JP2004218267A - Construction method of columnar structure made of pressurized and dehydrated ready mixed concrete - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To construct a pier capable of reducing the construction period by pressurizing and dehydrating ready mixed concrete immediately after placing it and early developing the early stage strength and early demolding, causing neither excess water on the surface of concrete nor laitance due to bleeding, and curtailing the construction joint work time. <P>SOLUTION: A water permeable form 3 is installed in a position where ready mixed concrete is placed and the placed concrete is pressurized and dehydrated to construct a columnar structure. A water permeable sheet 1 permeating water in ready mixed concrete and a water permeable form 3 that a reticular body 2 such as an expanded panel or the like supporting the sheet is assembled by reinforcing members are used. A fabric or the like having a function permeating water in the ready mixed concrete is used for the water permeable sheet 1. When pressurizing the ready mixed concrete placed in the water permeable sheet 1, as water in the ready mixed concrete is discharged, solid self-supportable concrete having nearly 0 cm in slump. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method of constructing a columnar structure obtained by dehydrating ready-mixed concrete under pressure, and in particular, using a conventional water-permeable form, casting ordinary fluid concrete, but resulting in concrete exhibiting early strength. The present invention relates to a method for constructing a columnar structure.
[0002]
[Prior art]
Up to now, columnar structures (for example, piers) are constructed by assembling reinforcing bars such as main bars and hoop bars, assembling a formwork support with veneer plywood, steel plate, etc., and then pouring ready-mixed concrete into the formwork. It was built by doing. Usually, after placing the ready-mixed concrete, the mold is dismantled after curing for about three days.
[0003]
According to the Concrete Standards Specification of the Japan Society of Civil Engineers (established in 1996), the concrete strength at which the formwork may be dismantled is 5.0 N / mm ² for piers. With ordinary concrete, the material reaches 5.0 N / mm ² at the age of one day, which can be almost removed. However, removal is often performed after 3 to 5 days for safety.
[0004]
Further, as a method of forming solid concrete, there is an example in which raw concrete is poured into a water-permeable bag, and a slump close to 0 is formed by using the driving pressure. However, the case of stacking the bagged concrete was unreasonable in terms of strength as a pier. (For example, see Patent Document 1).
[0005]
[Patent Document 1]
JP 2000-144740 A
[Problems to be solved by the invention]
However, the above-mentioned conventional pier construction method has the following problems.
(1) The veneer plywood used for the formwork has a problem of resource consumption, and its use must be suppressed from an environmental aspect such as protection of a tropical rain forest.
(2) It took several days to release the formwork, which was a bottleneck in shortening the construction period.
(3) In the conventional concrete hardening method, surplus water and breathing easily occur on the surface of concrete.
(4) Due to the occurrence of latencies, there is a possibility that the jointing of concrete may be adversely affected.
(5) Laittance treatment has also been a bottleneck in shortening the construction period.
[0007]
An object of the present invention is to omit the veneer plywood of the form, reduce the amount of tropical timber form used, and shorten the construction period of the concrete structure, and to reduce the excess water and breathing of the concrete and the latencies. It is an object of the present invention to provide a method for constructing a bridge pier with a low occurrence.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, a method for constructing a columnar structure (for example, a bridge pier) of the present invention in which ready-mixed concrete is depressurized and dewatered is provided by a method of permeating water in the ready-mixed concrete to a portion of the columnar structure where the ready-mixed concrete is cast. A concrete formwork is installed, and then the poured concrete is dehydrated under pressure to construct a concrete columnar structure.
[0009]
ADVANTAGE OF THE INVENTION According to this invention, pressurization is performed immediately after casting concrete, and water is discharged | emitted, and concrete will be in the state which can stand on its own. In addition, the early development of the strength is early, and the mold can be released from the mold early. By performing pressure dehydration, surplus water is not generated on the surface of the ready-mixed concrete, latencies due to breathing are reduced, and the process of jointing concrete can be shortened.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an example of a water-permeable mold used for the method of the present invention. FIG. 1A is a plan view, and FIG. 1B is a front view.
[0011]
As shown in FIG. 1, in one embodiment of the present construction method, a water-permeable sheet 1 permeable to moisture in concrete is installed on the ready-cast concrete placing portion side, and a mesh 2 supporting the water-permeable sheet 1 is placed on the outside. The installed water-permeable mold 3 is used.
[0012]
As the water-permeable sheet 1, a cloth sheet having a performance of transmitting moisture and not transmitting concrete is used. The cloth sheet is made by knitting a nylon thread, and has a property of transmitting moisture but not leaking cement or concrete.
[0013]
When the fresh concrete poured into the water permeable sheet 1 is pressurized, the concrete component does not leak and the water in the concrete is discharged. Therefore, the slump can quickly form a solid freestanding concrete of almost 0 cm.
[0014]
In order to prevent the water permeable sheet 1 from bulging outward due to pressure dehydration, an expanded metal is installed as a net 2 outside the water permeable sheet 1. In addition to expanded metal, lath netting, grating, punching metal and the like can be used. In addition, any material other than the mesh, such as a lattice, may be used as long as it can support the water-permeable sheet 1 so as to suppress the spread.
