JP5653952B2 - Method for constructing reinforced concrete structures - Google Patents

Description

  The present invention mainly relates to a method for constructing a reinforced concrete structure with concrete containing a concrete glass containing salt as an aggregate, or concrete prepared by mixing seawater with water.

  On March 11, 2011, a massive earthquake and tsunami hit the Tohoku region, causing tremendous damage. The infrastructure in the Tohoku region has been hit hard and it is hoped that it will be restored as soon as possible.

  However, the rubble generated by the tsunami is scattered over a wide area of the stricken area, and if the processing of the rubble does not progress, the recovery will not progress slowly. Debris includes inorganic materials such as concrete and metals, and organic materials such as wood, rubber, and plastic.

  Organic debris can be disposed of by incineration, but inorganic debris, especially concrete debris, has no added value and is bulky and important and is difficult to dispose of. The proposal of the effective utilization method of concrete glass is desired.

  Conventionally, as an effective utilization method of concrete glass, a method of utilizing as recycled aggregate has been proposed. However, most of the concrete galley that was damaged by the Tohoku earthquake was affected by the tsunami and contained high concentrations of salt.

  When using concrete glass as recycled aggregate, it is necessary to use it at the source. This is because it cannot be carried away and used as a feature of aggregates. In this case, consumption in the coastal area is desired, and it is realistic to use it for revetment work and seawalls during reconstruction work. For such use, it is desirable to prepare a ready-mixed concrete by installing a field plant, and further, procurement of fresh water is regarded as a problem. Therefore, seawater-mixed concrete has been proposed.

  In addition to aggregates containing a large amount of salt due to the influence of seawater, seawater is also used for kneaded water. Such special concrete cannot avoid the corrosion of reinforcing bars. Therefore, in order to promote reconstruction, there is a strong development of reinforced concrete technology that can suppress the corrosion of reinforcing bars, whether using concrete galley affected by salinity as recycled aggregates or using seawater as mixing water. It has been demanded.

  On the other hand, a method using a zinc sacrificial anode material is known as a method of suppressing corrosion of corrosion in a reinforced concrete structure (Patent Document 1). In this method, when repairing reinforced concrete deteriorated by salt damage with a cross-section repair material, it is attached to the reinforcing bar. However, in the new construction, there is no example of applying concrete gravel generated by tsunami damage to concrete that uses recycled aggregate, and no example of applying it to seawater-mixed concrete.

  In view of the above-mentioned problems, the present inventors arrange a sacrificial anode on a reinforcing bar when constructing a reinforced concrete structure using concrete containing a concrete glass generated by damage from an earthquake or tsunami as an aggregate. Thus, the inventors have found that the above-mentioned problems can be solved, and have completed the present invention.

Japanese Patent No. 3099830

  The present invention provides a method for producing a reinforced concrete structure having excellent durability using a concrete glass containing salt, or concrete prepared by mixing seawater into kneaded water.

In the present invention, (1) 5 to 20 sacrificial anodes per 1 m ² of the reinforcing bar surface area are disposed on a reinforcing bar when a reinforced concrete structure is constructed using concrete containing a concrete glass containing salt as an aggregate. (2) When constructing a reinforced concrete structure using concrete prepared using seawater as kneaded water, a sacrificial anode is provided on the reinforcing bar, and the surface area of the reinforcing steel is 5 per 1 m ² of surface area of the reinforcing bar. ~ 20 reinforced concrete structure creation method, (3) When building reinforced concrete structure using seawater as kneaded water and concrete containing salt-containing concrete glass as aggregate, how construction of reinforced concrete structures that the sacrificial anode to the reinforcing bar to 5 to 20 arranged per surface area 1 m ² of the rebar, distribution (4) sand (1) to (3) a method for constructing a reinforced concrete structure, (5) a concrete containing a chlorine fixing material (1) to (4) a method for constructing a reinforced concrete structure, 6) The method for producing a reinforced concrete structure according to any one of (1) to (5), wherein the chloride ion content of the concrete exceeds 0.3 kg / m ³ .

