CZ20002437A3 - Connector for use in cathodic protection and method of use thereof - Google Patents

Abstract

An assembly for use in the cathodic protection of steel reinforcement in reinforced concrete said assembly comprises: (i) an anode of a metal having a more negative electrode potential than steel and, in electrical contact therewith, (ii) an elongate electrical connector eg a wire made of a ductile metal capable of being wound around the steel reinforcing element to be protected. The anode may be in the form of a block cast around a portion of the length of the elongate connector and preferably the elongate connector comprises a plurality of wires twisted together over a portion of their length with the anode cast around the twisted portion.

Description

Technical field

The invention relates to the cathodic protection of steel in reinforced concrete using sacrificial anodes, and more particularly to an electrical connection for connecting the sacrificial anode to the reinforcing steel, and to a method for installing the anode.

BACKGROUND OF THE INVENTION

The sacrificial anodes are generally known. To be effective, the sacrificial anode is made of a metal that has a higher negative electrode potential than the steel to be protected, so it will corrode more than the steel. The sacrificial anodes are described, for example, in EP 0 707 667 or in US 5 292 411.

In order to perform its function, the sacrificial anode must be electrically connected to the steel to be protected. Previously, metal conductors were used for this purpose. These metal wires in the form of wires were attached to the steel reinforcement by drilling a hole into which a self-tapping screw was inserted. In alternative methods, clips or clips have been used to attach the wire to the metal reinforcement to be protected.

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The drawbacks of these methods have been drilling holes and the use of self-tapping demanding ones, and there is always a risk of disconnecting clamps or clips.

Especially in that the screws is time-wise that can occur

SUMMARY OF THE INVENTION

The present invention provides a solution to the above problems by utilizing a yieldable ductile elongated connector that is attached to the steel reinforcement element by wrapping the connector around the reinforcement element.

Accordingly, in accordance with the present invention, an assembly has been developed for use in the cathodic protection of steel reinforcement in reinforced concrete, comprising:

(i) a metal anode having a more negative electrode potential than steel and in electrical contact with it; (ii) a ductile steel elongate protected.

an electrical connection made of metal for wrapping it around the reinforcing element to be

The elongate connector may preferably be in the form of a wire.

The anode may preferably be in the form of a block cast around a portion of the length of the elongate connector.

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The elongate connector preferably comprises a plurality of wires twisted together around a portion of their length, the anode being cast around the coiled portion.

The wires are preferably twisted together at a position between their ends so that the wires extend on both sides of the cast anode.

The anode is preferably enclosed in a porous material that has been cast around the anode, the porous material comprising an electrolytic solution whose pH is sufficiently high to ensure corrosion of the anode and to prevent passive film formation on the anode when the anode is galvanically attached to the reinforcement.

The anode is preferably made of zinc, wherein the porous material is a cementitious mortar containing an electrolyte solution having a pH of at least about 14.

This assembly is preferably attached to the reinforcement by winding an elongate connector around the reinforcement.

In accordance with another aspect of the present invention, there is also provided a method of making an assembly for use in cathodic protection of steel reinforcement in reinforced concrete, wherein the assembly comprises a metal anode having a more negative electrode potential than steel and in electrical contact therewith. and an elongate electrical connection made of ductile metal for wrapping it around a steel reinforcing element to be protected.

In particular, the present method is characterized in that the anode is cast from a liquid metal in a mold to form a metal block around a portion of the length of the elongated electrical connection.

The method of the invention further comprises the step of forming around the anode a solid block of a liquid or semi-liquid mixture of porous material containing an electrolyte solution having a pH sufficiently high to provide corrosion of the anode and prevent passive film formation on the anode when attached to the steel reinforcement.

In accordance with yet another aspect of the present invention, there is also provided a method of installing a sacrificial anode for protecting steel reinforcement in reinforced concrete, comprising in any order the following steps (a) and (b):

(a) making an electrical connection between the sacrificial anode and the elongate connection, wherein the elongate connection is made of a ductile metal to be wound around the reinforcement, and (b) making electrical contact between the elongate connection and the steel reinforcement by winding the elongate connection around the steel reinforcement.

Preferably, step (a) comprises casting a liquid metal anode in a mold to form a metal block around a portion of the length of the elongate connector.

The method of the invention also comprises an additional step (c) that may be performed before or after step (b) and which comprises casting around the anode of a porous material containing an electrolyte solution having a pH sufficiently high to provide corrosion of the anode and prevent making passive film.

The anode is preferably zinc and the pH of the electrical solution is at least about 14.

For tightly tightening the wire around the reinforcement, the present method further preferably comprises twisting the ends of the flexible elongate connector together using a ratchet twisting tool.

The connector of the present invention can be installed in a much shorter time than in the previously used self-tapping screw methods, and is much safer than the previously used clamps or clips.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be explained in more detail by way of examples of specific embodiments thereof, the description of which will be given with reference to the accompanying drawings, in which:

Fig. 1 is an axonometric view of one embodiment of the present invention wherein two wires are twisted together;

Fig. 2 is a smaller scale axonometric view than Fig. 1, with the anode being cast around the connection wires, and Fig. 3 is a perspective view on the same scale as Fig. 2, but in another embodiment of the present invention wherein the anode is surrounded by mortar that was poured around it.

