JP7611100B2 - Construction method for concrete components - Google Patents

Description

The present invention relates to a method for constructing a concrete member.

It is known that curing concrete underwater is suitable for increasing the strength, density, crack resistance, and durability of concrete. Therefore, when curing concrete, curing methods are adopted that aim to prevent drying and create an environment similar to underwater curing.
The applicants have developed and put into practical use a concrete curing formwork that includes a formwork body, a water retention section that covers the inner surface of the formwork body, and a surface section that covers the inner surface of the water retention section and faces the concrete poured into the formwork, as shown in Patent Document 1. This curing formwork makes it possible to drain excess water in the early stages of pouring, and to create an environment similar to underwater curing by storing water in the water retention section after it has set.
When constructing a relatively large concrete component, it is necessary to pour the concrete in multiple layers. When pouring concrete in multiple layers, discoloration may occur along the overlapping surfaces, resulting in uneven coloring on the surface of the concrete component. Uneven coloring on the surface will spoil the aesthetic appearance.

Patent No. 5565921

From this perspective, an object of the present invention is to propose a method for constructing concrete members that makes it possible to suppress color unevenness that occurs on the surface of the concrete member.

In order to solve the above problems, the method of constructing concrete members of the present invention includes a formwork installation step of installing a concrete curing formwork, a pouring step of pouring concrete into the concrete curing formwork, and a curing step of curing the concrete in the concrete curing formwork, and calcium hydroxide is adhered to the surface of the concrete curing formwork prior to the pouring step.
The inventors have found that the amount of calcium hydroxide and calcium carbonate present on the surface of the concrete is related to color unevenness. According to the concrete curing formwork of the present invention, the amount of calcium hydroxide and calcium carbonate is adjusted by supplying calcium hydroxide previously attached to the surface of the concrete to the surface of the concrete, thereby suppressing color unevenness on the surface of the concrete member. In other words, the use of the concrete curing formwork of the present invention can improve the aesthetic appearance of the concrete member.

The calcium hydroxide is preferably attached to the surface by spraying 0.30 g to 0.35 g of saturated calcium hydroxide ^per 1 cm2 onto the surface.
In addition, if, during the pouring process, the concrete is compacted with a rod-shaped vibrator inserted into it and also compacted from the outer surface of the sheathing with a formwork vibrator, the effect of suppressing uneven coloring on the surface of the concrete member can be further improved.
Furthermore, if the sheathing of the concrete curing formwork is equipped with a water retention section capable of storing moisture and a reinforcing section provided on the outer surface of the water retention section, by supplying moisture to the water retention section during the curing process, the moisture that has permeated from the water retention section to the surface section is supplied to the surface of the concrete, creating an environment similar to underwater curing, thereby improving the strength, density, crack resistance and durability of the concrete.

According to the method for constructing a concrete member of the present invention, it is possible to suppress uneven coloring on the surface of the concrete member and improve the aesthetic appearance.

3 is a flowchart showing a construction method for a concrete member according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of a concrete curing formwork. FIG. 2 is an enlarged cross-sectional view of a concrete curing formwork. FIG. FIG. 1A is a cross-sectional view showing the state after concrete has been poured, and FIG. 1B is a cross-sectional view showing the curing process. 1A and 1B are schematic plan views showing the compaction conditions during the experiment, where (a) is an embodiment, and (b) and (c) are comparative examples. 1 is a graph showing the amount of calcium carbonate and the amount of calcium hydroxide on the surface of a concrete member.

In this embodiment, a method for constructing a concrete member will be described for suppressing color unevenness that occurs on the surface of the concrete member along the concrete pouring surface J when the concrete member is manufactured by pouring concrete in multiple steps (layers). Figure 1 shows a flowchart of the method for constructing a concrete member of this embodiment. As shown in Figure 1, the method for constructing a concrete member includes a formwork installation process S1, a pouring process S2, a curing process S3, and a demolding process S4.
The formwork installation step S1 is a step of installing a concrete curing formwork 1. Fig. 2 shows the concrete curing formwork 1. In the formwork installation step S1, the concrete curing formwork 1 is assembled by disposing a sheathing board 2 at a position where the concrete member is planned to be constructed, with a gap corresponding to the thickness of the concrete member. As shown in Fig. 2, the concrete curing formwork 1 includes the sheathing board 2, a surface portion 3 interposed between the sheathing board 2 and the poured concrete C1, C2, and a drainage hole 4.

