JP2007269560A - Hydrated hardened body having reinforcing rod excellent in neutralization resistance and salt damage resistance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydrated hardened body having a reinforcing rod excellent in neutralization resistance and salt damage resistance which can made into a structure member having durability over a long period even under environmental conditions that neutralization is apt to progress. <P>SOLUTION: The hydrated hardened body, which has with a reinforcing rod at the inside contains: one or more kinds selected from portland cement, blast furnace cement, fly ash cement and slaked lime; steel making slag; and blast furnace slag fine powder, and in which the value of portland cement+blast furnace cement×0.6+fly ash cement×0.85+slaked lime is ≥55 kg/m<SP>3</SP>. The reinforcing rod is composed of Cr-added steel comprising, by mass, >0.001 to <0.3% C, >0.001 to <0.3% N, >5.0 to <15.0% Cr, >0.1 to <4.0% Si, >0.1 to <4.0% Mn, >0.01 to <1.0% Co, <0.04% Al, <0.04% P and <0.03% S. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention is suitable for use in a structure used in an environment where neutralization and salt damage are likely to proceed, such as a coast where dryness and humidity are repeated, and is hydrated with a reinforcing bar excellent in neutralization resistance and salt damage resistance. It relates to a cured product.

  Reinforced concrete is a structural member that exhibits strength and durability over a long period of time because the passive component film is formed on the surface of the reinforcing bar by the alkali components in the concrete, thereby preventing corrosion of the reinforcing bar. Therefore, when the concrete is neutralized, the passive film is destroyed and the rebar is corroded, so that it does not function as a structural member.

  In recent years, the availability of concrete aggregates has deteriorated, and for example, andesite that may cause an alkali aggregate reaction may be used as an aggregate. When cracks occur in the concrete due to the alkali aggregate reaction, there is a problem that the neutralization of the concrete proceeds rapidly and the reinforcing bars corrode. Even in the case of concrete using high-quality aggregates, if it is used in an environment where neutralization is likely to proceed, such as repeated drying and wetting, the neutralization of the concrete causes the passivation of the reinforcing bar surface. The coating is destroyed and the rebar is corroded, and the concrete is peeled off by volume expansion caused by the generated rust. Naturally, increasing the thickness of the concrete (cover thickness) between the reinforcing bar and the outside world can delay the time for neutralization 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.

  As a means for improving the neutralization resistance of reinforced concrete as described above, a method of reducing the water-cement ratio is generally known.

  On the other hand, Patent Document 1 and Non-Patent Document 1 disclose a hydrated hardened body that can use steelmaking slag and blast furnace slag fine powder as main raw materials and can replace concrete.

By using these hydrated hardened bodies as a substitute for concrete, it is possible to effectively use slag generated in large quantities at steelworks.
JP 2001-049310 A “Steel Slag Hydrated Solid Technology Manual” Coastal Development Technology Research Center 2003

  However, the method of reducing the water-cement ratio in order to improve the neutralization resistance of reinforced concrete is effective when using high-quality aggregates that do not cause alkali-aggregate reaction, but alkali-aggregate reaction. There is no effect when using aggregates that cause Moreover, if the water-cement ratio is reduced, not only the cost is increased, but also the self-shrinkage of the concrete is increased.

  On the other hand, regarding the neutralization resistance when the hydrated cured body of Patent Document 1 and Non-Patent Document 1 is used as a concrete substitute, the hydrated cured body disclosed in Patent Document 1 is used for roadbed materials, The hydration hardened body disclosed in Non-Patent Document 1 is unclear to the extent that it is used for construction and earthwork, etc., and the target is limited to the replacement of unreinforced concrete that does not contain reinforcing bars. Is unknown. Then, when the present inventors investigated the neutralization resistance of these hydrated cured bodies, it was found that the dispersion was extremely large and it was difficult to stably use as a substitute for reinforced concrete.

  As described above, there is a limit to prevent corrosion of reinforcing bars by suppressing neutralization of a hydrated and hardened body made of concrete, steelmaking slag, blast furnace slag fine powder, or the like using conventional techniques.

  Therefore, the object of the present invention is to solve the problems of the prior art, and to make the structure member having long-term durability even under environmental conditions where neutralization is likely to proceed, An object of the present invention is to provide a hydrated cured body having a reinforcing bar excellent in salt damage resistance.

