JP2019162815A - Method of producing concrete structure - Google Patents

Abstract

To provide a method of producing a concrete structure capable of achieving higher compactness by modifying the nature of a concrete surface layer part.SOLUTION: A method of producing a concrete structure of this invention comprises: a sheet disposing step of disposing a first sheet 11 holding water-soluble amorphous silica on an inner surface 22 of an end plate 21 for a concrete framework; a concrete placing step of placing concrete to a framework 2 formed of the end plate 21 in which the first sheet 11 is disposed; and a framework removing step of removing the framework 2 in a state in which the first sheet 11 is left on a surface of a concrete structure 3 after the placing.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a method for manufacturing a concrete structure in which the quality of a surface layer portion is improved.

  In recent years, deterioration of concrete structures due to salt damage and neutralization has become a serious social problem.

  In order to suppress such deterioration of the concrete structure, it is known that it is effective to make the surface layer portion of the concrete structure dense and prevent the penetration of factors that induce deterioration.

  For this reason, conventionally, various concrete curing techniques for making the surface layer portion of a concrete structure dense have been proposed.

  For example, in the manufacturing process of concrete structures, by adhering a non-permeable base material to the surface of the concrete, the moisture in the concrete is prevented from being dissipated during the curing period, and the moisture in the concrete is used to hydrate the cement. A method for advancing the reaction has been proposed (see, for example, Patent Document 1).

Patent No. 5912203

  However, the above-described technique promotes a hydration reaction of cement for growing concrete and does not have an effect of improving the quality of the surface layer portion of the concrete structure.

  Then, an object of this invention is to provide the manufacturing method of the concrete structure which can modify | reform the property of a concrete surface layer part and can acquire high compactness by this.

  In the method for producing a concrete structure according to the present invention, a sheet disposing step of disposing a first sheet holding water-soluble amorphous silica on an inner surface of a slat for a concrete formwork, and the first sheet are disposed. A concrete placing step for placing concrete on the mold formed by the slats, and demolding the mold in a state in which the first sheet is left on the surface of the concrete structure after the placing. And a mold demolding step. Moreover, the manufacturing method of the concrete structure of this invention may have further the sheet | seat peeling process which peels a said 1st sheet | seat from the surface of the said concrete structure.

In this case, the first sheet preferably has water permeability, and preferably contains 20 g / m ² or more of the amorphous silica.

  Moreover, even if the said sheet | seat arrangement | positioning process arrange | positions the 2nd sheet | seat for assisting or supplementing curing, such as moisture retention and heat retention, between the inner surface of the said board and the said 1st sheet | seat. Good.

  In the manufacturing process of a concrete structure, the sheet holding water-soluble amorphous silica is brought into contact with the concrete structure, and the sheet is left on the concrete structure even after demolding. is there. For this reason, calcium silicate hydrate is generated in the surface layer of the concrete structure by the pozzolanic reaction between amorphous silica and calcium hydroxide generated by the hydration reaction of the cement, thereby providing a concrete structure with high compactness. It has the effect of being able to acquire things.

In the manufacturing method of the concrete structure of this invention, it is sectional drawing which shows the state by which the 1st sheet | seat was arrange | positioned at the dam. In the manufacturing method of the concrete structure of this invention, it is sectional drawing which shows the state by which the 1st sheet | seat and the 2nd sheet | seat were arrange | positioned at a dam. In the manufacturing method of the concrete structure of this invention, it is sectional drawing which shows the state which poured concrete into the formwork formed with the stone plate in which the 1st sheet | seat is arrange | positioned. In the manufacturing method of the concrete structure of this invention, it is sectional drawing which shows the concrete structure of the state which removed the formwork. It is sectional drawing which shows the concrete structure of the state which peeled the sheet | seat in the manufacturing method of the concrete structure of this invention.

  Below, the manufacturing method of the concrete structure of this invention is demonstrated. In addition, the concrete structure manufactured according to the present invention is a so-called “on-site”, in addition to a structure manufactured on-site, so-called “precast”, before being transported to the operation site, etc. Includes structures to be manufactured (eg, gutters, tubes, manholes, piles, bridges, blocks, walls, parts of buildings, etc.).

