JPH0478465B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to prestressed concrete (hereinafter referred to as
Synthetic resin coating using foamed synthetic resin material used in the post-tensioning method (denoted as PC)
This article relates to prestressing steel materials and coating layer processing methods. (Conventional technology) Conventionally, a prestressing steel material is inserted into concrete in advance, and after the concrete hardens, the prestressing steel material is inserted into the concrete.
In the so-called post-tensioning method, which applies stress to steel by tensioning it, the prestressing steel material must be able to move within the concrete, so conventionally, unbonded prestressing steel, which has a prestressing steel material and an unbonded coating layer covering it, has been used. steel is used. Conventional unbonded coating layer processing methods for unbonded PC steel materials can be roughly divided into: (1) asphalt-based coatings applied to the surface of the PC steel material and protective tape etc. wrapped around the surface, and (2) oil-based coatings. There are methods such as coating the surface of prestressed steel on the surface of prestressed steel, and then applying a resin coating layer to the surface using an extrusion molding method.Although both methods are satisfactory in terms of frictional resistance, they lack rust prevention ability. This is becoming a problem. The reason for this is that both the asphalt type and the oil type deteriorate over time and the coating state becomes incomplete, resulting in a decrease in rust prevention durability. Therefore, in recent years, a method has been developed in which a single layer of synthetic resin coating with excellent anti-rust properties is applied to the surface of prestressed steel material and used in the post-tensioning method, but it is not effective in terms of frictional resistance. The result is that it is inferior to the conventional one. In other words, when asphalt-based material is applied to the surface of prestressed steel and protective tape is wrapped around the surface, slippage with concrete occurs because the protective tape adheres to the concrete, causing slippage between the asphalt and the protective tape. Therefore, frictional resistance is reduced, and oil-based materials are
If a resin coating is applied to the surface of a prestressed steel material and then a resin coating is applied to the surface using an extruder molding method, the slippage with concrete will occur because the resin coating adheres to the concrete and slippage occurs between the oil and resin coating. Frictional resistance is small, but in the case of recently developed PC steel materials with a single-layer synthetic resin coating layer, slipping with concrete occurs between the surface of the resin coating layer and the concrete. The frictional resistance is determined by the smoothness of the resin-coated surface, and variations in the smoothness manifest as variations in the frictional resistance. (Problems to be Solved by the Invention) Conventionally, unbonded PC steel materials have been required to have excellent rust prevention and friction resistance. As mentioned above, a single-layer synthetic resin-coated PC steel material has been developed in response to this demand. However, although it has excellent properties in terms of rust prevention, it has a problem with frictional resistance, and improvements in this point have been desired. The reason for the increase in frictional resistance of single-layer synthetic resin-coated unbonded PC steel is determined by the smoothness of the synthetic resin-coated surface, since slippage with concrete occurs between the synthetic resin-coated surface and the concrete. Therefore, powder coated synthetic resin coated unbonded PC
In the case of the steel processing method, the prestressing steel material is coated while being rotated appropriately in the axial direction in order to obtain the surface smoothness, and the coated surface is cooled while being rotated to eliminate paint sag during cooling. We are trying to smooth the area. In addition, in the case of foam powder coating, the heating temperature of the prestressing steel material must be kept as low as possible to prevent foaming from reaching the coating surface, or adjustments such as lowering the resin foaming rate may be made to improve the coating surface. Although emphasis has been placed on smoothness, it has not been possible to obtain a satisfactory result in terms of frictional resistance. The present invention provides a synthetic resin-coated PC steel material and a method for coating the same, based on a completely different idea from the above-mentioned idea of reducing frictional resistance by increasing the smoothness of the coated surface. (Means for Solving the Problems) The features of the present invention for solving the conventional problems as described above are as follows: Firstly, in a synthetic resin-coated PC steel material in which a coating layer of a synthetic resin material is provided on the surface of the PC steel material. , the synthetic resin-coated PC steel material is characterized in that the foaming rate of the PC steel material side of the coating layer is smaller than that of the outer surface side of the coating layer,
Adhering a foamed synthetic resin powder coating to the surface of the steel material to form a coating layer of the foamed synthetic resin material,
A method for coating a synthetically coated PC steel material, which is characterized in that the coating layer is then heated from its outer surface to increase the foaming rate on the outer surface side, and thirdly, a synthetic resin coating that does not foam on the surface of a PC steel material. The method of coating a synthetic resin-coated PC steel material is characterized by forming a foamed synthetic resin coating layer on the outer surface of the prestressed steel material and then applying a foamed powder coating to the outer surface thereof to form a foamed synthetic resin coating layer. (Function) The slippage of the unbonded coating layer PC steel material with concrete in the method of the present invention is not due to the smoothness of the coating surface as in the case of conventional synthetic resin coatings, but the following effects prevent the slippage with concrete. arise. The surface of the synthetic resin coating becomes uneven due to foaming and adheres closely to the concrete, but slipping with the concrete occurs due to the elongation of the resin at about 20 to 30% of the introduced stress, but if it is introduced beyond that level, it will slip. When it comes to stress, the areas with maximum foaming (large bubbles) and the least foaming (small bubbles or no bubbles)
