JP2006233559A - Method for manufacturing prestressed concrete, and gas injecting/sealing device for end part of pre-grouted steel material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To sufficiently improve desired concrete bending proof stress and fatigue strength by integrating a pre-grouted steel material with concrete by curing a pre-grouted resin as quickly as possible in a relatively short period of time after constantly supplying oxygen in a stable amount to an oxidation curable resin being the pre-grouted resin embedded in the concrete. <P>SOLUTION: When tensing the pre-grouted steel material 2 after the curing of a concrete molding 1, an attachable airtight chamber 3 like a cap, which covers the end part of the pre-grouted steel material 2 protruding from the concrete molding 1, is provided protrusively from the concrete molding 1 so as to fill an oxidation curing gas for the oxidation curing resin into a gap formed between respective steel wires. An inlet hole 4 for the oxidation curing gas is formed to the uppermost part in the vertical direction of the airtight chamber 3. When the oxidation hardening gas such as oxygen is injected into the airtight chamber 3, the oxidation hardening gas entering the gap between the respective steel wires comes into contact with the oxidation hardenable resin and quickly harden the resin by oxidizing it. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing prestressed concrete in which pregrouting steel is embedded in order to increase compressive stress in advance by applying compressive stress to the concrete, and a gas injection / sealing device for the end portion of pregrouting steel used in this method.

  In general, prestressed concrete gives stress that compresses the concrete in advance by using the force that the tension material embedded in the concrete tries to shrink, and cancels the tensile stress that the concrete receives when the concrete is loaded by this compressive stress. Thus, it is a concrete molded body with improved load resistance, and can be applied to structures that receive a heavy load but need to be reduced in weight, such as bridge floor boards.

  The tension material embedded in such prestressed concrete (hereinafter sometimes abbreviated as “PC”) mainly consists of steel materials such as steel wires, steel stranded wires, hard steel wires, and steel bars, and is also commonly referred to as PC steel materials. It is what.

  In addition, a resin composition in which a metal catalyst is mixed with an oxidative curable resin such as an oil-modified alkyd resin, a fatty acid-modified epoxy resin, or an oil-modified urethane resin is previously coated on the surface of the steel material, thereby adjusting the curing time. In addition, a method of manufacturing a PC using a pre-grout steel material that can exhibit tension due to a PC tension material after 30 days of placing concrete is known (Patent Document 1).

  In addition, as a prestressed concrete tension material coating material, it contains polyester-modified fat or oil and a metal catalyst, mixed with a filler such as talc or calcium carbonate, and the tension of the prestressed concrete tension material after 30 days after placing the concrete. The thing of the cure speed which can be known is known (patent documents 2, 3).

JP 2004-99834 A JP 2004-76358 A JP 2004-76359 A

  However, in the above-described conventional PC manufacturing method, the pre-grout resin coated on the surface of the steel material is cured and integrated with the concrete, so that the expected bending strength and fatigue strength of the concrete can be sufficiently improved. There is a problem that it takes a long time of 1 to 2 years to achieve.

Such a problem that the curing time of the pregrout resin is prolonged is considered to be caused by the following mechanism of action.
That is, in order to harden the pre-grout resin composed of the oxidation-curing resin coated on the pre-grout steel material as quickly as possible, a sufficient supply of oxygen is necessary, but the air permeability of the concrete is not sufficient, especially for bridges, etc. The high strength concrete used had a low water / cement ratio and poor air permeability.

  First of all, at the beginning of pre-grout steel material embedded in concrete, in order to rust-proof the end fixed to the concrete, put a cap and inject resin, cement or paste, etc. The end is shielded from the outside air.

  Normally, when oxygen in the outside air enters through concrete, it is necessary to permeate the polyethylene resin layer called the outermost plastic sheath of pregrout resin, but general plastic has gas permeability at high temperature. The gas permeability decreases when the temperature is high and low.

  On the other hand, looking at the temperature history after concrete placement, it usually reaches a maximum temperature of about 40 to 95 ° C. during the hydration heat generation immediately after placement, and then drops to room temperature such as the temperature to which the concrete is exposed. In that case, it is expected that oxygen is supplied to the sheath and pregrout resin immediately after the concrete is placed, but immediately after the concrete is placed, the plastic sheath is covered with water, so that oxygen hardly reaches the sheath.

  In addition, when the heat generated by the hydration reaction of the concrete is almost finished and the temperature reaches almost room temperature, there is no moisture around the plastic sheath, and the concrete at this time is covered with a gas containing a relatively large amount of oxygen. However, since the temperature of the plastic sheath was lowered and the oxygen permeability was extremely low, sufficient oxygen was not supplied to the pregrout resin.

