JP2006273691A - Hydrated hardened body containing reinforcing bar excellent in salt damage resistance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydrated hardened body containing a reinforcing bar excellent in salt damage resistance capable of being used as a structural member with a long term durability even in the ocean having a severe salt damage environment without setting any special installation. <P>SOLUTION: The hydrated hardened body containing a reinforcing bar excellent in salt damage resistance contains at least steelmaking slag and blast furnace slag fine powder, and the reinforcing bar is made of a Cr-added steel which consists of C of >0.001 mass% and <0.3 mass%, N of >0.001 mass% and <0.3 mass%, Cr of >5.0 mass% and <15.0 mass%, Si of >0.1 mass% and <4.0 mass%, Mn of >0.1 mass% and <4.0 mass%, Co of >0.01 mass% and <1.0 mass%, Al of <0.04 mass%, P of <0.04 mass%, S of <0.03 mass%, and the balance consisting of Fe and unavoidable impurities. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a hydrated cured body having a reinforcing bar excellent in salt damage resistance suitable for use in a structure used in an extremely severe environment such as a marine environment.

  Reinforced concrete is a structural member that exhibits strength and durability over a long period of time, since a passive film is formed on the surface of the reinforcing bar due to the high alkali in the concrete, so that the reinforcing bar is anticorrosive.

  However, in recent years, the availability of aggregates has deteriorated, and for example, andesite that may cause an alkali-aggregate reaction, sea sand containing salt, etc., may have to be used as an aggregate. . When these aggregates were used, there were problems such as inferior rebar corrosion resistance compared to concrete using high-quality aggregates. Even in the case of concrete using high-quality aggregates, when it is applied to offshore structures, the chloride film that permeates the concrete destroys the passive film on the surface of the reinforcing bars and corrodes the reinforcing bars. The concrete peels off due to volume expansion caused by the generated rust. Naturally, increasing the thickness of the concrete (covering thickness) between the reinforcing bar and the outside world can delay the time for chloride ions to reach the surface of the reinforcing bar. There is a problem that the cost increases because the structure becomes larger due to the increase in the size of the structure.

  Examples of means for overcoming the salt damage of reinforced concrete as described above include the following known techniques (a) to (d).

  (A) Technology to polarize the reinforcement in the concrete to the cathode using the sacrificial anode and prevent corrosion: When the reinforcement in the concrete is polarized to the cathode using the sacrificial anode, the aerial part on the seawater immersion surface of the reinforced concrete structure From the splash zone, it is difficult to prevent corrosion due to the increase in electrical resistance due to the drying of the concrete, but the water is pumped up and the electrolyte is covered with a water retention material that covers the air surface of the structure in advance. This is a technology that makes the anticorrosion effective by holding the seawater to be reduced and reducing the electrical resistance of the concrete (see, for example, Patent Document 1).

  (B) Technology for laminating an epoxy resin and a silane coupling treatment layer on the surface of the reinforcing bar: A technology for improving the salt damage resistance of the reinforcing steel in the concrete by laminating the epoxy resin and the silane coupling treatment layer on the surface of the reinforcing bar (For example, refer to Patent Document 2).

  (C) Technology for improving salt damage resistance by spraying a pseudoalloy on the surface of the reinforcing bar: This is a technology for improving salt resistance by spraying a zinc / aluminum pseudoalloy on the surface of the reinforcing bar (for example, , See Patent Document 3).

(D) Technology using concrete reinforcing bars with improved corrosion resistance: After reducing the amount of S to 0.01 mass% or less, 0.05 to 3.00 mass% Cr or 0.03 to 0.60 mass% Cu is added in combination with this Cr. Further, if necessary, V, Mo, P, etc. are added to improve the corrosion resistance of concrete reinforcing bars (see, for example, Patent Document 4), 0.30 to 5.00 mass% Cr, and more than 0.50 to 1.50 mass. This is a technique using a reinforcing bar (for example, see Patent Document 5) in which corrosion resistance and bending workability are improved by adding Ni, Mo, and V together.
JP-A-6-65936 JP-A-5-9760 JP-A-9-41119 JP-A-60-92451 Japanese Patent Laid-Open No. 62-188754

  However, (a) using a sacrificial anode to polarize the reinforcing steel in the concrete to the cathode and to carry out the anticorrosion technology with an actual structure requires an extremely large device, and such a device is required for a long period of time. It is very expensive to operate, manage and maintain across.