The elongation rate of the resin changes at the portion , and as the bubbles become larger, the elongation rate decreases. The reason for this is that the larger the bubbles are, the more bubbles are connected to each other and breakage occurs, so the elongation limit is considerably smaller compared to those with very small bubbles or ordinary resins. The method of the present invention utilizes this phenomenon,
As mentioned above, when the introduced stress reaches about 20-30%, the resin stretches and slips with the concrete.
After that, the maximum foaming part (the upper surface layer of about 1/3 of the coating thickness or the boundary between normal resin and foamed resin) and the minimum foaming part are separated due to the difference in elongation, and the maximum foaming part and the minimum foaming part are separated. Otherwise, slipping occurs between the foam and the non-foamed parts, so the frictional resistance is lower than that of conventional single-layer synthetic resin-coated PC steel materials, and the rust prevention ability is exactly the same. (Example) Next, an example of the present invention will be described with reference to the drawings.
Figures 1 and 2 show a synthetic resin-coated PC according to the present invention.
3 shows different examples of steel materials. In the figure 1
2 to 4 are PC steel materials, and 5a and 5b are synthetic resin coating layers. What is shown in Figure 1 is
The synthetic resin layers 2 and 3 on the surface of the PC steel material 1 are both formed of foamed synthetic resin material, and the
The foaming rate of the layer 2 on the steel material side is smaller than the foaming rate of the layer 3 on the outer surface side. Also, what is shown in Figure 2 is the layer 4 on the PC steel material side.
is formed of a solid synthetic resin material that does not foam, that is, does not contain air bubbles, and the surface side layers 5a and 5b
is made of foamed synthetic resin material. The foaming rate of the inner foamed synthetic resin material layer 5a is smaller than that of the outer layer 5b. Next, a coating method for each of the above-mentioned synthetic resin-coated PC steel materials will be explained. First, to explain the process of coating the synthetic resin-coated PC steel material shown in FIG. 1 described above with reference to FIG.
In order to maximize the foaming rate of the upper part of the coating layer, after heating it to a predetermined temperature by using a fluidized dip powder coating device or electrostatic powder coating device 7, powder coating is performed using a foamed synthetic resin material. The surface of the coating layer is heated at a high temperature in a heating furnace 8, and after foaming is completed, it is cooled in a cooling tank 9. As a result, the synthetic resin coated PC steel material shown in FIG. 1 is completed. Note that the fluidized dip powder coating equipment used in this method suspends the powdered synthetic resin material to be coated by airflow, and then
By inserting the PC steel material 1, a foamed synthetic resin material is attached to the outer surface of the PC steel material 1, and a synthetic resin coating layer is formed on the outer surface. A positive or negative potential is applied, the opposite potential is applied to the prestressed steel material, the prestressed steel material is passed through a powdered synthetic resin material, and the prestressed steel material is attached to the outer surface of the prestressed steel material using static electricity. In addition, to explain the covering process of the synthetic resin covering material shown in Fig. 2, which was described above with reference to Fig. 4, first,
The PC steel material 1 is heated to a predetermined temperature in a heating furnace 6, and then is coated with normal powder using a non-foaming powder synthetic resin material in a fluidized dip powder coating device or an electrostatic powder coating device 10. After applying, immediately powder coating the surface with a foamed synthetic resin material using a fluidized dip powder coating device or an electrostatic powder coating device 7,
Next, the surface of the coating layer is heated at a high temperature in a heating furnace 8 in order to maximize the foaming rate in the upper part of the coating layer, and after foaming is completed, it is cooled in a cooling tank 9. As a result, the synthetic resin coated PC steel material shown in FIG. 2 is completed. Note that the fluidized immersion powder coating device and the electrostatic powder coating device are the same as those described above. In the case of the method shown in FIG. 3, the cross section of the coating layer according to the present invention completed through the above steps shows that foaming is small on the inside of the dotted line 11 of the coating layer (on the PC steel material side) as shown in FIG. The foaming (air bubbles) is large on the outside (surface side), so when the PC steel material 1 is embedded in the concrete 12 and pulled in the direction of the arrow as shown in Fig. 5, the coating layer within the concrete 12 will separate. The inner coating layer 2 with less foaming and the outer coating layer 3 with more foaming are separated, causing slippage between them and reducing frictional resistance. The method shown in Figure 4 is similar to this, and the cross-section of the coating layer shown in Figure 2 is similarly embedded in concrete, and when the PC steel material is pulled in the direction of the arrow, it becomes solid. The ordinary resin coating layer 4 and the foamed resin coating layer 5a separate and slip between them, reducing frictional resistance. In the above embodiment, the foamed synthetic resin material layer has different foaming rates on the inside and outside, but as shown in FIG. Alternatively, a foamed powder coating may be applied to the outer surface of the synthetic resin coating layer 5 to form a foamed synthetic resin coating layer 5 uniform on the inside and outside. The frictional resistance between the synthetic resin-coated PC steel material according to the present invention described above and the conventional synthetic resin-coated PC steel material was measured, and the results were as shown in Table 1.