3 is an enlarged view of the curing formwork. As shown in FIG 3, the sheathing 2 has a water retaining portion 5 capable of retaining water and a reinforcing portion 6 for reinforcing the water retaining portion 5.
The water retention section 5 is composed of a so-called twin-cone type resin hollow structure plate having a core material 50 formed by thermally fusing two thermoplastic resin sheets (hereinafter referred to as "projected sheets 51, 51") having a plurality of hollow protrusions 52, 52, ... with the hollow protrusions 52, 52 butted against each other, and face materials 53, 53 laminated on both sides of the core material 50. Fig. 4 is an exploded perspective view of the water retention section 5.
The hollow convex portions 52, 52, ... of the protrusion-equipped sheet 51, 51 of this embodiment are in the shape of a truncated cone and have the same dimensions, as shown in FIG. 4. The multiple hollow convex portions 52, 52, ... of the protrusion-equipped sheet 51 are regularly provided on one surface. The hollow convex portions 52 are open at the bottom side and have a hollow truncated cone shape. The outer peripheral surface of each hollow convex portion 52 is formed in the shape of a truncated cone with a tapered surface whose diameter gradually increases from the tip to the base, and each hollow convex portion 52 is formed in the same shape and size. The taper angle θ of each hollow convex portion 52 (the rising angle of the inner surface of each recess) is within the range of 45 to 80°, and preferably within the range of 50 to 70°. The diameter of the lower base 52a of the hollow convex portion 52 is preferably set within a range of 3 to 16 mm, and the diameter of the upper base 52b of the hollow convex portion 52 is preferably smaller than the lower base 52a and is preferably within a range of 1.5 to 4 mm. The height of the hollow convex portion 52 is preferably set within a range of 3 to 13 mm. The interval between the lower bases 52a of adjacent hollow convex portions 52, 52 is set to 10 mm or less. Since the multiple hollow convex portions 52, 52, ... are arranged at intervals, a continuous space 54 is formed inside the core material 50 as shown in FIG. 3. Thermoplastic resins that can be used for the protrusion sheet 51 are not particularly limited, but polypropylene-based resins such as homopolypropylene, random polypropylene, and block polypropylene are preferred from the viewpoints of productivity, cost, balance with physical properties, low temperature resistance, heat resistance, and other properties.

The facing materials 53, 53 laminated on both sides of the core material 50 are made of a plate material or sheet (thermoplastic resin sheet) made of a thermoplastic resin. The material of the facing material 53 is not limited, but from the viewpoints of compatibility with the core material 50 and capable of thermal fusion, and excellent balance of characteristics such as cost, physical properties, low temperature resistance, and heat resistance, etc., polypropylene-based resins such as homopolypropylene, random polypropylene, and block polypropylene are preferable. In addition, when high heat resistance and rigidity are required for the water retention portion 5, it is preferable to form the facing material 53 from a glass fiber reinforced thermoplastic resin sheet.
The core material 50 and the face materials 53, 53 may be bonded together, for example, by contacting and pressing the contact surfaces of at least either the core material 50 side or the face material 53 side in a melt-softened state.

The side end faces and bottom face of the water retention section 5 are sealed with a sealing material (not shown). In this embodiment, the sealing is performed by heat welding the sealing material, but the sealing method is not limited, and sealing may be performed with a filler, for example. The material constituting the sealing material is not limited, but in this embodiment, it is made of the same material as the face material 53. Since the sides and bottom faces of the water retention section 5 are sealed, there is no leakage even if water is passed through the internal space 54. Therefore, the water retention section 5 can create an environment similar to underwater curing when curing poured concrete.

As shown in Fig. 3, a plurality of through holes 55, 55, ... are formed in the protruding sheet 51 and the face material 53 on the concrete pouring surface side of the water retention section 5 (the lower side in Fig. 3). The through holes 55 penetrate the protruding sheet 51 and the face material 53, and some of the through holes 55 reach the space 54.
The through holes 55 preferably have a diameter of 1 mm or more so as not to be clogged with mortar, fine aggregate, etc. From the viewpoint of ensuring water permeability, the size of the through holes 55 is preferably larger than the diameter of the upper base of the hollow convex portion 52, and from the viewpoint of maintaining the strength of the water retention portion 5, the size of the through holes 55 is preferably smaller than the diameter of the lower base of the hollow convex portion 52. The arrangement of the through holes 55 is not limited, but in this embodiment, the interval between the through holes 55 (the distance between adjacent through holes 55, 55) is set to 10 mm or more.
In addition, the method of forming the through hole 55 is not limited, but in this embodiment, the through hole 55 is formed by pressing a plate material having a number of needle-shaped members implanted therein against one side of the water retention section 5 and inserting the needle-shaped members.