  In addition, (b) in the technique of laminating an epoxy resin and a silane coupling treatment layer on the surface of the reinforcing bar, the epoxy resin is hard and has only a few percent elongation at break. There exists a problem that a crack and peeling generate | occur | produce and the corrosion resistance of the part will be lost. Further, the reinforcing bars coated with the epoxy resin not only have poor weldability but also have welding defects, and there is a problem that the corrosion resistance is inferior because the resin layer is burned out at the welded portion.

  In addition, (c) In the technology that improves the salt damage resistance by spraying a zinc-aluminum pseudo-alloy on the surface of the reinforcing bar, the sprayed coating forms an intermetallic compound, so it is extremely brittle. However, there arises a problem that cracking occurs in the sprayed coating or the coating is peeled off and the corrosion resistance is lost.

  Furthermore, when the Cr content of the reinforcing steel for concrete (d) is 5 mass% or less, there is a problem that sufficient corrosion resistance cannot be obtained in a salt damage area or the like.

  In this way, it is difficult to overcome the salt damage of a hydrated cured body having reinforcing bars by preventing corrosion of the reinforcing bars in the hydrated cured body such as concrete and mortar using conventional techniques.

  Therefore, the object of the present invention is to solve the problems of the prior art, and to provide a salt-resistant damage that can be used as a structural member having long-term durability even in a sea where the salt damage environment is severe, without installing a special device. An object of the present invention is to provide a hydrated and cured body having a rebar having excellent properties.

The features of the present invention for solving such problems are as follows.
(1) A hydrated hardened body having a reinforcing bar inside contains at least steelmaking slag and blast furnace slag fine powder, and the reinforcing bar is C: more than 0.001 mass%, less than 0.3 mass%, N: more than 0.001 mass%, 0.3 Less than mass%, Cr: more than 5.0 mass%, less than 15.0 mass%, Si: more than 0.1 mass%, less than 4.0 mass%, Mn: more than 0.1 mass%, less than 4.0 mass%, Co: more than 0.01 mass%, 1.0 mass% Less than, Al: less than 0.04 mass%, P: less than 0.04 mass%, and S: less than 0.03 mass%, with the balance being Cr-added steel consisting of Fe and unavoidable impurities. Hydrated hardened body with excellent reinforcing bars.
(2) The rebar excellent in salt damage resistance according to (1), wherein the Cr-added steel further contains at least one of V: less than 1.0 mass% and W: less than 1.0 mass%. Hydrated cured product.
(3) The Cr-added steel further contains one or more selected from Ni: less than 3.0 mass%, Cu: less than 3.0 mass%, and Mo: less than 3.0 mass% ( A hydrated cured product having a reinforcing bar excellent in salt damage resistance according to 1) or (2).
(4) The Cr-added steel is further selected from Nb: less than 1.0 mass%, Ti: less than 1.0 mass%, Ta: less than 1.0 mass%, Zr: less than 1.0 mass%, and B: less than 0.01 mass%. Or the hydration hardening body which has a rebar excellent in salt-damage tolerance in any one of (1) thru | or (3) characterized by containing 2 or more types.
(5) The hydrated cured product having a reinforcing bar excellent in salt damage resistance according to any one of (1) to (4), wherein the fog is 20 mm or more.
(6) In any one of (1) to (5), the area ratio of the reinforcing bar to the area of the hydrated hardened body is 0.2 to 10% in a cross section perpendicular to the length direction of the reinforcing bar. A hydrated cured product having a reinforcing bar excellent in salt damage resistance.
(7) The rebar having excellent salt damage resistance according to any one of (1) to (6), wherein the content of fine blast furnace slag powder in the hydrated cured body is 100 to 600 kg / m ^3. Hydrated cured product.
(8) The hydrated cured body having a reinforcing bar excellent in salt damage resistance according to any one of (1) to (7), wherein the hydrated cured body further contains fly ash.
(9) The hydrated cured body having a reinforcing bar excellent in salt damage resistance according to (8), wherein the content of fly ash in the hydrated cured body is 50 to 300 kg / m ³ .
(10) The hydrated cured product further contains one or more selected from oxides, hydroxides, Portland cement, blast furnace cement, silica cement, fly ash cement, and eco-cement of alkaline earth metal. A hydrated and cured product having a reinforcing bar excellent in salt damage resistance according to any one of (1) to (9).

