JP4796419B2 - Hydrated cured body having reinforcing bars excellent in neutralization resistance and salt damage resistance and method for producing the same - Google Patents

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. The present invention relates to a cured body and a method for producing the same.

  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.

  In this way, using conventional technology, there is a limit to prevent corrosion of rebars by inhibiting neutralization of hydrated hardened bodies made of concrete, steelmaking slag and blast furnace slag fine powder, etc. .

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. Another object of the present invention is to provide a hydrated cured product having a reinforcing bar excellent in salt damage resistance and a method for producing the same.

The features of the present invention for solving such problems are as follows.
(1) A hydrated cured body having reinforcing bars inside is at least one selected from Portland cement , B type fly ash cement suitable for JIS R5213 “fly ash cement” , slaked lime, Contains steelmaking slag with a CaO / SiO ₂ ratio of less than 1.5 or a CaO concentration of less than 25% by mass, blast furnace slag fine powder and fly ash , “Portland cement (kg / m ³ ) + fly ash cement” ^{(kg / m 3) × 0.85} + slaked lime (kg / m ³⁾ "is a 55 kg / m ³ or more, further wherein the reinforcing bars Ri Ah of carbon steel having a weather resistance, the content of steelmaking slag 2239kg / m is ³ or more,耐中resistance resistance and salt damage, wherein the amount of ground granulated blast furnace slag in the mixture is 100~600kg / m ³ Hydrated cured product having excellent reinforcing bar.
(2) Reinforcing bars 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%, 0.0. 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: It contains 0.10% or more and 4.00% or less, and the balance consists of Fe and inevitable impurities.
(3) A method for producing a hydrated cured body having a reinforcing bar excellent in neutralization resistance and salt damage resistance, wherein “Portland cement (kg / m ³ ) + fly ash cement (kg / m ³ ) × 0 .85 + Slaked lime (kg / m ³ ) ”is selected from at least Portland cement , Class B fly ash cement and slaked lime that conform to JIS R5213“ Fly Ash Cement ” so that“ 55 + slaked lime (kg / m ³ ) ”is 55 kg / m ³ or more. Mixture obtained by mixing seed or two or more, steelmaking slag with a CaO / SiO ₂ mass ratio of less than 1.5 or a CaO concentration of less than 25% by mass, blast furnace slag fine powder and fly ash with water comprising the step of curing, the reinforcing bar Ri Ah of carbon steel having a weather resistance, the content of steel slag is at 2239kg / m ³ or more, blast slide in said mixture Method for producing a hydrated cured product having耐中resistance resistance and salt damage excellent in reinforcing bars, wherein the amount of the fine grayed fines is 100~600kg / m ^3.

  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. Used as a structural member that has a long-term durability even in an environment where neutralization and salt damage are likely to occur due to the combination of high salinity and repeated drying and wetting by combining a reinforcing bar with weather resistance. The present invention has been completed by finding out what can be done.

  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 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.

  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, super-early-strength 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.

  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.

  The 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% by mass%. .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 : It is preferable to use steel having a composition containing 0.10% or more and 4.00% or less, with the balance being Fe and inevitable impurities. 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 4.0%, there is a disadvantage 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 slags used were those 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 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.

  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.

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

According to the composition shown in Table 3 (Formulation Nos. 1 to 12), the hydrated cured material was kneaded with a mixer, poured into a mold of φ100 × 200 mm, cured, and no. Test pieces for measuring compressive strength of 1 to 22 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 manufactured according to each manufacturing condition of 1-22. 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 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.

  For comparison, a test piece (No. 23) of ordinary concrete without using steelmaking slag and blast furnace slag fine powder was prepared. 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. Steelmaking slag and blast furnace slag fine powder, "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 ) ”(corresponding to NP + 0.6BB + 0.85FB + CH in Table 3) 55 kg / m ³ or more, and a hydrated cured body (test pieces No. 1 to 12) 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. 23, and no corrosion was observed in the internal reinforcing bars even after the salt damage resistance test. On the other hand, when a hydrated cured body and a reinforcing bar that do not correspond to these are combined (test pieces No. 13 to 22), they are more resistant to neutrality than ordinary concrete with a 50% water binder ratio using high-quality aggregates. The corrosion of the reinforcing bars was observed after the salt damage resistance test.

Claims (3)

A hydrated cured body having a reinforcing bar inside is at least one selected from Portland cement , B type fly ash cement suitable for JIS R5213 “fly ash cement” , slaked lime, and CaO / SiO 2 ₂ containing steelmaking slag having a mass ratio of less than 1.5 or CaO concentration of less than 25% by mass, blast furnace slag fine powder and fly ash , “Portland cement (kg / m ³ ) + fly ash cement (kg / m ³⁾ × 0.85 + slaked lime (kg / m ³⁾ "is a 55 kg / m ³ or more, in addition the reinforcing bars Ri Ah of carbon steel having a weather resistance, the content of steelmaking slag 2239kg / m ³ or more There, Yu the耐中resistance resistance and salt damage resistance, wherein the amount of ground granulated blast furnace slag in the mixture is 100~600kg / m ³ Hydrated cured product having a rebar. Reinforcing bars 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, 0.100% or less, Ni: 0.2% or more, 4.0% or less, Cu: less than 0.1%, Mo: 0.10 The hydration hardening having a reinforcing bar excellent in neutralization resistance and salt damage resistance according to claim 1 , characterized in that it contains not less than 1% and not more than 4.00%, and the balance consists of Fe and inevitable impurities body. A method for producing a hydrated hardened body having a rebar excellent in neutralization resistance and salt damage resistance, comprising “Portland cement (kg / m ³ ) + fly ash cement (kg / m ³ ) × 0.85 + slaked lime (Kg / m ³ ) ”is 55 kg / m ³ or more, at least one selected from Portland cement , Class B fly ash cement conforming to JIS R5213“ Fly ash cement ”, or slaked lime curing the above species, the steel slag of less than 25% by weight less than 1.5 or CaO concentration CaO / SiO ₂ mass ratio, and a blast furnace slag and fly ash is mixed with water, the resulting mixture comprising the step, the reinforcing bars Ri Ah of carbon steel having a weather resistance, the content of steel slag is at 2239kg / m ³ or more, blast furnace slag in the mixture Method for producing a hydrated cured product having excellent reinforcing bar耐中resistance resistance and salt damage resistance, wherein the amount of end is 100~600kg / m ^3.