JP4827580B2 - Hydrated hardened body with reinforcing bars with excellent neutralization resistance and salt damage resistance - Google Patents

Description

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

  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 contains at least steelmaking slag, blast furnace slag fine powder, and fly ash, and CaO / SiO _{2 of the} steelmaking slag is 1.5 to 2.7 in terms of mass ratio. Or the CaO content is 25 mass% or more and 47.1 mass% or less, and the steelmaking slag includes steelmaking slag having a particle size in a range of 0.075 mm or more and 20 mm or less, and a steelmaking slag having a particle size of 5 mm or less. content is not more 500 kg / m ³ or more, a maximum particle size of the steel slag is is 20 mm, the amount of ground granulated blast furnace slag in the mixture is 100~600kg / ^{m 3,} steelmaking slag in the mixture and the content of the 1882kg / ^{m 3} or more, a MgO content of 1.8 to 4.3 wt% of steel slag, C further said reinforcing bars by mass%: 0.15% or less, Si: 0.7% 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, 0.100% or less, Ni: 0.2% or more, 4.0% or less, Cu: Less than 0.1%, Mo: 0.10% or more and 4.00% or less, with the balance being a carbon steel having weather resistance consisting of Fe and unavoidable impurities, excellent in neutralization resistance and salt damage resistance Hydrated and hardened body with rebar.
(2) The hydrated cured product further contains one or more selected from alkaline earth metal oxides, hydroxides, Portland cement, silica cement, fly ash cement, and eco-cement. The hydrated cured product having a reinforcing bar excellent in neutralization resistance and salt damage resistance as described in (1) .

  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. A body is obtained, and it is found that it can be used as a structural member having long-term durability even in an environment where neutralization is likely to proceed, such as repeated drying and drying, by combining this with a reinforcing bar having weather resistance. Was completed.

  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 cured body of the present invention contains at least steelmaking slag and fine powder of blast furnace slag, and the steelmaking slag has a CaO / SiO ₂ ratio of 1.5 or more and / or a CaO concentration of 25% by mass or more. .

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. Steelmaking slag for acting as a neutralization inhibiting material has a CaO / SiO ₂ mass ratio of CaO and SiO ₂ , which is a component of steelmaking slag, of 1.5 or more and / or a CaO concentration of 25% by mass or more. It is necessary to. CaO / SiO ₂ is 1.5 or more and / or CaO concentration 25 mass% or more steel slag in mass ratio, was dissolved in water CaO component in the steelmaking slag is contained in the hydrated cured body over a long period of time, Keeps the hydrated cured body weakly alkaline and prevents neutralization. More preferably, CaO / SiO ₂ is 2.0 or more in mass ratio and / 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, the CaO density | concentration in this invention is 25 mass% or more by the CaO density | concentration shown to the following (A) formula.
CaO concentration [mass%] = {CaO analytical concentration [mass%] / (100−metal iron analytical concentration [mass%])} × 100 (A)
The formula (A) corresponds to the CaO concentration of steelmaking slag that does not form an oxide mineral phase and excludes the influence of metallic iron whose concentration varies greatly.

In order to suppress neutralization, it is more preferable to use steelmaking slag as a material in the hydrated cured body of 500 kg / m ³ or more. Even more preferably, it is 700 kg / m ³ or more. The particle size is not particularly defined, but preferably contains particles of about 0.075 mm to 20 mm. This is because the fine steelmaking slag has an effect of suppressing neutralization at the beginning of the service period, and the coarse steelmaking slag maintains the effect of suppressing neutralization for a long period of service. . Further, it is more preferable that a steelmaking slag of 5 mm or less is contained in an amount of 500 kg / m ³ or more.

  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 occurrence 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.

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.

  It is preferable that the hydrated cured material further contains 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 material of the hydrated cured body, 1% by mass 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 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.

  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 fine rust on the surface by repeated appropriate drying and wetting in the atmosphere. There are few steel materials, and what is prescribed | regulated to the weather-resistant steel materials (SMA) for welded structures of JIS and high weather-resistant steel materials (SPA) can be used.