  ADVANTAGE OF THE INVENTION According to this invention, the hydration hardening body excellent in the corrosion resistance with respect to an internal reinforcement is obtained. For this reason, the structure which can be used for a long term can be provided also in the marine environment where the conventional reinforced concrete collapses in a short period by salt damage.

  In the present invention, by optimizing the blended raw material of the hydrated hardened body, a hydrated hardened body having a denser structure than concrete using conventional cement or the like as a binder is obtained, and this is used as a predetermined component. The present invention has been completed by finding that it can be used as a structural member having long-term durability even in the ocean where the salt damage environment is severe by combining with a reinforcing bar made of Cr-added steel. First, the blended raw material of the hydrated cured product will be described.

  The hydrated hardened body contains at least steelmaking slag and blast furnace slag fine powder.

  Among the raw materials of the hydrated cured body, the steelmaking slag acts as an aggregate and a binder. The particle size distribution of the steelmaking slag for acting as an aggregate is a particle size corresponding to fine aggregate or coarse aggregate for concrete, the particle size is about 0.075 mm or more, and the maximum particle size is about 40 mm or less. It is preferable to do. Moreover, it is preferable that the steelmaking slag for making it act as a binder is a fine powder, and it is preferable that a particle size is less than about 0.15 mm. Accordingly, a steelmaking slag having an appropriate particle size distribution containing slag particles satisfying the particle size as a binder and the particle size as an aggregate (for example, steelmaking slag pulverized under a certain condition and its pulverization treatment). It is desirable to use steelmaking slag that is sieved later.

Since steelmaking slag remains weakly alkaline for a long period of time, it exhibits an extremely high effect on the corrosion resistance of reinforcing steel. The effect is higher as the basicity (CaO / SiO ₂ ) of the steelmaking slag is larger. In addition, the basicity of the steelmaking slag used as a material of a hydrated hardening body is the range of 1-3 normally. In addition, steelmaking slag does not cause an alkali aggregate reaction unlike aggregates such as ordinary gravel, so not only the durability of the hydrated hardened body itself is excellent, but also cracks due to the alkali aggregate reaction can be suppressed, Penetration of oxygen and chloride ions through cracks does not occur, which is preferable from the viewpoint of corrosion prevention of reinforcing bars in the hydrated cured body.

  The reason why blast furnace slag fine powder is used as a raw material for the hydrated hardened body is not only because the blast furnace slag fine powder having latent hydraulic properties is subjected to alkali stimulation by steelmaking slag, but efficiently hydrates, compared to conventional concrete. This is because, since the cured product has a dense structure, permeation of oxygen and chloride ions, which are harmful to corrosion of reinforcing bars in the hydrated cured body, can be remarkably suppressed. Moreover, it is because the blast furnace slag fine powder and free CaO (free-CaO) in steelmaking slag react and suppress the hydration expansion of steelmaking slag. As the blast furnace slag fine powder, JIS A 6206 “Blast furnace slag fine powder for concrete” can be particularly preferably used.

The blending amount of the blast furnace slag fine powder in the hydrated cured product is preferably 100 to 600 kg / m ³ . If it is less than 100 kg / m ³ , the compressive strength of 18 N / mm ² or more necessary as a concrete substitute may not be obtained, and if it exceeds 600 kg / m ³ , there is almost no increase in strength and it becomes uneconomical. A more preferable blending amount of the blast furnace slag fine powder is 200 to 400 kg / m ³ .

  The hydrated cured body preferably further contains fly ash.

