Further, if it exceeds 5 mm, it becomes difficult to handle due to an increase in weight, which impairs workability.

Examples of the matrix fibers include synthetic fibers such as polyamide, polyester, polyethylene, polypropylene, polyacrylonitrile, polyvinyl chloride and polyvinyl acetate, natural fibers such as cotton, hemp and wool, and regenerated fibers such as rayon. Either can be used.

The above-mentioned "non-bulky molded article of super absorbent polymer" is a non-bulky molded article made of a super absorbent polymer having a water absorption capacity of about 800% by weight or more of its own weight, that is, a diameter or thickness. With a small diameter or fine dimensions of less than mm order,
For example, it means fibers, powders, granules, flakes, slit films and the like. Among them, the fibrous molded product is particularly preferably used. If the content of the non-bulky molded article of such a super absorbent polymer is less than 10% by weight, the water absorption / water retention capacity is practically insufficient, while if it exceeds 60% by weight, the water content and the water absorption capacity of the curing sheet increase. However, there is a fear that the strength of the sheet will be reduced and it will be a practical problem. In addition, in order to increase the water absorption amount of the curing sheet, it can be achieved by increasing the basis weight without changing the water content, but since the curing sheet becomes heavy and it becomes difficult to handle during construction, these circumstances In consideration of the above, it is desirable that the content ratio of the non-bulky molded article of the super absorbent polymer is limited to about 60% by weight.

As the super absorbent polymer, an acrylic acid graft polymer of starch, a cross-linked product of sodium polyacrylate, a cross-linked product of polyethylene oxide, for example, the water described in JP-A-61-266661. There are insoluble polyethylene oxide modified products and the like. "KI-Gel 201K" is an example of a commercially available super absorbent polymer.
(Manufactured by Kuraray), "Viscomate PX-112" (manufactured by Showa Denko), "Aronzap RS-2" (manufactured by Toagosei Kagaku), "Arasop S-100" (manufactured by Arakawa Chemical Industry),
"Aquamate AQ-100" (manufactured by Sekisui Plastics),
"Sumikagel S-50" (manufactured by Sumitomo Chemical Co., Ltd.) and the like (all are trade names) are available.

As the super absorbent fiber applied to the present invention, for example, surface-hydrolyzed acrylic fiber (trade name "Lanseal": manufactured by Toyobo Co., Ltd.) and fiber made of crosslinked sodium polyacrylate (trade name "Oasis": Technical Absorber company) etc. Among these, as an example of the highly water-absorbent fiber composed of a crosslinked sodium polyacrylate that is most preferably applied, for example, α, β-ethylenically unsaturated carboxylic acid monomers such as acrylic acid, methacrylic acid, and maleic acid are used. And an alkali metal salt of these carboxylic acids, preferably an α, β-ethylenically unsaturated carboxylic acid alkali metal salt monomer such as sodium salt, potassium salt, etc., and reacts with a carboxylic acid group to form an ester cross-linking bond. A hydroxyl group-containing monomer that can be used, such as the above α, β-ethylenically unsaturated carboxylic acid and glycol, glycerol, Tween,
A super absorbent polymer obtained by copolymerizing a monoester monomer with a polyol such as pentaerythritol is formed into a fiber. The weight ratio of the α, β-ethylenically unsaturated carboxylic acid monomer and the α, β-ethylenically unsaturated carboxylic acid alkali metal salt monomer is from 1/1 to 1/1.
0, and the total of both is 70% to 99.5% by weight, preferably 80% by weight or more. If it is less than 70% by weight, the water absorption rate of physiological saline is insufficient.

As the hydroxyl group-containing monomer, for example, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, glyceryl monomethacrylate, glyceryl monoacrylate and the like are particularly preferably used. These monomers may be used in plural types. The hydroxyl group-containing monomer is contained in an amount equal to or less than 0.5% by weight of free carboxylic acid.
If it is less than 0.5% by weight, crosslinking may be insufficient.

In addition to the above monomers, other α, β-ethylenically unsaturated hydrocarbon monomers such as vinyl acetate and acrylonitrile may be used for imparting plasticity.
The amount of these monomers for plasticization is less than 30% by weight.

