JPH0535043B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to a plywood formwork used for concrete or mortar casting in house construction, civil engineering work, etc. <Prior art> Conventional formwork is known to use plywood as is, but the concrete and mortar poured into the formwork adheres to the plywood surface of the formwork, making it difficult to remove the formwork. Because of this drawback, tar or paraffin/silicone-based release agents are applied to the plywood surface at construction sites to improve releasability. In addition, in recent years, in order to prevent this concrete/mortar from adhering to the plywood surface, painted formwork has been manufactured by applying synthetic resin such as acrylic resin or urethane resin at the factory to form a coating layer on the plywood surface. provided. <Problems to be solved by the invention> It is known from experience that when plywood is used as a formwork for pouring concrete, dark-colored poorly cured areas are formed at the concrete interface after the mold is released. . Such concrete materials are unfavorable in appearance, and when a wall is constructed by pouring concrete, they not only reduce the design of the wall but also significantly reduce its strength due to poor curing. In some cases, this poorly cured area affects not only the surface layer but also several millimeters deep, and if you touch that area with your hands or objects, it will turn into particles and fall off. exhibit a phenomenon. In addition, in the case of joint painting construction on a concrete surface, the joint mortar applied to the surface
After application, spray coating materials, finishing coating materials, tiling, etc., have the disadvantage of peeling off from poorly cured areas, lifting up, and sometimes peeling off. The formation of these poorly hardened areas is thought to be due to harmful substances contained in the formwork plywood leaching out of the wood and inhibiting the hydration reaction of cement, but the detailed mechanism is still not fully understood. Not yet. In conventional painted forms, a synthetic resin coating layer is formed on the surface, so the elution of harmful substances from the wood is suppressed to some extent in the early stages of use, but the elution of harmful substances through pinholes in the coating layer is suppressed to some extent. This is unavoidable, and elution is likely to occur due to cracks in the coating layer due to deterioration of the coating layer, damage to the coating layer due to external forces, etc. Therefore, it could not be a means to fundamentally solve the problem of contamination of the concrete surface and inhibition of hardening due to the elution of harmful substances from the wood. <Means for Solving the Problems> The present invention has been developed based on various studies on the phenomenon in which components eluted from plywood formwork inhibit the hydration reaction of cement and cause poor hardening. Extracted components such as cellulose, lignin, tannin, humic acid, and sugars are dissolved at the interface with the cement by the water in the cement slurry, and these extracted components release Ca ²⁺ , K ⁺ ,
It was found that this salt combines with Na ⁺ to form a salt, which covers the cement particles, thereby inhibiting the subsequent hydration reaction of the cement. In other words, the normally hardened mortar has
K ₂ SO ₄ , Na ₂ SO ₄ , and Ca(OH) ₂ are present in large amounts, but in the case of poorly hardened mortar, the amount of these mixed together decreases, and in the case of severely poorly hardened mortar, these are almost all present. It did not exist, and ettringite was found in abundance instead. This dissolves into the liquid phase during cement hydration and forms K ₂ SO ₄ , NaSO ₄ ,
Na ⁺ , K ⁺ , and Ca ²⁺ , which should be crystallized as Ca(OH) ₂ , are adsorbed or chemically combined with the above extract components eluted from the wood to form complex salts, so they cannot be crystallized. It is presumed that the excess SO ₄ ^2- at that time crystallized into ettringite. The present invention has been developed based on the above findings after further study, and the present invention is based on the above knowledge, and the present invention has been developed by adding iron, copper, bad lead, sulfides, chlorides, or hydroxides of iron, copper, bad lead, lead or aluminum to the veneer on at least one side of the plywood. To provide a formwork formed by arranging plywood coated or impregnated with powder or aqueous solution of one or more selected substances such that the treated veneer faces the inner surface of the formwork. It is something. That is, in view of the fact that in the prior art, attempts were made to prevent the elution of harmful components from the wood by forming a coating layer on the surface of the form plywood, but the results were insufficient, formation of a coating layer, etc. We have moved away from the technical idea of physically preventing the elution of wood extract components by using chemical means to prevent the wood extract components from combining with free ions from cement to form complex salts. I have considered this point of view repeatedly. By pre-bonding wood extract components with metal ions that generate complex salts that are more stable than these free ions, the wood extract components will more stably chelate with the metal ions, resulting in free ions. The present invention was achieved based on the discovery that it is possible to prevent the bonding. The configuration of the present invention will be explained below. In the present invention, at least the inner surface of the plywood constituting the form is coated and impregnated with a metal compound powder or aqueous solution using a coating device. There are no particular restrictions on the means for applying or impregnating it, but in the case of a metal compound, it is desirable to use a coating device to spray it on the surface of the plywood, and then rub it into the conduit grooves of the surface veneer with a blade or the like. Alternatively, the powder may be dispersed in latex or the like and applied. For metal compound aqueous solutions, use a roll coater,
Coating can be performed using a known coating device such as a sprayer or a flow coater. The metal compound aqueous solution applied in this way partially penetrates into the veneer on the surface of the plywood to form an impregnated layer, so that the sufficient effect of the present invention can be obtained over a certain thickness. Further, by applying the aqueous solution while the temperature of the plywood obtained by hot pressing is still high, penetration into the veneer becomes even better. The application or impregnation of the metal compound is not limited to the surface of the plywood, but may be applied to both the front and back surfaces and/or to the wood end. The metal compound used in the present invention is one that forms a highly stable complex by combining with extracted components such as cellulose, lignin, tannin, and sugars in the wood of plywood. When using plywood formwork, the present invention prevents the wood extract components from combining with free ions from the cement to form complex salts in the presence of water, and instead replaces them with more stable metal ions. Therefore, the metal compounds used elute metal ions that are soluble in water and have higher stability than free cement ions, and combine with the wood extract components. It must be capable of producing poorly soluble complex salts.
That is, the metal ions dissolved in the water in the wood and/or the water in the cement slurry combine with wood extract components to form chemically stable complex salts. Specifically, the metal compounds used to achieve this effect include one or more selected from iron, copper, zinc, lead or aluminum sulfides, chlorides or hydroxides, etc. They can be used alone, in combination, or in a mixture. <Function> The surface of the plywood is coated or impregnated with a powder or aqueous solution of one or more substances selected from iron, copper, bad lead, sulfates, chlorides, and hydroxides of lead or aluminum. When this is used as a formwork material for concrete pouring and the treated surface is placed on the inner surface of the formwork, extracted wood components such as cellulose, tannins, lignin, and sugars will be removed from the plywood surface. It combines with ions eluted from metal compounds to form stable complex salts. Therefore, the formation of complex salts due to the combination of these wood extracted components and free ions from cement is suppressed, and the formation of poorly hardened portions at the concrete or mortar interface after mold release is prevented. <Test Example> The influence of various metal compounds on the inhibition of cement hardening by wood extract components was tested. A mixture of cement and standard sand at a ratio of 1:2 was mixed with various solutions at a water/cement ratio of 0.65 to prepare various green mortars, and these were placed in iron molds (1 x 1 x 4 cm). and temperature 20
After curing for one day in a constant temperature bath at 80% humidity and 20°C, various mortar specimens were obtained. The mixed solution is 10×10×1
Various copper compounds, zinc compounds, lead compounds, aluminum compounds, and iron compounds were added to the wood extract obtained by soaking 18 cm2 plywood in a saturated Ca(OH) ₂ solution for 48 hours at 0.1% and 0.3%, respectively. They were added at a ratio of 0.5% and 1.0%. For comparison, mortar specimens prepared by blending solutions to which these metal compounds were not added were also prepared. Table 1 summarizes the results of measuring the compressive strength of these mortar specimens after curing and hardening for a predetermined period of time.