  The reason why fly ash is used as a raw material for the hydrated cured body is that the po component of fly ash proceeds by the efficient reaction between the Ca component in the steelmaking slag and the fly ash. Moreover, it is for the free CaO in fly ash and steelmaking slag to react, and to suppress the hydration expansion of steelmaking slag. Furthermore, there is an effect of improving workability by blending an appropriate amount of fly ash. As fly ash, JIS A 6201 “Fly ash for concrete” is preferably used, but it is also possible to use raw powder and pressurized fluidized bed ash.

The blending amount of fly ash in the hydrated cured product is preferably 50 to 300 kg / m ³ . If it is less than 50 kg / m ³ , the effect of suppressing the hydration expansion of steelmaking slag is low, and if it exceeds 300 kg / m ³ , the viscosity of the fresh state after adding water and kneading increases, and workability deteriorates. Moreover, it is because the effect which suppresses the hydration expansion of steelmaking slag is also uneconomical. A more preferable blending amount of fly ash is 50 to 150 kg / m ³ . When the blending amount is within this range, in addition to the effect of suppressing the hydration expansion of steelmaking slag, a great workability improvement effect is obtained.

  As a raw material of the hydrated cured product, it is preferable to contain one or more selected from alkaline earth metal oxides, hydroxides, and various cements.

  When one or more selected from alkaline earth metal oxides, hydroxides, and various cements are used as the raw material for the hydrated cured product, the mass ratio is 1% with respect to the blast furnace slag fine powder. It is preferable to mix the above. This is blended as an alkali stimulating material for efficiently expressing the latent hydraulic properties of the blast furnace slag fine powder, and is desirably blended when only the alkali stimulation of the steelmaking slag is insufficient. The reason why it is 1 mass% or more is that if it is less than 1 mass%, the effect as alkali stimulation is low. Although the upper limit is not particularly set, in the case of an oxide or hydroxide of an alkaline earth metal, even if it exceeds 100 mass%, the alkali stimulating effect does not change and it becomes uneconomical. In the case of blending an alkaline earth metal oxide or hydroxide, the blending is preferably 5 to 20 mass%. In the case of various cements, not only the alkali stimulation of the blast furnace slag fine powder but also the hydraulic properties of the cement itself are exhibited, so that even if blended in excess of 100 mass%, the compressive strength is increased. In the case of various cement blends, the blend is preferably 10 to 150 mass%.

  The various cements are JIS R 5210 “Portland Cement”, JIS R 5211 “Blast Furnace Cement”, JIS R 5212 “Silica Cement”, JIS R 5213 “Fly Ash Cement”, and JIS R 5214 “Eco Cement”. is there.

  Next, the reinforcing bars in the hydrated cured body will be described.

  As a steel material used for the reinforcing bars, a Cr-added steel having good corrosion resistance and containing the following components is used.

  As Cr added steel, C: more than 0.001 mass%, less than 0.3 mass%, N: more than 0.001 mass%, less than 0.3 mass%, Cr: more than 5.0 mass%, less than 15.0 mass%, Si: more than 0.1 mass%, 4.0 Less than mass%, Mn: more than 0.1 mass%, less than 4.0 mass%, Co: more than 0.01 mass%, less than 1.0 mass%, Al: less than 0.04 mass%, P: less than 0.04 mass%, and S: less than 0.03 mass% It is preferable to use one containing Fe and inevitable impurities, and further containing at least one of V: less than 1.0 mass% and W: less than 1.0 mass%. Furthermore, Ni: less than 3.0 mass%, Cu: less than 3.0 mass%, and Mo: containing one or more selected from less than 3.0 mass%, furthermore, Nb: less than 1.0 mass%, It is preferable to contain one or more selected from Ti: less than 1.0 mass%, Ta: less than 1.0 mass%, Zr: less than 1.0 mass%, and B: less than 0.01 mass%.

  Hereinafter, the reasons for limiting each chemical component will be described.

  C: Over 0.001 mass% and less than 0.3 mass%. C is an austenite phase and carbide forming element. The austenite phase produces a martensite structure in the welded portion to improve the strength, and fine carbides also contribute to the strength improvement. However, if the C content is 0.001 mass% or less, the austenite phase and the amount of carbide generated are too small and the strength is insufficient. On the other hand, if it is 0.3 mass% or more, it becomes too hard and the toughness is deteriorated. Therefore, the C amount is limited to a range of more than 0.001 mass% and less than 0.3 mass%.