The method for polymerizing the above monomers is not particularly limited. If the monomer composition is water-soluble, aqueous polymerization is preferable, and sodium persulfate generally used may be used as the polymerization initiator.

As the spinning method for producing fibers from the superabsorbent polymer thus obtained, dry spinning is preferred in the case of aqueous polymerization.
In the case of wet spinning, since water cannot be used as a coagulant, an organic solvent system must be used.

After the dry spinning, the film is stretched 1.3 times or more by dry heat with 10% by weight or more of water remaining, and then crosslinked by dry heat. Also, staple cutting according to the usual method,
Apply crimp. The fiber strength is improved by drawing 1.3 times or more by dry heat while leaving 10% by weight or more of water. A fiber having a large molecular weight has a high water absorbency, but it tends to be difficult to draw and the fiber strength tends to decrease.

The superabsorbent fiber used in the present invention produced by the above method contains at least 800% by weight of physiological saline.
It preferably has the ability to absorb at least 1200% to 2000% by weight. If it exceeds 2000% by weight, the fiber strength may decrease.

In the curing sheet of the present invention, it is preferable to mix a heat-sealing fiber in addition to the matrix fiber and the non-bulky superabsorbent polymer molding. A heat-fusible fiber is a coexisting constituent fiber, and, for example, a fiber containing a polymer that develops adhesiveness by softening at a temperature below the softening point or melting point of a matrix fiber and a superabsorbent polymer non-bulky molded article. However, it is not particularly limited, but, for example, one having such an adhesion development temperature lower than the melting point of the matrix fiber and the highly water-absorbent polymer non-bulky molded product by 30 ° C. or more is preferable. In the case of using the highly water-absorbent fiber exemplified in, polypropylene, highly polymerized polyester, etc. may be mentioned. Further, as such a heat-sealing fiber component, it is preferable to use, for example, a composite fiber obtained by composite spinning a polypropylene or polyethylene terephthalate core component and a polyethylene sheath component because high strength can be maintained even after the heat-sealing. The amount of the heat-sealing fibers contained in the curing sheet of the present invention is preferably 15 to 40% by weight of the whole. If it is less than 15% by weight, the effect of improving the morphological stability and strength of the sheet does not substantially appear, and if it exceeds 40% by weight, the flexibility of the sheet decreases and the adhesion to the concrete surface due to water swelling is reduced. There is a risk of being hindered.

The base cloth used for the curing sheet of the present invention may be manufactured by a general manufacturing method. Especially in the case of non-woven fabric,
Using a sliver, a fleece, a wrap, etc., in which a matrix fiber and a super absorbent fiber are mixed with a heat-bonding fiber if necessary, a well-known conventional method such as a method of molding while mixing with a needle punch method, an air lay method, etc. It can be applied as appropriate. Since super absorbent fibers and the like are used, a method of entangling the fibers with a water stream and a method of using an emulsion to bond the fibers are not preferable. Also, in the case of a non-fibrous super absorbent polymer non-bulky molded article, unlike the air-laid method of fibers, it is not possible to mix them, so it is preferable to use a method of spraying on a web.

When the heat-fusible fibers are mixed, the sheet is molded and then subjected to an appropriate heat treatment at the adhesiveness-developing temperature of the heat-fusible fibers and / or heat-fusible fibers and / or heat-fusible fibers and matrix fibers and / or The intersections and contacts with the superabsorbent polymer non-bulky molded article are heat-bonded to fix the arrangement of the superabsorbent polymer non-bulky molded article, and at the same time, give strength to the sheet to stabilize the form.