  Accordingly, an object of the present invention is to prevent a shortage of oxygen supply to the pre-grouting resin (oxidation curable resin) embedded in the concrete, so that oxygen is always supplied to the pre-grouting resin in a stable amount. The pre-grout resin is hardened in a short time, thereby promoting the integration of the concrete and the pre-grout steel material, thereby improving the expected concrete bending strength and fatigue strength sufficiently in a short time.

  In order to solve the above problems, in the present invention, a pre-grout steel material obtained by coating a steel material in which a plurality of steel wires are aggregated with an oxidation-curable resin is embedded in a concrete molded body, and after the concrete molded body is cured. This is a prestressed concrete manufacturing method comprising tensioning the pre-grout steel material and then filling the gap formed between the steel wires with an oxidation-curable gas for the oxidation-curable resin.

In the method for producing prestressed concrete according to the present invention comprising the steps described above,
Since oxygen is not actively supplied to the oxidative curable resin before the concrete molded body is cured, the oxidative curable resin remains soft for a while after the concrete molded body is cured. I can be nervous enough.

  Next, when the gap formed between the steel wires is filled with an oxidation-curable gas for the oxidation-curable resin, the oxidation-curable gas that has entered the gap between the steel wires comes into contact with the oxidation-curable resin covering the steel material. This is oxidized and cured rapidly.

  Therefore, after tensioning the pre-grout steel material, the problem in the prior art that the oxidative curable resin becomes deficient in oxygen supply from the surroundings and the curing speed is slow is solved. It can be integrated, and the expected increase in bending strength and fatigue strength of concrete can be achieved quickly.

  As another prestressed concrete manufacturing method for solving the problems of the present invention, when the above-described method is adopted, an airtight chamber is provided to cover the end portion of the pregrout steel material protruding from the concrete formed body, and the airtight chamber is oxidized. By adopting a means for press-fitting the oxidative curable gas of the curable resin, the press-fitting process of the oxidative curable gas can be performed easily and reliably, and this process can be repeated a plurality of times as necessary. .

  In addition, in order to manufacture prestressed concrete using the above means, both ends of the pregrout steel material are protruded and fixed to the concrete molded body, and airtight chambers are provided to cover both ends of the pregrout steel material, respectively. And the other airtight chamber is filled with an oxidative curable gas of an oxidative curable resin, and the oxidative curable gas is filled into the airtight chamber and the gap between the steel wires connecting them. It is preferable to seal the closed chamber and enclose the oxidative curable gas.

  According to this method, it is possible to reliably fill the oxidative curable gas into both the hermetic chambers and the gaps between the steel wires connecting them. If it does as mentioned above, the resin coat | covered on the surface of the pre-grout steel material can be integrated with concrete in a short time.

In addition, the anti-corrosion treatment of the pre-grout steel material is performed by filling the gas-tight chamber with a gap between the two airtight chambers and the steel wires connecting them, and then oxidizing the gas and the vaporizable rust inhibitor or N ₂ , Ar After replacing the inert gas such as the like, it is preferable to add a step of filling the airtight chamber with a rust preventive to produce prestressed concrete. In that case, if the rust preventive agent is a curable rust preventive agent, the rust preventive effect will surely last for a long time.

  Further, in order to employ the above-described prestressed concrete manufacturing method, an airtight chamber is provided to cover an end portion of the pregrout steel material protruding from the concrete molded body, and a gas introduction hole press-fitted into the airtight chamber is formed to be openable and closable. It is preferable to employ a gas press-fitting / sealing device at the end of the pre-grout steel material.

  If the gas introduction hole to be pressed into the hermetic chamber is made openable and closable, it can be sealed after filling with an oxidative curable gas. It is also possible to introduce gas or to fill with a rust preventive or grout paste in the same manner.

  If a gas introduction hole or a gas / rust preventive agent introduction hole is formed at the top of the airtight chamber, after filling with an oxidative curable gas, the gas tightness will be reduced when filling with a rust preventive or grout paste as necessary. The air can be surely removed from the room.

  For the same purpose, an airtight chamber is provided to cover the end portion of the pre-grout steel material protruding from the concrete molded body, and a gas introduction hole for degassing is formed at the top of the airtight chamber so as to be openable and closable. It is also possible to provide a gas press-fitting / sealing device for the end portion of the pre-grout steel material in which an introduction hole that is also used as a gas / rust inhibitor is formed to be openable and closable at one or more locations excluding. When this device is used, when the oxidative curable resin coated with the pre-grout steel material is brought into contact with the oxidative curable gas and integrated with the concrete in a short time, when the rust preventive agent is further charged, By removing the air from the room, it is possible to reliably prevent rusting of the pre-grout steel material.