  N: Over 0.001 mass% and less than 0.3 mass%. N is also an austenite phase and nitride-forming element. The austenite phase generates a martensite structure in the welded portion to improve the strength, and the fine nitride also improves the strength. However, if the N content is 0.001 mass% or less, the austenite phase and the amount of nitride produced are too small and the strength is insufficient. On the other hand, if it is 0.3 mass% or more, it becomes too hard and the toughness is deteriorated. Therefore, the N amount is limited to a range of more than 0.001 mass% and less than 0.3 mass%. In particular, when it is desired to increase the strength, C and N are each preferably 0.02 mass% or more, more preferably 0.03 mass% or more.

  Cr: More than 5.0 mass% and less than 15.0 mass%. Cr is an important element as a component for improving corrosion resistance in the present invention. In order to ensure the corrosion resistance at a level that enables long-term use in the concrete as the reinforcing bars targeted in the present invention, at least 5.0 mass% of Cr is required. On the other hand, when the Cr content is 15.0 mass% or more, the corrosion resistance is improved, but not only the cost is increased, but the amount of ferrite phase generated is increased and the toughness of the welded portion is insufficient. Therefore, the Cr content is limited to a range of more than 5.0 mass% and less than 15.0 mass%.

  Si: Over 0.1 mass% and less than 4.0 mass%. Si is an element useful as a deoxidizer, but if the content is 0.1 mass% or less, a sufficient deoxidation effect cannot be obtained. On the other hand, if it is 4.0 mass% or more, it becomes hard and deteriorates mechanical properties. Therefore, the amount of Si is limited to a range of more than 0.1 mass% and less than 4.0 mass%.

  Mn: More than 0.1 mass% and less than 4.0 mass%. Mn is an austenite phase-forming element like C, but if the content is 0.1 mass% or less, the austenite phase is not sufficiently generated, so the martensitic structure of the welded portion is reduced and the strength is insufficient. On the other hand, when the Mn content is 4.0 mass% or more, the inclusions remaining in the steel increase and the corrosion resistance deteriorates. Therefore, the amount of Mn is limited to a range of more than 0.1 mass% and less than 4.0 mass%.

  Co: Over 0.01 mass% and less than 1.0 mass%. Co is an important component of the present invention, and the addition of Co can reduce the corrosion rate of the Cr-added steel base in the concrete and improve the corrosion resistance. Such an effect of improving the corrosion resistance by a small amount of Co has been found for the first time in concrete in which the cathode reaction due to dissolved oxygen is restricted in an alkaline environment. Here, when the Co content is 0.01 mass% or less, the above effect cannot be sufficiently obtained. On the other hand, when the Co content is 1.0 mass% or more, the above effect reaches saturation, and rather causes an increase in cost. The range was more than 0.01 mass% and less than 1.0 mass%.

  Al: Less than 0.04 mass%. Al is an element useful as a deoxidizer. When deoxidation with Si is insufficient, deoxidation with Al is performed. However, when the content is 0.04 mass% or more, inclusions increase and corrosion resistance deteriorates. Therefore, Al is contained at less than 0.04 mass%.

  P: The content is less than 0.04 mass%. When the P content is 0.04 mass% or more, deterioration of mechanical properties such as toughness becomes remarkable, so the P content is limited to less than 0.04 mass%.

  S: Less than 0.03 mass%. S combines with Mn to form MnS and serves as an initial starting point. S is also a harmful element that segregates at the grain boundaries and promotes embrittlement of the grain boundaries, so it is preferable to reduce S as much as possible. In particular, when the S content is 0.03 mass% or more, the adverse effect becomes remarkable, so the S content is limited to less than 0.03 mass%.

  As described above, the essential component and the suppressing component have been described. However, in the present invention, various elements described below can be appropriately contained.

  Furthermore, it is preferable to contain any one or more of V: less than 1.0 mass% and W: less than 1.0 mass%.

  V: Less than 1.0 mass%. By adding V, the precipitation of Cr carbonitride is reduced and the corrosion resistance is improved. V also contributes to the improvement of the corrosion resistance of the Cr-added steel base. In particular, in a corrosive environment such as in concrete, it was found that V can contribute effectively to improving corrosion resistance even when added in a small amount. However, when the content is 1.0 mass% or more, the above effect reaches saturation, and rather costs increase. Therefore, V is contained at less than 1.0 mass%.

