JP2003055966A - Preparation method of prestressed concrete pile member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To quickly and easily provide a high-strength prestressed concrete pile product having a higher strength from a relatively low-strength prestressed concrete pile product mass-produced and largely stocked. SOLUTION: An unused high-strength prestressed concrete pile material is reinforced by adhesively winding a high-strength fiber sheet impregnated with an adhesive resin on the cylindrical circumferential surface thereof, whereby a fiber-reinforced high-strength prestressed concrete pile member enhanced in strength is provided. The high-strength fiber includes, for example, aramid fiber, and the impregnating adhesive resin includes, for example, epoxy resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for procuring fiber-reinforced high-strength prestressed concrete pile material obtained by reinforcing unused prestressed concrete pile material with high-strength fibers. More specifically, it is a material of a plurality of grades with different strengths developed and produced for construction and civil engineering, for example, JIS A5373 standard product.
Among high-strength prestressed concrete pile materials, a relatively low-grade mass-produced stock product is used as a starting material, and by reinforcing this with high-strength fibers, the same performance, that is, strength physical properties, as a high-grade small-volume custom-made product is obtained. The present invention relates to a method of procuring a high-strength prestressed concrete pile material, which has the following features, and a pile material produced in this way.

[0002]

2. Description of the Related Art Concrete piles of various strengths and shapes have been provided as concrete piles that are driven in and embedded in buildings such as buildings and bridge piers and foundation works for civil engineering. For example JI
A prestressed concrete pile material that is compatible with the high-strength prestressed concrete pile specified in S A5373 has been developed, and is classified into Category A (hereinafter abbreviated as A type),
There are a section B (hereinafter abbreviated as B type) and a section C (hereinafter abbreviated as C type). These piles have a hollow cylindrical shape, and there are various types of product lineups having different outer diameters, thicknesses, and lengths for each of the A, B, and C types. Such high-strength prestressed piles (abbreviated as PHC piles) are the most standard, but other than that, they have a thick PH at the bottom.
ST pilings which are C piles, PHC pilings which are knotted PHC piles and PRC pilings which are pilings using deformed reinforcing bars are known, and ST pilings and knottings are each of type A,
Classified into B type and C type, PRC piles are I type, II type
It is classified into species, III, IV and V.

[0003] Explaining the examples of the above-mentioned A type, B type and C type, in the three types of high-strength prestressed concrete pile materials, the production amount of them is 70% of the A type having relatively low strength physical properties. The next-highest class B is 2
The C type, which has the highest strength, occupies only 10%, but the A type is a prospective production and has a large inventory,
B and C are made to order. In such an industrial situation, if there is a case where a design change or specification change is often required during the construction work, and for example, there is a case where the type A is changed to the type B or the type C, the inventory quantity of them is small, and it is immediately I couldn't make it in time, and I had no choice but to let someone else in my industry take advantage of it, or if that was not possible, it would hinder the continuation of the construction. PR
The same applies to types I to V related to C piles. It is unavoidable that there will be a discrepancy between the stock amount of such production amount and the actual required amount as far as the estimated production is concerned, but it is a large and heavy material or an expensive material. In terms of cost and storage location, the production of sucrose tends to be limited in quantity, and it is inherently extremely difficult to eliminate such discrepancy early.

However, if a mass-produced grade A product is used as a starting material, a higher grade B product can be obtained.
If it can be easily transformed into a product with the same physical properties as those of the type C or C type product, it will be possible to respond quickly to changes in specifications, and if only the type A product is exclusively mass-produced, the B It becomes possible to procure C and C type substitutes from it, and as a result, it is possible to narrow down the product types from a large variety to a smaller variety, which improves efficiency and shortens the period for civil engineering and construction work, which is extremely convenient. Is.

[0005]

In view of the existing state of the existing high-strength prestressed concrete pile product lineups and the current state of the art, the present inventor has found that products having relatively low-grade strength physical properties are changed to high-grade products. As a result of various researches and searches for a concrete pile material having the above-mentioned strength physical properties, a weight increase is achieved by adopting an approach of further fiber-reinforcing the existing low grade pile material such as Class A high-strength prestressed concrete pile material. The present inventors have completed the present invention by discovering that the physical properties of the concrete can be increased with almost no increase in the strength, and that a concrete pile material equivalent to a higher grade concrete pile material such as B type or C type can be obtained. Therefore, it is an object of the present invention to enable existing mass-produced, high-stock, relatively low-grade, high-strength prestressed concrete pile materials to be easily upgraded in response to design changes and specification changes. Therefore, it is to provide a method for easily procuring a higher-grade, high-strength prestressed concrete pile material that can meet all construction conditions. Conventionally, such a problem did not exist at all.

