JP2012251401A - Concrete curing sheet and curing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a concrete curing sheet which enables reliable curing by improving water retention for long-lasting wetting effects, and which is recyclable, well economical and free from harmful material formation when discarded, and to provide a curing method.SOLUTION: The lower side of a layer of bentonite or sepiolite clay mineral 1, a layer of concrete curing mat 2 is provided for developing water absorption.

Description

  The present invention relates to a concrete curing sheet and a curing method used for curing vertical surfaces and horizontal surfaces of concrete structures.

  The purpose of concrete curing is to maintain the humidity and temperature of the concrete surface for a specified period after placement, and to prevent harmful forces from acting. It is extremely important for improving the quality of the concrete surface by sufficiently exerting the hardening action of the concrete.

  Curing methods can be categorized into three categories: (1) wet curing, (2) temperature controlled curing, and (3) protection against harmful effects. Among these, moisture is further supplied to moisture curing. And a method for preventing evaporation of moisture.

  It is said that the amount of water necessary for hydration of cement in concrete is about 40% of the cement weight. Ordinary concrete retains sufficient water for cement hydration when it is mixed, but water gradually evaporates from the exposed surface of the poured concrete and there is a shortage of water required for hydration. There is. Further, in order to improve the quality of concrete such as strength, durability and water tightness, it is necessary to keep the wet state as long as possible. However, in general structures, it is often difficult to perform wet curing for a long time in terms of workability and economy.

  Methods for supplying moisture include underwater, flooding, watering (spraying), poultice (key, curing mat), and wet sand curing.

  If wet curing is discontinued at a relatively early stage, the concrete will be exposed to the air before the hydration reaction is completed, causing problems such as cracking due to the effect of cold outside air and drying, or slowing down the strength. Therefore, conventionally, in order to perform such curing, a sheet or mat is installed on the surface of the concrete after placing, and moisture is prevented from escaping or water is supplied.

  Concrete curing mats are commercially available in the form of foamed urethane and PP cloth, or foamed urethane, PP cloth and nonwoven fabric.

Further, as the concrete curing sheet, a water-absorbing material such as a nonwoven fabric or a highly water-absorbing polymer is used, and a nonwoven fabric is laminated on both sides of a foamed polyurethane sheet having a thickness of about 5 mm as shown in the following patent document 3 A layered structure or a sheet-like material such as a nonwoven fabric mixed with a water-absorbing material such as a highly water-absorbing polymer is produced and used on the surface of the cast concrete.
JP-A-60-51263 JP-A 63-70765 JP-A-6-212799 JP 2001-48676 A JP 2007-77754 A JP 2007-46270 A

  Patent Document 1 uses a mat having a structure in which a fiber assembly in which a water-retaining water-absorbing material is mixed is interposed between a nonwoven fabric and a synthetic resin sheet having substantially the same area as the nonwoven fabric. The water-absorbing material is a porous oxalate powder such as magnesium silicate powder.

  Patent Document 2 is selected from the group consisting of wood pulp, rayon, cotton and other cellulosic fibers and / or superabsorbent polymers as water-absorbing materials, and is considered to be a sheet-like body.

  Patent Document 3 includes a non-woven fabric containing 10 to 50% by weight of a superabsorbent polymer non-bulky molded product and 15 to 40% by weight of a heat-sealing fiber. A concrete curing sheet characterized in that the content of the bulky molded product decreases from one side of the nonwoven fabric to the other side with a slope of at least 2.5% by weight per 1 mm thickness. A water-absorbing curing sheet is mounted on the concrete placement surface in a wet state after removal, and then the water is swollen by water supply so that the sheet adheres to the concrete surface and keeps the concrete surface moist during the curing period. Then, the sheet is peeled off.

  Patent Document 4 discloses a concrete curing sheet in which a water-absorbing material is laminated between a water-permeable material and a water-impermeable material, and the water-absorbing material is obtained by reacting a polyalkylene oxide and a polyol with an isocyanate compound. A concrete curing sheet comprising an alkylene oxide modified product. The water permeable material is at least one nonwoven fabric, woven fabric or perforated film selected from the group consisting of polyethylene resin, polypropylene resin and polyester resin, and the water impermeable material is polyethylene resin, polypropylene resin, polyester resin and polyurethane. It is at least one film selected from the group consisting of resins.

  In Patent Document 5, a water-soluble polymer layer is provided on one surface of a plastic film or sheet in a concrete curing sheet that is attached to a mold in advance and then used by placing concrete.