  In this invention, after tensioning the pre-grout steel material in the hardened concrete molded body, the gap formed between the steel wires is filled with an oxidative curable gas, so in the concrete cooled to near the outside temperature after hardening. The amount of oxygen necessary to cure the oxidative curable resin is stably supplied, and this makes it possible to integrate the oxidative curable resin (pregrout resin) covering the pregrout steel with the concrete in a short time. It is possible to shorten the time required to improve the bending strength and fatigue strength of the concrete as expected, and there is an advantage that the production efficiency of prestressed concrete is improved.

  Further, the gas injection / sealing device for the end portion of the pre-grout steel material according to the present invention has a cap-type airtight chamber covering the end portion of the pre-grout steel material, and can open and close a gas introduction hole for degassing at a predetermined position of the airtight chamber. Therefore, after the resin coated on the surface of the pre-grout steel material is integrated with the concrete in a short time, there is an advantage that the rust prevention treatment of the steel material can be easily performed.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
As shown in FIG. 1, the gas press-fitting / sealing device at the end of the pre-grout steel material is an oxidative curable resin in the gap formed between the steel wires when the pre-grout steel material 2 is tensioned after the concrete molded body 1 is hardened. In order to fill the oxidatively curable gas with respect to the gas, the airtight chamber 3 that can be attached like a cap that covers the end of the pre-grout steel material 2 protruding from the concrete molded body 1 is provided protruding from the concrete molded body 1. The oxidatively curable gas introduction hole 4 is formed at the top in the vertical direction so as to be openable and closable.
A gas / rust preventive introduction hole may be formed so as to be openable and closable at one or more locations excluding the uppermost portion of the hermetic chamber 3.

  The end portion of the pre-grout steel material 2 protrudes from the end surface of the embedded concrete molded body 1 by a required length that can be gripped in the airtight chamber 3, and this is inserted into the tapered hole 6 of the grip 5 with a wedge (the outer shape is a truncated cone shape). When the pre-grout steel material 2 is pulled by holding the cylindrical body having a circular hole around the axis and pulling the pre-grout steel material 2, the pre-grout steel material 2 is prevented from being pulled back by the tension.

  The airtight chamber 3 is made of steel that is airtightly adhered to an anchor plate 8 such as a steel plate embedded so as to form the same plane as the end surface of the concrete molded body 1 and a rubber O-ring 9 thereon. The cap 10 is fixed on the anchor plate 8 with bolts 11.

  The introduction hole 4 can be connected to a tubular part 12 such as a pressure-resistant hose that can be appropriately press-fitted with an oxidative curable gas such as oxygen or a liquid rust preventive agent by matching the screw surfaces with each other. It can be opened and closed by providing an airtight lid (not shown).

  As shown in FIG. 2, the pre-grout steel material 2 is obtained by coating a steel material made of a stranded wire or the like in which a plurality of steel wires 13 are gathered with an oxidation curable resin 14 by coating or the like. A resin layer such as a high-density polyethylene resin is extruded and coated by composite molding.

  The type of steel material used in the present invention is not particularly limited, but steel materials such as steel wires, steel stranded wires, hard steel wires, and steel bars, and other high-strength iron-based metals that are strong against tensile forces, such as chromium and nickel, are used. A well-known tension material including a steel material which is made of an iron-based alloy or other metal and which is also called PC steel material can be adopted. For example, high-strength steel, high-strength steel, etc. can be used so that the intended load resistance can be obtained for concrete.

  As the oxidative curable resin used in the present invention, an oxidative curable resin such as an oil-modified alkyd resin, a fatty acid-modified epoxy resin, or an oil-modified urethane resin can be used, and usually cured by mixing a metal catalyst and a curing accelerator. Use it to make the time shorter.

  For example, examples of the epoxy resin include bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, and novolak glycidyl ether.

  The alkyd resin is a resin obtained by a polycondensation reaction between a polyhydric alcohol and a polybasic acid. Examples of the polyhydric alcohol component used herein include glycerin, pentaerythritol, and ethylene glycol. Examples of the polybasic acid component include phthalic anhydride and maleic anhydride.