The reinforcing section 6 is attached to the surface of the water retention section 5 opposite the surface on which the concrete is poured (the upper surface in FIG. 3). The reinforcing section 6 has a strength and rigidity that can ensure that the sheathing 2 does not deform (bend, etc.) against the pressure (lateral pressure) of poured concrete. In this embodiment, the reinforcing section 6 is formed by combining pieces of wood in a lattice pattern.

The surface portion 3 is a sheet material having water permeability. The surface portion 3 is made of a material capable of allowing the passage of water and preventing the passage of cement particles. As shown in FIG. 3, the surface portion 3 of this embodiment has a two-layer structure consisting of a first layer 31 on the poured concrete side (lower side in FIG. 3) made of woven fabric and a second layer 32 on the water retention side made of nonwoven fabric. The materials constituting the first layer 31 and the second layer 32 are not limited, and may be made of, for example, natural organic fibers or synthetic fibers, or woven or nonwoven fabrics containing water-absorbent polymers. The surface portion 3 may be placed on the surface of the water retention portion 5 during the assembly of the formwork, or may be fixed to the water retention portion 5 before the assembly of the formwork.
Once the concrete curing formwork 1 is assembled, saturated calcium hydroxide is sprayed onto the surface portion 3 to adhere the calcium hydroxide to the entire surface (the surface that contacts the concrete) of the surface portion 3. For the calcium hydroxide to be sprayed onto the surface portion, 0.30g to 0.35g of saturated calcium hydroxide solution is used per ^1cm2 . In other words, an amount of saturated calcium hydroxide solution equal to 0.30g to 0.35g multiplied by the surface area of the surface portion 3 is sprayed toward the surface portion 3 so as to ensure that no unevenness occurs.

As shown in FIG. 1, the drainage holes 4 are formed in the sheathing 2 so as to communicate with the space 54. The drainage holes 4 are formed by passing a pipe through the outer surface material 53 (opposite the surface portion 3) and the reinforcing portion 6. The arrangement and number of the drainage holes 4 are not limited. The drainage holes 4 are provided with valves (not shown), and the drainage holes 4 can be closed by operating the valves.

The casting process S2 is a process of casting concrete into the concrete curing formwork 1. First, concretes C1 and C2 are poured into the concrete curing formwork 1 (see FIG. 2). The concretes C1 and C2 are poured after the saturated calcium hydroxide sprayed on the surface has dried. As shown in FIG. 2, the concretes C1 and C2 are poured in a plurality of layers. The following concrete C2 is poured after the preceding concrete C1 poured earlier is compacted and then poured onto the top surface of the preceding concrete C1. After the concretes C1 and C2 are poured into the concrete curing formwork 1, the concretes C1 and C2 are compacted. FIG. 5 shows the compaction state of the concretes C1 and C2. In this embodiment, the concretes C1 and C2 are compacted by a rod-shaped vibrator B1 inserted into the concretes C1 and C2, and are compacted from the outer surface of the sheathing board 2 by a formwork vibrator B2.
After pouring the concretes C1 and C2, the rod-shaped vibrator B1 is inserted into the center (near the middle between the opposing sheathing boards 2) of the concrete curing formwork 1 and compacts it for, for example, 10 seconds. After pouring the concretes C1 and C2, the formwork vibrator B2 is placed against each surface (the outer surface of the sheathing board 2) near the overlapping surface J (see FIG. 2) of the concretes C1 and C2 and compacts it for, for example, 20 seconds.
As shown in Fig. 6(a), excess water Ws, including bleeding water, generated after pouring of concretes C1 and C2 permeates into the surface portion 3. Fig. 6(a) is a cross-sectional view showing the state after concrete has been poured. The excess water Ws that has permeated into the surface portion 3 passes through the through-holes 55 and flows out into the space 24 of the water retention portion 5. The excess water Ws that has accumulated in the space 24 may be used as moisture _W0 (see Fig. 6(b)) to be supplied to the surface of the poured concrete in the curing process S3, or may be drained from the drainage holes 4.

The curing step S3 is a step of curing the concretes C1 and C2 in the concrete curing formwork 1. Fig. 6(b) shows the curing step S3.
In the curing step S3, as shown in Fig. 6(b), water _W0 is supplied to the space in the water retention section 5, and the cast concrete is cured in an environment similar to underwater curing. The water _W0 is supplied to the space by pouring water W from above the water retention section 5 with the drainage holes 4 closed.
The moisture _W0 supplied to the water retention portion 5 permeates into the surface portion 3 through the through holes 55. The moisture _W0 that has permeated into the surface portion 3 permeates into the entire surface portion 3 due to capillary action, and as a result, is evenly supplied to the entire surface of the poured concrete.

