Concrete curing sheet

Abstract

The present invention provides a concrete curing sheet for curing concrete surfaces after concrete placement or removal of formwork, which retains the necessary moisture, prevents contact with carbon dioxide in the atmosphere to provide sufficient strength to the concrete, and releases gases generated from the concrete to create a uniform finished surface. [Solution] An adhesive sheet for covering the surface of concrete during the curing of concrete, wherein the sheet has a base layer and an adhesive layer formed on one side of the base layer, and the base layer is a polyolefin resin film made of a mixture of polypropylene resin and polyethylene resin, with the ratio of polypropylene resin to polyethylene resin being 95-50%:5-50%.

Description

[Technical Field]

[0001] This invention relates to a concrete curing sheet used to prevent drying, temperature changes, and carbonation of the concrete surface after concrete placement, thereby preventing hardening defects. [Background technology]

[0002] Conventional concrete is made by mixing Portland cement with aggregates such as sand and gravel, admixtures such as water-reducing agents, and water. It hardens through a hydration hardening reaction and achieves its required strength. Concrete hardening requires moisture, temperature, and time. If drying is rapid after placement, or if the temperature is extremely low or high, hardening failure may occur, resulting in insufficient strength.

[0003] Conventionally, concrete curing methods have included preventing the evaporation of moisture from the surface, such as sealing and coating curing, and methods that involve supplying water to the surface of the poured concrete, such as watering and flooding curing, to prevent the poured surface from drying out.

[0004] On the other hand, regarding the surface of the concrete in contact with the formwork, there is little need to worry about drying and temperature as long as the formwork is in place. However, due to constraints on the construction period and the efficiency of formwork use, the formwork may be removed before the concrete has fully hardened. In such cases, there is a risk of insufficient curing of the concrete due to the effects of drying and temperature.

[0005] Furthermore, it is widely known that concrete undergoes a deterioration mechanism called carbonation due to carbon dioxide in the atmosphere. This is because calcium hydroxide in the concrete changes to calcium carbonate due to the intrusion of carbon dioxide, lowering the pH of the concrete. This destroys the passive film on the reinforcing steel in the concrete, causing the reinforcing steel to corrode due to water and oxygen, and the expansion of the corroded areas leads to deterioration phenomena such as cracking of the concrete. Countermeasures after deterioration include cross-sectional repair methods and re-alkalization methods, but these require additional work, and there is a need for simpler countermeasures that prevent deterioration from occurring in the first place.

[0006] In order to improve the quality of concrete, and especially to provide the required strength and durability as a structural material, it is necessary to maintain a moist state so that there is enough water for the hydration reaction of the cement contained in the concrete, and to cure it sufficiently by maintaining a temperature suitable for hydration. Furthermore, it is desirable to minimize contact with carbon dioxide in the atmosphere even after curing.

[0007] On the other hand, if the concrete curing sheet is made too airtight, it may cause blistering between the sheet and the concrete, resulting in an uneven concrete surface. This is because it prevents air bubbles that inevitably form when concrete hardens from being released to the outside, and a certain degree of breathability is aesthetically preferable.

[0008] Patent Document 1 discloses a curing method in which concrete is poured into a formwork, and after the formwork is removed, a water-impermeable synthetic resin film made from polypropylene is attached to the concrete surface with an adhesive.

[0009] Furthermore, Patent Document 2 discloses a curing sheet that covers the surface of concrete, and is characterized by a base layer having water permeability and air permeability in order to prevent drying of the concrete pouring surface and to release air bubbles that inevitably occur when the concrete hardens to the outside. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Patent No. 4360342 [Patent Document 2] Patent No. 7003519 [Overview of the project] [Problems that the invention aims to solve]

[0011] However, the concrete curing sheet described in Patent Document 1 had the following problems due to excessive moisture during concrete hardening: (1) reduced strength, (2) shrinkage and cracking, and (3) reduced durability.

[0012] Furthermore, the concrete curing sheet described in Patent Document 2 may be insufficient to block carbon dioxide from the atmosphere because it is permeable, and there is a risk that it may not adequately prevent deterioration due to carbonation.

