JP2006273689A - 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 carbon steel having weatherability. Preferably, the cover is 20 mm or more, the area ratio of the reinforcing bar vs. the area of the hydrated hardened body at a cross section perpendicular to the longitudinal direction of the reinforcing bar is 0.2-10%, the content of blast furnace slag fine powder in the hydrated hardened body is 100-600 kg/m<SP>3</SP>, and the hydrated hardened body contains fly ash in addition. <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.

  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 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 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 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.

  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) Reinforcing bar excellent in salt damage resistance, characterized in that the hydrated hardened body having a reinforcing bar therein contains at least steelmaking slag and fine powder of blast furnace slag, and the reinforcing bar is a carbon steel having weather resistance. Hydrated cured body having
(2) Carbon steel in mass% C: 0.15% or less, Si: 0.7% or less, Mn: 0.10% or more, 2.00% or less, P: more than 0.03%, 0.15% or less, S: 0.020% or less, Al: 0.010 %, 0.100% or less, Ni: 0.2% or more, 4.0% or less, Cu: less than 0.1%, Mo: 0.10% or more, 4.00% or less, with the balance being Fe and inevitable impurities A hydrated cured product having a reinforcing bar excellent in salt resistance as described in (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 excellent in salt damage resistance.
(5) The rebar excellent in salt damage resistance according to any one of (1) to (4), wherein the content of fine blast furnace slag powder in the hydrated cured body is 100 to 600 kg / m ^3. Hydrated cured product.
(6) The hydrated and cured product having a reinforcing bar excellent in salt damage resistance according to any one of (1) to (5), wherein the hydrated and cured product further contains fly ash.
(7) The content of fly ash in the hydrated and cured product is 50 to 300 kg / m ³ , and the hydrated and cured product having a rebar excellent in salt damage resistance according to (6).
(8) The hydrated cured body 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 excellent in salt damage resistance according to any one of (1) to (7).

  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 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 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.

  Carbon steel having weather resistance is used as the steel material used for the reinforcing bars. By using the carbon steel having weather resistance, the salt damage resistance of the hydrated cured body having reinforcing bars can be sufficiently improved. Incidentally, the carbon steel having weather resistance contains an appropriate amount of alloying elements such as Cu, Cr, Ni, P, etc., and forms a dense rust on the surface by repeated appropriate drying and wetting in the atmosphere. There are few steel materials, and it is prescribed in JIS weathering steel materials for welded structures (SMA) and high weathering steel materials (SPA).

  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.

  Carbon steel having weather resistance is C: 0.15% or less, Si: 0.7% or less, Mn: 0.10% or more, 2.00% or less, P: more than 0.03%, 0.15% or less, S: 0.020% or less, Al in mass% : 0.010% or more, 0.100% or less, Ni: 0.2% or more, 4.0% or less, Cu: less than 0.1%, Mo: 0.10% or more, 4.00% or less, with the balance consisting of Fe and inevitable impurities Is preferably used. Hereinafter, the reasons for limiting each chemical component will be described. In the following description, all units represented by% are mass%.

  C: 0.15% or less. C is added to ensure a predetermined strength, but if it exceeds 0.15%, weldability and toughness deteriorate, so the upper limit is made 0.15%.

  Si: 0.7% or less. Si is added as a deoxidizing agent and a strength improving element during steelmaking, but if added in excess, the toughness is remarkably lowered, so the content is made 0.7% or less.

  Mn: 0.10% or more and 2.00% or less. Mn is added in an amount of 0.10% or more in order to ensure a predetermined strength, but if it exceeds 2.00%, the weldability deteriorates, so the content is made 2.00% or less.

  P: Over 0.03% and 0.15% or less. P is an important element and has the effect of improving the strength of steel and the effect of improving corrosion resistance, so it is added in a necessary amount. Addition of 0.03% or less has no effect in improving corrosion resistance, and addition exceeding 0.15% deteriorates weldability. Therefore, the addition is made over 0.03% and 0.15% or less.

  S: Set to 0.020% or less. Since S is an element harmful to corrosion resistance, it is set to 0.020% or less.

  Al: 0.010% or more and 0.100% or less. Al is added in an amount of 0.010% or more as a deoxidizer at the time of steelmaking, but if added in excess, inclusions that become the starting point of corrosion tend to occur, so the content is made 0.100% or less.