Further, the curing sheet of the present invention has a multi-layer structure of two or more layers, and the content of the non-bulky superabsorbent polymer molded article of the non-woven fabric of the first layer on the side in contact with concrete is high. It is preferable that the content of the highly water-absorbent polymer non-bulky molded article in the second and subsequent layers is reduced to increase the content of the water-absorbent fiber, for example, because the anti-drying effect is further improved. That is, the first layer, which has a high content of the highly water-absorbent polymer non-bulky molded product, has a larger water-absorbing capacity, prevents the concrete from being dried well, and swells with water to a large extent so that it easily adheres to the concrete. The anti-drying effect is further improved. The content of the non-bulky molded article of the super absorbent polymer in the first layer is preferably 30% by weight or more. On the contrary, it is preferable that the content of the superabsorbent polymer non-bulky molded article in the second and subsequent layers is lower than that in the first layer, preferably by 5% by weight or more. The lower the water retention rate on the side in contact with the air, the better the effect of preventing drying as a whole.

When heat-fusible fibers are applied, the first layer preferably has a high water-swelling property, and thus the content of the heat-fusible fibers is preferably low. On the other hand, after the second layer, it is preferable that the content of the heat-sealing fiber is large in order to maintain the strength. The preferable content of the heat-sealing fibers after the second layer is 20% by weight or more.

The curing sheet of the present invention preferably has a film laminated on one side thereof. The film surface is located on the side that comes in contact with air during construction, and prevents the curing sheet from drying. Such films are preferably porous.
That is, when the curing sheet of the present invention is installed, after the curing sheet is attached to the concrete surface, water is sprinkled, the curing sheet is swollen, and when the film is laminated, the water is an end surface of the curing sheet. Since it is absorbed only from the body, it takes a long time to sprinkle water. If the film is porous, the effect of preventing drying by the film is reduced, but the water absorption surface is increased, and the sprinkling time can be reduced. Therefore, although the anti-drying effect and the reduction of the sprinkling time are contradictory to each other, it is possible to obtain the total economic efficiency by making the film porous so that a large number of small openings are formed with a uniform distribution. A suitable opening ratio is about 200
It was experimentally confirmed that the total opening area of the openings of ˜1000 μm is 10 to 30% of the film area. If the pore size and the opening ratio are smaller than the above, the water permeation time increases and it takes a lot of labor and time to sprinkle, and if they exceed the above range, the anti-drying effect decreases and the sprinkling frequency needs to be increased. Is more likely to occur and similar inconveniences occur.

The film used for the curing sheet of the present invention is not particularly limited as long as it has low moisture permeability. For example, inexpensive films such as polyethylene, polypropylene, polyester and polyvinyl chloride are suitable. A thickness of 20 microns is sufficient if you do not worry about damage during handling, but in consideration of the relatively rough handling at the construction site, it is recommended to use a slightly thicker layer in some cases. It

[0037]

The curing sheet of the present invention is cut so that the vertical moisture difference is less than 200% by weight. As far as the curing sheet alone is concerned, this difference in water content between the upper and lower sides depends on various factors such as the moisture content of the curing sheet, the water absorption capacity, the drying rate, the installation conditions such as the installation angle, the sprinkling frequency, the installation location, and the installation time, as described above. It depends to some extent. However, when the curing sheet of the present invention is installed on a vertical or inclined surface such as a wall surface and sprinkled and left as it is, the initial excess moisture contained in the curing sheet shifts downward with time and the difference in vertical moisture increases. . However, by appropriately setting the fiber composition and the length in the longitudinal direction of the sheet, the hydrophilicity of the constituent fibers, the water retention ability due to the capillary action, and the water fixing ability due to the permeation and diffusion of the water content of the coated concrete are mutually effective. Due to the action, the downward movement of the water that has been sufficiently saturated is prevented, and the difference between the upper and lower water contents is kept at a small value for a longer time than expected.

[0038]

EXAMPLES The present invention will be described in more detail by way of examples. In the examples, "%" is "% by weight" unless otherwise specified.

The water content of physiological saline in the super absorbent fiber is DIN
It measured according to 53814. To measure the water retention capacity of the curing sheet, a test piece sufficiently impregnated with physiological saline was hung vertically, and after 10 minutes it was weighed after confirming that no water droplets dripped.
It was determined by dividing the difference from the weight of the test piece before impregnation by the original weight. When water drops dripped after 10 minutes, the water droplets were hung as they were for 10 minutes, and the same measurement was performed.