[0006]

Means for Solving the Problems The inventors of the present invention have made earnest studies in search of means for efficiently solving the above new problems. As a result, they have found that the above problems can be solved by attaching a high-strength fiber sheet to the outer periphery of an unused prestressed concrete pile. As a result of further studies, the present inventors have carried out a treatment for smoothing the outer peripheral surface of an unused prestressed concrete pile, preferably a grinder treatment, a sandblast treatment, a high-pressure water washing treatment, etc., and then a smooth treatment. The outer peripheral surface, which has become a uniform surface, is preferably treated with a primer resin, and then a high-strength fiber impregnated with an adhesive resin, preferably a high-strength fiber sheet, is attached to the outer peripheral surface to firmly bond the high-strength fiber to the concrete surface. It is found that the above-mentioned problems are fixed and that the above-mentioned problems are quickly and simply achieved, and that the strength properties of the high-strength prestressed concrete pile thus obtained are excellent, and the present invention is further studied. completed.

That is, the present invention is: (1) a method of procuring a prestressed concrete of higher strength by attaching a high-strength fiber sheet to the outer periphery of the prestressed concrete pile, and (2) polishing the outer peripheral surface of the prestressed concrete pile. Then, a method of converting into a higher strength prestressed concrete pile material, characterized in that high-strength fiber is attached to the outer peripheral surface together with the adhesive resin, (3) The outer peripheral surface of the prestressed concrete pile is subjected to polishing treatment, and then the adhesive resin Pre-stressed concrete pile material that has been strengthened by attaching high-strength fibers to the outer peripheral surface together with (4) high-strength fibers are para-aramid fibers, carbon fibers, wholly aromatic polyester fibers, glass fibers and polyparaphenylene benzo. From bisoxazole fiber The high-strength prestressed concrete pile material according to (1) above, which is at least one fiber selected from the group consisting of: (5) the adhesive resin is a thermosetting resin; )
The present invention relates to a high-strength prestressed concrete pile material.

Further, the present invention provides (6) unused JIS
The outer surface of the prestressed concrete pile belonging to category A specified in A5373 is preferably flattened, and then high strength fibers impregnated with an adhesive resin are attached to the outer surface.
The prestressed concrete pile of Category A specified in 3 is procured a high-strength prestressed concrete pile material having the physical properties of Category B or C specified in JIS A5373, (7) Unused JIS
The outer peripheral surface of the prestressed concrete pile belonging to Category A specified in A5373 is preferably grinder, sandblasted or water jet treated, primer resin treated, and then a high strength fiber impregnated with an adhesive resin is attached to the outer peripheral surface. J characterized by
Method for converting pre-stressed concrete piles of Category A specified in IS A5373 to pre-stressed concrete pile materials having strength properties of Category B or Class C specified in JIS A5373, (8) Prescribed in unused JIS A5373 The outer peripheral surface of the prestressed concrete pile to be treated is preferably treated with a grinder and a primer resin, and then a high strength fiber impregnated with an adhesive resin is attached to the outer peripheral surface according to JIS.
A high-strength prestressed concrete pile characterized by having enhanced strength physical properties specified in A5373, (9) Prestressed concrete pile is JIS
A reinforced high-strength prestressed concrete pile material that belongs to Class A specified in A5373 is JIS A53.
The high-strength prestressed concrete pile according to (8) above, which has strength physical properties of B type or C type specified in No. 73.

[0009]