[Table] (Effects of the Invention) As mentioned above, the present invention is an unbonded coated PC steel material that has excellent rust prevention and friction resistance, and satisfies various conditions that have been required of unbonded coated PC steel materials for many years. It was forced upon me. Therefore, by using the method of the present invention, there is no need for protective sheaths, etc., and the unbonded coating layer PC steel material of the present invention can be directly buried in concrete, reducing the construction cost of the prestressed concrete method. It's cheap, and
Since smoothness of the resin coating surface is not required, the coating method is simplified and productivity is improved.This is an industrially groundbreaking invention and has great effects.

[Brief explanation of the drawing]

Figures 1 and 2 are cross-sectional views showing different embodiments of the synthetic resin-coated PC steel material of the present invention, and Figures 3 and 4 show processing steps of different embodiments of the coating method of the present invention. 5 is a sectional view showing the state of the synthetic resin-coated PC steel material in concrete according to the present invention under stress, and FIG. 6 is a sectional view of still another embodiment. 1...PC steel material, 2, 3, 4, 5, 5a, 5b
... Synthetic resin coating layer, 6 ... Heating furnace, 7 ... Powder coating device, 8 ... Heating furnace, 9 ... Cooling tank, 10 ...
...Powder coating equipment.

Claims (1)

[Claims] 1. In a synthetic resin-coated PC steel material comprising a coating layer made of a synthetic resin material on the surface of the PC steel material, the foaming rate of the coating layer on the PC steel material side is lower than that on the outer surface side of the coating layer. Synthetic resin coated PC steel material is characterized by: 2 A foamed synthetic resin powder coating is applied to the surface of the PC steel material to form a coating layer made of the foamed synthetic resin material, and then the coating layer is heated from the outer surface to increase the foaming rate on the outer surface side. A coating processing method for synthetically coated PC steel material, which is characterized by: 3. A method for coating a synthetic resin-coated PC steel material, which is characterized by forming a non-foaming synthetic resin coating layer on the surface of the PC steel material, and then applying a foamed powder coating to the outer surface to provide a foamed synthetic resin coating layer.