JP4882259B2 - Hydrated hardened body with rebar having excellent salt resistance - Google Patents

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.

  As means for overcoming the salt damage of reinforced concrete as described above, for example, the following known techniques (a) to (c) can be mentioned.

  (A) Technology to polarize the reinforcing bar in the concrete to the cathode using the sacrificial anode and prevent corrosion: When the reinforcing bar 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 zinc / aluminum pseudo-alloy on the surface of the reinforcing steel: Technology for improving salt resistance by spraying a zinc / aluminum pseudo-alloy on the surface of the reinforcing steel Is known (for example, see Patent Document 3).
JP-A-6-65936 JP-A-5-9760 JP-A-9-41119

  However, (a) using a sacrificial anode to polarize the reinforcing steel in the concrete to the cathode and to carry out the anticorrosion technology on 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.

  Furthermore, (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.

  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 rebar inside contains at least steelmaking slag, blast furnace slag fine powder, and fly ash, and the rebar is in mass% C: 0.001 to 0.025%, Si: 0.60% or less, Mn : 0.10 to 3.00%, S: 0.01% or less, Al: 0.10% or less, B: 0.0001 to 0.0050%, P: 0.005 to 0.030%, Ni: 0.1 to 6.0%, Cu: 0.1 to 1.5%, Mo : Carbon steel containing one or more selected from 0.005 to 0.5%, the balance being weatherable carbon steel composed of Fe and inevitable impurities, and the content of steelmaking slag in the hydrated hardened body is 1927 kg / m ³ or more, fly ash content of 90 to 150 kg / m ³ , blast furnace slag fine powder content of 100 to 600 kg / m ³ , CaO and SiO contained in the steelmaking slag ₂ mass ratio CaO / SiO ₂ is 1 or more 3 A hydrated cured body having a reinforcing bar excellent in salt damage resistance, characterized in that the MgO content is 1.5 mass% or more and 2.4 mass% or less .
(2) The carbon steel further contains 1% or more selected from the group consisting of Nb: 0.005 to 0.20%, V: 0.005 to 0.20%, Ti: 0.005 to 0.20%, and REM: 0.02% or less. The hydrated and cured product having a reinforcing bar excellent in salt damage resistance according to (1).
(3) The hydrated cured body having a reinforcing bar excellent in salt damage resistance according to (1) or (2), wherein the fog is 20 mm or more.
(4) In any one of (1) to (3), 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 with excellent salt damage resistance.
( 5 ) The hydrated cured product further contains one or more selected from oxides of alkaline earth metals, hydroxides, Portland cement, blast furnace cement, silica cement, fly ash cement, and eco cement. A hydrated and cured product having a reinforcing bar excellent in salt damage resistance according to any one of (1) to ( 4 ).

  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 cured body, a hydrated cured body having a denser structure than concrete using a conventional cement or the like as a binder is obtained, and this has weather resistance. 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 carbon 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 can be 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 set to 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 addition, in the case of various cements, not only the alkali stimulation with respect to 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 blending various cements, the blending 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 steel materials used for the reinforcing bars, C: 0.001 to 0.025%, Si: 0.60% or less, Mn: 0.10 to 3.00%, S: 0.01% or less, Al: 0.10% or less, B: 0.0001-0.0050%, P: 0.005-0.030%, Ni: 0.1-6.0%, Cu: 0.1-1. 5%, Mo: One or more selected from 0.005 to 0.5% is used, and a carbon steel having weather resistance, the balance of which consists of Fe and inevitable impurities, is used.

  Further, the carbon steel is in mass%, and Nb: 0.005 to 0.20%, V: 0.005 to 0.20%, Ti: 0.005 to 0.20%, REM: 0.02% or less It is preferable to contain 1 type, or 2 or more types selected from.

  Hereinafter, the reasons for limiting each chemical component will be described. In the following description, all units represented by% are mass%.

  C: 0.001 to 0.025%. When the amount of C decreases, it is advantageous for improving the weather resistance. If it exceeds 0.025%, the effect is small. If it exceeds 0.025%, toughness and weldability deteriorate. If it is less than 0.001%, the desired strength cannot be ensured. Therefore, the content is limited to 0.001 to 0.025%. More preferably, it is 0.001 to 0.02%.