[Table] Regarding the compressive strength in Table 1, × marks indicate no increase in strength compared to mortar prepared using a solution containing no metal compounds, and ○ marks indicate a slight increase in strength. The ◎ marks indicate those in which the strength increased significantly. Moreover, the numerical value shown in the box under the mark ◎ is the amount of metal compound added when the strength development reaches the maximum. From the results shown in Table 1, although the effect is not necessarily constant depending on the type of metal compound or the amount added, it is generally found that mixing these metal compounds can inhibit the cement hardening effect of wood extract components. It is known that it can be suppressed. In particular, copper chloride and copper sulfide are prominent in copper compounds, zinc sulfate in zinc compounds, lead chloride and lead sulfate in lead compounds, aluminum chloride and aluminum sulfate, and iron chloride in aluminum compounds. It was found to have an inhibitory effect. Furthermore, when we investigated the fine structure of the mortar specimens in which these remarkable inhibitory effects were obtained using a scanning electron microscope, we found that in both cases, gel-like particles were adsorbed and chemical bonding was observed. Polymerized fibrous, granular, or lumpy products were confirmed. This is because metal ions such as Fe, Cu, Zn, Pb, and Al, which have greater stability than the ions Ca ²⁺ , K ⁺ , Na ⁺ , etc. released from cement into the liquid phase, elute from the added metal compounds. It was determined that these metal ions were complex salts produced by combining with wood extract components. <Example> Copper sulfate, zinc chloride, aluminum chloride, alum, and ferric chloride were used as metal compounds on the surface of a plywood board made of 3 x 6 x 12 mm thick merape material, and a 10% aqueous solution and a 20% aqueous solution of each of these were used. Prepared as an aqueous solution, use a roll coater to coat 40g/
m ² and a coating weight of 100 g/m ² . Then,
These plywoods were dried to prepare various treated plywoods. For comparison, we also prepared untreated plywood that was not coated with an aqueous solution of these metal compounds. These treated plywood and untreated plywood were used as concrete molds, and the molds were removed three days after concrete pouring, and the conditions of the concrete surfaces were comparatively observed to examine the effects of applying the metal compound aqueous solution. The results are shown in Table 2 below.

[Table] As is clear from the results shown in Table 2, concrete that is hardened and cured in untreated plywood formwork that is not coated with a metal compound is inhibited from hardening to a depth of 2 to 4 mm from the surface. was detected and the entire surface exhibited a deep dark brown color, whereas in the case of the material coated with the aqueous solution of the metal compound according to the present invention, there was almost no curing inhibition and the surface color was generally uncontaminated. Ta. <Effects of the Invention> According to the present invention as described above, extracted components such as cellulose, lignin, tannin, and sugars in the plywood material combine with the metal compound coated or impregnated on the surface of the plywood material to form a highly stable insoluble material. Since the complex is formed, the elution of the extracted components can be sufficiently suppressed. The present invention is a formwork formed by framing such plywood with the treated veneer surface facing the inner surface of the formwork, so when pouring concrete or mortar, the wood will not be damaged by water penetration in the cement slurry. Since the extracted components are not eluted, curing inhibition caused by the extracted components can be effectively suppressed and the design is not impaired. Therefore, the present invention can be effectively utilized particularly in the case of interior wall construction and repainting construction.

Claims (1)

[Claims] 1 Multiple sheets of plywood coated or impregnated on at least one surface with powder or aqueous solution of one or more substances selected from sulfates, chlorides, or hydroxides of iron, copper, zinc, lead or aluminum. 1. A formwork characterized in that the surface coated or impregnated with the powder or aqueous solution is placed on the inner surface of the formwork.