  W: Less than 1.0 mass%. W, like V, not only improves the corrosion resistance by reducing the precipitation of Cr carbonitride, but also contributes to the improvement of the corrosion resistance of the Cr-added steel base. In particular, in a corrosive environment such as in concrete, the knowledge that W, like V, can effectively contribute to the improvement of corrosion resistance even when added in a small amount. However, if the content is 1.0 mass% or more, the mechanical properties are deteriorated, so W is contained at less than 1.0 mass%.

  Furthermore, it is preferable to contain one or more selected from Ni: less than 3.0 mass%, Cu: less than 3.0 mass%, and Mo: less than 3.0 mass%.

  Ni: Less than 3.0 mass%. Ni is a useful element that reduces the active dissolution of Cr-added steel and improves corrosion resistance. However, if the content is 3.0 mass% or more, the cost increases, so Ni should be contained at less than 3.0 mass%. To do.

  Cu: Less than 3.0 mass%. Cu also has the effect of reducing the active dissolution of Cr-added steel and improving the corrosion resistance. However, when the content exceeds 3.0 mass%, the corrosion resistance tends to deteriorate, so Cu is contained at less than 3.0 mass%. I decided to let them.

  Mo: Less than 3.0 mass%. Mo is also an extremely effective element for improving the corrosion resistance of Cr-added steel. However, since addition of 3.0 mass% or more increases the cost, Mo is contained at less than 3.0 mass%.

  Further, Nb: less than 1.0 mass%, Ti: less than 1.0 mass%, Ta: less than 1.0 mass%, Zr: less than 1.0 mass% and B: less than 0.01 mass% contain 1 type or 2 or more types It is preferable.

  Nb: Less than 1.0 mass%, Ti: less than 1.0 mass%, Ta: less than 1.0 mass%, Zr: less than 1.0 mass%. Nb, Ti, Ta, and Zr all have a function of improving the corrosion resistance by reducing the precipitation of Cr carbonitride. However, since mechanical properties deteriorate at 1.0 mass% or more, these elements should be contained at less than 1.0 mass% in both cases of single addition and composite addition.

  B: Less than 0.01 mass%. B, when combined with N, has the effect of reducing the precipitation of Cr nitride and improving the corrosion resistance. However, if the content is 0.01 mass% or more, the hot workability at the time of manufacturing the steel material deteriorates, so B is contained at less than 0.01 mass%.

  The balance other than the above is Fe and inevitable impurities.

There is no special limitation on the production of the reinforcing bar having the above chemical composition, and it may be produced according to a conventional method. For reference, typical manufacturing conditions are shown below.
(A) Refining process: Blast furnace hot metal decarburized while adding Cr in the converter, or molten steel in which Fe and Cr raw materials such as scrap were melted in an electric furnace were decarburized and the components were adjusted The product is made into a bloom by continuous casting, or an ingot is produced by ingot forming.
(B) Hot rolling process: After heating a bloom or an ingot to 1100-1200 degreeC, it is set as a billet about 50 mm square by hot rolling or hot forging. This billet is again heated to about 1100 ° C., and is then made into a steel bar of about 15 mmφ with a wire rod rolling mill.
(C) Finishing step: The steel bar produced by hot rolling can be used as it is, but the strength is adjusted by an appropriate heat treatment if necessary. In order to further improve the corrosion resistance, the steel bar after hot rolling and, in some cases, after heat treatment, is subjected to a descaling treatment by shot blasting, and further nitric acid + hydrofluoric acid.

  Moreover, what is necessary is just to use said Cr addition steel as a reinforcing bar for the hydration hardening body which has a reinforcing bar of this invention. There is no particular restriction on the construction method at this time, and in accordance with a conventional method, for example, Cr-added steel is arranged as a reinforcing bar, and a mold is set around, and the above hydrated cured material raw material is placed inside the mold. Is added, water is added and kneaded, and then cured and manufactured.