  Si: Set to 0.60% or less. Si is an element that acts as a deoxidizer and further increases the strength of the steel, but if contained in a large amount, it deteriorates toughness and weldability, so it is limited to 0.60% or less. In addition, Preferably it is 0.15-0.50%.

  Mn: 0.10 to 3.00%. Mn is an element that greatly contributes to an increase in the strength and toughness of the steel, and is added in an amount of 0.10% or more in order to ensure the desired strength, but if contained in a large amount exceeding 3.00%, the toughness and weldability are improved. In order to adversely affect, it is limited to the range of 0.10 to 3.00%. In addition, when high toughness is required in cold districts or the like, lowering Mn is effective.

  S: 0.01% or less. S degrades the weather resistance and further degrades the weldability and toughness, so it is limited to 0.01% or less.

  Al: 0.10% or less. Al is added as a deoxidizer, but if it exceeds 0.10%, the weldability is adversely affected, so 0.10% is made the upper limit.

  B: Set to 0.0001 to 0.0050%. B is an element that increases the hardenability and further improves the weather resistance, and is an important element. Such an effect is recognized when the content is 0.0001% or more, but even if the content exceeds 0.0050%, an effect commensurate with the content cannot be expected. For this reason, B is limited to 0.0001 to 0.0050% of range. More preferably, it is 0.0003 to 0.0030% of range. The detailed mechanism for improving the weather resistance of B is not clear, but is considered as follows. The salt adhering to the rust layer is ionized by rainfall and dew condensation water (or deliquescence) to become Cl ions and lower the pH in the rust layer. This decrease in pH promotes anodic dissolution of iron and degrades weather resistance. B is considered to have an action of preventing pH reduction due to chlorine.

  Contains one or more selected from P, Ni, Cu, and Mo.

  P: Set to 0.005 to 0.030%. P is an element that improves the weather resistance, but addition of less than 0.005% has no effect of improving the weather resistance. However, when the content exceeds 0.030%, the weldability deteriorates. For this reason, P is limited to 0.005 to 0.030% of range.

Ni: 0.1 to 6.0%. Ni improves the weather resistance, but if it is less than 0.1%, its effect is small. On the other hand, even if the content exceeds 6.0%, the effect is saturated and an effect commensurate with the content is not recognized, which is economically disadvantageous. For this reason, Ni was taken as 0.1 to 6.0% of range. When the amount of salt is large, it is preferable that the amount of Ni is large. However, in consideration of economy, the range of 2.0 to 3.5% is preferable, and 2.5 to 3.0% is more preferable.
Cu: 0.1 to 1.5%. Cu improves the weather resistance. However, when the Cu content is less than 0.1%, the effect is small. On the other hand, when the Cu content exceeds 1.5%, hot workability is impaired and the weather resistance improvement effect is saturated, which is economically disadvantageous. For this reason, Cu content is limited to 0.1 to 1.5% of range.

  Mo: 0.005 to 0.5%. Mo improves the weather resistance and further increases the strength. However, if the content is less than 0.005%, the effect is small. On the other hand, if the content exceeds 0.5%, the effect is saturated and an effect commensurate with the content is not recognized, which is economically disadvantageous. For this reason, Mo is taken as 0.005 to 0.5% of range. In addition, from the viewpoint of toughness, the range of 0.005 to 0.35% is preferable.

  Further, Nb: 0.005 to 0.20%, V: 0.005 to 0.20%, Ti: 0.005 to 0.20%, REM: one selected from 0.02% or less or It is preferable to contain 2 or more types. Nb, V, and Ti are elements that increase the strength of the steel material, and any of them is effective when contained in an amount of 0.005% or more. However, the effect is saturated even if the content exceeds 0.20%. For this reason, it is preferable that Nb, V, and Ti are all 0.005 to 0.20%. REM has the effect | action which improves weldability, and can be added as needed. REM is effective when added in an amount of 0.001% or more, but adding a large amount deteriorates the cleanliness of the steel material, so 0.02% is made the upper limit.

  The balance other than the above is Fe and inevitable impurities. As unavoidable impurities, Cr: 0.05% or less, N: 0.010% or less, and O: 0.010% or less are acceptable. Although Cr is said to be an element that improves weather resistance, it is effective in a low salt environment, and conversely in a high salt environment such as a coastal area using the present invention. It is an element that degrades the weather resistance and is not added intentionally in the present invention, but up to 0.05% is acceptable.