  Ni: 0.2% or more and 4.0% or less. Ni is also an important element and has the effect of improving the corrosion resistance in a salty environment by coexistence with Mo. If Ni is added less than 0.2%, there is no effect, and if it exceeds 4%, it is disadvantageous in terms of economy, so 0.2% or more and 4.0% or less.

  Cu: Less than 0.1%. Cu is an element that improves the corrosion resistance. However, if added in an amount of 0.1% or more, the effect is saturated and disadvantageous in terms of economy, so the content is made less than 0.1%.

  Mo: 0.10% or more and 4.00% or less. Mo is also an important element and has the effect of improving the corrosion resistance in a salty environment by coexistence with Ni. If the addition is less than 0.10%, there is no effect, and if it exceeds 4.00%, it is disadvantageous in terms of economy, so the content is made 0.10% or more and 4.00% or less.

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

  Here, the details of the effects of Ni and Mo on the corrosion resistance are not clear, but are considered as follows. Mo is considered to have an effect of increasing the density of rust and preventing corrosion factors such as moisture and salt from contacting the steel surface. On the other hand, Mo has the property of making rust brittle, and defects such as cracks are likely to occur. Ni has the property of improving the property of rust which is easily broken and making it difficult to cause defects such as cracks. Since a synergistic effect is exhibited by these two different properties, it is considered that the corrosion resistance is remarkably improved by adding Mo together with an appropriate amount of Ni.

  Note that Cr, which is normally actively added, is an element that rather promotes perforated corrosion in a salty environment, and is an element that significantly deteriorates weldability. .

  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.

  A hydrated hardened body having a reinforcing bar therein was manufactured using reinforcing bars (steel types A to X) made of carbon steel having the chemical components shown in Table 1.

  Steelmaking slag having the chemical composition and physical properties shown in Table 2 (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 3, the hydrated cured material is kneaded, cured, and concrete No. 1 is obtained. 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 3.

  In addition, in the composition of the raw material of hydrated hardened body shown in Table 3, the reinforcing bar made of carbon steel having the chemical composition shown in Table 1 is 2 The cover thickness was changed from 20 to 40 mm under the condition of%, 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 100 cycles of accelerated corrosion test, break the hydrated hardened body and take out the reinforcing bar, remove the reinforcing bar with 10 mass% ammonium dihydrogen citrate aqueous solution, and measure the corrosion area ratio and maximum corrosion depth 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 steel material having a predetermined component, both show good corrosion resistance when the cover thickness is 20 mm or more, Even after 100 cycles of the accelerated corrosion test, no corrosion was observed in the reinforcing bars in the cured body (Invention Examples 1 to 22). Moreover, when using conventional concrete using ordinary cement or blast furnace cement type B, the rebar in any of the hydrated hardened bodies was corroded on the entire surface with a cover thickness of 20 mm, and the corrosion resistance was poor (Comparative Examples 12 to 12). 15). In addition, when steel types N to X whose steel material components deviated from the preferred range of the present invention were used, corrosion was observed in all the samples, and sufficient corrosion resistance was not obtained.

Claims (8)

  Water having a reinforcing bar excellent in salt damage resistance, characterized in that the hydrated hardened body having a reinforcing bar inside contains at least steelmaking slag and blast furnace slag fine powder, and the reinforcing bar is a carbon steel having weather resistance. Japanese cured body.   Carbon steel in mass% C: 0.15% or less, Si: 0.7% or less, Mn: 0.10% or more, 2.00% or less, P: more than 0.03%, 0.15% or less, S: 0.020% or less, Al: 0.010% or more, 2. The content of Ni is 0.200% or less, Ni is 0.2% or more and 4.0% or less, Cu is less than 0.1%, Mo is 0.10% or more and 4.00% or less, and the balance is Fe and inevitable impurities. A hydrated and cured product having a reinforcing bar excellent in salt damage resistance.   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 hydration having a reinforcing bar excellent in salt damage resistance according to any one of claims 1 to 4, wherein the content of the blast furnace slag fine powder in the hydrated cured body 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 5, wherein the hydrated cured body further contains fly ash. The content of fly ash in the hydrated and cured product is 50 to 300 kg / m ³ , and the hydrated and cured product having a rebar excellent in salt damage resistance according to claim 6.   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 7.