The demolding process S4 is a process for demolding the concrete curing formwork 1, and is performed after the poured concrete has developed a predetermined strength. In the demolding process, first, the water _W0 stored in the space 54 is drained from the drainage holes 4, and then the concrete curing formwork 1 is removed from the surface of the hardened poured concrete.

According to the method for constructing a concrete member of this embodiment, it is possible to suppress uneven coloring on the concrete surface caused by the difference in the amount of calcium hydroxide and calcium carbonate present on the surface of the concrete. That is, by supplying calcium hydroxide that has been previously attached to the surface of the concrete curing formwork 1 to the surface of the concrete, the balance between the amounts of calcium hydroxide and calcium carbonate is adjusted, so that uneven coloring on the surface of the concrete member is suppressed and the aesthetic appearance of the concrete member can be improved.
In addition, during the pouring process, a rod-shaped vibrator B1 is used to vibrate the center of the concrete, and a formwork vibrator B2 is used to vibrate the outer surface of the concrete board to compact it, thereby equalizing the uneven amounts of calcium hydroxide and calcium carbonate present on the surface of the concrete, thereby further improving the effect of suppressing uneven color on the surface of the concrete member.
Furthermore, since the sheathing 2 of the concrete curing formwork 1 has a water retention section 5 capable of storing water and a reinforcing section 6 provided on the outer surface of the water retention section 5, by supplying water to the water retention section 5 during the curing process, the water that has permeated from the water retention section 5 to the surface section 3 is supplied to the surface of the concrete, creating an environment similar to that of underwater curing. As a result, the strength, density, crack resistance, and durability of the concrete are improved.

Next, the results of an experiment conducted to confirm the effect of suppressing color unevenness occurring on the surface of a concrete member in the construction method for a concrete member of this embodiment will be described.
In this experiment, saturated calcium hydroxide was sprayed onto the surface 3 of the concrete curing formwork 1, and then concrete was poured into the concrete curing formwork 1. As shown in Fig. 7(a), a rod-shaped vibrator B1 was inserted into the center to compact the concrete, and the surface of the concrete member was checked when the concrete was compacted from the sides (four sides) with a formwork vibrator B2. In this experiment, the concrete curing formworks 1 were combined in a square shape in a plan view to form a formwork 10.
In parallel with this experiment, experiments were also conducted on comparative example a, in which a rod-shaped vibrator B1 was inserted in the center of the formwork 10 and compacted (without formwork vibrator B2), as shown in Figure 7(b), and on comparative example b, in which a rod-shaped vibrator B1 was inserted in the center and sides (near the four side surfaces) of the formwork 10 and compacted (without formwork vibrator B2), as shown in Figure 7(c).
Furthermore, for Comparative Examples c to e, the surface of the concrete member was also checked when water was sprayed onto the surface of the concrete curing formwork 1. In Comparative Example c, a rod-shaped vibrator was inserted into the center of the formwork to compact it, and the side surfaces were compacted using a formwork vibrator. In Comparative Example d, a rod-shaped vibrator was inserted into the center of the formwork to compact it (no formwork vibrator). And in Comparative Example e, rod-shaped vibrators were inserted into the center and side portions of the formwork to compact it (no formwork vibrator).
Table 1 shows the calcium hydroxide used in the experiment, and Table 2 shows the experimental results.

As shown in Table 2, in Comparative Examples c to e in which water was sprayed on the surface, color unevenness was noticeable regardless of the difference in compaction method. On the other hand, it was confirmed that the Example (the concrete curing formwork 1 and the construction method of the concrete member of this embodiment) reduced color unevenness on the surface of the concrete member. This is thought to be because the calcium hydroxide attached to the surface portion 3 was supplied to the surface of the concrete, improving the balance between the amounts of calcium hydroxide and calcium carbonate on the surface of the concrete.
In addition, in Comparative Examples a and b, where the concrete was compacted only within the formwork using a rod-shaped vibrator, color unevenness was noticeable. On the other hand, in the Example, where the concrete was compacted in the center using a rod-shaped vibrator and compacted from the outside of the sheathing using a formwork vibrator, color unevenness was reduced. Therefore, it was confirmed that color unevenness can be improved by compacting in the center and compacting from the outside of the sheathing using a formwork vibrator.

