JPH02308066A - Form for placing concrete - Google Patents

Abstract

PURPOSE:To prevent the trace of gas from being generated and reduce a cost by fitting a synthetic resin sintering sheet having hydrophilic property, on the weir plate of a form. CONSTITUTION:With the synthetic resin of polyethylene or the like which can be molded to be sintered having low water-absorbing property, the synthetic resin sintering sheet of the thickness of 1mm or more having the apparent density of about 0.2 - 0.8 g/cm<3> and hydrophilic property is formed. Then, the sheet is fitted on the weir plate of a form and after that, concrete is placed in the form.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to formwork used in various concrete works. More specifically, the present invention relates to a formwork for concrete work which is characterized by releasing excess water and air bubbles from poured concrete to the outside and finishing the concrete surface with a smooth finish.

[Prior art]

Conventional formwork used in concrete construction consists of a weir plate and template made of iron or wood, and the surface that comes into direct contact with the concrete is impermeable to water and air. As a result, excess water in the concrete is not sufficiently drained.
Bleeding is likely to occur, the curing speed is slow, and the initial strength is not fully demonstrated, and the large amount of air bubbles in the concrete is not sufficiently degassed, resulting in the formation of a large number of air bubbles on the surface. there were.

As a countermeasure to this problem, various improvement methods using breathable water-permeable sheets have been proposed. For example, a weir board with multiple through holes can be used with a formwork (Japanese Patent Application Laid-open No. 137923/1983) whose surface is covered with a breathable and water-absorbing sheet such as non-woven fabric or synthetic resin net, or with A sheet consisting of a double structure consisting of an outer layer with a dense structure that does not allow solids such as cement particles to pass through, and an inner structure with a coarse structure that allows the synthetic resin adhesive to penetrate is bonded to the weir board. formwork (Unexamined Japanese Patent Publication No. 61-2
No. 74046) is known.

However, these methods require multiple holes to be made in the weir board, it is time-consuming to attach the sheet to the weir board, and the sheet is not strong enough, making it difficult to use it repeatedly. have.

(Problems to be Solved by the Invention) The present invention provides a formwork for efficiently removing water and air during concrete pouring to obtain high-quality concrete, and which has a large number of holes in the weir plate of the formwork. This was achieved as a result of research into a low-cost formwork that can remove water and air without having to build it up, and can also attach a layer that can remove water and air to a weir board with a simple operation.

[Means to solve the problem]

The present invention is a formwork for concrete construction in which a sintered synthetic resin sheet having hydrophilic properties is adhered to a weir plate of the formwork.

Describe the hydrophilic synthetic resin sintered sheet0
As the synthetic resin, any synthetic resin can be used as long as it is sinterable and has low water absorption, but polyethylene, polypropylene, polyvinyl chloride,
Examples include polystyrene, acrylic resin, polyvinyl acetate, and phenol resin. Particularly preferably, polyethylene is used, which has a good balance between rigidity and flexibility, is excellent in hydrophobicity and weather resistance, and is available at low cost.

The sintered sheet is obtained by molding synthetic resin powder using a known sintering method. For example,
A long synthetic resin sintered sheet can be obtained by the method described in Japanese Patent No. 786. In other words, the method involves filling a mold with synthetic resin powder and heating and sintering it in a heating furnace.The powder is evenly spread from a hopper onto the top of an endless metal conveyor belt, and the powder is passed through a heating furnace at a constant speed for sintering. , a method of continuously obtaining a sintered synthetic resin sheet by performing cooling is adopted. This sheet must have continuous pores,
This allows water and air in the concrete to pass through the sintered sheet and be removed. It is recommended that the average pore diameter is in the range of about 1 to 500 microns, preferably about 5 to 300 microns. If it is larger than 500 μm, a large amount of concrete particles will enter the sheet, making it impossible to use the sheet repeatedly and reducing the effect of improving the concrete surface, which is not preferable. On the other hand, if the average pore diameter is smaller than 1 μm, the passage resistance of water and air is large and water and air in the concrete cannot be effectively removed.

In the present invention, having hydrophilicity means that water permeates into the pores of the sintered sheet without applying pressure. In order to achieve the effects of the present invention, the water droplet absorption time is preferably 300 seconds or less, more preferably 200 seconds or less. If the water droplet absorption exceeds 300 seconds, excess water may not be sufficiently drained. This phenomenon is particularly noticeable in the upper part of concrete pouring.

Examples of methods for imparting hydrophilicity include JP-A-57-16
The methods described in Japanese Patent Application No. 7330 and Japanese Patent Application No. 63-61981 can be employed. In other words, synthetic resin powder and a special surfactant are blended at high speed and then sintered, or the surface of the synthetic resin powder or sintered sheet is sulfonated or treated with electron beams, and then hydrophilic groups are grafted. , a method of bonding a hydrophilic group to the surface, etc. can be adopted. Since the surface of the sintered synthetic resin sheet has hydrophilic properties in this manner, water can be easily absorbed into the sintered synthetic resin sheet and moved through the siphon phenomenon.

It is also necessary that the synthetic resin constituting the sintered sheet does not exhibit water absorption. If it is water-absorbing, the continuous pores of the sintered sheet will be blocked due to the swelling of the synthetic resin due to water absorption, which will greatly impair the effect of the present invention, as well as impair the surface smoothness and strength of the sheet, and make it difficult to reuse. However, there are drawbacks such as the fact that it takes a lot of time to dry.