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, a relatively low grade prestressed concrete pile can be changed to the strength physical properties of a higher grade prestressed concrete pile. The change is illustrated below. (I) PHC pile of type A → PHC pile of type B or C (ii) ST pile of type A → ST pile of type B or C (iii) Section pile of type A → Section of type B or C Pile (iv) Type I PRC pile → Type II, III, IV or V
PRC pile of type (v) PRC pile of type A → PRC pile of type I, type II, type III, type IV or type V A preferred embodiment of the present invention is a treatment for smoothing the outer peripheral surface of a prestressed concrete pile. , The smoothed outer peripheral surface is preferably treated with a primer resin, and a high-strength fiber cloth or string-like material impregnated with an adhesive resin is wound around the outer peripheral surface to obtain, for example, compressive strength, bending strength, axial bending strength, and shear strength. It is a high-strength prestressed concrete pile in which at least one strength physical property such as strength is reinforced. Examples of the treatment means for smoothing the outer peripheral surface of the prestressed concrete pile as a preferred embodiment include a grinder treatment, a sandblast treatment, and a high-pressure water washing treatment. Furthermore, a preferred embodiment of the present invention is that the outer peripheral surface of the prestressed concrete pile belonging to Class A specified in JIS A5373 is treated with a grinder, and then the outer peripheral surface is treated with a primer resin to impregnate the adhesive resin with high strength. By winding a fiber cloth or string on the outer peripheral surface, J
It is carried out by producing a high-strength prestressed concrete pile material having physical properties of B type or C type specified in IS A5373. According to JIS A5373, prestressed concrete piles are classified by outer diameter,
For each category, A according to the difference in the strength of physical properties
It is classified into species, species B, and species C. The physical properties are strengthened in the order of A type, B type, and C type. The following is an excerpt from the JIS standard. The prestressed concrete pile and the high-strength pressed pile of the present invention include the JIS standard PHC pile. J
Taking IS A5373 as an example, the strength physical properties of the present invention such as compressive strength, bending strength, axial bending strength, shear strength, etc. will be explained and the measuring method of those strength physical properties will be shown.

Annex 5 (normative) Prestressed concrete pile 1. Scope This Annex specifies pre-tensioning high-strength prestressed concrete piles (hereinafter referred to as PHC piles) in which the compressive strength of concrete produced by applying centrifugal force is 78.5 N / mm ² or more.

2. Type PHC piles are 300 mm, 350 mm, 400 mm, depending on the outer diameter.
450 mm, 500 mm, 600 mm, 700 mm, 800 mm, 900 mm, 100
It is divided into 0 mm, 1100 mm and 1200 mm, and depending on the size of effective prestress, A type, B type and C type (hereinafter,
Called A, B and C respectively. ). Note that P
The effective prestress of HC piles A, B and C are
3.92 N / mm ² , 7.85 N / mm ² and 9.81 N / mm ² . The effective prestress is obtained by calculation, and the calculated value is within ± 5% of each value.

3. Performance 3.1 Compressive strength Concrete shall be subjected to the compressive strength test specified in 6.1 and shall be at least 78.5 N / mm ² . 3.2 Bending strength The bending strength of the PHC pile body is 6.
When the bending strength test specified in 2 is carried out and the crack bending moment shown in Table 1 of Annex 5 (Table 1 below) is applied, no crack should occur. The breaking bending moment must be at least the value shown in Table 1 of Annex 5.

[0013]

[Table 1]

3.3 Axial force bending strength The axial force bending strength of the PHC pile body is as follows. a) As a general rule, the PHC piles with the following representative outer diameters were subjected to the axial bending strength test specified in 6.3, and the crack bending moment shown in Table 2 (Table 2) of Annex 5 was added. Sometimes cracks should not occur.
However, in this case, the length of the PHC pile should be 8 m or more. The breaking bending moment must be equal to or greater than the value shown in Annex 5, Table 2. 1) Typical outer diameter for those with an outer diameter of 300 to 600 mm
400 mm 2) For items with an outside diameter of 700 to 1200 mm, a typical outside diameter is 800 mm. b) The axial bending strength of the PHC pile body when the test cannot be performed with the representative outer diameter specified in a) is shown in Annex 5 Table 3 (Tables 3 and 4 below).

[0015]

[Table 2]

[0016]

[Table 3]

[0017]

[Table 4]

3.4 Shear strength The shear strength of the PHC pile body is as follows. a) As a general rule, the PHC pile main body shall be subjected to the shear strength test specified in 6.4 for the following representative outer diameters.
When a load equivalent to the shear strength shown in Annex 5 Table 4 (Table 5 below) is applied, no cracks should occur. 1) Typical outer diameter for those with an outer diameter of 300 to 600 mm
400 mm 2) For items with an outside diameter of 700 to 1200 mm, a typical outside diameter is 800 mm. b) The shear strength of the PHC pile main body when the test cannot be performed with the representative outer diameter specified in a) is shown in Annex 5 Table 5 (Table 6 below).

[0019]

[Table 5]

[0020]

[Table 6]

3.5 Bending Strength of Joint Section The bending strength of the joint section must be greater than or equal to the breaking bending moment of the bending strength of the main body specified in 3.2.

6. Test method 6.1 Compressive strength test In the compressive strength test, the same curing as that of the product is performed, and the specimen that has been subjected to predetermined curing is used.
According to A1136.