  By adopting the method for building a reinforced concrete structure of the present invention, for example, rubble that hinders reconstruction can be processed, and aggregates containing a large amount of salt that cannot be originally used for reinforced concrete structures, and seawater as kneading water are used. However, it is possible to prolong the life of the reinforced concrete structure obtained, and to improve the strength development, neutralization resistance, and freeze-thaw resistance of the concrete.

  Hereinafter, the present invention will be described in detail.

  In the present invention, for example, rubble of concrete rubble generated by tsunami damage is used as a concrete aggregate. The concrete glass can be used after being pulverized to an appropriate size.

  The concrete galley generated by the tsunami is salty because it is bathed in seawater. In general, aggregates containing a large amount of salt, such as sea sand, are used after being washed with water and desalted. However, in this invention, salt removal is not performed but it uses as it is. This is indispensable for smooth disaster recovery.

  Originally, aggregates containing a large amount of salt cannot be used because they induce corrosion of reinforcing steel bars. However, by attaching the sacrificial anode material of the present invention to a reinforcing bar, it is possible to create a durable reinforced concrete structure even when using a concrete containing a large amount of salt.

The concrete glass referred to in the present invention contains a tsunami and therefore contains salt. The content is generally 0.01 to 0.05% by mass. In general, the amount of coarse aggregate in concrete is 800 to 1200 kg / m ³ . Therefore, when using the concrete Gala wearing a tsunami as recycled aggregate, salinity derived from the bone material, a 1 m ³ per 0.08~0.60kg / ^{m 3.}
According to the provisions of JISA 5308 “Ready mixed concrete”, the salinity contained in the concrete is 0.3 kg / m ³ or less. Accordingly, a salt content of 0.3 kg / m ³ or less is an excessive measure and is economically disadvantageous.

In the present invention, seawater can be used as the kneaded water. The salt content of seawater is generally in the range of 3-4% by weight. Moreover, the unit water amount of concrete is generally in the range of 150 to 185 kg / m ³ . Therefore, the amount of salt derived from seawater as the kneaded water can be calculated. For example, when a concrete having a salt content of 3.5% by mass and a unit water amount of 170 kg / m ³ is prepared, the salt derived from the kneaded water is 170 × 0.035 = 5.95 kg / m ^3. .

  In the present invention, a reinforced concrete structure can be made of concrete containing aggregates of concrete glass generated by earthquake or tsunami damage, or concrete prepared by mixing seawater with water.

  In the present invention, sea sand can be used as the fine aggregate. Usually, sea sand is washed with water to reduce the salt level to an acceptable level (0.04% by mass or less according to JIS 5308 “Ready mixed concrete” Annex A), but in the present invention, it is not washed with water. It can also be used as it is.

The sacrificial anode material referred to in the present invention is a material having the ability to form a galvanic battery by forming a rebar and a circuit of a metal having a higher ionization tendency than iron constituting the rebar and to prevent corrosion of the iron.
Specifically, these metals are used using chromium, zinc, manganese, lead, titanium, uranium, aluminum, magnesium, sodium, lithium, or an alloy or pseudoalloy composed of two or more kinds selected from them. A circuit is formed by bundling with steel bars through mild steel wires.
These metals are preferably made into briquettes of about 50 to 70 g per piece, wrapped with a backfill material composed of an inorganic mortar using a binder such as cement or gypsum, and capable of maintaining the anticorrosion effect over a long period of time. .
The shape of the briquette may be any shape as long as the object of the present invention is not hindered, but is preferably a lump shape such as a disk shape, a rectangular parallelepiped shape, a cubic shape, or a spherical shape. The method for installing the backfill material is not particularly specified, but it is preferable that the metal in-frame is placed so as to embed the briquette-shaped metal lump, and the backfill material is poured into the mold and cured. The sacrificial anode material is connected with a soft steel wire or the like from a metal lump, and is confirmed to be electrically connected to the rebar by being tightly coupled to the rebar.
The sacrificial anode material of the present invention is disposed and used together with a reinforcing bar.