  Examples of the unsaturated fatty acid used in the esterification reaction for making the resin oxidatively curable (oil-modified, fatty acid-modified) include those obtained by saponifying unsaturated fatty acids of vegetable oil components with sodium hydroxide. For example, linseed oil fatty acid, safflower oil fatty acid, soybean oil fatty acid, cottonseed oil fatty acid, castor oil fatty acid and the like.

  In order to make the above-mentioned epoxy resin react with the unsaturated fatty acid as described above to form an uncured oxidation-curing type epoxy resin, the epoxy resin and the above-mentioned fatty acid are blended, and curing is accelerated as necessary. Mixing with an agent (such as a tertiary amine compound), the modification reaction proceeds sufficiently under heating conditions in an inert atmosphere (eg, 100 ° C. for 45 hours) to obtain an oxidatively curable resin.

  Examples of the metal catalyst include naphthenic acid salts (such as cobalt naphthenate, lead naphthenate, and manganese naphthenate), and octyl acid salts (such as cobalt octylate, manganese octylate, and copper octylate).

  The kind of the oxidative curable gas may be appropriately adjusted according to the kind of the oxidative curable resin described above so that it can be cured efficiently, and pure oxygen gas can be used. A mixed gas of oxygen and another gas (such as an inert gas), oxygen-enriched air, or the like can be used.

  In order to manufacture prestressed concrete using the apparatus having the above-described structure, first, as shown in FIG. 1, the pregrout steel material 2 is embedded so that the ends protrude from both ends of the concrete compact 1.

  And after concrete hardens, the anchor plate 8 which formed the hole which can penetrate the pregrout steel material 2 in the predetermined position of the both end surfaces of the concrete molded object 1 is attached, and the wedge 7 is attached to the terminal of the pregrout steel material 2 which protruded from the through hole. The grip 5 is used to prevent it from coming off.

  Next, the end of the pre-grout steel 2 is pulled with a tensioning machine (such as a jack capable of lifting the grip 5) to be sufficiently tensioned, and then tightly adhered to the anchor plate 8 through the O-ring 9 in an airtight manner. An airtight chamber 3 is formed by covering the cap 10 and fixing it with a bolt 11 to the fitting recess on the end face of the concrete molded body 1.

  In this way, at the uppermost portion in the vertical direction of the hermetic chamber 3 formed on both end faces of the concrete molded body 1, a gas introduction hole 4 for degassing is formed so as to be openable and closable. Fill.

  The filling can be performed by press-fitting pressurized curable gas such as oxygen from a gas tank such as an oxygen cylinder, but the introduction hole 4 and the gas tank are securely connected in an airtight state by a pipe line such as a pressure hose.

  The filling of the oxidation curable gas is performed from the introduction hole 4 of one of the hermetic chambers 3 at both ends of the pregrout steel material 2, and the introduction hole (not shown) of the other hermetic chamber is opened, and the pregrout steel material 2 is opened. The oxidative curable gas is circulated through the gap 16 formed between the steel wires 13 inside the steel wire. In this way, after the air existing inside the pre-grout steel material 2 is completely replaced with the oxidation curable gas, both the introduction holes 4 are sealed with a screw lid (not shown) or the like. If necessary, the oxidation-curable gas can be circulated from the gas tank for a certain period.

  In this state, the oxidative curable resin cures quickly, but the curing time is shortened to 1/8 to 1/2 or less of the case where the filling of the oxidative curable gas as described above is not performed. Conventionally, the curing time which took 1 to 2 years can be shortened to about 3 to 6 months.

  The oxidative curable gas to be filled is preferably a dry gas. This is to prevent the occurrence of rust due to condensation.

  In addition, when a gas vent hole is formed at the top of the hermetic chamber, and a gas introduction hole or a rust preventive agent introduction hole or a gas / rust preventive agent introduction hole is formed at any location except the top of the hermetic chamber Further, a rust preventive agent or the like may be filled from the introduction hole as necessary, and the gas may be vented from the airtight chamber.

  After the resin coated on the surface of the pre-grout steel material is integrated with the concrete in a short time, the pre-grout steel material can be reliably rusted by filling the airtight chamber with a rust preventive agent. For example, when a curable rust preventive agent composed of a rust preventive agent mixed with a resin such as an epoxy resin or a urethane resin is employed, the rust preventive effect becomes more reliable.

  Oxidation curable resin (pre-grout resin) obtained by adding a metal catalyst to the modified alkyd resin was applied to a PC steel material having a diameter of 28.6 mm with a maximum thickness of 3 mm, and high-density polyethylene was extrusion coated on the outer surface to prepare a pre-grout steel material. This pre-grout steel material was embedded in concrete having a length of 3 m, a width of 30 cm, and a thickness of 30 cm, and was hardened under the condition that the maximum temperature during casting was 50 ° C.