  Patent Document 6 is a concrete curing sheet used by placing concrete in advance after being attached to a formwork, and is a concrete curing sheet obtained by laminating a plastic film or a sheet and a fiber sheet. It consists of 1 or 2 or more materials selected from the nonwoven fabric, the woven fabric, or the net-like sheet | seat material, or consists of 1 type or 2 or more types of materials in PE, PP, PET, or nylon.

  In order to supply sufficient moisture as a concrete curing, if water is sprayed frequently, the labor cost for water management will rise, and the cost of watering equipment will increase.

  Further, in the conventional concrete curing mat, the foamed urethane is mainly responsible for the moisture retention and water retention, but the moisture evaporates immediately and the moisture curing cannot be performed sufficiently.

  The water-absorbent sheet described in Patent Document 1 still does not exhibit a sufficient anti-drying effect. This water-absorbing sheet is used when placing concrete in slabs that do not use a formwork. After the concrete is placed, it is laid down while the concrete is not solidified, removing the breathing water, and once removed, the concrete surface is finished. Do. Thereafter, a curing sheet containing breathing water is placed once again on the slab to prevent drying. Therefore, since this curing sheet has already absorbed water at the time of attachment, it is heavy and difficult to handle. Therefore, it can be placed on the slab, but it is very difficult to attach it to the bottom of the slab, the column surface, the beam surface, the wall surface or the like. Moreover, even if the curing sheet that has already swollen and swelled in this way is attached to the concrete surface and sprayed, the curing sheet and the concrete surface cannot be brought into close contact with each other.

  Furthermore, an attempt is made to achieve effective self-leveling by bringing a water-absorbent sheet into contact with the concrete surface to be cast, quickly absorbing and removing the breathing water on the concrete surface, removing the sheet, and spreading self-leveling material on the exposed concrete surface. Therefore, it is not originally intended to provide moisture retention or water retention during the curing period, nor does it suggest it.

  The same applies to the concrete curing sheets of Patent Document 2 and below. The nonwoven fabric has insufficient water absorption performance, and a water absorbent material such as a highly water absorbent polymer cannot be reused once it has a water absorbing action. In addition, it is an organic substance and becomes a hazardous waste on site.

  The object of the present invention is to eliminate the disadvantages of the conventional methods described above, increase water retention, so that the wetting action lasts long, enables reliable curing, is reusable and is economical, An object of the present invention is to provide a concrete curing sheet and a curing method that do not become harmful substances when discarded.

  In order to achieve the above object, the gist of the present invention described in claim 1 is that a concrete curing mat layer exhibiting water absorption is provided under the clay mineral layer of bentonite or sepiolite.

  According to the first aspect of the present invention, by combining a clay mineral having a high water retention capacity with a concrete curing mat, the wetting effect can be exhibited longer than in the case of using only a concrete curing mat, and a reliable curing can be achieved. Also, since clay minerals are inorganic, they are not harmful when discarded. Moreover, the water retention of the clay mineral can be repeated many times and can be reused.

  The gist of the present invention described in claim 2 is that the curing mat of the concrete curing mat layer is made of foamed urethane and PP cloth, or foamed urethane, PP cloth and nonwoven fabric.

  According to the second aspect of the present invention, a commercially available mat can be used and the cost can be reduced.

  The gist of the present invention described in claim 3 is that a curing mat layer is also provided above the clay mineral layer, and the clay mineral layer is sandwiched between the curing mats.

  According to the third aspect of the present invention, the clay mineral layer is easily formed into a mat shape or a sheet shape by being sandwiched between the curing mats, and the handling is also simplified.

  The gist of the present invention described in claim 4 is that the surface is combined with a sheet having high heat shielding properties.

  According to this invention of Claim 4, by combining with a sheet | seat (for example, aluminum sheet) with high heat-shielding property, evaporation of a water | moisture content can be prevented and water retention will become higher.

  In the present invention according to claim 5, as a concrete curing method, water is sprayed on a concrete placement surface in a wet state after the concrete formwork is removed, and on the lower side of the clay mineral layer by bentonite or sepiolite. The gist is to lay a concrete curing sheet provided with a concrete curing mat layer exhibiting water absorption.

  According to the present invention described in claim 5, there is sufficient water on the concrete casting surface by sprinkling water onto the wet concrete placing surface after removing the concrete formwork, and bentonite or sepiolite from above. By laying a concrete curing sheet with a concrete curing mat layer that exhibits water absorption under the clay mineral layer, the concrete curing mat absorbs the water first, and the clay mineral absorbs it. Water is retained here.

