JPH0420068B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Object of the Invention [Field of Industrial Application] The present invention relates to a concrete curing method for a marine concrete structure constructed using movable formwork.

[Prior art] In general, marine concrete structures are adapted to sea conditions (waves, currents), so it is necessary to finish the concrete more precisely and increase its strength compared to ordinary land-based concrete structures. , rich mix concrete is used. especially,
When the marine concrete structure is constructed in a deep sea area (for example, an oil production platform), it is necessary to prevent cracks from forming on the surface of the concrete structure (i.e., seawater can enter into the cracks). ), and construction management becomes even more difficult.

Therefore, the conventional formwork construction method has the advantage of making it relatively easy to cure concrete with a rich mix by appropriately determining the timing of removing the formwork and the subsequent moistening period. On the other hand, it takes time and effort to install and remove formwork,
Furthermore, since the formwork is left unremoved for a relatively long period of time, it has the disadvantage of poor construction efficiency.

For this reason, the so-called movable formwork method (also called the slip form method) uses movable formwork to construct concrete structures by moving the formwork one after another.
It is expected to be applied to marine concrete structures as it has good construction efficiency.

However, when applying the movable formwork method to offshore concrete structures using the aforementioned rich mix concrete, there are
As a result of research conducted by the present inventors, it has been found that the following problems exist.

Concrete with a rich mixture generates a large amount of heat after being poured, and the temperature inside the concrete body increases, resulting in a large temperature difference between the inside and outside of the concrete body, making cracks more likely to occur due to temperature stress. In the frame construction method, the formwork is demolded early and the concrete body is exposed to the outside air, so the temperature difference between the inside and outside of the concrete body becomes even larger, and the tendency for cracks to occur becomes even greater.

In the movable formwork method, water is usually sprinkled to keep the cast concrete structure moist, but construction is carried out in a floating state (by adjusting the buoyancy in a body of water with almost no waves after being pulled out of a dry dock). The outflow of curing water caused by water sprinkling on marine concrete structures causes marine pollution.

[Technical Problems of the Present Invention] In view of the above-mentioned circumstances, the present invention has been made to overcome the above-mentioned problems. The purpose (technical problem) is to provide a concrete curing method suitable for

B. Structure of the invention [Means for solving the problem] In order to achieve the above object, the concrete curing method for marine concrete structures of the first invention (hereinafter referred to as the "first invention") has the following structure (technical Adopt appropriate measures). That is, in a marine concrete structure constructed using movable formwork, a heat insulating sheet whose upper end is fixed to the movable formwork and is suspended from the movable formwork is used to remove the mold from the movable formwork. The surface of the concrete body is thermally covered over a predetermined length while maintaining a required distance from the surface of the concrete body, and as the concrete body is constructed, the movable formwork is moved upwardly, and the heat insulating sheet is used to cover the movable formwork. It is characterized by curing the concrete frame from which the formwork has been removed for a required period of time.

Here, the heat insulation sheet linked to the movable formwork includes a mode in which it is attached directly to the movable formwork, a mode in which it is attached via a hanging scaffold attached to the movable formwork, etc., and in short, a heat insulating sheet that is linked to the movable formwork includes a mode in which it is attached via a hanging scaffold attached to the movable formwork. It performs the function of continuously covering the surface of the concrete structure in a thermally insulating manner immediately after it is applied.

In addition, the heat insulating sheet maintains a space width that does not cause harmful temperature differences from the surface of the concrete structure for a required period of time, but the distance between the two should be selected as appropriate depending on the type of concrete to be cast, the material of the heat insulating sheet, etc. shall be carried out, and
It goes without saying that the method of the present invention is not limited to the embodiment of the holding means.

In this first invention, an aspect can be adopted in which a film curing agent is applied to the surface of the demolded concrete frame of the movable formwork in order to secure hydration water.

The concrete curing method for a marine concrete structure according to the second invention (hereinafter referred to as the "second invention") includes, in addition to the structure of the first invention, humidification in the space between the heat insulation sheet and the surface of the concrete frame. It supplies gas.

Here, humidifying water vapor is usually used as the humidifying gas, but humidifying water vapor or other humidified gases may be used.

[Effect]

In the concrete curing method for a marine concrete structure of the first invention, even if the movable formwork is removed from the cast concrete, the temperature difference between the inside and outside of the concrete frame can be reduced due to the heat insulation effect of the heat insulation sheet. As a result, the occurrence of cracks due to rapid cooling of the outer surface of the concrete structure is prevented.

In the concrete curing method for a marine concrete structure according to the second invention, the humidifier efficiently moistens the concrete body within the heat insulation sheet, and together with the action of the heat insulation sheet, alleviates the temperature difference between the inner and outer surfaces of the concrete body. I will do it.

[Example] Figures 1 to 4 show an example of the method for curing a concrete structure of the present invention.

Each member shown in the figure will be explained below.