The concrete test wall is a normal portland
Doce cement, concrete 1 ³The amount of water per 18
0 kg, cement: water 1: 0.55, fine aggregate ratio
(Volume ratio of sand to the total volume of sand and gravel) is 4
Mix as 5.7%, pour into a mold, thickness 50 cm,
Vertical wall 2m after placing a concrete wall with a height of 2m
Remove the frame and attach a test curing sheet to the vertical wall for 1 week
After a lapse of time, measure the rebound hardness by the Schmidt hammer method
Then, the compressive strength of the surface was estimated. Also, after 3 weeks,
Cut a concrete test piece from the wall and use carbon dioxide gas
A neutralization acceleration test was conducted.

Production Example 1 Polyethylene terephthalate short fibers (made by Nippon Ester)
3 denier x 51 mm as a matrix fiber, the above super absorbent fiber (trade name: Oasis) 10 denier x 51
mm and commercially available Kanebo Co., Ltd. core polyester, sheath polyethylene heat-sealed composite fiber (trade name: Bellcombi) 2 denier x 51 mm were mixed at the ratio shown in Table 1 and mixed, carded and cross-laid. Then, needle punching was carried out by a conventional method, and further heated and pressed by a heater roller at 110 ° C. to produce a nonwoven fabric having a basis weight of 200 g / m ² .
The resulting non-woven fabric had a thickness of about 1.8 to 2 mm.
The water retention rate of the physiological saline of this non-woven fabric is shown in Table 1.

[0042]

[Table 1]

Example 1 From the non-woven fabric produced in Production Example 1, a curing sheet having longitudinal lengths changed as shown in Table 2 was prepared. Two days after the concrete test wall was cast, the form was removed, a curing sheet was attached to the vertical wall surface, and water was sprinkled once a day until water drips from the curing sheet at a fixed time. After one week, the Schmidt hammer strength of the concrete wall surface was measured, and the compression strength obtained therefrom is shown in Table 2.

[0044]

[Table 2]

Next, a sample piece having a diameter of 10 cm in the central portion of the cured portion was cut out from the concrete wall surface and subjected to a neutralization accelerating test at 20 ° C. for 1 month with 5% carbon dioxide gas. The surface was cut in half, the cut surface was colored with phenolphthalein, and the neutralized depth was measured. Table 3 shows the results.

[0046]

[Table 3]

Example 2 Sheet No. of Example 1 3 as the first layer, and the sheet No.
1 was laminated as a second layer and integrated by needle punching. Further, as the third layer, an opening having a pore diameter of 400 μm is provided.
A test wall was cured in the same manner as in Example 1 except that a curing sheet having a three-layer structure, in which a polyethylene film having a thickness of 20 μm was laminated per mm ^2, was laminated and the watering was changed every other day. , Schmidt hammer strength measurement and neutralization acceleration test were performed. As a result, the Schmidt hammer strength was 220 kgf / cm ² , and the neutralization depth was 13
mm.

[0048]

EFFECTS OF THE INVENTION The curing sheet of the present invention and the concrete curing method using the same are used in construction and civil engineering work.
It is possible to promote uniform and effective curing of cast concrete, improve the strength of concrete, and suppress deterioration of concrete due to acidification. Further, since it is lightweight, it is convenient to handle, has good workability, and can be easily applied to a concrete surface which is vertically or downwardly inclined. Further, it becomes possible to remove the formwork at an early stage, and the formwork can be effectively utilized, which is economically advantageous.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location E04F 15/12 F 8702-2E E04G 21/02 104 21/24 A (72) Inventor Toshio Yonezawa Chiba 1-5, Otsuka, Inzai-cho, Inba-gun, Kenchi Ltd., Technical Research Institute, Takenaka Corporation (72) Inventor Masaaki Kojima 1-5, Otsuka, Inzai-cho, Inza-gun, Chiba Institute, Technical Research Institute, Takenaka

Claims (20)