The features of the present invention for solving such problems are as follows.
(1) A hydrated hardened body having a reinforcing bar inside is at least one selected from Portland cement, blast furnace cement, fly ash cement, slaked lime, steelmaking slag, and blast furnace slag fine powder. Contains "Portland cement (kg / m ³ ) + blast furnace cement (kg / m ³ ) x 0.6 + fly ash cement (kg / m ³ ) x 0.85 + slaked lime (kg / m ³ )" 55 kg / m ³ or more, and the above-mentioned rebar is in mass% 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: less than 0.04 mass%, P: less than 0.04 mass%, and S : Cr-added steel containing less than 0.03 mass% with the balance being Fe and inevitable impurities耐中 of resistance and salt damage excellent in hydration cured product having a reinforcing bar, characterized in that.
(2) Cr-added steel further contains at least one of V: less than 1.0 mass% and W: less than 1.0 mass%. Hydrated hardened body with rebar having excellent properties.
(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 neutralization resistance and salt damage resistance as described in 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 reinforcing bar excellent in neutralization resistance and salt damage resistance in any one of (1) thru | or (3) characterized by containing 2 or more types.
(5) The neutralization resistance and salt damage resistance according to any one of (1) to (4), wherein the content of fine blast furnace slag powder in the hydrated cured product is 100 to 600 kg / m ^3. Hydrated hardened body with rebar having excellent properties.
(6) The hydrated cured product further contains fly ash, and the hydration has a reinforcing bar excellent in neutralization resistance and salt damage resistance according to any one of (1) to (5) Cured body.

  According to this invention, since it is excellent in neutralization resistance and salt damage resistance, the hydration hardening body excellent in the corrosion resistance with respect to a reinforcing bar is obtained. For this reason, the structure which can be used for a long period of time can be provided even in the environment where the conventional reinforced concrete collapses in a short period of time by neutralization.

  In the present invention, by optimizing the material of the hydrated hardened body, the hydration hardening having better neutralization resistance than conventional hydrated hardened bodies made of concrete, steelmaking slag and blast furnace slag fine powder, etc. As a structural member that has a long-term durability even in an environment where neutralization and salt damage are likely to occur, it contains high salinity and repeats drying and wetting by combining it with a reinforcing bar made of Cr-added steel. The present invention has been completed by finding that it can be used.

  First, materials constituting the hydrated cured body will be described.

  In the present invention, the content (in the hydrated cured body) (in the hydrated cured body) of the hydrated cured body includes each material (including kneading water and admixture) that is a raw material for blending the hydrated cured body. ) In the mixed mixture. The hydrated cured product in the present invention is obtained by curing a mixture formed by mixing materials to be blended raw materials.

  The hydrated hardened body of the present invention contains steelmaking slag, blast furnace slag fine powder, and one or more selected from Portland cement, blast furnace cement, fly ash cement, and slaked lime.

Among the materials of the hydrated hardened body, the steelmaking slag acts as an aggregate and a binder, and further as a neutralization inhibitor for the hydrated hardened body. 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. The steelmaking slag for acting as a neutralization inhibiting material preferably has a CaO / SiO ₂ ratio of 1.5 or more, or a CaO concentration of 25% by mass or more. CaO / SiO ₂ is in a weight ratio of 1.5 or more, or CaO concentration of 25 mass% or more steel slag is dissolved in water CaO component in the steelmaking slag is contained in the hydrated cured body over a long period of time, water Keep the Japanese cured body weakly alkaline and suppress neutralization. More preferably, CaO / SiO ₂ is 2.0 or more by mass ratio, or the CaO concentration is 30% by mass or more. Generally, when the CaO / SiO ₂ and CaO concentrations are increased, the hydration expansion due to free CaO (free-CaO) in the steelmaking slag increases, but there is no problem if the expansion stability of the hydrated cured body is ensured. These upper limits are not specified.

  In addition, steelmaking slag does not cause an alkali-aggregate reaction unlike ordinary gravel aggregates, so that not only the durability of the hydrated hardened body itself is excellent, but also the generation of cracks due to the alkali-aggregate reaction can be suppressed. Therefore, neutralization through cracks does not occur, which is preferable from the viewpoint of corrosion prevention of reinforcing steel in the hydrated cured body.

  The reason why blast furnace slag fine powder is used as a 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 and efficiently hydrates but also more than conventional concrete. This is because, since the cured product has a dense structure, the permeation of carbon dioxide that causes neutralization of the hydrated cured product can be remarkably suppressed. Moreover, it is because the free blast furnace slag fine powder and free CaO (free-CaO) in the steelmaking slag react to suppress the hydration expansion of the steelmaking slag. As the blast furnace slag fine powder, JIS A 6206 “Blast furnace slag fine powder for concrete” can be particularly preferably used.