[0015]
Further, in order to maintain the shape of the entire formwork, that is, the plane shape in FIG. 1, the form is constituted by a steel material 4 such as L-shaped steel or flat steel plate. Maintain strong strength.
[0016]
The installation method of the water permeable form 3 shown in FIG. 1 is the same as that of the conventional steel form (metal foam). The water-permeable form 3 is manufactured in advance in a factory or a workplace, and is formed by reinforcing the water-permeable sheet 1 and, for example, expanded metal 5 with a steel material 4 such as an L-shaped steel.
[0017]
According to the material test data of concrete subjected to pressure dehydration, the compressive strength at the age of 24 hours is
▲ 1 ▼ in pressure 0.25kgf / cm ² 9.72N / mm ²
( ² ) 10.11 N / mm ² at a pressure of 0.5 kgf / cm ²
▲ 3 ▼ in pressure 1.0kgf / cm ² 11.06N / mm ²
Met.
[0018]
For pressureless, the age of 24 hours 3.0~5.0N / mm ^2, in the age of 3 days, about 7~11.0N / mm ^2. By performing pressure dehydration, surplus water and breathing do not occur on the surface of the ready-mixed concrete, and the occurrence of latencies that adversely affect the jointing of concrete is reduced. Laittance processing can be completed easily in a short time as compared with ordinary construction.
[0019]
In this way, if the pressurization is performed immediately after placing the ready-mixed concrete, the concrete is in a state in which the slump is almost 0 cm and can stand alone. In addition, the early development of the strength is early, and the mold can be released from the mold early. By being able to release the mold at an early stage, the work process is sped up.
[0020]
In addition, by using a steel frame in which a permeable sheet is set inside the form or a porous form as the permeable form, the fresh water surplus water is actively drained from the eyes of the permeable sheet. By doing so, air bubbles and the like can be removed, and the strength of concrete increases.
[0021]
Furthermore, the degree of filling of the ready-mixed concrete can be visually confirmed, and there is no junka on the surface. In addition, by applying pressure after placing the ready-mixed concrete, concrete strength is developed early and the construction period is shortened.
[0022]
In the following, considering each element such as formwork,
(Form)
{Circle around (1)} The water-permeable formwork should be light. Since the pressure is applied after placing the ready-mixed concrete, it must be stronger than usual.
[0023]
(2) Plywood can be light, but drainage is poor. Since the form itself is weak in strength, it is necessary to construct a support as reinforcement.
[0024]
(3) Plywood used for formwork has a problem of resource consumption. For protection of the rainforest, a construction method that does not use plywood is better.
[0025]
(4) The formwork should be large and built with a crane.
[0026]
(5) A large format in which the formwork, the shoring and the scaffolding are integrated may be used.
[0027]
(6) Form 1 proposal: Use a lath net instead of plywood. A lath net has good drainage. Instead of piers, use reinforced steel plates or L-shaped steel (angle).
[0028]
(7) Form 2 plan: Use a porous concrete plate (precast concrete plate, etc.).
[0029]
(Rebar)
(1) Main rebar 1 plan: The main rebar is replaced with H-section steel and assembled first. Alternatively, they may be assembled sequentially. If it can be assembled first, it will be advantageous in terms of construction. When assembling a reinforcing bar, the material cost is lower than that of the H-section steel, but the assembly labor cost and the construction period are disadvantageous.
[0030]
(2) Main bar 2 plan: When assembling with steel bars, as in the case of the conventional construction method, after concrete is cast, it is assembled sequentially.
[0031]
{Circle around (3)} Regarding the hoop streak, in the case of the lath net of one formwork, the assembly is the same as the conventional method. In addition, when using the precast concrete board of the two formwork, a board incorporating hoop streaks can be prepared in advance.
[0032]
(Pressurization method)
{Circle around (1)} Proposed pressurization method 1: Mechanical pressurization is difficult to take a reaction force, so a method using gravity is preferred. Use a water bag to apply pressure. After pressurization, drain water. The supply of water to the water bag shall be a pump or a water hose.
[0033]
According to the above method, a lid is placed on the poured ready-mixed concrete, a bag for water is placed, water is supplied into the bag, and the ready-mixed concrete is pressed as a weight. Unloading after pressurization is simple because the water is drained. However, when it takes a long time to supply a large amount of water, or when a large pressing force is required in a high pier, an anchor is installed on the existing building to provide a reaction force to perform mechanical pressurization.
[0034]
{Circle around (2)} Pressing method 2 plan: There is a method in which an anchor is set at the time of casting concrete and the anchor is pressed as a reaction force. For example, a pier can be constructed like the caisson method, and the method of the present invention can be applied to the caisson method as described later.
[0035]
[Concrete final form]
{Circle around (1)} In the case of the lath net of one formwork, the columnar structure (for example, a bridge pier) is finished casting concrete to a predetermined height, and after removing the formwork, remove the water-permeable sheet and remove the ordinary concrete. Expose the surface.