[0013] The object of the present invention is to provide a concrete curing sheet for curing concrete surfaces after pouring or after formwork removal, which retains the necessary moisture, prevents contact with carbon dioxide in the atmosphere to give the concrete sufficient strength, and releases gases generated from the concrete to produce a uniform finished surface. [Means for solving the problem]

[0014] As a means to solve the above problems, the invention described in claim 1 is an adhesive sheet used during concrete curing to cover the surface of concrete, wherein the sheet has a base layer and an adhesive layer formed on one side of the base layer, the base layer is a polyolefin resin film made of a mixture of polypropylene resin and polyethylene resin, and the ratio of the polypropylene resin to polyethylene resin is 95-50%:5-50%.

[0015] Furthermore, the invention described in claim 2 is such that the water vapor permeability of the concrete curing sheet is 1 to 50 g / m².2 ·day, and the carbon dioxide permeability is 30,000 ml / m 2 ·day or less. The concrete curing sheet according to claim 1, characterized in that.

Effect of the Invention

[0016] The concrete curing sheet according to the present invention has a base material layer having water retention, carbon dioxide barrier properties, and appropriate water permeability, and an adhesive layer provided on one side of the base material layer. Therefore, by pressing the adhesive layer against the concrete placement surface after removing the formwork, it functions as a concrete curing sheet that covers the concrete surface and promotes the curing of the concrete. Further, the base material layer is a polyolefin resin film made of a mixture of polypropylene resin and polyethylene resin, and the ratio of the polypropylene resin to the polyethylene resin is 95 to 50%: 5 to 50%. Therefore, a sea-island structure is formed in the base material layer, and fine pores are formed, so that the gas generated during the curing of the concrete can be released, and a uniform finish surface can be obtained.

[0017] In addition, the concrete curing sheet according to the present invention has a water vapor permeability of 1 to 50 g / m 2 ·day, so it can prevent the volatilization of moisture and retain the moisture required for the hydration reaction. Furthermore, since the carbon dioxide permeability is 30,000 ml / m 2 ·day or less, it can prevent the intrusion of carbon dioxide in the atmosphere and suppress the deterioration due to neutralization.

Brief Description of the Drawings

[0018] [Figure 1] It is a cross-sectional view showing the configuration of a concrete curing sheet which is an embodiment of the present invention.

Mode for Carrying Out the Invention

[0019] The concrete curing sheet according to the present invention is used to prevent concrete from drying out and to mitigate the effects of temperature, thereby ensuring the concrete hardens completely, while also maintaining its strength by preventing the intrusion of carbon dioxide from the atmosphere. This is achieved by applying the sheet to the concrete surface after concrete placement and removal of the formwork, before the concrete has fully hardened.

[0020] As shown in Figure 1, the concrete curing sheet 1 according to the present invention consists of a base layer 2 and an adhesive layer 3 provided on one side of the base layer 2.

[0021] [Base material layer] The base layer 2 is a polyolefin resin film made of a mixture of polypropylene resin and polyethylene resin.

[0022] Examples of polypropylene resins include propylene homopolymers such as isotactic homopolypropylene and syndiotactic homopolypropylene, which are obtained by homopolymerizing propylene, and propylene copolymers, which are mainly composed of propylene and copolymerized with ethylene, 1-butene, 1-hexene, 1-heptene, 1-octene, 4-methyl-1-pentene, and other α-olefins. The propylene copolymer may be a binary system or a multi-component system of three or more components, and may be a random copolymer or a block copolymer.

[0023] Examples of polyethylene resins include high-density polyethylene, medium-density polyethylene, linear low-density polyethylene, copolymers mainly composed of ethylene and copolymerized with propylene, butene, hexene, heptene, octene, 4-methyl-1-pentene and other α-olefins, maleic acid-modified ethylene-vinyl acetate copolymer, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-alkyl acrylate copolymer, ethylene-alkyl methacrylate copolymer, metal salts of ethylene-methacrylic acid copolymer (metals include zinc, aluminum, lithium, sodium, potassium, etc.), ethylene-cyclic olefin copolymer, and maleic acid-modified polyethylene.

[0024] Among the polypropylene resins mentioned above, propylene homopolymer is preferred from the viewpoint of water vapor and carbon dioxide barrier properties, chemical resistance, and cost. Furthermore, among polyethylene resins, high-density polyethylene or ethylene-cyclic olefin copolymer is preferred.