  Reinforcing bars with the above chemical composition are melted by a generally known melting method such as a converter or electric furnace, made into a steel material by a continuous casting method or an ingot forming method, and heated in a heating furnace or directly without heating. It is manufactured by rolling into a desired shape by hot rolling. As the melting method, vacuum degassing smelting or the like may be performed.

  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 the bars. When producing a structure with a hydrated cured body having reinforcing bars of the present invention, if the cross-sectional area of the reinforcing bars 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 bars is This is not preferable because the effect of enhancing the resistance is not obtained. In addition, when the cross-sectional area of the reinforcing bar exceeds 10% of the cross-sectional area of the hardened body in the cross-section of the structure, it is not only possible to obtain an effect commensurate with the material cost, but also work efficiency is significantly reduced, which is preferable. Absent.

  The hydrated cured body is produced by blending the above raw materials, adding water, kneading, driving into a predetermined mold or the like, and curing. 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 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.

  Steelmaking slags having the chemical components and physical properties shown in Table 1 (maximum particle size, coarse particle rate, fine aggregate rate, surface dry density) were 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 formulation shown in Table 2, the hydrated cured material is kneaded, 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 together in Table 2.

  In addition, the hydration hardening in the direction perpendicular to the longitudinal direction of the reinforcing bars is made of carbon steel having the chemical composition shown in Table 3 (steel type Nos. 1 to 16) by blending the raw material of the hydrated hardening body shown in Table 2. The cover thickness was changed from 20 to 40 mm under the condition of 2% with respect to the cross-sectional area of the body, 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 a surface with a controlled cover thickness, and all other surfaces were coated with an 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 150 cycles of corrosion acceleration tests, the hydrated hardened body was destroyed and the rebar was taken out. The rebar was derusted with 10 mass% ammonium dihydrogen citrate aqueous solution, and the corrosion area ratio and maximum corrosion depth were 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 4 with a cover thickness of 20 mm.

  Table 5 shows the results of the accelerated corrosion test of the (reinforced) hydrated cured body having these reinforcing bars.

  By using at least steelmaking slag, blast furnace slag fine powder and water as a raw material for the hydrated hardened body, and further combining with a reinforcing bar having a predetermined component, all show good corrosion resistance when the cover thickness is 20 mm or more, Even after 150 cycles of the accelerated corrosion test, no corrosion was observed in the reinforcing bars in the cured body (Invention Examples 1 to 19). Moreover, when using conventional concrete using ordinary cement or blast furnace cement type B, the reinforcing bars in any of the hydrated cured bodies corroded on the entire surface with a cover thickness of 20 mm, and the corrosion resistance was inferior (Comparative Examples 1 to 2). 4). 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 5 to 10).

Claims (5)

The hydrated hardened body having rebar inside contains at least steelmaking slag, blast furnace slag fine powder and fly ash, and the rebar is in mass% C: 0.001 to 0.025%, Si: 0.60% or less, Mn: 0.10 to 3.00%, S: 0.01% or less, Al: 0.10% or less, B: 0.0001 to 0.0050%, P: 0.005 to 0.030%, Ni: 0.1 to 6.0%, Cu: 0.1 to 1.5%, Mo: 0.005 to It is a carbon steel containing one or two or more selected from 0.5%, the balance being Fe and inevitable impurities and having a weather resistance, and the content of steelmaking slag in the hydrated hardened body is 1927 kg / m ³ or more, fly ash content is 90 to 150 kg / m ³ , blast furnace slag fine powder content is 100 to 600 kg / m ³ , and mass of CaO and SiO ₂ contained in the steelmaking slag The ratio CaO / SiO ₂ is 1 or more and 3 or less A hydrated cured body having a reinforcing bar excellent in salt damage resistance, characterized in that the MgO content is 1.5 mass% or more and 2.4 mass% or less .   The carbon steel further contains one or more selected from the group consisting of Nb: 0.005 to 0.20%, V: 0.005 to 0.20%, Ti: 0.005 to 0.20%, and REM: 0.02% or less. The hydrated cured product having a reinforcing bar excellent in salt damage resistance according to claim 1.   The hydrated cured body having a reinforcing bar excellent in salt damage resistance according to claim 1 or 2, wherein the fog is 20 mm or more.   The area ratio of the reinforcing bar to the 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 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 product having a reinforcing bar with excellent salt damage resistance according to any one of claims 1 to 4 .