  In this way, even when a highly heat-insulating sheet (such as an aluminum sheet) is provided on the surface, water can be retained easily and effectively even when the water from the top is not enough to spread the water on the mat or sheet. It can be carried out.

  As described above, the concrete curing sheet and the curing method of the present invention can increase the water retention and maintain the wetting action longer than the case of the concrete curing mat alone, thereby enabling reliable curing. In addition, no harmful substances are emitted during disposal.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a sectional view showing a first embodiment of the present invention, in which a layer of a concrete curing mat 2 that exhibits water absorption is provided below a layer of clay mineral 1 made of bentonite or sepiolite.

  Bentonite is a kind of clay mineral created by alteration of volcanic ash and lava deposited on the seabed and lake bottom. The name bentonite is a rock name (general name for mineral aggregates), and its composition varies depending on the region and location. .

  The component composition is mainly composed of a mineral called montmorillonite, and also contains minerals such as quartz, mica, feldspar, and zeolite. Although many minerals are mixed, the specific physical properties of montmorillonite are the same as those of bentonite.

  The physical properties of bentonite include swelling / thickening, caking / water absorption, adsorptive / suspension stability, cation exchange, and thixotropy. The Na type is particularly excellent in swelling property, thickening and suspension stability, and the Ca type is particularly excellent in caking property.

The crystal of montmorillonite is an octahedral water-containing layered silicate mineral in terms of mineralogy, and is ideally expressed by the following chemical formula.
(Al _2-y Mg _y ) Si ₄ O ₁₀ (OH) ₂・ (M ⁺ .M _1/2 ²⁺ ) _y nH ₂ O
y = 0.2-0.6
M: Exchangeable cations Na, K, Ca, Mg, H, etc.
n: Amount of interlayer water

Sepiolite is a clay mineral mainly composed of hydrous magnesium silicate, and its chemical structure is Mg ₈ Si ₁₂ O ₃₀ (OH ₂ ) ₄ (OH) ₄ 6-8H ₂ O. Adsorption performance, thixotropic properties and plasticity Has three basic properties: rheological properties peculiar to the material, and dry solidification.

  Both bentonite and sepiolite are highly swellable clay minerals with high water absorption and water retention.

The swelling property of bentonite will be described with reference to FIG. 7. The swelling mechanism varies depending on the type of interlayer cation of montmorillonite. When the interlayer cation is Na ^+, the attracting force of the crystal layer is weaker than Ca ²⁺ , and water molecules enter by the hydration power of Na ^{+ at} the beginning, and water molecules enter one after another if the water supply is sufficient. In this way, the layer spacing increases and swells indefinitely. On the other hand, the interlayer cations For Ca ^2+, although the force to attract the crystal layer is stronger than Na ^+, hydration energy to water molecules 5 times stronger second layer than Na ⁺ may be easily formed. However, even if the supply of water is sufficient, it is limited to the force that attracts the crystal layer, and is limited to three molecular layers between the layers.

  Describing the water absorption of sepiolite, the unit cells of sepiolite are connected in a chain as shown in FIG. While kaolin and bentonite are called layered clay, sepiolite is classified as chain clay.

  There are regular gaps between the lattices (the shaded area in FIG. 9), and the small pores in the shaded area have a size of about 5.6 × 11 mm. In the vertical direction of the figure, the crystal grows and becomes fibrous, and elongated pores are formed in the fiber. Sepiolite has pores (α in the figure) formed between fibers in addition to pores in the fibers. It is about 200mm in size and has the property of sucking up liquid substances by capillary action. When it is poured, it absorbs water in a short time.

  Bentonite and sepiolite are completely inorganic minerals, so they do not rot themselves, meet the standards of the soil environment standards and the Japanese Pharmacopoeia, and are guaranteed to be friendly to the human body and the environment. .

  The concrete curing mat 2 of the concrete curing mat layer may be a commercially available one, and is a three-layered sheet of PP cloth + foamed urethane + nonwoven fabric or a two-layered sheet of foamed urethane and PP cloth sheet.

  The two-layered sheet is a lightweight, easy-to-handle product that combines urethane foam and PP cloth sheet by sewing at the factory, and has excellent heat retention and water retention.

  The three-layered sheet combines the strength of PP cloth, the moisture retention and water retention of urethane foam, and the flexibility of non-woven fabrics, and is suitable for concrete curing in high temperatures in summer and cold seasons in winter.