6.2 Bending Strength Test The bending strength test is
Do the following: Remarks The bending strength test shall be performed using a tester of grade 1 or higher specified in JIS B7733 or a tester with a tolerance equal to or higher than this. a) In the bending strength test of the main body, as shown in Annex 5 Fig. 2 (Fig. 1 below), 3/5 of the length of the PHC pile is supported as a span, and Annex 5 Table 1 (above table) at the center of the span. 1)
The load P corresponding to the crack moment shown in is applied to check for cracks. If there is a possibility that local damage will occur at the loading point or fulcrum before the PHC pile breaks in bending, measures will be taken. Load P
Is calculated by the following formula.

[0024]

[Equation 1]

B) The breaking bending moment is calculated from the maximum value of the load (P) shown until the PHC pile breaks according to the formula specified in a). C) The bending strength test of the joint is performed at the center of the span. Align the joints of the joints and perform as in a).

[0026]

[Table 7]

6.3 Axial Force Bending Strength Test (Positive and Negative Alternating Repeated Axial Force Bending Strength Test) The axial force bending strength test is carried out as follows: Remark: The bending strength test is a grade 1 or higher tester specified in JIS B7733 or Use a tester with a tolerance equal to or greater than this. a) The axial force bending strength test of the main body was carried out using the PHC pile to which the axial force N was applied, as shown in FIG.
₁ as a span, and Annex 5 Table 2 in the center of the span
A load P corresponding to the crack bending moment shown in (Table 2 above) is applied to check for the presence of cracks. In addition,
If there is a possibility that local damage will occur at the loading point or fulcrum before the PHC pile breaks in bending, measures will be taken.

The load P is calculated by the following equation.

[Equation 2]

B) The axial force N, the load P, and the number of positive / negative alternating repetitions must satisfy the following conditions. 1) The axial force N must be kept constant until the completion of the test. 2) Axial force N is N ₁ , N ₂ , and N shown in Annex 5 Table 2 (above Table 2) or Annex 5 Table 3 (above Tables 3 and 4).
_There are 3 levels. 3) The cyclic load P is a value that produces 1 / 1.2 of each of the crack bending moment and the breaking bending moment in the state where the axial force N is applied, and the number of repetitions is 1
0 cycles or more. It should be noted that one cycle of positive and negative is one cycle. c) The breaking bending moment is
The PHC pile applies a load P, and it is calculated from the maximum value of the load P shown until the PHC pile breaks according to the formula defined in a).

6.4 Shear Strength Test The shear strength test of the main body is carried out by the method shown in Annex 5 FIG. 4 (FIG. 3 below), Annex 5 Table 4 (above Table 5) and Annex 5 Table 5 (above table). The load P _c corresponding to the shear strength shown in 6) is applied, and the presence or absence of oblique tensile cracks in the shear span is examined. Remarks The bending strength test shall be performed using a tester of grade 1 or higher specified in JIS B7733 or a tester with a tolerance equal to or higher than this. If there is a possibility that local damage will occur at the loading point or fulcrum before the PHC pile breaks shear, take measures. The load P _c is
It is calculated by the following formula.

[0031]

[Equation 3]

According to the present invention, a prestressed concrete pile of, for example, type A is used as a type B or C type JI.
It can be tailored to a higher-strength prestressed concrete pile having the strength properties specified in the S standard. In addition, according to the present invention, for example, a prestressed concrete pile of type B may be processed into a prestressed concrete pile having physical properties of higher strength defined as type C. Any type of virgin concrete pile product used in the present invention may be manufactured by known methods. Usually, between the inner and outer concentric cylindrical molds, PC steel rods are arranged in the axial direction, spiral streaks are arranged in the circumferential direction, and after pouring fresh concrete, centrifugal molding is performed while rotating at high speed to solidify. Manufactured.

A preferred embodiment of the invention is carried out as follows. The cylindrical outer peripheral surface of this relatively low-grade prestressed concrete pile material is preferably surface-treated before the high-strength fiber sheet is attached (before the impregnation adhesive is applied). That is, after removing fine irregularities and dirt on the concrete surface with a grinder or the like, after confirming the drying of the concrete surface, for example as a primer, a low viscosity room temperature curing type epoxy resin (viscosity
5,000 mPa ・ s / 20 ° C or less) with a roller, brush, etc.,
Then, it is preferable that the steps and the like be finished flat by using an unevenness adjusting material such as an epoxy putty. The amount of primer resin used is usually 0.1 to 0.3 kg / m ^{2, although} it depends on the surface condition. The type of resin used in the primer treatment is preferably the same as that of the impregnated adhesive resin. The grinder may be, for example, a buffing grinder. The grinder treatment is performed to remove dirt on the concrete surface or a weak layer on the surface, and may be performed by sandblasting or high-pressure water washing (jet water) instead of the grinder. Any of these may be performed according to known methods. It may be omitted if there is no brittle layer on the outer peripheral surface of the concrete pile.

