JP2003512518A - Encapsulated metal nodules for forming sacrificial anodes in reinforced concrete and methods of making the nodules - Google Patents

Abstract

  (57) [Summary] Reinforced concrete and mortar for architectural and civil engineering. Each nodule of the present invention comprises: a metal core containing one or more metals or metal alloys selected from those exhibiting an electrochemical potential lower than iron; and a protective film surrounding the core, comprising concrete. First, when the nodules are used in the preparation and practice of mortar, etc., the first is that the protective film exhibits sufficient mechanical strength to withstand mixing with aggregates constituting concrete, mortar, etc .; The protective film constitutes a temporary barrier to water, at least until the concrete, mortar, etc. is partially hardened. The present invention is applicable to the repair of reinforced concrete structures damaged by corrosion.

Description

Detailed Description of the Invention

TECHNICAL FIELD The present invention relates to a technical field of protecting a metal reinforcing material of a structure made of reinforced concrete or the like from corrosion.

[0002] Metal reinforcements, especially metal reinforcements made of steel, undergo a passivation phenomenon when used in hydraulic concrete or mortar due to the high alkalinity caused by the dissolution of the alkaline raw materials in the cement. It is known. In many common applications, this passivation provides good protection for the metal reinforcement of the concrete.

However, this technique of protecting the reinforcement is not effective in structures that tend to be submerged in seawater or in contact with chloride ions Cl ⁻ , which destroys the passivated state of the steel reinforcement. This is especially true for structures that receive seawater to prevent icing, especially in winter. In the presence of high concentrations of chloride ions, the pH of the concrete decreases and the passivation state is lost, at which time the metal reinforcement becomes a focus of oxidation phenomena leading to structural destruction.
Expansive rust forms on the surface of the reinforcement, causing cracks and collapses in the concrete of the structure. Further, when the reinforcing material is oxidized, its structure is weakened and the strength of the structure in question is impaired.

The presence of high concentrations of chloride ions not only lowers the initial high pH, but also accelerates concrete aging to a greater or lesser extent. This drop in pH over time is also a result of the action of carbon dioxide in the atmosphere, and in the presence of moisture, a reaction called carbonation sticks on the lime that is released at the end of cement hydration. By this reaction, the reinforcing material of the reinforced concrete is depassivated and corrosion and expansive rust are generated.

(Background Art) In order to prevent such a corrosion phenomenon, so-called “anode protection (anodic protection) of a reinforcing material is used.
protection) ". This protection includes connecting the stiffener to a DC power source so that a protective current flows therethrough, or providing a sacrificial anode of one or more metals having a lower electrochemical potential than iron. More particularly, the present invention relates to a second method of protecting metal reinforcement by working a sacrificial anode.

In this particular field, French patent application FR 2689921 discloses that zinc-based particles are locally applied to the interior of restored concrete or mortar in the area where the reinforcement is in need of repair of structures that have undergone a high degree of corrosion. Propose to insert. The difference in the electrochemical potential between iron and zinc causes an oxidation-reduction reaction inside the repaired mortar that is in contact with the oxidized reinforcement, thereby reducing the rust formed on the reinforcement. Contribute to. In addition, one type of battery that electrically biases the reinforcement is constructed to protect the reinforcement. The sacrificial anode thus constituted by the zinc particles is oxidized instead of the metallic stiffener, whereby the stiffener is protected.

Under certain circumstances, such methods may provide sufficient repair, refurbishment and protection of the reinforcement and the concrete containing it. Unfortunately, in other situations, it has been found that the electrochemical potential difference between the reinforcing steel and zinc is insufficient to effectively protect the reinforcement. In that case, it is necessary to consider using a metal or an alloy having an electrochemical potential lower than that of zinc, such as aluminum. However, aluminum is extremely reactive in a highly alkaline aqueous medium composed of fresh concrete and mortar. Therefore, a large amount of hydrogen is generated by this reaction, and the inside of the mortar or concrete is destroyed and weakened.

[0008] Thus, the gas produced as a result of the electrolytic reaction in cooperation with the metal anode is highly reactive in a strong alkaline aqueous medium without the risk of impairing the mechanical properties of concrete or mortar. What is needed is a method that allows the metal or metal alloy that it has to be used as a sacrificial anode in mortar, concrete and the like. Furthermore, it has been found that when zinc is used in hydraulic concrete or mortar, an electrolytic reaction naturally occurs between zinc, the alkaline raw material of cement and water. As a result, these reactions result in the zinc pieces being consumed before they can react with the reinforcement for repair or protection. Therefore, the sacrificial anode used and the concrete or mortar, as alloys or compounds with a lower or much lower electrochemical potential than the iron or steel used for reinforcement are used as the sacrificial anode in concrete or mortar. There is a need for a method in which the electrochemical reaction between the raw materials is temporarily shielded.

