JPH1060790A - Antirust coated pc strand having high adhering strength and processing thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an antirust coated prestressing (PC) strand not damaging the antirust coating of the PC strand but capable of manifesting a sufficient adhesion strength with a concrete and to provide a method for processing the same. SOLUTION: This method for processing an antirust coated prestressing (PC) strand, consists of a process of preliminary heating a PC strand for the antirust coating, a primary compression extruding process for compressing the preliminary heated PC strand with a cross head type first extruding molder for filling an antirust material consisting of a thermoplastic resin to an outer peripheral surface O of the PC strand 1 and in inside gaps G, a forming process for forming a primary coated layer I by passing the above coated layer through a rotary forming die, a secondary extrusion molding process for forming a cylindrical secondary coated layer II installed with many small projected strip parts 6 with the antirust material by passing the outer peripheral surface of the primary coated layer I through a secondary extrusion molder, a cooling process for solidifying both coated layers I, II by cooling, and a coating process for forming a tertiary coated layer III by filling a cement miscible type coating material in valley parts of the small projecting strips on the surface of the secondary coated layer II with a coating device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention, when used mainly as a stress-introducing material for prestressed concrete (hereinafter referred to as "PC concrete"), has enhanced adhesion to concrete and solidifying grout. The present invention relates to a rust-proof coated PC strand having a high adhesive force and a method for processing the same.

[0002]

2. Description of the Related Art Conventionally, a PC strand is inserted into a steel sheath buried in a concrete and tensioned, and thereafter, a grout material such as cement milk is filled in the sheath and integrated with concrete to form a post tension bond method. Furthermore, a PC strand is pre-tensioned without using a sheath, embedded in concrete, and after solidification of the concrete, the end is cut off.

[0003] In these methods, the PC strand is in direct contact with the concrete, and the water reaches the PC strand through the concrete, thus lacking in rust prevention performance.

[0004] In recent years, there has been developed a type in which the outer surface of a PC strand is coated with a synthetic resin. Low adhesion. To solve this,
In the post-tension bond method, a grout material mixed with an expanding material is used to increase the adhesion of the PC strand to the rust-preventive layer, or the surface of the rust-preventive coating material of the PC strand is sanded before solidification. In some cases, a solid material is sprayed or a solid material is mixed in the rust preventive coating material in advance to improve the adhesion of the rust preventive PC strand itself to the concrete.

[0005] However, as described above, mixing the expanding material with the grout material is very difficult and time-consuming work at the work site, and purchasing the mixed grout material increases the cost and raises the problem. Has become.

Further, if a projection made of a solid material such as sand is present on the surface of the PC strand, it comes into contact with the inner surface of the sheath during a tensioning operation, so that the frictional force is increased and the workability is deteriorated. There is a problem such as damage to the rust-preventive coating.

[0007]

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention does not deteriorate the workability during tensioning work or damage the rust preventive coating of the PC strand, and provides a sufficient concrete. The purpose of the present invention is to provide a rust-proof coated PC strand exhibiting an adhesive force and a method of processing the same.

[0008]

In order to solve the above-mentioned conventional problems, a rust-proof coated PC strand having a high adhesive force according to the present invention is provided inside a PC strand formed by twisting a plurality of single strands. A primary coating layer having a spiral groove formed by coating the voids and the outer peripheral surface with a rust inhibitor made of a thermoplastic synthetic resin, and a surface coated with the rust inhibitor made of a thermoplastic synthetic resin on the outer peripheral surface of the primary coating layer. A cylindrical secondary coating layer provided with a large number of small ridges, and a tertiary coating layer formed by filling a cement-mixing type paint in the valleys of the small ridges on the surface of the secondary coating layer. It is constituted so that it consists of.