  After the concrete has hardened, the airtight chambers 3 are formed by covering the caps 10 of the shape shown in FIG. 1 on both ends of the pre-grout steel material protruding from the concrete compact, and the oxygen is dried from the introduction hole 4 of one cap 10. (100%) was introduced from the oxygen cylinder at a flow rate of 0.5 to 1.0 liter / min, and the introduction hole 4 of the other cap was kept open, and this state was continued for 10 minutes. Then, both the introduction holes 4 were sealed with a lid, and after 3 months passed in that state, the strain transmission rate of the pre-grout steel material was evaluated.

  In the tension transmission rate evaluation test, one end of the pre-grout steel material 2 exposed by removing the cap 10 is lifted with a jack together with the grip 5 to introduce a tension force, and similarly to the other end of the pre-grout steel material against the pressure P at this time. The pressure Q transmitted to the attached jack was measured, and Q / P% was used as an evaluation value.

  As a result, it was found that the oxidative curable resin covering the pre-grout steel material and the concrete were well integrated.

  In Example 1, the first dry oxygen (100%) was introduced for 10 minutes, and then after one month, the second dry oxygen (100%) was introduced again for 10 minutes by the same operation, followed by encapsulation. Then, after 3 months from the first introduction date, the tension transmission rate evaluation test was performed in the same manner as described above.

  As a result, it was found that the oxidation curable resin and the concrete covering the pre-grout steel material were better integrated than in Example 1.

[Comparative example]
In Example 1, a room temperature curing type epoxy putty was used instead of the oxidation curable resin as the pre-grout resin, and the airtight chamber 3 was sealed from the beginning of installation to block the inflow of outside air, and the same as above when 3 months passed. The tension transmission rate was evaluated.

  As a result, it was found that the epoxy putty covering the pre-grout steel material was uncured, and the integration of the pre-grout steel material and the concrete was insufficient.

Sectional view of the operating state of the gas injection / sealing device at the end of the pre-grout steel Cross section of pre-grout steel edge

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Concrete molded object 2 Pre-grout steel material 3 Airtight chamber 4 Introduction hole 5 Grip 6 Tapered hole 7 Wedge 8 Anchor plate 9 O-ring 10 Cap 11 Bolt 12 Tubular component 13 Steel wire 14 Oxidation hardening resin 15 Sheath 16 Gap

Claims (7)

  A pre-grout steel material made by coating a steel material in which a plurality of steel wires are aggregated with an oxidation-curable resin is embedded in a concrete molded body, and after the concrete molded body is cured, the pre-grout steel material is tensioned and then formed between the steel wires. A method for producing prestressed concrete, comprising filling a gap formed with an oxidative curable gas for the oxidative curable resin.   The method for producing prestressed concrete according to claim 1, wherein an airtight chamber is provided to cover an end portion of the pregrout steel material protruding from the concrete molded body, and an oxidative curable gas of an oxidative curable resin is press-fitted into the airtight chamber.   Both ends of the pre-grout steel material are protruded and fixed to the concrete molded body, and airtight chambers are provided to cover both ends of the pre-grout steel material, one airtight chamber is opened, and the oxidation-curable resin is oxidized in the other airtight chamber. The curable gas is injected and the oxidative curable gas is filled in the airtight chambers and the gaps between the steel wires connecting them, and then the oxidative gas is sealed by sealing the airtight chambers. The manufacturing method of the prestressed concrete of description.   The method for producing prestressed concrete according to claim 3, wherein the oxidation-curable gas is filled in both the hermetic chambers and the gaps between the steel wires connecting them, and then the oxidation-curable gas and the rust preventive agent are replaced and filled. .   The method for producing prestressed concrete according to claim 4, wherein the rust inhibitor is a curable rust inhibitor.   A gas press-fitting / sealing device for an end portion of a pre-grout steel material provided with an air-tight chamber covering the end portion of the pre-grout steel material protruding from the concrete molded body and capable of opening and closing a gas introduction hole to be press-fitted into the air-tight chamber.   An airtight chamber is provided to cover the end of the pre-grout steel projecting from the concrete molded body, and a gas introduction hole for degassing is formed at the top of the airtight chamber so that it can be opened and closed, and one place excluding the top of the airtight chamber A gas press-fitting / sealing device for the end part of a pre-grout steel material in which the introduction hole for both gas and rust preventive is formed to be openable and closable.

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