  As a curing method for the hydrated cured body, any method that is usually used, such as underwater curing, on-site curing, and steam curing, can be used as long as a predetermined strength can be secured.

  The fog from the surface of the reinforcing bar to the outer surface of the hydrated cured body (hereinafter referred to as “cover thickness”) is preferably 20 mm or more. This is because when the cover thickness is less than 20 mm, chloride ions that are corrosion factors penetrating from the outside may not be sufficiently blocked.

  The ratio of the reinforcing bars in the hydrated hardened body is such that the cross-sectional area of the reinforcing bars is 0.2 to 10% of the cross-sectional area of the hydrated hardened body part in the cross section perpendicular to the length direction of the reinforcing bars. It is preferable to arrange bars. When manufacturing a structure with a hydrated and cured body having a reinforcing bar of the present invention, if the cross-sectional area of the reinforcing bar is less than 0.2% of the cross-sectional area of the cured body in the cross section of the structure, the yield strength of the reinforcing bar combination This is not preferable because the effect of enhancing the resistance is not obtained. Moreover, when the cross-sectional area of the reinforcing bar exceeds 10% with respect to the cross-sectional area of the cured body in the cross-section of the structure, it is preferable because not only an effect commensurate with the material cost can be obtained, but also the work efficiency is significantly reduced. Absent.

  50 kg of steel ingots having chemical components shown in Tables 1 to 4 were melted in vacuo. Next, after grinding the 5 mm surface of the steel ingot, annealing was performed at 1200 ° C. for 1 h, and a billet of 50 mm square was formed by hot forging. The billet was annealed at 1100 ° C. for 1 hour, and then a 15 mmφ steel bar was formed by a wire rod rolling mill. Then, the steel bar was descaled with a mixed acid of shot blast and 3% hydrofluoric acid-12% nitric acid to produce steel bars of steel types A to AZ. In this example, the shot-pickling treatment was performed to remove the hot scale, but when the corrosive environment in the hydrated cured body is weak, only the shot or no descaling may be used. . Furthermore, after manufacturing steel bars by hot forging and rolling, heat treatment for adjusting strength may be performed.

  Steelmaking slag having the chemical composition and physical properties shown in Table 5 (maximum particle diameter, coarse particle ratio, fine aggregate ratio, surface dry density) was used. The coarse particle ratio is the coarse particle ratio of No. 3115 described in JIS A 0203. The fine aggregate rate is a value representing the absolute volume ratio of the amount of steelmaking slag having a particle size of 5 mm or less with respect to the amount of steelmaking slag of all particle sizes as a percentage.

  Blast furnace slag fine powder used was blast furnace slag fine powder 4000 in JIS A 6206 “Blast furnace slag fine powder for concrete”, and fly ash used type II in JIS A 6201 “Fly ash for concrete”. As the alkali stimulating material, ordinary Portland cement conforming to JIS R 5201 or industrial slaked lime / special name conforming to JIS R 9001 was used. As the admixture, a polycarboxylic acid-based high-performance AE water reducing agent conforming to JIS A 6204 was used.

  According to the composition shown in Table 6, the hydrated cured material was mixed, cured, and concrete no. Test pieces for measuring compressive strength of 1 to 8 were produced. The compressive strength was measured according to JIS A 1108 “Method for testing compressive strength of concrete”. The curing conditions were standard curing 28 days. The measurement results of the compressive strength are shown in Table 6 together.

  Moreover, the cross-sectional area of the hydrated hardened body in the direction perpendicular to the length direction of the reinforcing bar is obtained by blending the reinforcing bars (steel types A to AZ) having chemical components described in Tables 1 to 4 with the composition of the hydrated hardened body raw material in Table 6. The cover thickness was set to 20 mm under the condition of 2%, and it was driven into a 100 × 100 × 400 mm mold. After removing the frame, the specimen was cured in water at 20 ° C. until the age of 28 days, leaving one surface with a cover thickness of 20 mm, and covering all the other surfaces with epoxy resin. A corrosion acceleration test by repeated wet and dry tests was performed in which one cycle consists of dipping in a 3% NaCl aqueous solution at 60 ° C. for 3 days and then drying in a constant temperature and humidity bath at 60 ° C. and 50% RH for 4 days. After 200 cycles of corrosion acceleration test, the hydrated hardened body is destroyed and the rebar is taken out. The rebar is derusted with 10 mass% ammonium dihydrogen citrate aqueous solution, and the corrosion area ratio and maximum corrosion depth are measured with a micrometer. did. A similar test was performed on the conventional concrete (concrete Nos. 9 to 12) having the composition shown in Table 7 with a cover thickness of 20 mm.