Further, the processing method of the present invention comprises a step of preheating the PC strand and a step of pressurizing the preheated PC strand with a crosshead type first extruder to extend the thermoplastic strand to the outer peripheral surface and the internal space of the PC strand. A primary pressure extrusion step of filling and coating a rust preventive material made of resin, and forming the primary coating layer having a spiral groove on the outer peripheral surface by passing the coating layer after the pressure extrusion step through a rotary molding die. Process, the outer peripheral surface of the primary coating layer is passed through a crosshead type second extruder equipped with a forming die having a large number of small concave streaks on the inner surface, and a large number of rustproof materials made of thermoplastic synthetic resin are applied to the surface. A secondary extrusion forming step of forming a cylindrical secondary coating layer provided with a small ridge, and a cooling step of cooling and solidifying both coating layers,
A coating step of coating a valley of a small ridge on the surface of the secondary coating layer after cooling with a coating machine with a cement-mixing type paint to form a filled tertiary coating layer. is there.

[0010] The rust-proof coated PC strand according to the present invention comprises:
With the above configuration, when embedded in a concrete or solidifying grout material, a primary coating layer having a spiral groove is formed so that the outer peripheral surface corresponds to the spiral shape of the PC strand instead of the cylindrical shape. I have. Therefore, the concrete or grout material is fitted into the spiral groove, thereby preventing the PC strand from moving in the axial direction, and the outer peripheral surface of the primary coating layer has a large number of small ridges on its surface. , Which enhances the fitting. Furthermore, since the tertiary coating layer filled with the cement-mixing type paint is formed in the valleys of the small ridges on the surface of the secondary coating layer, it can be more firmly adhered to the concrete. If the small ridge is provided in a direction intersecting the spiral direction of the spiral groove, the phenomenon that the PC strand is twisted and slipped along the spiral groove can be prevented, so that a higher adhesive force can be obtained. preferable.

In the method of forming a roughened layer on the outermost surface, if a filler such as sand-like particles is used as it is, it is poorly familiar and may damage the underlying coating layer, thereby deteriorating the rust prevention. Is not preferred. In this regard, the tertiary coating layer filled in the valleys of the small ridges of the present invention was coated using a coating material using a polymer material in which aggregate and cement were previously mixed. It has good familiarity and does not have to worry about lowering rust prevention.

In the processing method according to the present invention,
Since the molten rust preventive material is filled under pressure by passing the PC strand through the crosshead of the primary pressure extrusion process, the resin enters the internal gap from the gap between the individual strands of the PC strand. Will be filled. At this time, a rust preventive material having a thickness greater than the required thickness once adheres to the outer peripheral surface, but is passed through a rotary forming die in the next forming step to remove extra rust preventive material. It is formed into a shape having a spiral groove corresponding to the spiral groove of the PC strand. Next, by passing through a cross head in a secondary extrusion molding process, a cylindrical die having a large number of small convex ridges on the surface is formed by a molding die having a large number of small concaves on an inner surface attached to the tip thereof. A next coating layer is formed. In addition, in the painting process, the coating of cement-mixed type is applied by a coating machine on the small ridges on the surface, and a filled tertiary coating layer is formed. You. It is preferable that the forming die having a large number of small ridges on the inner surface be rotatable, since the small ridges can be provided also in the direction intersecting the spiral direction of the PC strand.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail based on embodiments. 1 to 3 show an embodiment of a rust-proof coated PC strand according to the present invention. 1 is a PC strand and 2 is a rust preventive. P
The C strand 1 is configured by twisting side wires 4,..., 4 which are six single wires, around the outer periphery of a core wire 3 which is a single wire. The rust preventive material 2 also covers the inner space G of the PC strand 1 and covers the outer circumference O of the core wire 3 and the side wire 4. The outer circumference O is a spiral groove D of the PC strand 1,
, D, the primary coating layer I having the corresponding spiral groove portions 5,..., 5 is formed. In this embodiment, a polyethylene resin is used as the material of the rust preventive material 2. In addition to this, in addition to a polypropylene resin or a copolymer of polyethylene and polypropylene and a modified product thereof, a nylon resin, vinyl chloride, etc. Can be used.