[0025] By mixing the polypropylene resin and polyethylene resin and molding them into a film, a base layer 2 of the concrete curing sheet can be obtained. The ratio of polypropylene resin to polyethylene resin is preferably 95-50%:5-50%, and more preferably 90-60%:10-40%. By mixing the polypropylene resin and polyethylene resin in a predetermined ratio and molding them into a film, a sea-island structure is formed in the base layer, and fine pores are formed, allowing gases generated during concrete hardening to be released. If the polyethylene resin content is less than 5%, the formation of the sea-island structure will be insufficient, preventing sufficient release of generated gases and causing blistering, leading to a decrease in concrete quality. Furthermore, if the polyethylene resin content exceeds 50%, it will lead to a decrease in water vapor permeability, carbon dioxide permeability, and film properties.

[0026] In the present invention, the substrate layer 2 may optionally contain known additives as needed. Examples of known additives include, but are not limited to, antioxidants, light stabilizers, ultraviolet absorbers, fillers and filler dispersants, crystal nucleating agents, antiblocking agents, plasticizers, slip agents such as fatty acid amides, dyes, pigments, mold release agents, and flame retardants.

[0027] The base layer 2 may be an unstretched film or a stretched film. It may also be a single-layer structure or a multi-layer structure.

[0028] The thickness of the base layer 2 is preferably 10 to 500 μm, and more preferably 20 to 300 μm. If the thickness is 10 μm or more, sufficient strength and cohesive force of the base layer 2 can be easily obtained, and if the thickness is 500 μm or less, sufficient flexibility of the curing sheet can be easily obtained, making it easy to attach to concrete.

[0029] [Adhesive layer] As the adhesive that serves as the raw material for the adhesive layer 3, EVA-based hot-melt adhesives, rubber-based hot-melt adhesives, acrylic emulsions, EVA emulsions, SBR emulsions, aqueous adhesives such as vinyl acetate-based emulsions, and solvent-based adhesives such as acrylic-based, EVA-based, SBR-based, and vinyl acetate-based adhesives are used. As methods for forming the adhesive layer 3, there are cases where an adhesive is applied to the base material layer 2 to form the adhesive layer, and cases where an adhesive sheet-like material is bonded to the base material layer 2 to form it, etc., and it is not particularly limited.

[0030] The water vapor permeability of the concrete curing sheet of the present invention is 1 to 50 g / m 2 ·day, preferably 1 to 30 g / m 2 ·day. When the water vapor permeability is 50 g / m 2 ·day or less, the dissipation of the water bleeding from the concrete can be effectively suppressed, and a high curing effect can be obtained. When the water vapor permeability is less than 1 g / m 2 ·day, there is an excess of moisture during the curing of the concrete, resulting in problems such as a decrease in strength and cracking. Therefore, in the present invention, the water vapor permeability is set to 1 to 50 g / m 2 ·day or more.

[0031] The carbon dioxide permeability of the concrete curing sheet of the present invention is 30,000 ml / m 2 ·day or less, preferably 25,000 ml / m 2 ·day or less, more preferably 20,000 ml / m 2 ·day or less. When the carbon dioxide permeability is 30,000 ml / m 2 ·day or less, the contact between the concrete and carbon dioxide in the atmosphere can be prevented, and high-strength concrete can be obtained. Also, the lower the carbon dioxide permeability, the more the carbon dioxide in the atmosphere can be blocked, resulting in higher strength. However, it is necessary to change the resin component of the base material layer 2, and from the perspective of cost and the possibility that generated gases cannot be released, in the present invention, it is set to 30,000 ml / m 2 ·day or less.

[0032] The water vapor and carbon dioxide transmission rates were measured in accordance with JIS-K7126 under conditions of 40°C and 90% relative humidity.