  The method for producing a concrete structure according to the present invention includes a sheet disposing step of disposing a first sheet 11 holding water-soluble amorphous silica on an inner surface 22 of a slat plate 21 for a concrete mold, and a first sheet 11. A concrete placing process in which concrete is placed on the mold 2 formed of the siding plate 21 on which the metal is disposed, and the first sheet 11 is left on the surface of the concrete structure 3 after the placement. And a mold removing step for removing the mold 2.

[Sheet placement process]
As shown in FIG. 1, the sheet arrangement process is a process of arranging the first sheet 11 holding water-soluble amorphous silica on the inner surface 22 of the slat plate 21 for concrete formwork. Here, the inner surface 22 of the weir plate 21 refers to a surface on the side where concrete is placed among the surfaces constituting the weir plate 21. The material of the dam plate 21 is not particularly limited, and wood, plywood, steel material, light metal, resin, or the like can be used as appropriate.

  The arrangement of the first sheet 11 on the inner surface 22 of the dam plate 21 may be performed before the mold 2 is assembled, or may be performed after the mold 2 is assembled and predetermined installation is performed. The arrangement may be performed by any means as long as the first sheet 11 is fixed to the inner surface 22 of the dam 21. For example, a base having a predetermined adhesive force such as a double-sided tape may be used. What is necessary is just to stick the back surface of the 1st sheet | seat 11 on the inner surface 22 of the dam plate 21 using a material. In this case, it is preferable that the adhesive force between the dam plate 21 and the first sheet 11 is smaller than the adhesive force between the first sheet 11 and the concrete structure 3. The mold demolding step in the present invention is performed in a state in which the first sheet 11 is left on the surface of the concrete structure 3, so that the operation of the step is facilitated.

  In the sheet arranging step, as shown in FIG. 2, a second sheet 12 for curing such as moisture retention and heat retention is arranged between the inner surface 22 of the dam plate 21 and the first sheet 11. Also good. The arrangement of the second sheet 12 can be performed similarly to the case of the first sheet 11 described above. In this case, the first sheet 11 may be arranged on the inner surface 22 of the slat plate 21 via the second sheet 12 by being fixed to the second sheet 12, or directly on the inner surface 22 of the slat plate 21. It may be arranged by fixing.

  The first sheet 11 is capable of supplying water-soluble amorphous silica to the concrete structure 3 by contacting the surface of the concrete structure 3 after the concrete is placed by the concrete placing process. is there.

  Although it does not specifically limit as a raw material of the 1st sheet | seat 11, It is preferable that it has water permeability, For example, a nonwoven fabric, a mesh-shaped textile fabric, etc. can be used. As a result, moisture supplied from the outside of the concrete structure during curing can be sufficiently distributed to the surface of the concrete structure 3, and air bubbles and surplus water are discharged, thereby generating a flutter on the surface of the concrete structure. It is because it can suppress.

  In this case, the average pore diameter and porosity of the sheet may be determined in consideration of good water permeability and water content.

  The raw material used for the material of the first sheet 11 described above may be any material that has weather resistance suitable for curing, but has excellent heat resistance, water resistance, and chemical resistance. Is preferred. For example, thermoplastic resins such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyester, and polyamide can be used.

  Moreover, it is preferable that the first sheet 11 has a predetermined strength that can withstand the curing after the mold is removed or the peeling from the concrete structure 3.

  The water-soluble amorphous silica retained on the first sheet 11 may be any material as long as at least a part thereof is dissolved before the first sheet 11 is peeled from the concrete structure 3.

  The method for retaining the water-soluble amorphous silica on the first sheet 11 is not particularly limited. For example, an acrylic resin mixed with water-soluble amorphous silica is pressure-bonded to the first sheet 11 with a roller. After that, a method of heat treatment can be mentioned. Further, a method of impregnating the first sheet 11 with a solution containing water-soluble amorphous silica, a method of spraying water-soluble amorphous silica particles on the first sheet 11, and the like can be mentioned.

In this case, the retained amount of amorphous silica per unit area is preferably 20 g / m ² or more, preferably 25 g / m ² or more, because the surface layer portion of the concrete structure 3 is judged to be dense. More preferably, it is 28 g / m ² or more.