There is no particular regulation on the thickness of the synthetic resin sintered sheet, but it is 0, 5.
A sheet with a thickness of ttm or more, preferably 1 mm or more is used. If it is thinner than 0.5 mm, the rigidity of the sheet will be low and it will be difficult to handle, and the amount of water and air passing through the sheet will be small, which may be undesirable. The thickness is recommended to be 30 mm or less in order not to increase the weight of the synthetic resin sintered sheet.

Further, the recommended apparent density is 0.2 to 0.8 g/ci, more preferably 0.3 to 0.7 g/c11.

If the apparent density is lower than 0.2, the strength of the sintered sheet will be low and it will break easily, making it undesirable to handle.On the other hand, if the density is higher than 0.7, there will be fewer pores, making it difficult for water and air to pass through. It can become difficult.

The formwork is usually made of wood, metal, or resin. Various known methods may be employed for attaching the synthetic resin sintered sheet to the weir plate of the formwork. For example, methods such as applying an adhesive to the entire surface or a portion of the weir board and attaching a synthetic resin sintered sheet, attaching with double-sided tape, and nailing are used.

〔Example〕

Examples of the present invention are shown below.

<Average pore diameter> Take a photograph of the surface and cross section of the synthetic resin sintered sheet magnified approximately 50 to 100 times, measure the long axis and short axis of 100 or more adjacent pores individually, and calculate the average value as the pore diameter. It is calculated from the average of 5 or more locations.

<Measurement of Water Droplet Absorption> A sintered synthetic resin sheet is placed horizontally, a droplet (approximately 0.5 d) is dropped onto the sheet using a dropper, and the time required for the droplet to be absorbed is measured.

<Appearance is density> 3 cm wide x 3 cm wide (
Take a sample (the thickness remains the same as the thickness of the sheet), measure its weight, and calculate it using the formula below.

The apparent density (g/c+d) = sample weight (g)/sample volume (cut) Example 1 High-density polyethylene powder (manufactured by Asahi Kasei Corporation, Sunfine 5H800, particle size 100-20゛0 mesh is approximately 70
%) and 0.4 part of polyoxyethylene sorbitan monolaurate were mixed with 100 parts by weight while heating to 85° C. using a high-speed mixer. Mold (inner size = 800X800X2.2a
+ m) was filled with 680 g of this powder, heated in a 200° heating furnace for 20 minutes, cooled at room temperature, and made into a 2 mm thick
A synthetic resin sintered sheet was obtained. The average pore size of this is 23
μ, water droplet absorption measurement is less than 1 second, apparent density is 0.5
It was 5 g/CTA. Concrete formwork (80
The sheet cut to the same size as the weir board was attached to a weir board (c+nx 70 cm) using double-sided tape.

Example 2 0.5 part of tetraglycerin monoisostearate was added to 100 parts by weight of high-density polyethylene powder (Sunfine 511820 manufactured by Asahi Kasei Corporation) at 85°C using a high-speed mixer.
The mixture was mixed while heating to C. Using this powder, a synthetic resin sintered sheet having a thickness of 31I11 was obtained by sintering molding. The average pore diameter of this is 52μ, and the water droplet absorption measurement is less than 1 second.
The apparent density was 0.58 g/cJ. The sheet cut to the same size as the weir board was attached to the weir board of a concrete formwork (80 cm x 70 cn+) using an epoxy adhesive.

Comparative Example 1 High-density polyethylene powder (Sunfine 5H800, manufactured by Asahi Kasei Kogyo ■) was sintered and shaped in the same manner as in Example 1 to obtain a 2 on thick synthetic resin sintered sheet.

The average pore diameter of this material was 23 microns, water droplet absorption was measured over 30 minutes, and the apparent density was 0.55 g/cd.

This was adhered to the weir board of a concrete formwork in the same manner as in Example 1.

Comparative example 2 The wooden concrete formwork was used as is.

<Concrete placement and evaluation> One concrete formwork of Examples 1 and 2 and Comparative Examples 1 and 2 was used.
Use one piece at a time to make a square prism (inner size: 80 x 80 x 70c)
m) was made, concrete with a slump of 18 cm was placed thereon, and the mold was removed after 3 days. Table 1 shows the results of the visual inspection of the concrete surface at this time and the results of the Schmidt hammer test 28 days after pouring.

Table 1 Comparative Example 3 P-A resin powder (90% particle size 40-150 mesh)
0.7 parts by weight of hexaglycerol monoisostearate was mixed with 100 polymerization parts while heating at 70°C using a high-speed mixer. 740 g of this powder was filled into the mold used in Example 1, heated in a heating furnace at 200° C. for 20 minutes, and then cooled at room temperature to obtain a 2 um thick synthetic resin sintered sheet. The average pore diameter of this is 180μ, and the apparent specific gravity is 0.
．． 48, water droplet absorption was 20 seconds. A concrete placement test similar to that in Example 1 was conducted using this sintered sheet.

As a result, there were almost no pockmarks on the exterior, and no stone dust was generated even when polished with a whetstone. Also, the Schmidt hammer test values are 310 kgf/cd for the upper part and 335 kgf/cd for the lower part.
kgf/c! It was II.

Claims (1)

[Claims] 1. Formwork for concrete construction made by pasting a sintered synthetic resin sheet with hydrophilic properties to the weir plate of the formwork.