[0033] The concrete curing sheet of the present invention is used by being attached to the concrete surface after the formwork has been removed following concrete placement using an adhesive layer 3. Alternatively, in another embodiment, the concrete curing sheet of the present invention may be installed in the formwork beforehand before concrete is placed. In this case, the surface of the base layer 2 of the concrete curing sheet that does not have the adhesive layer 3 formed on it may be fixed to the formwork with tape or adhesive, or a removable adhesive layer may be formed in advance on the surface of the base layer 2 that does not have the adhesive layer 3 formed on it, and then attached to the formwork before use. [Examples] [Examples]

[0034] A concrete curing sheet was obtained by coating an 80 μm polyolefin resin film, blended in a ratio of 70% polypropylene resin and 30% polyethylene resin, as the base layer, with an adhesive (Olivine BPS6080TFK, manufactured by Toyo Chem Co., Ltd.) as the adhesive layer, and then drying the film to a thickness of 30 μm after drying. [Examples]

[0035] A concrete curing sheet was obtained in the same manner as in Example 1, except that the base layer was made of polypropylene resin:polyethylene resin = 90%:10%. [Examples]

[0036] A concrete curing sheet was obtained in the same manner as in Example 1, except that the base layer was made of polypropylene resin:polyethylene resin = 50%:50%.

[0037] <Comparative Example 1> A concrete curing sheet was obtained in the same manner as in Example 1, except that the base layer consisted solely of polypropylene resin.

[0038] <Comparative Example 2> A concrete curing sheet was obtained in the same manner as in Example 1, except that the base layer was made of polypropylene resin:polyethylene resin = 30%:70%.

[0039] [Test specimen] Concrete molded bodies were formed, and immediately after removal from the formwork, curing sheets for each example and comparative example were attached to the surface of the concrete molded bodies. After curing for a predetermined period, the bodies were evaluated using the method described below.

[0040] [Water vapor transmission rate] Measurements were taken in accordance with JIS-K7126, under conditions of 40°C and 90% relative humidity.

[0041] [Swelling] The swelling on the sheet surface was visually observed one month after curing and evaluated according to the following criteria. Excellent: No swelling is observed across the entire surface of the seat. Good: Some small bulges are visible across the entire surface of the seat. Unacceptable: The entire surface of the sheet has many or large bulges.

[0042] [Accelerated Neutralization Test] In accordance with JIS A1153, the carbonation depth was measured after 1 month and 6 months of curing and evaluated according to the following criteria. Excellent: Accelerated neutralization depth is less than 30 mm. Good: Accelerated neutralization depth is 30mm or more but less than 50mm. Not permitted: Accelerated neutralization depth of 50 mm or more

[0043] [Compressive strength] In accordance with JIS A1108, the compressive strength was measured one month after curing and evaluated according to the following criteria. Excellent: Compressive strength of 35 N / mm² 2 That's all. Good: Compressive strength of 20 N / mm² 2 More than 35N / mm 2 less than Not suitable: Compressive strength of 20 N / mm² 2 less than

[0044] Table 1 below shows the evaluation results. [Table 1]

[0045] From the performance evaluation described above, it was found that by setting the ratio of polypropylene resin to polyethylene resin in the base layer of the concrete curing sheet of the present invention to 95-50%:5-50%, blistering is reduced, and concrete with sufficient strength can be formed by preventing carbon dioxide penetration while maintaining a moist state. On the other hand, when polyethylene resin was not blended (Comparative Example 1), the generated gas was not released because a sea-island structure was not formed, and numerous blisters occurred between the concrete and the curing sheet. Furthermore, when polyethylene resin was blended at 50% or more (Comparative Example 2), although blistering was reduced, the water vapor and carbon dioxide barrier properties of the curing sheet itself decreased, resulting in a decrease in carbonation and compressive strength. [Industrial applicability]

[0046] The concrete curing sheet of the present invention can improve the quality of concrete by being applied to the concrete surface after the formwork has been removed, and the work is easy. Furthermore, by suppressing deterioration caused by carbon dioxide, repair work can be reduced. [Explanation of Symbols]

[0047] 1. Concrete curing sheet 2...Base material layer 3... Adhesive layer

Claims

1. An adhesive sheet for covering the surface of concrete during the curing of concrete, wherein the sheet has a base layer and an adhesive layer formed on one side of the base layer, the base layer is a polyolefin resin film made of a mixture of polypropylene resin and polyethylene resin, and the ratio of the polypropylene resin to polyethylene resin is 95-50%:5-50%.

2. The water vapor permeability of the adhesive sheet is 1 to 50 g / m². ２ • It is a day, and the carbon dioxide transmission rate is 30,000 ml / m². ２ The concrete curing sheet according to claim 1, characterized in that it is less than or equal to 2 days.

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