As a desired constituent feature of the present invention, the cylindrical outer peripheral surface of the surface-treated prestressed concrete pile material is coated with a high-strength fiber sheet immediately after applying an impregnating adhesive resin, and wound up. Examples of the high-strength fiber as the reinforcing fiber used in the present invention include aramid fiber, for example, polyparaphenylene terephthalamide (manufactured by Toray DuPont Co., Ltd., trade name: Kevlar); carbon fiber, glass fiber, etc., wholly aromatic polyester. Fiber: Polyparaphenylene benzobisoxazole fiber and the like can be mentioned. In particular, aramid fiber is excellent in all properties such as light weight, high strength, flexibility, non-conductivity, durability, heat resistance, cold resistance, water resistance, chemical resistance, toughness, impact resistance, cut resistance, etc. It is excellent and is preferable.

Examples of the adhesive resin applied to the outer peripheral surface of the prestressed concrete pile or impregnated with the high-strength fiber cloth or string-like material wound around the surface of the prestressed concrete pile include epoxy resin, methacrylate resin, unsaturated polyester resin or Thermosetting resins such as vinyl ester resin and urea urethane resin may be mentioned. An epoxy resin is preferable for the aramid fiber, and a room temperature curable epoxy resin having a viscosity higher than that of the primer (viscosity 7,000 to 100,000 mPa · s / 20 ° C.,
A specific gravity of 1.0 to 1.3) is used. The standard amount used in this case depends on the type of fiber, but in the case of undercoating, 0.2 to 1.5 kg
/ m ² and 0.2 to 0.5 kg / m ² for the topcoat (total range of 0.5 to 2.0 kg / m ² ).

After undercoating the impregnated adhesive resin, a high-strength fiber sheet is attached to the outer peripheral surface of the piling material and wound up, but at that time, a defoaming roller or a rubber spatula is used so that air pockets do not remain. It is desirable to apply it while squeezing. After confirming that the undercoat resin is sufficiently impregnated,
Further, a top coat of the impregnated adhesive resin is similarly applied thereon. Finally, it is preferable to cover the impregnated resin with a vinyl sheet or the like for curing. In some cases, the fiber-reinforced prestressed concrete pile to which a high-strength fiber sheet is attached and wound up may be further finished with a resin coating material or the like in order to protect it from external force at the time of embedding. The high-strength fiber sheet may be a woven or knitted fabric of high-strength fibers. Examples of the woven fabric include plain weave and twill weave. A string-like material may be used as an equivalent to the high strength fiber sheet. The string-like material is preferably a cord-made material. Further, the high-strength fiber sheet may have a narrow tape-shaped band. For the pasting work, for example, the device described in JP-A-9-268775 may be used.

[0037]

The present invention will be described in more detail with reference to the following examples.

Example 1 Effective prestress amount of about 3.92 N / mm ² , outer diameter of 300 mm, thickness of 60
0.2 kg of room temperature curing type epoxy resin primer (Sumitomo Rubber Industries, Ltd. product name: GB30) to high strength concrete pile material Class A (manufactured by Hoshu Pile Co., Ltd., Ube US Pile-PHC) with a length of 10 mm and a length of 10 mm. / After applying on square meters, the same room temperature curing type epoxy resin (trade name: GB35 manufactured by Sumitomo Rubber Industries, Ltd.) as an impregnating adhesive is evenly applied on the outer peripheral surface with a roller, and then immediately aramid fiber sheet (Toray DuPont A unidirectional sheet using Kevlar 49 manufactured by K.K. Co., Ltd.) having a width of 50 cm was pasted and wound up according to a conventional method of this type of sheet construction method. The amount of impregnated resin is 50
It was 0 g / square meter. This sheet has a basis weight of 415
g / m ² , yield strength 60 tf / m, thickness 0.286 mm, specific gravity 1.45, elongation at break 2.4%, tensile strength 2.1 × 10 ³ kgf / cm ² , tensile elastic modulus 1.20 × 10 ⁶ kgf / cm ² . The impregnating resin was completely cured the day after construction. The compressive strength, bending strength, axial bending strength and shear strength of the obtained fiber-reinforced high-strength prestressed concrete pile were measured according to JIS A53.
When measured according to 73, it is found that this is a product equivalent to class B. In addition, tensile strength and tensile elastic modulus guaranteed proof strength are based on JISK7073, and fiber weight is JIS.
It was measured by K1096.