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DETAILED DESCRIPTION OF THE INVENTION

The anode is preferably made of zinc, but aluminum, cadmium or magnesium may also be used. References to these metals also include alloys containing them.

Preferably, the electrical contact between the connection and the anode is provided such that the anode is in the form of a block that has been cast (wherein casting is to allow the liquid metal to solidify as a block) around a portion of the length of the elongate connection. Alternatively, the electrical contact may be secured by winding the elongate connector around the anode, or by soldering the connector or similarly attaching it to the anode.

The elongate connection is preferably in the form of a wire, but other elongate forms may also be used. The wire may preferably be of steel, especially mild steel.

The wire is preferably of noble metal or of noble metal than the steel in the reinforcement.

The connector may comprise a plurality of wires that are twisted together over a portion of their length, and the anode may be cast around the twisted portion. The term curled should also include the terms bent or folded or wavy. The purpose of the coiled portion is to increase the surface area of the wire forming the interface with the cast anode, thereby improving electrical contact. The wires may be coiled together at a position that lies between their ends (for example near the center of their length) so that the lengths of the wires lie on either side of the cast anode.

Patent Application WO 94/29496 (European Patent Application 0 707 667) describes a cathodic protection method in which, in order to maintain cathodic protection for a certain maintenance period, the anode is surrounded by a high pH electrolyte containing material. In order to prevent anode passivation, it is recommended that the pH of the zinc anode be at least about 14.

Suitable materials described in this patent are cementitious mortars which can be cast around the anode to form a unit. It is not essential that the mortar be cement, although such mortars are much more readily available. The mortar may be prepared from a cement that has a truly high alkaline content, or an additional alkali may be added to the mortar, for example sodium hydroxide or lithium hydroxide, with lithium hydroxide being recommended.

The anode and connector assembly of the present invention may have a porous material, such as a cement mortar, cast around the anode. By this casting we mean the formation of a solid block of liquid or semi-liquid mortar. The casting is preferably carried out in a mold. The porous material is such that it preferably comprises a high pH electrolyte as described in European Patent Application 0 707 667, i.e. it comprises an electrolyte solution whose pH is sufficiently high to maintain anode corrosion and prevent passive film formation on the anode. when the anode is galvanically connected to the steel reinforcement. In the case of cement mortar, the electrolyte solution is a porous solution.

The mortar preferably has an alkali content equivalent to at least one percent of lithium hydroxide, based on the dry weight of the ingredients used to make the mortar. The equivalent amount of sodium hydroxide is 2% by weight.

Preferably, the amount of lithium hydroxide is greater than 2%, with an equivalent amount of sodium hydroxide of 4%.

Lithium hydroxide is the recommended alkali since lithium ions provide protection against the reaction of alkaline silica or alkaline silica (or alkaline aggregate) in concrete. However, mixtures of alkalis, for example mixtures of lithium hydroxide and sodium hydroxide, may also be used.

The anode, the porous material, for example mortar, and the corresponding casting may be as described, for example, in European Patent Application 0 707 667.

In accordance with another aspect of the present invention, there is provided a method of installing a sacrificial anode for protecting reinforcement in a reinforced concrete, the method comprising the following steps (a) and (b) in any order:

(a) making an electrical connection between the elongate connection and the anode, and (b) making electrical contact with the steel reinforcement by winding the elongate connection around the steel reinforcement.

Step (a) may comprise casting the anode around a portion of the length of the elongate connector.

Before step (b), a further step (c) may be carried out, which step (c) comprises casting the porous material around the anode, the porous material comprising an electrolytic solution having a pH sufficiently high to provide corrosion of the anode and prevent formation of the passive film.

The anode is preferably zinc, in which case the pH of the electrolyte solution is preferably at least about 14. If the anode is of another metal, such as aluminum, the pH may be lower, for example at least 13.3 or 13.5.

The pH can be determined by measuring the concentration of hydroxyl ions using the following Sorensen equation:

pH = 14 + log (OH)

The present invention is useful in constructing new reinforced concrete structures in which the anode assembly is attached to the reinforcement through a connector, wherein a high pH porous material such as mortar is cast around the anode.

The present invention is also useful for the purpose of protecting existing concrete structures, wherein, in accordance with the present method, a hole can be made in the concrete and (i) the anode is inserted into the hole, (ii) the connection is connected to the reinforcement, and (iii) the high pH material is poured around the anode.

The individual steps (i), (ii) and (iii) may be performed in any order.

Figure 1 shows two wires, each made of mild steel 16 SWG (standardized wire thickness number), which are twisted together in a coiled portion 6 of its length. The length of the coiled portion 6 is usually from about 38 mm to 42 mm. The four wire lengths in the form of arms 2, 4, 6 and 10 extend from the coiled portion 6. The lengths of these legs 8, 8, 8 and 10 are generally from about 14 8 mm to 152 mm, with loops 12, 13, 14 and 15 being formed at the end of each leg 2, 8, 8 and 10. , £, 8 and 10 are wrapped around the reinforcement. One or two complete threads around the reinforcement are usually sufficient to ensure sufficient electrical contact.