The outer peripheral surface of the primary coating layer I is a cylindrical secondary coating layer II similarly covered with a rust preventive material 12 made of a thermoplastic synthetic resin. A large number of small ridges 6,..., 6 are provided on the surface of the secondary coating layer II.

In the embodiment shown in FIG. 2, the small ridges 6,..., 6 are provided in a straight line along the axial direction B of the PC strand 1 so as not to intersect the helical grooves 5. ing. However, as in the other embodiment shown in FIG.
, 15 in a spiral direction C opposite to the spiral direction S, that is, in a direction intersecting the concave grooves 15,.
.., 16 can be provided, so that sliding due to torsion can be prevented, but of course, it can also be provided in various other directions.

The valley 1 of the small ridge on the surface of the secondary coating layer II
3. Tertiary deposited layer I filled with cement-mixed paint 7
II. The PC strand 8 of the rustproof coating is composed of the three layers as described above. In addition, the PC strand 1 may be a multi-strand such as a three-strand without using a core wire or a 19-twist such as a 19-strand in which side wires are twisted in a multiplex arrangement around a core wire, in addition to the above-described seven-strand. Can also be used.

Next, an embodiment of the processing method of the present invention will be described with reference to FIGS. FIG. 5 is a schematic diagram of one embodiment according to the method of the present invention. The PC strand 1 before the rust prevention coating is wound around a reel 21 and placed on a feeding device 22. Then, the leading end thereof is passed through a feeding device 23, a heating device 24, a crosshead type first synthetic resin extruder 25, a rotary molding die 26, a crosshead type second synthetic resin extruder 27, and a cooling device. It is passed through a device 28 and further passed through a coater 29, a dryer 30 and a take-up device 31, and is wound up on a reel 33 of a winder 32.

The first heating device 24 preheats the PC strand 1 to a temperature slightly higher than the melting temperature of the synthetic resin, and is a preheating step for improving the adhesiveness. The PC strand 1 is passed through the crosshead type first extruder 25 while maintaining the preheated temperature.

As shown in FIG. 6, in the first extruder 25, an auxiliary pressing head 35 is connected to a tip of a crosshead 34, and a forming die 36 is attached to the tip. A heater 37 is disposed on the outer periphery of the auxiliary pressurizing head 35 and heats the resin to a temperature at which the molten state of the resin inside is maintained. However, when the thermoplastic synthetic resin to be used is an amorphous polymer having a low molecular weight, heating is not required.

In the first extruder 25 of the crosshead type through which the PC strand 1 after the preheating step is passed, the rust preventive material 2 made of a thermoplastic synthetic resin, which is heated and extruded into the crosshead 34, is subjected to auxiliary pressing. The PC strand 1 enters the head 35 and passes through the forming die 36 attached to the tip thereof.
Are filled and covered. At this time, in the auxiliary pressure head 35, the resin pressure is pressed to a certain level or more. By this pressing, the rust preventive material 2 penetrates not only into the outer periphery O of the PC strand 1 but also through the gaps between the side wires 4,. The internal gap G around the core wire 3 is also filled, so that the outer circumference of the core wire 3 is completely covered. This is the primary pressure extrusion step of the present invention.

The PC strand 1 after the pressure extrusion step enters the rotary forming die 26 next. The rotary molding die 26
Is supported rotatably R ₁ with respect to the holder 40 as shown in FIG. 6, heat - is adapted to be heated by the motor 41. As shown in FIG.
It conforms to the outer shape of the C strand 1.

As shown in FIG.
Is about 0.1 to 0.2 mm larger than the outer shape of the PC strand 1 and is helical in the axial direction B of FIG. 2, and therefore has a cross section equivalent to a cloverleaf 42 having concave grooves 5,. Is made of In the rotary molding die 26,
By being pressed and extruded in the auxiliary pressurizing head 35, the raised portion of the rust preventive material 2 is scraped off, and as shown in FIG. It is formed so as to leave a rust preventive material 2 having a thickness of 0.2 mm. This is the molding step of the present invention, and the primary coating layer I of the present invention is thus formed.