  One or more types selected from Portland cement, blast furnace cement, fly ash cement, and slaked lime are used as the material of the hydrated cured body. Is to keep the alkalinity. The Portland cement in the present invention is described in JIS R 5210 “Portland cement”, ordinary Portland cement, early-strength Portland cement, ultra-early strong Portland cement, moderately hot Portland cement, low-heat Portland cement, sulfate resistant salt Portland cement. Further, the blast furnace cement is A type, B type or C type described in JIS R 5211 “Blast furnace cement”. Moreover, fly ash cement is A class, B class, and C class as described in JIS R 5213 “fly ash cement”.

In the present invention, the blending amount of Portland cement, blast furnace cement, fly ash cement, and slaked lime in the hydrated hardened body is expressed as “Portland cement (kg / m ³ ) + blast furnace cement (kg / m ³ ) × 0.6 + fly. Ash cement (kg / m ³ ) × 0.85 + slaked lime (kg / m ³ ) ”is set to 55 kg / m ³ or more. By large amount is contained so that 55 kg / m ³ or more, even if 1.5 or below CaO concentration CaO / SiO ₂ mass ratio of hydrated hardened body using steel slag of less than 25 wt%, The inside can be kept alkaline for a long time. This value is preferably 70 kg / m ³ or more. The upper limit of this value is not particularly set, but even if it exceeds 150 kg / m ³ , there is almost no improvement in neutralization resistance.

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 the material of the hydrated and cured body is that the Ca component in the steelmaking slag and the fly ash react efficiently so that the pozzolanic reaction of fly ash proceeds. 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. The fly ash is preferably JIS A 6201 “Fly Ash for Concrete”, but it is also possible to use raw powder and pressurized fluidized bed ash.

Although the compounding quantity in the hydrated hardening body of fly ash is not specifically limited, It is preferable that it is 50-300 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.

  Next, the reinforcing bars used in the present invention will be described. In addition, the non-muscle hydrated cured product does not cause a problem even when the resistance to neutralization is not excellent.

  As Cr-added steel used for reinforcing 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: 0.1 mass% More than, 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: less than 0.04 mass%, P: less than 0.04 mass%, and S: 0.03 mass It is preferable to use a material containing less than% and the balance being 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 concrete, the reinforcing steel targeted in the present invention requires at least 5.0 mass% of Cr. 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 also 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 the 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. Limited to a range of 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, it was found that W, like V, can contribute effectively to improving corrosion resistance even when added in a small amount. However, if the content is 1.0 mass% or more, the mechanical properties are deteriorated. Therefore, 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 the corrosion resistance. However, if the content is 3.0 mass% or more, the cost is increased, 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 will let you.

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 causes an increase in 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 particular limitation on the production of the reinforcing bar having the above chemical composition, and it may be produced according to a normal production method. For reference, typical production conditions are shown in the following (A) to (C).

  (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 manufactured 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 square mm by hot rolling or hot forging. This billet is heated again to about 1100 ° C., and then is made into a steel bar of about 15 mmφ by 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.

  In addition to performing the shot-pickling treatment to remove the hot scale, if the corrosive environment in the hydrated cured body is weak, only the shot or no descaling may be performed. Furthermore, after manufacturing a steel bar by hot forging and rolling, a heat treatment for adjusting the strength may be performed.

  The hydrated cured body is produced by blending the above materials, adding water, kneading, and driving and curing in a predetermined formwork or the like. Reinforcing bars are placed during driving to obtain a hydrated hardened body having reinforcing bars.

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

  Steelmaking slags having the chemical components and physical properties shown in Table 1 (maximum particle diameter, coarse particle ratio, fine aggregate ratio, surface dry density) were used (steelmaking slag Nos. A and B). 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.

  The 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 Portland cement, ordinary Portland cement conforming to JIS R 5201 “Portland cement” was used. As the blast furnace cement, type B suitable for JIS R 5211 “blast furnace cement” was used. As the fly ash cement, type B conforming to JIS R 5213 “fly ash cement” was used. As the slaked lime, 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.

  The reinforcing bars were manufactured as follows. 50 kg of steel ingots having chemical components shown in Tables 2 to 5 were melted in vacuum. Next, after grinding 5 mm of the 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 h, and then a 25 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 A to AZ.