DISCLOSURE OF THE INVENTION (Technical Problem to be Solved by the Invention) In order to achieve this object, the present invention provides a metal nodule that constitutes a sacrificial anode in reinforced concrete, mortar or the like. Nodules are: 1) a metallic core containing one or more metals or metal alloys selected from metals or metal alloys having an electrochemical potential lower than that of iron; and 2) When covering the surroundings and when the nodule is used during the production and use of concrete, mortar, etc .: First, it has sufficient mechanical strength to withstand the mixing with the aggregate constituting the concrete, mortar, etc. Second, to form a temporary barrier to water, at least until the concrete, mortar, etc. have partially hardened; Uni fabricated protective film, characterized in that it comprises a.

The nodules of the invention have the advantage of not reacting immediately when used in concrete or mortar during the production and use of concrete or mortar. Thus, a sacrificial anode composed of a metal core, even though it is suitable for strongly reacting with concrete or mortar, does not immediately consume and does not evolve gas in time.

This favorable property of nodules is primarily a result of the mechanical and physicochemical properties of the overcoat on the core. This membrane has sufficient strength to withstand the impact and wear stresses the core receives during the production and mixing of concrete, mortar, etc. in mixers and truck mixers without breaking. This combination of strength and waterproof properties of the membrane prevents premature contact of the core with the alkaline aqueous medium.
In addition, the temporary water-repellent properties of the overcoat provide a retarding effect which allows the redox reaction occurring on the core only after the concrete or mortar has at least partially hardened. Thus, these reactions are sufficient that mortar or concrete can be used to withstand the evolution of any gas, in particular hydrogen gas, without the risk of plastic deformation and / or structural damage, eg microcracks. It will occur after the strength has already developed.

The use of the nodules of the invention thus provides both mechanical strength properties that can be used, for example, in structures and chemical properties suitable for the production and / or repair of metal reinforcements. It is possible to obtain concrete, mortar, etc.

It is preferable that the core of the nodule is made of a metal selected from aluminum, magnesium, zinc and alloys thereof, or contains these as a main component. As a preferred feature of the present invention, the core is made of aluminum casting waste, which is a relatively low cost material. Thus, the present invention provides a way to recycle waste material that would otherwise be difficult to reuse.

Preferably, but not by way of exclusion, the core of the nodule has an average particle size in the range of about 1 mm to about 10 mm, and the nodule preferably, but not otherwise. Although not a thing, the particle size is in the range of about 2 mm to about 11 mm. This particle size may vary depending on the application for which the nodules are used. Therefore, this particle size range is for inclusion in concrete. However, when incorporated into a mortar, it is preferred to use nodules having an average particle size of about 2 mm to about 6 mm, i.e., nodules having a core having an average particle size of about 1 mm to about 4 mm.

The overcoat of the nodules may be made of any suitable material or substance with mechanical strength and physicochemical properties compatible with the function of the nodules of the present invention.

[0016] Thus, the protective membrane is sufficient to form a waterproof shell around the core that, after polymerization, can withstand the shock and friction that occurs when mixed with the concrete or mortar aggregate used. It can be manufactured from a polymer or resin having various hardness. In addition, the polymer or resin depends on the alkaline properties of the concrete or mortar so that the redox reaction involving the core can be initiated after a certain amount of time, at least corresponding to the time required for the concrete or mortar to partially cure. It must be suitable for breaking down.

As a preferred property of the present invention, the protective film is constituted by a water-permeable porous shell having appropriate mechanical strength and impregnated with or coated with a water-repellent substance. However, this water-repellent substance is disintegrated over time due to the alkaline properties of the medium in which the nodules are used, and thus constitutes a temporary barrier to water.

The porous shell is preferably made of a calcium compound. It may for example be chalk or limestone based, more preferably cement based.

The water-repellent substance is selected so that it is disintegrated by the alkaline raw material of the mortar, and when disintegrated, water and ions can pass through it to cause a redox reaction. Preferably, but not absolutely necessary, the water repellent material is selected from silicones, silanes, siloxanes, stearates, fatty acids, paraffins, and mixtures thereof.

According to another feature of the invention, each nodule carries one or more conductive strands associated with the core. While making direct contact with the nodule core,
The strands coated with the nodules with a protective coating promote the flow of electric current in the mortar or concrete containing the nodules according to the invention. The conductive strands may be made of any suitable material that is inert to the volta electrode pair formed of the core and reinforcement. Conductive strands made of carbon fiber are preferred.