The PC strand 1 coated with the primary coating layer I subsequently enters a crosshead type second extruder 27. As shown in FIG. 9, the second extruder 27 is an ordinary crosshead type extruder for a synthetic resin having no auxiliary pressurizing head. A forming die 43 as shown in FIG. 10 is attached to the tip. The forming die 43 is
.., 44 on its inner surface. Below the rear end of the crosshead 45,
A decompression device for depressurizing the inside by the vacuum pump 46 is connected to improve the close contact with the primary coating layer I.

In the second extruder 27, while the rust preventive material 2 is left thin in the molten state on the outer peripheral surface, the molten rust preventive material 47 is covered on the outside in a cylindrical shape. At this time, since the inner side is decompressed, the rust preventive material 47 adheres to the rust preventive material 2 of the primary coating layer and is integrally coated. Also, a cylindrical molten rust preventive material 47
The small convex stripes 6,..., 6 of FIG.

When the forming die 43 is fixed, the small ridges 6 are formed continuously in the axial direction of the PC strand 1 as shown in FIG. This is FIG.
In the case of the embodiment as shown, the molding die 143 is attached to the turnable R ₂ with respect to the crosshead 145, mode - if such force rotated by motor 100, to adjust the rotational speed Thus, as shown in FIG. 4, it is possible to form the small ridges 16,..., 16 in the direction intersecting the helical grooves 15,. This is the secondary extrusion molding step of the present invention,
Thus, the secondary coating layer II of the present invention is formed.

In this way, the small ridges 6,.
The secondary coating layer II coated with the tubular rust preventive material 47 having 6, 16,..., 16 is then passed through the cooling device 28 to cool and solidify the two rust preventive materials 2, 47. This is the cooling step of the present invention.

After cooling, the secondary coating layer II is sent to the next coating step, and its surface is coated with a cement mixing type paint by a coating machine 29 using small ridges 6,..., 6, 16,. , 16 are coated and filled to form a tertiary deposition layer III. For this coating, any ordinary coating method such as air spraying and dip coating can be used. The coating material was a coating material 7 in which cement and silica sand were mixed with an acrylic acid ester emulsion-based base material.
M401 Coat "(trademark), which has been adjusted to a viscosity suitable for painting and exhibits excellent adhesion to concrete. In this embodiment, the mixing ratio of AM401 to cement and silica sand is used. Was 1: 1.2: 0.4.

Next to the coating machine 29, a drying machine 30 is provided. This is because it is necessary to dry the coating at about 80 ° C. for about 3 minutes because the coating is an aqueous emulsion and an alkali reaction type. The PC strand 8 of the rust-proof coating thus produced is composed of the primary coating layer I and the secondary coating layer I.
I, is coated with three layers of the tertiary deposition layer III, the surface of which is filled with a cement-mixed paint at the valleys of the small ridges,
This is wound on a reel 33 by a winder 32.

[0029]

The rust-preventive coated PC strand of the present invention has very good adhesion to concrete. In addition, the concrete member can have a desired bending strength,
Further, the rust-preventive coating of the PC strand is not damaged, so that the rust-preventive force does not decrease. Further, the workability at the time of the tension work is not deteriorated at all.

[0030] The processing method of the present invention can also be applied to pressurizing an extruder in a conventional rust preventive coating processing line, rotating a forming die, providing a concave groove on the inner surface of the forming die, forming a coating step. Add a coating machine and a dryer to the
By appropriately combining these, it is possible for the first time to process a rust-preventive coated PC strand having a three-layer structure, which has an unprecedented high adhesive force.