  The second sheet 12 is disposed between the inner surface 22 of the dam plate 21 and the first sheet 11 so as to assist or supplement curing such as moisture retention and heat retention.

  The second sheet 12 may be any sheet as long as it has a function of assisting or supplementing curing such as moisture retention and heat retention. For example, the second sheet 12 is as described above in the first sheet 11. For the same reason, it is preferable to have water permeability and water content and further to have heat retention.

  The material of the second sheet 12 may be determined in consideration of the above functions. For example, a nonwoven fabric or a mesh-like fabric can be used.

  In this case, the average pore diameter and porosity of the sheet may be determined in consideration of good water permeability and water content.

  As a raw material used for the material of the second sheet 12, as in the case of the first sheet 11 described above, for example, a thermoplastic resin such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyester, polyamide or the like is used. it can.

  Moreover, it is preferable that the second sheet 12 has a predetermined strength that can withstand the curing after the mold is removed and the peeling from the concrete structure 3.

[Concrete placing process]
The concrete placing step is a step of placing concrete on the mold 2 formed by the siding plate 21 on which the first sheet 11 is disposed. FIG. 3 is a sectional view showing an example of a state in which the concrete 3 is placed.

  Placing can be performed by any conventionally known method. For example, after “driving” in which concrete is poured into the mold 2, tamping with a stick or squeezing with a vibrator may be performed.

[Form removal process]
The mold demolding step is a step of demolding the mold 2 with the first sheet 11 remaining on the surface of the concrete structure 3 after placing. By leaving the first sheet 11 on the surface of the concrete structure 3, water-soluble amorphous silica can be supplied to the concrete structure 3 even after the mold 2 is removed, and the concrete structure 3 Can be cured. FIG. 4 is a cross-sectional view showing an example of the concrete structure 3 in a state where the mold is removed.

  The mold release is performed after hardening of the cast concrete 3 progresses and the concrete structure 3 develops a predetermined strength. In a state where the concrete structure 3 expresses a predetermined strength, the concrete structure 3 and the first sheet 11 are appropriately adhered as the concrete hardens. Therefore, if the concrete structure 3 has developed a predetermined strength, it is possible to easily remove the formwork 2 with the first sheet 11 left on the surface of the concrete structure 3. Even if the adhesive force between the inner surface 22 of the dam plate 21 and the first sheet 11 exceeds the adhesive force between the concrete structure 3 and the first sheet 11, the mold 2 can be removed as appropriate. Just do it.

  After the mold is removed, curing may be performed for a predetermined period in a state where the first sheet 11 is left on the surface of the concrete structure 3. Curing may be appropriately performed by any conventionally known method in addition to humidification curing by spraying or watering.

[Sheet peeling process]
The method for manufacturing a concrete structure of the present invention may include a sheet peeling step for peeling the first sheet 11 from the surface of the concrete structure 3 in addition to the above-described steps. FIG. 5 is a sectional view showing an example of the concrete structure 3 in a state where the first sheet 11 is peeled off.

  The sheet peeling is preferably performed after a predetermined curing period has elapsed after the mold is removed.

  Below, the test which investigated the influence which the manufacturing method of the concrete structure of this invention has on the surface layer part of a concrete structure is demonstrated by an Example.

[Production of sheet holding water-soluble amorphous silica]
Acrylic resin mixed with water-soluble amorphous silica (manufactured by Fuji Silysia Chemical Co., Ltd., product number: FHD-30) is pressure-bonded with a roller to a nonwoven fabric made of polyester resin, and then heat treated to produce water-soluble The sheet | seat which hold | maintained the characteristic amorphous silica was obtained. At this time, the maximum particle size of the water-soluble amorphous silica held on the sheet was 0.2 mm. The amount of water-soluble amorphous silica retained was 28 g / m ² or more.

[Manufacture of concrete structures]
The mold was placed so that the inner diameter was 15 cm × 15 cm × 12 cm, and the above-mentioned sheet holding the water-soluble amorphous silica was adhered to the inner surface of the dam plate with a double-sided tape.

  Next, concrete was placed in the mold. In addition, as concrete, the concrete of slump 15cm was used, the casting was divided into two layers, and tamping was performed 25 times per layer.