The present invention is a method for producing a nodule that constitutes an internal sacrificial anode of reinforced concrete, mortar, etc., which comprises one or more metals or metal alloys that exhibit an electrochemical potential lower than that of iron. When the nodule is used as a protective coating for the metal nodules contained therein, that is, in the preparation or application of concrete, mortar, etc., (i) First, it is intended to withstand mixing with the aggregate that constitutes concrete, mortar, etc. Coat with sufficient mechanical strength, and (ii) secondly coat with a protective coating that has the property of forming a temporary barrier to water until concrete, mortar, etc. at least partially harden. A method for producing the nodule is also provided.

Accordingly, the coating may be prepared by coating the core with any material that imparts the necessary properties to match the function of the nodules. This coating may be done by any method that is compatible with the properties of the core and the materials that make up the protective coating. Examples of such a good coating method include, but are not particularly limited to, a deposition method in a fluidized bed, a mixing method, a dipping method, and a spraying method.

According to a preferred feature of the invention, the process for producing the nodules comprises the steps of (i) to (iv) in the preparation of the protective coating: (i) optionally sieving the core, (Ii) a powder is aggregated around the core to form a porous shell around the core,
(Iii) crystallizing the shell to impart wear resistance and protection to the core, and (iv) depositing a water repellent material on the crystallized shell that is disintegrated by the alkaline medium in contact with the nodules.

The powder to be used is, for example, a powder based on calcium or a calcium compound, for example, a powder based on chalk or limestone.

When dry cement is used as the shell forming material, the amount of cement used is 50 to 70% of the total weight of the nodules.

After the powder is aggregated to form a kind of shell around the core, the shell is crystallized to give the core sufficient mechanical strength. If powders based on chalk, limestone or cement are used, an aqueous silicate solution as crystallization agent is applied to the shell. It is preferable to use a water glass aqueous solution as the crystallization agent. To ensure that the shell formed by the cement powder that agglomerates around the core crystallizes, an aqueous sodium silicate solution with a concentration of about 20% is used. The amount of the aqueous solution used is 10% by weight of the cement used to form the shell.
The amount does not exceed.

Since the shell thus formed is porous, it is recommended in the present invention to bring about coating and / or impregnation of said shell with a water-repellent substance. This water repellent material is selected from those suitable for being destroyed by the alkaline properties of concrete, mortar, etc. which are mixed with the nodules at the time of use. The water repellent material prevents the diffusion of water and ions through the shell of the nodules. The time to prevent this diffusion is no less than the time required to cure the concrete or mortar, or the time to obtain sufficient rigidity to ensure that the core is not oxidized by the evolved gas. Then, due to the collapse of the water repellent material, the temporary barrier once formed is destroyed, thereby initiating the oxidation / reduction reaction associated with the core.

The properties of this porous shell are advantageous as they contribute to the agglomeration between the nodules and the concrete or mortar mixed in use.

As mentioned above, the water repellent material is preferably selected from silanes, silicones, siloxanes, stearates, fatty acids, paraffins and any mixtures thereof, but silanes are particularly preferred. The concentration of the water-repellent substance attached to the crystallization shell is
Although not particularly limited, it is preferably 1 to 5% of the total weight of nodules.

The nodules according to the invention prepared in this way are used in concrete and mortar for the creation of new structures or the repair of damaged structures.

The amount of nodule used for preparing hydraulic concrete or mortar is not particularly limited, but it is preferably not more than 10% of the total weight of aggregate and cement.

As long as the nodules are used in concrete or mortar that does not inherently show high alkalinity, for example, concrete or mortar that uses an organic binder, by adding an alkaline active ingredient, such as soda, The degree can be adjusted appropriately.

The following examples facilitate an understanding of the present invention and its various variations on nodules, methods of making the nodules, and methods of using the nodules.

Example 1 Production of Nodules According to the Invention Using Carbon Fiber Conductive Strands Aluminum foundry waste was used to form nodules. Nodules according to the invention were produced from the waste according to the following method. 1) Crushed the metal waste by agitating the metal waste for about 5 minutes.
2) A core having a particle size cutoff of 1 to 4 mm was selected by subjecting the waste to sieving treatment. 3) The selected cores were subjected to a washing treatment with running water under stirring for about 5 minutes. 4) The washed core was drained and then dried in hot air. 5) 10 kg of the core thus prepared was mixed with 10 g of carbon fiber for dispersion in a concrete mixer, mill or other mixer.
6) Aggregated the shell of cement around each core by continuing to mix for 15-20 minutes while gradually adding 5 kg of CPA CEM Type I cement or CMJ CEM Type II cement. Add 1 to 1 cement as needed to complete the coating
You may add 2 kg.