  FIG. 2 shows a second embodiment of the present invention, wherein the upper side (surface side) of the layer of clay mineral 1 made of bentonite or sepiolite is covered with a highly heat-insulating sheet 3 such as an aluminum sheet. Good. Thus, by combining the sheet 3 having a high heat shielding property such as an aluminum sheet, evaporation of moisture can be prevented.

  FIG. 3 shows a third embodiment. A layer of the curing mat 2 is provided on the upper side of the layer of the clay mineral 1, and the layer of the clay mineral 1 is sandwiched between the curing mats 2. In this case as well, the upper side (front side) may be covered with a highly heat-shielding sheet 3 such as an aluminum sheet.

  In the third embodiment, the curing mat 2 is cut at the center to form a bag shape, and the clay mineral 1 is packed in the bag, whereby the clay mineral 1 and the curing mat 2 can be easily combined as a layer.

  At that time, as shown in FIG. 6, the lower curing mat 2 is formed in a grid-like section, and the clay mineral 1 is placed in the partitioned recess 4. In this way, the clay mineral 1 is stored in a small compartment and can be stably stored without being biased to one place.

  In this way, the concrete curing sheet of the present invention is laid on the concrete placement surface in a wet state after removing the concrete formwork, but in that case, after laying, the water may be sprinkled from above, If there is a highly heat-insulating sheet 3 such as an aluminum sheet, the water spray from above is blocked by the highly heat-insulating sheet 3 such as the aluminum sheet.

  In that case, as shown in FIG. 4, the concrete curing mat 2 that exhibits water absorption under the layer of the clay mineral 1 made of bentonite or sepiolite is sprayed on the casting surface of the concrete 5. You may make it lay the concrete curing sheet of this invention which provided the layer.

  According to the present invention, the moisture is absorbed by the layer of the concrete curing mat 2 and further retained in the clay mineral 1, and the moisture stored in the concrete curing sheet of the present invention wets the casting surface of the concrete 5 Let

  FIG. 5 shows the case of only the concrete curing mat 2, the case of the sheet 3 having a high heat shielding property such as an aluminum sheet and the concrete curing mat 2, and the sheet 3 having a high heat shielding property such as the aluminum sheet of the present invention and the concrete curing mat 2. And the mass change rate with respect to the number of days elapsed for the clay mineral 1.

  In the case of the concrete curing mat 2 alone, the water evaporates immediately, and in the case of the sheet 3 having a high heat shielding property such as an aluminum sheet and the concrete curing mat 2, about 40% of the water evaporates after 28 days.

  The water retention can be further increased by using the clay mineral 1 as in the present invention, and the evaporation of water after 28 days is about 10%.

It is a vertical side view which shows 1st Embodiment of the concrete curing sheet of this invention. It is a vertical side view which shows 2nd Embodiment of the concrete curing sheet of this invention. It is a vertical side view which shows 3rd Embodiment of the concrete curing sheet of this invention. It is a vertical side view which shows one Embodiment of the curing method using the concrete curing sheet of this invention. It is a graph which shows the comparison with the concrete curing sheet of this invention, and a prior art example. It is a disassembled perspective view which shows the preparation example of the concrete curing sheet of this invention. It is explanatory drawing which shows the swelling property of a bentonite. It is a sepiolite crystal structure figure. It is a crystal structure diagram of water retention of sepiolite.

1 Clay mineral 2 Curing mat 3 High heat-shielding sheet such as aluminum sheet
4 Recess 5 Concrete 6 Watering

Claims (5)

  A concrete curing sheet characterized by providing a concrete curing mat layer exhibiting water absorption under a layer of clay mineral made of bentonite or sepiolite.   The concrete curing sheet according to claim 1, wherein the curing mat of the concrete curing mat layer is made of foamed urethane and PP cloth, or foamed urethane, PP cloth, and nonwoven fabric.   The concrete curing sheet according to claim 1 or 2, wherein a curing mat layer is also provided on the upper side of the clay mineral layer, and the clay mineral layer is sandwiched between the curing mats.   The concrete curing sheet according to any one of claims 1 to 3, wherein a sheet having a high heat shielding property is combined with the surface.   Concrete curing with a concrete curing mat layer that exhibits water absorption on the lower side of the clay mineral layer by bentonite or sepiolite on the wet concrete surface after removing the concrete formwork. A concrete curing method characterized by laying a sheet.

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