[Brief description of the drawings]

FIG. 1 is a cut end view showing one embodiment of a rust-proof coated PC strand having a high adhesive force according to the present invention.

FIG. 2 is a side view in which a lower half of FIG. 1 is omitted.

FIG. 3 is a partially enlarged cut end view of FIG. 1;

FIG. 4 is a side view of another embodiment of the rust-proof coated PC strand having a high adhesive force according to the present invention, in which a lower half is omitted.

FIG. 5 is a schematic side view showing an embodiment in which apparatuses of the steps of the processing method according to the present invention are connected.

FIG. 6 is an enlarged cross-sectional view showing one embodiment around the crosshead of the first extruder of the present invention.

FIG. 7 is a cut end view showing one embodiment of a rotary molding die used in the first extruder of FIG. 6;

FIG. 8 is a cut end view of a PC strand showing a primary coating layer after a shaping step of the present invention.

FIG. 9 is an enlarged cross-sectional view showing one embodiment around the crosshead of the second extruder of the present invention.

FIG. 10 is a cut end view showing one embodiment of a forming die used in the second extruder of FIG. 9;

FIG. 11 is an enlarged sectional view showing another embodiment around the forming dies of the second extruder of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 PC strand 2 Rust prevention material 3 PC strand core wire 4 PC strand side line 5 Concave groove part 6 Small convex part 7 Cement admixture type paint 8 PC strand of rust prevention coating 12 Rust prevention material 13 Small convex part valley part 15 Groove 16 Small ridge 21 Reel 22 Feeding device 23 Feeding device 24 Heating device 25 First extruder 26 Rotary forming die 27 Second extruder 28 Cooling device 29 Painter 30 Dryer 31 Puller 32 Winding machine 33 Reel 34 Cross head 35 Auxiliary pressurizing head 36 Forming die 37 Heater 40 Holder 41 Heater 42 Sectional shape of forming auxiliary die 43 Forming die 44 Small concave streak 45 Cross head 46 Vacuum pump 47 Prevention Rust material 100 Motor 143 Forming die 145 Cross head B PC strand axial direction C PC strand Internal voids O PC strand outer peripheral R ₁ rotation of the forming die R ₂ forming die S PC strand helical direction I primary coating layer II secondary coating layer III of the groove G PC strand helix opposite to the direction D PC strand Tertiary deposition layer

Claims (2)

[Claims] 1. A primary coating layer having a spiral concave groove in which an inner space and an outer peripheral surface of a PC strand in which a plurality of single strands are twisted are coated with a rust preventive material made of a thermoplastic synthetic resin, and the primary coating layer. A cylindrical secondary coating layer provided with a number of small ridges on the surface of which the outer peripheral surface is coated with a rust preventive material made of a thermoplastic synthetic resin, and valleys of the small ridges on the surface of the secondary coating layer A rust-preventive coated PC strand having a high adhesive force, characterized by comprising a tertiary coating layer formed by filling a cement-mixable coating material with a tertiary coating. 2. A step of preheating a PC strand, and pressurizing the preheated PC strand with a crosshead type first extruder to form a rust preventive material made of a thermoplastic synthetic resin up to an outer peripheral surface and an inner space of the PC strand. A primary pressure extrusion step of filling and coating; a molding step of passing the coating layer after the pressure extrusion step through a rotary molding die to form a primary coating layer having a spiral groove on the outer peripheral surface; The outer peripheral surface was passed through a crosshead type second extruder equipped with a forming die having a large number of small concave stripes on the inner surface, and a number of small convex stripes were provided on the surface with a rust preventive material made of thermoplastic synthetic resin. A secondary extrusion forming step of forming a cylindrical secondary coating layer, a cooling step of cooling and solidifying both coating layers, and cement mixing into the valleys of the small ridges on the surface of the cooled secondary coating layer. Form a tertiary coating layer painted and filled with mold paint A method for processing a rust-proof coated PC strand having a high adhesive force, comprising a coating step of forming a coating.