The usage ratio of the sacrificial anode material is preferably 5 to 20 and more preferably 10 to 15 per 1 m ² of the surface area of the reinforcing bar installed in the concrete. If the number is less than 5, the corrosion of the reinforcing bars may not be suppressed over a long period of time, and even if the number is more than 20, the further effect cannot be expected.

  By using the sacrificial anode material, it is possible to greatly extend the period until corrosion of the reinforcing bars occurs. In addition, the effect of reducing the salinity concentration in the vicinity of the reinforcing bar is also exhibited. According to the results of the accelerated test, the life can be extended for 20 to 30 years depending on the conditions. Furthermore, in addition to the improvement of the compressive strength, the neutralization speed is reduced, and the freeze-thaw resistance is improved, thereby improving the durability.

The chlorine immobilization material used in the present invention is to prevent the rusting of the reinforcing bars by fixing chloride ions in the concrete so that they do not elute into the free water in the concrete by taking them into crystals. It refers to all concrete admixtures intended.
For example, monosulfate, hydrotalcite-like compound, etc. are produced and immobilized in the form of Friedel's salt, and the molar ratio of blast furnace slag, lithium nitrite hydrocalumite, CaO / Al ₂ O ₃ is Examples include 0.3 to 0.7 calcium aluminate. In the present invention, any existing chlorine fixing material can be used. Among them, it is preferable to apply calcium aluminate having a CaO / Al ₂ O ₃ molar ratio of 0.3 to 0.7.

Hereinafter, although an example and a comparative example are given and the contents are explained in detail, the present invention is not limited to these.

"Experiment 1"
Using various coarse aggregates, fine aggregates and kneading water shown in Table 2, unit cement amount 300 kg / m ³ , unit water amount 170 kg / m ³ , s / a = 42%, slump 8 cm, air amount 4.5 ± 1.0% concrete was prepared. Using this concrete, a wall made of reinforced concrete having a rebar ratio of 0.7% was constructed. It should be noted that 13 sacrificial anode materials per 1 m ^{2 of} the reinforcing bar surface are arranged with a soft steel wire connected to the sacrificial anode material in close contact with the reinforcing bar, and the corrosion current of the reinforcing bar of this reinforced concrete is examined, and the salinity near the reinforcing bar The concentration was examined. Furthermore, concrete compressive strength, accelerated neutralization test, and freeze-thaw resistance test were conducted. The results are shown in Table 2.

<Materials used>
Sacrificial anode material: 55 g of zinc made into a disk-shaped briquette and wrapped with a cement-based backfill material. Mild steel wire is connected to the zinc, and conduction is ensured by tightening to the reinforcing bar.
Cement: Ordinary Portland cement. Commercial product, specific gravity 3.15.
Coarse aggregate A: Crushed concrete glass damaged by tsunami. Gmax 25 mm. Salinity content 0.05 mass%, specific gravity 2.25. The coarse aggregate is 900.16 kg / m ³ , and the salt content derived therefrom is 0.45 kg / m ³ .
Coarse aggregate B: from Himekawa, Niigata Prefecture, crushed stone, Gmax 25 mm, specific gravity 2.65.
Fine aggregate i: Himekawa, Niigata Prefecture, river sand, specific gravity 2.64.
Fine aggregate B: sea sand, salt content 0.1% (according to the method described in JIS A5308 “Ready mixed concrete” Annex A), specific gravity 2.75. The fine aggregate is 796.68 kg / m ³ , and the salt content derived therefrom is 0.797 kg / m ³ .
Fine aggregate C: sea sand, salt content 0.039%, specific gravity 2.75. The fine aggregate is 796.68 kg / m ³ , and the salt content derived therefrom is 0.31 kg / m ³ .
Kneaded water a: tap water.
Kneaded water b: Seawater, salt content 3.5% by mass (according to the method described in JIS A 5308 “Ready mixed concrete” Annex C)
Chlorine fixing material: Calcium aluminate having a CaO / Al ₂ O ₃ molar ratio of 0.6. Reagent primary calcium carbonate and reagent primary aluminum oxide were blended so that the molar ratio of CaO / Al ₂ O ₃ was 0.6 in terms of oxide, and then fired in an electric furnace. After calcination at 1450 ° C. for 3 hours, it was synthesized by slow cooling. All the brain specific surface area values were adjusted to 4,000 cm ² / g. The amount used was 10% by mass substitution with respect to ordinary cement.