Example 2 Except for using an aramid fiber sheet having a basis weight of 830 g / m ² , a guaranteed yield strength of 120 tf / m and a width of 30 cm (one-way sheet using Kevlar 49 manufactured by Toray DuPont), exactly the same as in Example 1. As a result, a fiber-reinforced high-strength prestressed concrete pile was obtained from a class A high-strength prestressed concrete pile material. As a result of measuring the strength in the same manner as in Example 1, the same physical properties as those of the C type were exhibited.

[0040]

The high-strength prestressed concrete pile material having the strengthened physical properties of the present invention is, for example, JIS A5.
It is possible to manufacture from a similar product, which is a mass-produced product with smaller strength physical properties specified in 373, using a high-strength fiber sheet that is lightweight and easy to handle, and is extremely quick and easy due to its easy and easy workability. Therefore, it is possible to promptly respond to various design changes and specification changes that may occur due to, for example, unexpected ground conditions encountered during the construction and foundation works of civil engineering. Furthermore, if this type of high-strength concrete pile product is integrated, for example, from the conventional 3 types to the majority of A types, it will be possible to replace the B-type and C-type products that were made to order, and the time required for order-made production. It can eliminate the delay and speed up the construction, and it also helps to improve the efficiency of production equipment. Further, since the high-strength fiber is water-resistant and corrosion-resistant, it can play a role of protecting the surface of the concrete pile in the ground which may be affected by ground water or various chemicals which may be dissolved.

[Brief description of drawings]

FIG. 1 shows a loading method for a bending strength test.

FIG. 2 shows a loading method of an axial bending strength test.

FIG. 3 shows a loading method for a shear strength test.

   ─────────────────────────────────────────────────── ─── Continued front page    (71) Applicant 000183233             Sumitomo Rubber Industries, Ltd.             3-6-9 Wakihama-cho, Chuo-ku, Kobe-shi, Hyogo (71) Applicant 000219266             Toray DuPont Co., Ltd.             1-5-6 Nihonbashihonmachi, Chuo-ku, Tokyo (72) Inventor Masaharu Matsumoto             3-5-1, Nakajima-nishi, Oita-shi, Oita Stock             Company Saiki Construction (72) Inventor Ichiro Ueki             Oita-shi, Oita Prefecture Matsuoka 2020 Address Hoyo pie             Le Co., Ltd. (72) Inventor Riro Sakai             1 Sakai from 1349 Hosojima, Shimada City, Shizuoka Prefecture             Business (72) Inventor Tetsuya Kanmoto             3-6-9 Wakihama-cho, Chuo-ku, Kobe-shi, Hyogo             Tomo Rubber Industries Co., Ltd. (72) Inventor Atsushi Tsunoda             1-5-6 Nihonbashihonmachi, Chuo-ku, Tokyo             Toray DuPont Co., Ltd. F-term (reference) 2D041 AA02 BA04 DB09                 4G028 CA01 CB02 CC03 DA01 DB00                       DB02 DB11 GA05

Claims (5)

[Claims] 1. A method of procuring a prestressed concrete pile material having higher strength by attaching a high-strength fiber sheet to the outer periphery of the prestressed concrete pile. 2. A method of converting a prestressed concrete pile to a higher strength prestressed concrete pile material, which comprises polishing the outer peripheral surface of the prestressed concrete pile and then attaching high-strength fibers to the outer peripheral surface together with an adhesive resin. 3. A prestressed concrete pile material that has been strengthened by polishing the outer peripheral surface of the prestressed concrete pile and then attaching high strength fibers together with an adhesive resin to the outer peripheral surface. 4. The high-strength fiber is at least one fiber selected from the group consisting of para-aramid fiber, carbon fiber, wholly aromatic polyester fiber, glass fiber and polyparaphenylene benzobisoxazole fiber. The high-strength prestressed concrete pile material according to claim 1. 5. The high-strength prestressed concrete pile material according to claim 3, wherein the adhesive resin is a thermosetting resin.