  The next day after the casting, the sheet holding the water-soluble amorphous silica was left in the concrete structure, and the mold was removed from the mold, and the surface holding the sheet was immersed for 6 days underwater curing. .

  In addition, as a comparative example, the special construction was not performed on the inner surface of the siding plate, and a material subjected to casting, mold removal and curing as described above was prepared.

[Surface water absorption test]
After water curing, a surface water absorption test was performed. The test was conducted by a technique called SWAT. In this method, a water absorption cup with a cylindrical cylinder is brought into close contact with the concrete surface, and the water absorption rate of the surface concrete is calculated by reading the water level change in the cylinder from time to time immediately after the water is filled in the water absorption cup. This is an evaluation method. When there are many voids in the concrete to be measured, the amount of water absorption increases and the drop in water level becomes large. Therefore, it is possible to evaluate the compactness of the surface concrete by analyzing the drop in the water level. In addition, the index of evaluation is determined using the water absorption rate (ml / m ² / s) of concrete 600 seconds after completion of water injection (10 minutes later), and the water absorption rate is 0.25 or less. "Good", those exceeding 0.25 to 0.5 or less are considered "general", and those exceeding 0.5 are considered "poor".

As a result of the measurement, the water absorption rate (ml / m ² / s) of the concrete 600 seconds after completion of the water injection (10 minutes later) was 0.30 on the surface of the concrete structure of the comparative example, whereas it was water soluble. It was 0.07 in the surface which performed the construction by the sheet | seat which hold | maintained the characteristic amorphous silica. From this, it is possible to modify the concrete surface layer to one that can be evaluated as “good” from the quality grade “general” by performing construction with a sheet holding water-soluble amorphous silica, It can be seen that the degree of modification is very remarkable.

[Surface permeability test]
Three days after the surface water absorption test, a surface air permeability test was performed. The test was conducted by a technique called the Trent method. This method is a method of evaluating the air permeability of one-dimensional surface concrete from the time until the concrete surface layer is evacuated by suction of the double chamber and then the suction by the vacuum pump is stopped and the pressure in the chamber is restored. is there. A smaller surface air permeability coefficient kT (× 10 ⁻¹⁶ m ² ) means that the surface layer is denser. The evaluation index is “excellent” when the surface air permeability coefficient kT (× 10 ⁻¹⁶ m ² ) is 0.001 to 0.01, “good” when 0.01 to 0.1, 0 .1 to 1 are “general”, 1 to 10 are “poor”, and 10 to 100 are “extremely poor”.

As a result of the measurement, the surface layer air permeability coefficient kT (× 10 ⁻¹⁶ m ² ) was 0.42 on the surface of the concrete structure of the comparative example, whereas the construction using a sheet holding water-soluble amorphous silica was performed. It was 0.0012 in the side which performed. From this, by performing construction with a sheet holding water-soluble amorphous silica, the surface layer of concrete can be modified to one that can be evaluated as “excellent” from the quality grade “general”, It can be seen that the degree of modification is very remarkable.

  From the above, it can be seen that the method for producing a concrete structure of the present invention can produce a concrete structure having a very high density by modifying the surface layer of the concrete structure.

2 Formwork 3 Concrete structure
11 First sheet
12 Second sheet
21 Cough board
22 Inside

Claims (5)

A sheet disposing step of disposing a first sheet holding water-soluble amorphous silica on the inner surface of a slat for a concrete mold;
A concrete placing step of placing concrete on a formwork formed of the piercing plate on which the first sheet is disposed;
A mold removal process for removing the mold in a state in which the first sheet is left on the surface of the concrete structure after the placing;
A method for producing a concrete structure, comprising:   A method for producing a concrete structure comprising a sheet peeling step of peeling the first sheet from the surface of the concrete structure.   The method for producing a concrete structure, wherein the first sheet has water permeability. The said 1st sheet | seat contains 20 g / m < ² > or more of said amorphous silica, The manufacturing method of the concrete structure in any one of the Claims 1 thru | or 3 characterized by the above-mentioned.   The said sheet | seat arrangement | positioning process arrange | positions a 2nd sheet | seat between the inner surface of the said board and a said 1st sheet | seat, The manufacturing of the concrete structure in any one of the Claims 1 thru | or 4 characterized by the above-mentioned. Method.

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