<Test method>
Reinforcing bar corrosion determination: The natural potential of the reinforcing bar relative to the copper / copper sulfate electrode serving as the reference electrode was measured according to ASTM C 876 after half a year, 1 year, and 3 years later, and the corrosion state of the reinforcing bar was determined. The corrosion of the reinforcing bars is judged as shown in Table 1.

Total salt content of concrete: Measured according to JIS A 1154 “Testing method for chloride ions contained in hardened concrete”.
Measurement of salinity in the vicinity of the reinforcing bar: The concrete core was extracted from the specimen at the age of 1 year, and the salinity in the vicinity of the reinforcing bar was measured from the concrete piece in the vicinity of the reinforcing bar in accordance with JISA 1154.
Compressive strength: Measure compressive strength at age 28 days according to JIS A 1108.
Accelerated neutralization test: After demolding at a material age of 1 day, water curing at 20 ° C. was carried out for 13 days, followed by accelerated neutralization in an environment of 30 ° C., RH 60%, CO ₂ concentration 5% for 91 days. The neutralization depth was determined by the phenolphthalein method.
Freezing and thawing resistance test: In accordance with JIS A 1148 “Concrete Freezing and Thawing Test Method”, the test was conducted with the starting material age as 28 days. However, a maximum of 400 freeze-thaw cycles were performed. When the number of cycles in which the relative kinematic modulus is maintained at 60% or more exceeds 400 cycles, ◎, when it exceeds 300 cycles and less than 400 cycles, ○, when it exceeds 200 cycles, and when it is less than 300 cycles The case where it was less than 200 cycles was rated as x.

From Table 2, it can be seen that rebar corrosion does not occur in the method of the present invention. Moreover, it turns out that the salt content near a reinforcing bar is also falling. In addition, it can be seen that compressive strength, neutralization resistance, and freeze-thaw resistance are improved.

"Experimental example 2"
The same procedure as in Experimental Example 1 was performed except that coarse aggregate B, fine aggregate B, and kneading water b were used, and the number of sacrificial anode materials used per 1 m ² of surface area of the reinforcing bar was changed as shown in Table 2. . The results are also shown in Table 3.

From Table 3, it can be seen that rebar corrosion does not occur in the method of the present invention. It can also be seen that the amount of salt in the vicinity of the reinforcing bar is also reduced.

  By adopting the method for building a reinforced concrete structure of the present invention, for example, rubble that hinders reconstruction can be processed, and aggregates containing a large amount of salt that cannot be originally used for reinforced concrete structures, and seawater as kneading water are used. Can increase the life of the reinforced concrete structure obtained, and also has the effects of improving the strength development, neutralization resistance, and freeze-thaw resistance of the concrete. Can be used for

Claims (6)

Reinforced concrete structure characterized in that 5 to 20 sacrificial anodes per 1 m ² of surface area of the reinforcing bar are disposed on the reinforcing bar when a concrete structure including a concrete glass containing salt is used as an aggregate. How to create things. When constructing a reinforced concrete structure using concrete prepared using seawater as kneaded water, 5 to 20 sacrificial anodes are disposed on the reinforcing bar per 1 m ² of surface area of the reinforcing bar. Creation method. When constructing a reinforced concrete structure using seawater as kneaded water and concrete containing salted concrete as an aggregate, 5 to 20 sacrificial anodes per 1 m ² of the reinforcing bar surface area are placed on the reinforcing bar. A method for constructing a reinforced concrete structure, characterized by comprising: Sea sand is mix | blended, The creation method of the reinforced concrete structure of any one of Claims 1-3 characterized by the above-mentioned. 5. The method for producing a reinforced concrete structure according to any one of claims 1 to 4, wherein the concrete contains a chlorine fixing material. The method for creating a reinforced concrete structure according to any one of claims 1 to 5, wherein the chloride ion content of the concrete exceeds 0.3 kg / m ³ .