7) By continuing mixing for about 30 minutes while spraying an aqueous solution of water glass (
The amount of spraying is at most 10% with respect to the weight of the added cement) and crystallizes the agglomerated cement shell. Because of the exothermic reaction, the mixing vessel needs to be cooled by an external stream of water or an internal stream of cold air. The exothermicity of the reaction is advantageous in that water evaporates from the silicate solution before the oxidation / reduction reaction takes place on the core. 8) The core coated with the crystallization shell is cooled, for example, by spreading the nodule on a flat surface in a ventilated state. Two to four hours are required for complete cooling of the nodules. 9) After complete cooling, the water repellent solution was applied to the crystallized shell of nodule with mixing. Of course, a sufficient amount of the solution (about 1-5% based on the total weight)
A) ensures sufficient coverage and / or sufficient impregnation of the shell with a water repellent material. 10) Finally, spread the noju wool on a ventilated flat surface for 24 hours, or
Alternatively, it is dried by mixing in a dry air stream.

The nodule according to the present invention produced by the above method can be easily used when preparing concrete, mortar or the like. Co-coating the carbon fibers forming the conductive strands and the core together with a common protective coating ensures an electrically effective intimate contact between the sacrificial anode constituted by the core and the carbon fibers. Be done. When using such nodules, such electrical contact is further facilitated by the aluminate crystals formed in the immediate vicinity of the core.

Example 2: Production of a nodule according to the invention without conductive strands This production method is substantially the same as in Example 1 except that the step 5) of mixing the core with the carbon fibers is omitted. .

Example 3: Use of nodules in mortar By using the nodules according to the invention, mortars with a workable time of about 30 minutes were produced. The compounding composition of the mortar is as follows: CPA CEM type I cement or CPJ CEM type II cement 300 kg Lime, silica or silico-lime sand with a particle size of 0-4 mm 900 kg Nodules according to Example 1 or 2 : 2 to 6 mm) 100 kg Total aggregate 1300 kg Mixed water according to desired consistency Approx. 150 L The obtained mortar can be used as a base coat especially in repair work or corrosion prevention work.

Example 4: Use of nodules in concrete By using the nodules according to the invention, concrete with a workable time of about 30 minutes was produced. The composition of the mortar is as follows: CPA CEM type I cement or CPJ CEM type II cement 350 kg lime, silica or silico-lime sand 900 kg with a particle size of 0-25 mm 900 kg Nodules according to the invention (particle size: 2 to 2) 6mm) 100kg Total aggregate 1300kg Mixed water according to the desired consistency About 175L

When the nodules produced in Example 1 are used in the mortar of Example 3 or in the concrete of Example 4, the spontaneous electrolysis reaction on the core is about after the first contact with mixed water. It is triggered in 2 hours. The hydrogen generated in this reaction does not affect the rigidity of the mortar or concrete which is already partially hardened.

The occurrence of a potential difference between the slurry applied to a structure in need of repair after being manufactured by the above method and the steel reinforcement of the structure is referred to as “Canion”.
Type of wet electrode potential measuring device. 300-1500mV
The potential difference of can be observed.

In the embodiments described above, the nodules can be used directly in the production of concrete or mortar, which is ready for immediate or very rapid use. However, the nodules according to the invention can also be added to ready-to-use commercially available wet or dry concrete or mortar. In such cases, nodules should be added just before using this type of material. Of course, precautions should be taken to ensure that the ready-to-use commercial concrete or mortar processing time is compatible with the nodule reaction time.

─────────────────────────────────────────────────── ─── Continued front page    (81) Designated countries EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, I T, LU, MC, NL, PT, SE), OA (BF, BJ , CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG), AP (GH, GM, K E, LS, MW, SD, SL, SZ, TZ, UG, ZW ), EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AE, AG, AL, AM, AT, AU, AZ, BA, BB, BG, BR, BY, CA, CH, C N, CR, CU, CZ, DE, DK, DM, DZ, EE , ES, FI, GB, GD, GE, GH, GM, HR, HU, ID, IL, IN, IS, JP, KE, KG, K P, KR, KZ, LC, LK, LR, LS, LT, LU , LV, MA, MD, MG, MK, MN, MW, MX, NO, NZ, PL, PT, RO, RU, SD, SE, S G, SI, SK, SL, TJ, TM, TR, TT, TZ , UA, UG, US, UZ, VN, YU, ZA, ZW (72) Inventor Jack-Henri Luwae             France, F-69600 Uhren, Bourg             Var de roup rope 17 F-term (reference) 4K060 AA02 BA13 BA43 DA03 EB01