1 is the frame of the marine concrete structure to be constructed, 11 is its outer surface, and 12 is its inner surface. The frame 1 of the concrete structure is formed in the shape of a closed wall, and has a bottom 1A, so that the entire structure can float in water.
The planar shape thereof may be any shape such as a circle, a square, a triangle, or a cross, and the wall may be formed vertically or inclined. .

The concrete frame 1 has a unit cement amount of 500
It is constructed of high-strength, lightweight concrete with a rich mix of Kg and water-cement ratio of 35%, and its wall thickness is approximately 45cm, which is equivalent to a normal concrete structure.

A rod 2 is installed inside the concrete frame 1 and projects from the top of the frame. 21 is a sheath tube on which the rod 2 slides.

Reference numeral 3 denotes a movable formwork device, which consists of the main members of a formwork 31, a yoke 32 (a yoke horizontal member 32a, a yoke leg 32b), and a hydraulic jack 33.

4 is a hanging scaffold attached to the movable formwork device 3, and moves in conjunction with the movable formwork device 3.
The suspended scaffold 4 is mainly assembled from pipe materials.

The above-mentioned movable formwork device 3 and suspended scaffolding 4 are known, and are not limited to those shown in the drawings.

Reference numeral 5 denotes a heat insulating sheet, which is stretched along the outside of the suspended scaffolding 4 and along the concrete frame 1. The heat insulating sheet 5 may be any material as long as it can maintain a sealed state, but it is more preferable to select a material that is flexible and lightweight, such as a plastic sheet.

6 is a spacer. The spacer 6 is made of a lightweight and perforated pipe and is attached to the inner surface of the heat insulating sheet 5.
They will be fixed in parallel with a vertical spacing of 1.5m.

7 is a sealing member fixed to the lower end of the heat insulating sheet 5. The sealing member 7 fixes a rubber plate 72 via a pipe member 71 fixed to the lower end of the heat insulating sheet 5, and the weight of the pipe member 71 presses the rubber plate 72 against the surface of the concrete frame 1 to bring it into close contact.

Next, the concrete curing method of this example will be explained in detail.

Construction of the concrete frame 1 using the movable formwork device 3 is carried out according to the procedure of a normal movable formwork construction method.

That is, the formwork 31 is slid at an appropriate speed via a hydraulic jack 33 that takes a reaction force to the rod 2 installed in the concrete frame 1, and the concrete frame 1 is constructed upward. The rate of rise of the formwork 31 is limited by the supply of materials and the speed of each work (installing reinforcing bars, pouring concrete, etc.), but basically the concrete immediately after demolding is under its own weight. It is determined based on the speed that is sufficient to develop a strength that is twice the withstand strength (0.76 Kg/cm ² ).

The demolded concrete frame 1 is secured with hydration water (ensuring moisture level) to solidify the concrete.
However, in order to ensure this level of moisture, water curing is not performed, and a film curing agent is applied to the surface of the concrete that has not yet hardened.

As the film curing agent, for example, commercially available antisol (manufactured by Nippon Sika Co., Ltd., trade name) or Saran Latex (manufactured by Asahi Dow Co., Ltd., trade name) may be used.
By using the film curing agent, there is no outflow of contaminated water into the sea area unlike in watering curing, and the curing can be carried out without any pollution.

The demolded concrete frame 1 is further heat-retained and cured using a heat-insulating sheet.

That is, the concrete frame 1 immediately after being demolded is cured via the heat insulating air layer H formed by the heat insulating sheet 5 stretched on the outer surface of the suspended scaffolding 4. According to the heat insulating air layer H, the worker can work comfortably and not only can the coating curing agent be applied easily, but also the external force acts on the surface of the concrete frame 1 immediately after being demolded. This provides a suitable heat insulating space without any problems.

In addition, the concrete frame 1 below the suspended scaffolding 4
The curing is carried out by a heat insulating air layer I formed by a heat insulating sheet 5 suspended from a suspended scaffold 4 along the concrete frame 1. The insulating air layer I requires a gap width of at least 2 cm, and in this embodiment, for example, by using a perforated pipe with a diameter of 5 cm as a spacer, even if the heat insulating sheet 5 sag, the minimum gap width is required. is ensured.

Thermal curing of the concrete body 1 is carried out for a required period of time (usually about 7 days) until the concrete exhibits the required strength and to prevent cracks from occurring on the surface of the concrete body 1. Therefore, the heat insulation sheet 5 needs to have a length of about 10 m.

Concrete frame 1 with a wall thickness of 45 cm does not generate that much heat if it is concrete with a normal mix, but when the unit cement amount is 500 kg as in this structure, it generates a considerable amount of heat, and the inside of the wall As the temperature of the concrete increases, the temperature gradient between the inside of the wall and the wall surface becomes steeper. For this reason, it is impossible to avoid the occurrence of temperature stress cracks in a concrete frame without a heat insulating sheet as in this embodiment.