[Claims] 1. A longitudinal length commensurate with the difference in water content between the upper end portion and the lower end portion being less than 200% by weight in a state in which physiological saline is fully filled and held in a vertically suspended posture. The curing sheet with the height is attached to the vertical or sloping or downward facing concrete placing surface in the wet state after removing the concrete formwork, and then water is sprinkled on it to bring the curing sheet into close contact with the concrete surface. A method for curing concrete, which is characterized in that the water content is maintained at an appropriate water content. 2. The method according to claim 1, wherein the watering is intermittently performed at a frequency of at least once every 2 days immediately after the curing sheet is attached to the concrete placing surface. 3. The method according to claim 2, wherein the watering frequency is once / day. 4. A fiber cloth containing 10 to 60% by weight of a non-bulky superabsorbent polymer molded article capable of absorbing 800 to 2000% by weight of physiological saline, and physiological saline in a vertically suspended posture. A concrete curing sheet characterized by having a length in the longitudinal direction commensurate with the difference in water content between the upper end and the lower end being less than 200% by weight in a state in which water is sufficiently filled and retained. 5. The curing sheet according to claim 4, which has a water absorption capacity capable of retaining at least 1000% by weight of physiological saline. 6. The curing sheet according to claim 4, which is made of a non-woven fabric having a thickness of 0.5 to 5 mm. 7. The curing sheet according to claim 6, which has a thickness of 1 to 2 mm. 8. The curing sheet according to claim 4, wherein the non-bulky molded product of the super absorbent polymer is a super absorbent fiber made of surface-hydrolyzed acrylic fiber or sodium polyacrylate cross-linked product. . 9. The sodium polyacrylate crosslinked product has an α, β-ethylene having a hydroxyl group capable of reacting with an α, β-ethylenically unsaturated carboxylic acid monomer and an carboxylic acid to form an ester crosslinked bond. A glycolate or polyol monoester monomer of an unsaturated carboxylic acid,
The curing sheet according to claim 8, which is formed from a polymer obtained by copolymerizing α, β-ethylenically unsaturated carboxylic acid alkali metal salt monomer and crosslinking by heat. 10. The molar ratio of the α, β-ethylenically unsaturated carboxylic acid monomer and the α, β-ethylenically unsaturated carboxylic acid alkali metal salt monomer is from 1/1 to 1/10, The total amount of both is 70 to 99.5% by weight of all monomers,
The α, β-ethylenically unsaturated carboxylic acid glycolate or polyol monoester monomer is the above α, β-
The curing sheet according to claim 9, wherein the curable sheet has an amount of 0.5% by weight or less, which is equal to or less than the equivalent of the free carboxylic acid of the ethylenically unsaturated carboxylic acid monomer. 11. The α, β-ethylenically unsaturated carboxylic acid is at least one mono- and / or dicarboxylic acid selected from the group consisting of acrylic acid, methacrylic acid and maleic acid. Curing sheet. 12. The non-bulky molded article of the superabsorbent polymer,
The curing sheet according to any one of claims 4 to 7, which is at least one kind of finely dimensioned superabsorbent polymer molding selected from the group consisting of powder, granules and flakes. 13. The superabsorbent polymer is at least one selected from the group consisting of an acrylic acid polymer of starch, a crosslinked product of sodium polyacrylate and a crosslinked product of polyethylene oxide. One of
Section curing sheet. 14. The curing sheet according to any one of claims 4 to 13, which contains 15 to 40% by weight of heat-sealing fibers. 15. The multilayer structure according to claim 4, wherein at least two layers including a first layer having a high content of superabsorbent fibers and a second layer having a smaller content of superabsorbent fibers than the first layer are laminated. Curing sheet. 16. The curing sheet according to claim 15, wherein the content of the superabsorbent fiber is at least 30% by weight in the first layer, and the second and subsequent layers are at least 5% by weight less than the first layer. 17. The curing sheet according to claim 4, wherein a film is laminated on the surface on the side in contact with air. 18. The film of claim 1, wherein the film is porous.
7 curing sheet. 19. The film has a pore size of 200 to 100.
The total opening area is 0 μm and the total opening area is 10
The curing sheet according to claim 18, wherein a large number of holes are distributed and distributed on average at a ratio of -30%. 20. The curing sheet according to claim 17, wherein the film has a thickness of at least 20 μm.