FIG. 8 shows the results of measuring the amount of calcium carbonate (CaCO3) and calcium hydroxide (Ca(OH)2) using a differential thermogravimetric analyzer. The amount of calcium carbonate and calcium hydroxide was measured in the uneven color parts (discolored parts) where uneven color occurred on the surface of the concrete member, and in the normal parts where no uneven color occurred except for the poured surface. Measurements were also performed on the surface of the concrete member (after countermeasures) where countermeasures were taken using the construction method for a concrete member of this embodiment. The same concrete member was used for the measurement of the uneven color parts and the normal parts. The measurement of the "after countermeasures" was performed using a concrete member created by the construction method for a concrete member of this embodiment using concrete of the same composition as the concrete member used for the measurement of the uneven color parts and the normal parts.
As shown in Fig. 8, the uneven color area had a large amount of calcium carbonate and a large difference between the amount of calcium carbonate and the amount of calcium hydroxide. On the other hand, the normal area (area without uneven color) had a small amount of calcium carbonate and a small difference between the amount of calcium carbonate and the amount of calcium hydroxide compared to the uneven color area. After the countermeasure, the amount of calcium carbonate was significantly reduced, and the difference between the amount of calcium carbonate and the amount of calcium hydroxide was small, as in the normal area. Therefore, it was confirmed that the concrete curing formwork of this embodiment and the construction method of a concrete member using the formwork improved the balance between the amount of calcium hydroxide and calcium carbonate on the surface of the concrete.

Although an embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and each of the above-described components can be appropriately modified without departing from the spirit of the present invention.
In the above embodiment, the hollow convex portion 52 is formed in a truncated cone shape, but the shape of the hollow convex portion 52 is not limited to this and may be, for example, a truncated pyramid shape. Furthermore, the size and arrangement of the hollow convex portion 52 are not limited.
The material constituting the reinforcing portion 6 is not limited to wood as long as it has the necessary strength, and may be, for example, a resin material, a steel material, etc. Furthermore, the reinforcing portion 6 does not necessarily have to be lattice-shaped, and may be, for example, a plate material, or a ladder-shaped member in which vertical or horizontal members are provided in the inner space of a frame material.
The sheathing 2 may be composed of only the reinforcing part 6, in addition to being composed of the water retention part 2 and the reinforcing part 6. In that case, the surface part 3 is disposed on the surface (the side on which concrete is poured) of the reinforcing part 6. When the water retention part 2 is not provided, the step of pouring water W from above the water retention part 2 in the curing step S3 is omitted.
The surface portion 3 may be a sheet having a two-layer structure consisting of a nonwoven fabric layer and a woven fabric layer, or a sheet having a single-layer structure consisting of a nonwoven fabric layer or a woven fabric layer.
The method of forming the drainage holes 4 is not limited, and for example, they may be through holes formed in the reinforcing portion 6 and the face material 53 .
In the above embodiment, calcium hydroxide is adhered to the surface portion 3 by spraying calcium hydroxide onto the surface portion 3, but the method of adhering calcium hydroxide is not limited thereto, and for example, calcium hydroxide may be applied to the surface portion 3, or a solution of calcium hydroxide may be impregnated into the sheet constituting the surface portion 3.

Reference Signs List 1 Concrete curing formwork 2 Sheathing 3 Surface portion 31 First layer 32 Second layer 4 Drain hole 5 Water retention portion 6 Reinforcement portion

Claims (4)

A formwork installation process for installing a concrete curing formwork;
A pouring step of pouring concrete into the concrete curing formwork;
A method for constructing a concrete member comprising: a curing step of curing the concrete in the concrete curing formwork,
The concrete curing formwork includes a sheathing and a surface portion made of a water-permeable sheet material interposed between the sheathing and the concrete;
A method for constructing a concrete member, comprising the steps of: adhering calcium hydroxide to the surface portion prior to the pouring step. The method for constructing a concrete member according to claim 1 , characterized in that the calcium hydroxide is adhered to the surface portion by spraying 0.30 g to 0.35 g of saturated calcium hydroxide solution per ¹ cm2 onto the surface portion. 3. The method for constructing a concrete member according to claim 1 , wherein in the casting step, the concrete is compacted by a rod-shaped vibrator inserted into the concrete, and the concrete is compacted from the outer surface of the sheathing by a formwork vibrator. The sheathing includes a water retaining portion capable of retaining moisture and a reinforcing portion provided on an outer surface of the water retaining portion,
4. A method for constructing a concrete member according to claim 1 , wherein in the curing process, moisture is supplied to the water retention portion, and the moisture that has permeated from the water retention portion to the surface portion is supplied to the surface of the concrete.

Images