In this embodiment, a rubber plate 72 is provided at the lower end of the heat insulation sheet 5.
is attached in the width direction of the sheet, and the rubber plate 72
By bringing the heat insulating sheet 5 into close contact with the surface of the concrete body 1, the inflow of air from below the heat insulating sheet 5 is blocked and the heat insulation effect is promoted.

Furthermore, by adjusting the draft of the floating marine concrete structure and positioning the lower end of the heat insulating sheet 5 approximately 1 m below the sea surface as in this embodiment, the structure can be constructed without using the rubber plate 72. The inflow of air into the heat insulating air layer I can be blocked.

FIG. 5 shows another embodiment of the concrete curing method of the present invention. Here, the same reference numerals are given to the same members as in the previous embodiment.

In this embodiment, the spacer that should be fixed to the heat insulating sheet 5 is omitted, and the humidifying steam supply device 8
is added. The humidifying steam supply device 8 includes a steam blower 81 and a flexible hose 82.
J is a barge on which the humidifying steam supply device 8 is mounted.

The construction of the concrete frame 1 is carried out in the same manner as in the previous embodiment, but for the curing of the concrete, a flexible hose 8 is used by a steam blower 81.
Humidifying steam is sent into the heat insulating air layer between the heat insulating sheet 5 and the surface of the concrete frame 1 through the heat insulating sheet 5 and the surface of the concrete frame 1.

The humidifying steam efficiently moistens the concrete body 1 within the heat insulating sheet 5, and together with the action of the heat insulating sheet, the temperature difference in the concrete body is alleviated. Therefore, in this example, application of a film curing agent can be omitted. Also,
The heat insulating sheet 5 swells outward due to the pressure applied by the air blast, and a suitable gap can be maintained between the heat insulating sheet 5 and the surface of the concrete body, thereby eliminating the need for a spacer.

[Other aspects of the present invention] The concrete curing method of the present invention is not limited to the configuration of the above-described embodiments, and various design changes can be made within the scope of the basic technical idea of the present invention.

That is, the following aspects are included within the technical scope of the present invention.

In the illustrated embodiment, concrete is poured and cured for a caisson frame of a marine concrete structure, but the present invention is also applied to the construction of a tower-like structure on the upper part of a caisson frame.

The spacer is not limited to a pipe member, and may be of any type as long as it can appropriately determine the gap between the heat insulating sheet and the surface of the concrete body.

C. Effects of the Invention According to the curing methods of the first and second inventions, cracks do not occur in the framework of marine concrete structures, and movable forms are used to construct large marine concrete structures, such as petroleum platforms, etc. Construction becomes possible.

It is sufficient for the heat insulation sheet to have a specified length.
Can be used repeatedly.

Furthermore, according to the second invention, it is possible to simultaneously achieve heat retention and moisture retention for concrete that has not hardened yet, and it can be carried out without causing pollution to the ocean.

[Brief explanation of drawings]

The drawings show an embodiment of the method for curing marine concrete structures of the present invention, FIG. 1 is a vertical cross-sectional view showing an outline of one embodiment, FIG. 2 is an enlarged view of a movable formwork device, and FIG. 4 is a detailed view of the lower end of the heat insulating sheet, and FIG. 5 is a longitudinal sectional view of another embodiment. 1... Concrete frame, 11... External surface, 12
...Inner surface, 2... Rod, 21... Sheath tube, 3...
... Movable formwork device, 31 ... Formwork, 32 ... Yoke, 33 ... Hydraulic jack, 4 ... Hanging scaffold, 5 ...
... Heat insulation sheet, 6 ... Spacer, 7 ... Sealing member, 71 ... Rubber plate, 8 ... Humidifying steam supply device,
H, I...Insulating air layer.

Claims (1)

[Scope of Claims] 1. In a marine concrete structure constructed using movable formwork, the movable formwork is provided with a heat insulating sheet whose upper end is fixed to the movable formwork and suspended from the movable formwork. The surface of the concrete frame is thermally covered over a predetermined length by maintaining a required distance from the surface of the concrete frame from which the formwork has been demolded, and the movable form is moved upward as the concrete frame is constructed; A concrete curing method for a marine concrete structure, comprising: curing the demolded concrete frame of the movable formwork for a required period of time using a heat-insulating sheet. 2. The concrete curing method for a marine concrete structure according to claim 1, which comprises applying a film curing agent to the surface of the concrete frame from which the movable formwork has been demolded. 3. In marine concrete structures constructed using movable formwork, a heat insulating sheet whose upper end is fixed to the movable formwork and is suspended from the movable formwork is used to remove the movable formwork from the mold. the surface of the concrete body is insulatively covered over a predetermined length while maintaining a required distance from the surface of the concrete body, and supplying humidifying gas to the space between the heat insulating sheet and the surface of the concrete body; Concrete for a marine concrete structure, characterized in that the movable formwork is moved upward as the concrete frame is constructed, and the concrete frame from which the movable formwork has been removed is cured for a required period of time by the heat-insulating sheet. Curing method.