Claims (29)

[Claims] 1. A metal nodule for constructing a sacrificial anode in reinforced concrete, mortar, etc., each nodule comprising: one or more metals or metals selected from those exhibiting an electrochemical potential less than iron; A metal core containing an alloy; and a protective film surrounding the core, when nodules are used in the preparation and implementation of concrete, mortar, etc., firstly: the protective film comprises concrete, mortar, etc. Exhibits sufficient mechanical strength to withstand mixing with the constituent aggregates; and secondly the protective membrane constitutes a temporary barrier to water, at least until the concrete, mortar, etc. have partially hardened; A nodule characterized by being formed as described above. 2. The metal nodule of claim 1, wherein each nodule comprises one or more conductive strands attached to the core. 3. The nodule according to claim 2, wherein the conductive strands are composed of carbon fibers. 4. The protective film is composed of a water-porous shell exhibiting appropriate mechanical strength, impregnated or coated with a water-repellent substance, in which nodules will eventually collapse due to the alkaline nature of the medium in which they are used. A nodule according to any one of claims 1 to 3, characterized in that it constitutes a temporary barrier to water. 5. The nodule according to claim 4, wherein the porous shell contains a calcium-based compound. 6. The porous shell is cementitious.
Nodules described in. 7. The nodule according to claim 4, wherein the porous shell is Cretaceous or limestone. 8. The water repellent material is selected from silicones, siloxanes, stearates, fatty acids, paraffins, preferably silanes, and mixtures thereof. The listed nodules. 9. The nodule according to claim 1, wherein the core is made of a metal selected from aluminum, magnesium, zinc, and alloys thereof. 10. The nodule according to claim 1, wherein the core is manufactured from aluminum foundry waste. 11. The nodule according to claim 1, wherein the core has an average particle size of 1 mm to 10 mm. 12. The nodule according to claim 1, wherein the nodule has an average particle size of 2 mm to 11 mm. 13. A mortar containing the metal nodule according to claim 1. 14. The mortar according to claim 13, which contains nodule in an amount of 10% by weight or less. 15. The mortar according to claim 13 or 14, wherein the average particle size of the nodules is about 2 mm to about 6 mm. 16. Concrete comprising the metal nodule according to claim 1. 17. The concrete according to claim 16, containing 10% by weight or less of metal nodules. 18. The concrete according to claim 16 or 17, wherein the average particle size of the nodules is about 2 mm to about 11 mm. 19. A method for producing a metal nodule for constructing a sacrificial anode in reinforced concrete, mortar, etc., which comprises one or more metals or metal alloys selected from those exhibiting an electrochemical potential less than iron. When the nodule is used in the preparation and use of concrete, mortar, etc., the metal nodules it contains are: First, of sufficient mechanical strength to withstand mixing with the aggregates that make up the concrete, mortar, etc .; and -Secondly, forming a temporary barrier to water, at least until the concrete, mortar, etc. are partially hardened; coating with a protective film. 20. In order to form a protective film, in particular: optionally screening the core; agglomerating powder around the core to form a porous shell around the core; Crystallizing the shell, imparting abrasion resistance and protection; and characterized by applying to the crystallizing shell a water repellent material suitable for being destroyed by the alkalinity of the medium in which the nodules are used. The method for producing a metal nodule according to claim 19. 21. The method according to claim 20, wherein the shell is formed using powder based on calcium or a calcium compound. 22. The method of claim 20, wherein the cement-based powder is used to form the shell. 23. Method according to claim 22, characterized in that a cement filler is used which constitutes 50% to 70% by weight of the nodules. 24. The method according to claim 20, wherein the shell is formed using a limestone-based or a chalk-based powder. 25. The method according to claim 21, wherein an aqueous silicate solution, preferably a sodium silicate solution, is used as the crystallization agent. 26. The method according to claim 22, characterized in that an aqueous silicate solution, preferably a water glass solution, is used as the crystallizing agent, up to about 10% by weight of the cement used. 27. As the water-repellent substance, a substance selected from silicones, siloxanes, stearates, fatty acids, paraffins, preferably silanes, and mixtures thereof is applied. 27. The method according to any one of to 26. 28. The method of claim 27, wherein the water repellent material is used in about 1-5% by weight of the total weight of the core coated with the crystallized shell. 29. A method according to any of claims 19 to 28, characterized in that the metal core is attached to the strands before the simultaneous coating of the core and the conductive strands.