[0036]
{Circle around (2)} In the case of two mold forms, the PCa plate (precast concrete plate) is finished as it is.
[0037]
Next, each work procedure will be described.
<Ascent work of permeable formwork>
(In case of expanded metal formwork)
(1) Assemble the rebar.
(2) Assemble the formwork.
(3) Pour ready-mixed concrete into the formwork.
(4) Set the pressure device.
(5) The ready-mixed concrete is dewatered under pressure.
(6) The part where the mold can be removed is removed.
(7) Concrete is repeatedly poured to a predetermined height.
(8) Remove the mold.
(9) Peel off the cloth on the concrete surface.
[0038]
(For porous concrete plate)
(1) Assemble the rebar.
(2) Assemble a porous concrete plate (embedded formwork).
(3) Pour ready-mixed concrete into the formwork.
(4) Set the pressure device.
(5) The ready-mixed concrete is dewatered under pressure.
(6) Repeatedly cast concrete up to the specified height.
[0039]
Next, with reference to FIG. 2 to FIG. 4, a construction order of a columnar structure (pier) construction method using the water-permeable formwork 3 as the water-permeable formwork will be described. As shown below, (a) to (d) are repeated to continue the concrete of the pier.
[0040]
(A) First, as shown in FIG. 2, the reinforcing bar 26 is assembled. Next, the water-permeable form 3 is assembled. Reference numeral 24 is a scaffold, 25 is a lifting device, and 27 is a lifting stair.
[0041]
(B) Next, as shown in FIG. 3, after the ready-mixed concrete 10 is cast and the top end is covered and cured, a lid 28 on which a water bag is placed is installed. The reference numeral 20 is an example of the PCa version.
[0042]
(C) Next, a water bag 29 is placed on the lid 28 as shown in FIG. Water is poured into a water bag and the ready-mixed concrete is pressurized by its weight to drain the water in the ready-mixed concrete. Reference numeral 30 denotes a wall frame that is set up so that the drainage does not scatter.
(D) Next, the water load is removed, and the water bag 29 and the lid 28 are removed.
[0043]
The load for pressing the ready-mixed concrete may be placed on the lid 28 by using an iron lump, a concrete block, or the like as a counter, instead of using a water bag. In addition, when anchoring the existing skeleton, it is only necessary to pressurize the lid 28 with a jack to drain the water in the ready-mixed concrete.
[0044]
Next, a method of applying pressure with a jack will be described using the caisson method as an example. 5 and 6 are explanatory diagrams when the method of the present invention is applied to the caisson method. As shown in FIG. 5, the surrounding wall concrete 41 is cast using the water-permeable mold 40 indicated by the reference numeral 3 in FIG. A lid 42 is placed on the cast concrete, and a counterforce is applied from the ground surface 43 to the anchor 44 installed deeply.
[0045]
Next, as shown in FIG. 6, after the concrete has been poured, the pressurizing beam 46 is installed when the strength of the concrete is increased, the reaction force is applied to the anchor 44, and the hydraulic jack 45 is used. From the ground surface 43. According to this example, the anchor 44 can also be used for a load for dewatering ready-mixed concrete.
[0046]
【The invention's effect】
ADVANTAGE OF THE INVENTION As mentioned above, according to this invention, the construction method of shortening a construction period by omitting the veneer plywood of a formwork, and producing the surplus water and breathing of concrete, and generating less latencies is obtained. .
[Brief description of the drawings]
FIG. 1 is a plan view and a front view showing an example of a water-permeable mold in the method of the present invention.
FIG. 2 is an explanatory diagram showing a construction order of a pier construction method using a water-permeable form.
FIG. 3 is an explanatory view showing a construction order of a pier construction method using a water-permeable formwork.
FIG. 4 is an explanatory diagram showing a construction order of a pier construction method using a water-permeable formwork.
FIG. 5 is an explanatory view of a pressure dehydration method when the method of the present invention is applied to the caisson method.
FIG. 6 is an explanatory diagram of a pressure dehydration method when the method of the present invention is applied to the caisson method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Water-permeable sheet 2 Net-like body 3 Water-permeable form 4 Steel 5 Expanded metal 10 Fresh concrete 26 Reinforcement 28 Cover 29 Water bag 40 Water-permeable form 41 Perimeter wall concrete 42 Cover 44 Anchor 45 Hydraulic jack 46 Pressure beam

Claims (3)

It is necessary to install a water-permeable formwork that allows the moisture in the ready-mixed concrete to permeate the concrete-filled section of the concrete columnar structure, and then pressurize and dewater the poured ready-mixed concrete to construct the columnar structure. Characteristic construction method. The water-permeable mold is characterized in that a porous concrete mold is continuously installed, and a water-permeable sheet that transmits moisture in ready-mixed concrete is installed in a gap between the molds. 2. The method for constructing a columnar structure according to 1. The method for constructing a columnar structure according to claim 1 or 2, wherein the poured concrete is dewatered under pressure until the slump becomes approximately 0 cm.

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