According to the formulations shown in Tables 6 to 8 (Formulation Nos. 1 to 12), the hydrated cured material was mixed with a mixer, poured into a φ100 × 200 mm mold, cured, and No. Test pieces for measuring compressive strength 1 to 49 were produced. The compressive strength was measured in accordance with JIS A 1108 “Concrete compressive strength test method”. The curing conditions were standard curing 28 days. At the same time, a test piece for a neutralization promotion test of φ100 × 200 mm in which steel bars of the steel types shown in Tables 2 to 5 were inserted in the center was No. Two pieces were manufactured for each manufacturing condition of 1 to 49. The curing conditions were standard curing 28 days. The neutralization promotion test is a test piece that was exposed to a test piece after 28 days of standard curing for 91 days under conditions of CO ₂ concentration 5%, temperature 40 ° C, and humidity 60% RH. The chemical depth was measured and evaluated from the average value. The neutralization depth was measured by using a 1% solution spray method of phenolphthalein to make the non-colored portion a neutralized portion.

  Of the specimens that had been subjected to the neutralization promotion test, those that were not cut into pieces were subjected to a salt damage resistance test. In the salt damage resistance test, one cycle consists of immersing 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 one cycle. The hardened body was destroyed and the rebar was taken out. The rebar was derusted with a 10 mass% aqueous solution of ammonium hydrogen citrate, and the corrosion area ratio and the maximum corrosion depth were measured with a micrometer.

  For comparison, a test piece (No. 50) of ordinary concrete that does not use steelmaking slag and blast furnace slag fine powder was prepared. Mix the concrete material with a mixer according to the formulation shown in Table 9 (mixing No. 13), pour it into a mold of φ100 × 200mm, cure it, and measure it for compressive strength measurement, neutralization promotion test, and salt damage resistance test The test piece was made. The curing conditions for the test pieces for compressive strength measurement were standard curing 28 days. The compressive strength test, neutralization acceleration test, and salt damage resistance test were performed in the same manner as described above. The aggregate used was a high-quality one determined to be “harmless” in the test according to JIS A 1145 “Aggregate Alkali Silica Reactivity Test Method (Chemical Method)”.

The compression strength measurement results, the neutralization promotion test results, and the salt damage resistance test results are also shown in Tables 6 to 9. It contains at least steelmaking slag and fine powder of blast furnace slag, “Portland cement (kg / m ³ ) + blast furnace cement (kg / m ³ ) × 0.6 + fly ash cement (kg / m ³ ) × 0.85 + slaked lime (kg / M ³ ) ”(corresponding to NP + 0.6BB + 0.85FB + CH in Table 6) 55 kg / m ³ or more, and a hydrated cured body (test pieces No. 1 to 22) combined with a reinforcing bar having a predetermined component, Test piece No. 50% water binding material ratio (water cement ratio) using good quality aggregates. The neutralization depth was smaller than that of ordinary concrete No. 50 (compound No. 13), and no corrosion was observed in the internal reinforcing bars even after the salt damage resistance test. On the other hand, when a hydrated hardened body that does not fall under these conditions and a reinforcing bar are combined (test pieces No. 23 to 49), the water-binding material ratio (water-cement ratio) using high-quality aggregate is 50% than that of ordinary concrete. However, it was inferior in neutralization resistance, and corrosion of the reinforcing bars was observed after the salt damage resistance test.

Claims (6)

The hydrated cured body having a reinforcing bar inside contains at least one or more selected from Portland cement, blast furnace cement, fly ash cement, slaked lime, steelmaking slag, and blast furnace slag fine powder, “Portland cement (kg / m ³ ) + blast furnace cement (kg / m ³ ) × 0.6 + fly ash cement (kg / m ³ ) × 0.85 + slaked lime (kg / m ³ )” is 55 kg / m ³ or more In addition, the rebar is in mass% 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: 0.1 mass% More than, 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: less than 0.04 mass%, P: less than 0.04 mass%, and S: 0.03 mass Cr-added steel containing less than% and the balance consisting of Fe and inevitable impurities Hydrated cured product having excellent reinforcing bar 耐中 resistance resistance and salt damage resistance, wherein.   The Cr-added steel further contains at least one of V: less than 1.0 mass% and W: less than 1.0 mass%, and is excellent in neutralization resistance and salt damage resistance. Hydrated and hardened body with rebar.   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 neutralization resistance and 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 body having a reinforcing bar excellent in neutralization resistance and salt damage resistance according to any one of claims 1 to 3, characterized by containing the above. The blast furnace slag fine powder content in the hydrated cured body is 100 to 600 kg / m ³ , and is excellent in neutralization resistance and salt damage resistance according to any one of claims 1 to 4. Hydrated and hardened body with rebar.   The hydrated cured body having reinforcing bars excellent in neutralization resistance and salt damage resistance according to any one of claims 1 to 5, wherein the hydrated cured body further contains fly ash.