  Table 8 shows the results of the corrosion acceleration test of the (reinforced) hydrated cured body having these reinforcing bars.

  As the raw material of the hydrated hardened body, at least steelmaking slag, blast furnace slag fine powder and water are used, and when Cr-added steel having a predetermined component is used as a reinforcing bar, all show good corrosion resistance and corrosion promotion test Even after 200 cycles, no corrosion was observed on the reinforcing bars in the cured body (Invention Examples 1 to 46). Moreover, when using conventional concrete using ordinary cement or blast furnace cement type B, the reinforcing bars in any of the hydrated hardened bodies corroded on the entire surface, and the corrosion resistance was inferior (Comparative Examples 5 to 8). Moreover, when the component of the reinforcing bar was outside the range of the present invention, corrosion was observed in the reinforcing bars in all the cured bodies, and sufficient corrosion resistance was not obtained (Comparative Examples 1 to 4).

Claims (10)

  The hydrated hardened body having rebar inside contains at least steelmaking slag and blast furnace slag fine powder, and the rebar is C: more than 0.001 mass%, less than 0.3 mass%, N: more than 0.001 mass%, less than 0.3 mass% , Cr: more than 5.0 mass%, less than 15.0 mass%, Si: more than 0.1 mass%, less than 4.0 mass%, Mn: more than 0.1 mass%, less than 4.0 mass%, Co: more than 0.01 mass%, less than 1.0 mass%, Al : Reinforcing bar excellent in salt damage resistance, characterized by containing less than 0.04 mass%, P: less than 0.04 mass%, and S: less than 0.03 mass%, the balance being Cr-added steel consisting of Fe and inevitable impurities Hydrated cured body having   The hydration having a reinforcing bar excellent in salt damage resistance according to claim 1, wherein the Cr-added steel further contains at least one of V: less than 1.0 mass% and W: less than 1.0 mass%. Cured body.   The Cr-added steel further contains one or more selected from Ni: less than 3.0 mass%, Cu: less than 3.0 mass%, and Mo: less than 3.0 mass%. A hydrated cured product having a reinforcing bar with excellent salt damage resistance according to claim 2.   One or two Cr-added steels selected from Nb: less than 1.0 mass%, Ti: less than 1.0 mass%, Ta: less than 1.0 mass%, Zr: less than 1.0 mass% and B: less than 0.01 mass% The hydrated cured product having a reinforcing bar excellent in salt damage resistance according to any one of claims 1 to 3, characterized by containing the above.   The hydrated cured body having a reinforcing bar excellent in salt damage resistance according to any one of claims 1 to 4, wherein the fog is 20 mm or more.   The resistance ratio according to any one of claims 1 to 5, wherein an area ratio of the reinforcing bar to an area of the hydrated hardened body in a cross section perpendicular to the longitudinal direction of the reinforcing bar is 0.2 to 10%. Hydrated hardened body with rebars with excellent salt damage. The hydration having a reinforcing bar excellent in salt damage resistance according to any one of claims 1 to 6, wherein the content of the blast furnace slag fine powder in the hydrated cured product is 100 to 600 kg / m ^3. Cured body.   The hydrated cured body having a reinforcing bar excellent in salt damage resistance according to any one of claims 1 to 7, wherein the hydrated cured body further contains fly ash. The hydrated cured body having a reinforcing bar with excellent salt damage resistance according to claim 8, wherein the content of fly ash in the hydrated cured body is 50 to 300 kg / m ³ .   The hydrated cured product further contains one or more selected from alkaline earth metal oxides, hydroxides, Portland cement, blast furnace cement, silica cement, fly ash cement, and eco-cement. A hydrated cured body having a reinforcing bar with excellent salt damage resistance according to any one of claims 1 to 9.