  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 deoxidizer and a strength improving element during steelmaking, but if added in excess, the toughness is significantly reduced, 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 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.

  The steelmaking slag used was one having the chemical components and physical properties shown in Table 1 (maximum particle size, coarse particle ratio, fine aggregate ratio, surface dry density) (steelmaking slag Nos. A to E). 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.

  Reinforcing bars were manufactured by using 25φ × 200 mm reinforcing bars having chemical components shown in Table 2 (steel types A to W).

According to the formulation shown in Table 3, the hydrated cured material is kneaded, poured into a φ100 × 200 mm mold, cured, and no. Test pieces for measuring the compressive strength of 1 to 23 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 a steel type reinforcing bar shown in Table 3 was inserted in the center was No. Two pieces were produced for each production condition of 1 to 23. 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 a CO ₂ concentration of 5%, a temperature of 40 ° C., and a humidity of 60% RH. The chemical depth was measured and evaluated from the average value. The neutralization depth was measured by using a phenolphthalein 1% solution spray method and setting the non-colored portion to the 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.

  Moreover, the test piece (No. 24) which does not use steelmaking slag and blast furnace slag fine powder for the comparison was produced. According to the composition shown in Table 4, concrete materials were mixed with a mixer, poured into a φ100 × 200 mm mold, and cured to produce test pieces for compressive strength measurement, neutralization promotion test, and salt damage resistance test. . 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, neutralization promotion test results, and salt damage resistance test results are also shown in Tables 3 and 4. CaO / blending SiO ₂ is contained steelmaking slag (steelmaking slag No.A～D) and blast furnace slag is 1.5 or more and / or CaO concentration above 25 wt% in mass ratio No. When combined with reinforced hardened bodies of 1 to 8 and reinforcing bars having a predetermined steel component (test pieces No. 1 to 13), the water binder ratio (water cement ratio) 50% using a high-quality aggregate Test piece No. The neutralization depth was smaller than that of ordinary concrete No. 24 (Blend No. 11), and no corrosion of the internal reinforcing bar surface was observed after the salt damage resistance test. On the other hand, test piece No. 2 containing steelmaking slag (steelmaking slag No. E) having a CaO / SiO ₂ mass ratio of less than 1.5 and a CaO concentration of less than 25 mass% and blast furnace slag fine powder. The hydrated cured bodies of Nos. 14 to 23 (Blend Nos. 9 and 10) are inferior in neutralization resistance to ordinary concrete (test piece No. 24) having a water binder ratio of 50% using high-quality aggregates. The rebar also corroded.

Claims (2)

The hydrated hardened body having rebar inside contains at least steelmaking slag, blast furnace slag fine powder, and fly ash, and the steelmaking slag has a CaO / SiO ₂ ratio of 1.5 to 2.7 and / or mass ratio. Containing a steelmaking slag having a CaO concentration of 25 mass% or more and 47.1 mass% or less, the steelmaking slag including a steelmaking slag having a particle size in a range of 0.075 mm or more and 20 mm or less, and a particle size of 5 mm or less. the amount is not more 500 kg / m ³ or more, a maximum particle size of the steel slag is is 20 mm, a 100~600kg / ^{m 3} content of ground granulated blast furnace slag in the mixture, containing steelmaking slag in the mixture The amount is 1882 kg / m ³ or more, the MgO content of the steelmaking slag is 1.8 to 4.3% by mass, the rebar is mass% by C: 0.15% or less, Si: 0.7% 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, 0.100% or less, Ni: 0.2% or more, 4.0% or less, Cu: Less than 0.1%, Mo: 0.10% or more and 4.00% or less, with the balance being a carbon steel having weather resistance consisting of Fe and unavoidable impurities, excellent in neutralization resistance and salt damage resistance Hydrated and hardened body with rebar. Claim hydration cured product further oxide of an alkaline earth metal, hydroxide, portland cement, silica cement, fly ash cement, characterized in that it contains one or more selected from Ecocement 1. A hydrated cured product having a reinforcing bar excellent in neutralization resistance and salt damage resistance according to 1 .