The diameter of the loops 12, 13, 14 and 15 is generally from about 9 mm to 11 mm. The purpose of these loops 12, 13, 14, and 15 is to facilitate the use of a tool of the type used to seal paper bags for tomatoes, and the like. Direct Wire Ties Limited. By means of this tool, the arms 2, 4, 4 and 10 that have been wrapped around the steel reinforcement (not shown) in the reinforced concrete can then be rolled together. The effect of this measure is to tightly fasten the wire around the reinforcement.

Figure 2 shows a cylindrical zinc block or ring 20 having a diameter of about 40 mm and a thickness of about 7 mm, which has been cast around coiled wires. In Fig. 2, the center of the cylindrical block or ring 20 has been omitted to omit the center of the cylindrical block or ring 20. · ···· ·· ··· see wires. The upper and lower edges of the block or ring 20 have been rounded to prevent wire breakage.

The assembly shown in FIG. 2 was made by first twisting the wires together near the center of their length, after which the coiled part was placed in a ceramic mold. Molten zinc was then poured into this mold. After solidification, the article was removed from the mold. The wire legs 2, 4, 8 and 10 extend on both sides of the anode and allow the anode to be connected to more than one reinforcing element if necessary.

FIG. 3 shows a mortar block 24 that has been cast around the zinc block or ring 20 of FIG. 2 at a thickness of 10 mm around the zinc block or ring 20.

The assembly shown in Figure 3 has been made by placing the assembly of Figure 2 in a pre-formed plastic mold so that the zinc block or ring 20 is positioned in the center of the mold. A high pH cement mortar containing a porous solution with a pH greater than 14 was prepared by mixing Portland cement powder (containing 2% by weight of added lithium hydroxide) based on the weight of the cement powder, and pouring the mixture into a mold where was allowed to cure for four hours, and then the finished product was removed from the mold to obtain the product shown in Figure 3.

Claims (15)

PATENT CLAIMS An assembly for use in cathodic protection of steel reinforcement in reinforced concrete, the assembly comprising: (i) a metal anode having a more negative electrode potential than steel and in electrical contact with it; (ii) a ductile steel elongate protected. an electrical metal for the reinforcement connection made by winding it around the element to be 2. An assembly characterized in the form of a wire. according to claim 1, by the elongated connection Assembly according to claim 1, characterized in that the anode is in the form of a block cast around a portion of the length of the elongated connector. The assembly of claim 3, wherein the elongate connector comprises a plurality of wires twisted together about a portion of their length, the anode being cast around the twisted portion. Assembly according to Claim 4, characterized in that the wires are twisted together in a position between their ends so that the wires extend on both sides of the cast anode. The assembly of claim 1, wherein the anode is enclosed in a porous material that has been cast around the anode, wherein the porous material comprises an electrolytic solution whose pH is sufficiently high to provide corrosion of the anode and prevent passive film formation on the anode. when the anode is galvanically connected to the reinforcement. The assembly of claim 6, wherein the anode is made of zinc, wherein the porous material is a cementitious mortar containing an electrolyte solution having a pH of at least about 14. The assembly of claim 1, wherein the assembly is attached to the reinforcement by winding an elongate connector around the reinforcement. A method of manufacturing an assembly for use in cathodic protection of steel reinforcement in reinforced concrete, the assembly comprising a metal anode having a more negative electrode potential than steel and in electrical contact with it, an elongate electrical connection made of ductile metal for wrapping it around a steel reinforcing element to be protected, characterized in that the anode is cast from liquid metal in a mold to form a metal block around a portion of the length of the elongated electrical connection. The method of claim 9, further comprising the step of forming around the anode a solid block of a liquid or semi-liquid mixture of porous material containing an electrolyte solution having a pH sufficiently high to provide corrosion of the anode and prevent passive film formation at the anode when attached. to the steel reinforcement. A method of installing a sacrificial anode for protecting steel reinforcement in reinforced concrete, the method comprising the steps (a) and (b) in any order: (a) making an electrical connection between the sacrificial anode and the elongate connection, wherein the elongate connection is made of a ductile metal to be wound around the reinforcement, and (b) making electrical contact between the elongate connection and the steel reinforcement by winding the elongate connection around the steel reinforcement. The method of claim 11, wherein step (a) comprises casting an anode of liquid metal in a mold to form a metal block around a portion of the length of the elongate connector. The method of claim 12, wherein the further step (c), which may be carried out before or after step (b), comprises casting around the anode of a porous material comprising: An electrolytic solution having a pH sufficiently high to ensure corrosion of the anode and to prevent the formation of a passive flux. ilmu. The method of claim 13, wherein the anode is zinc and the pH of the electrical solution is at least about 14. The method of claim 11, wherein for tightly tightening the wire around the reinforcement, the method further comprises twisting the ends of the flexible elongate connector together using a ratchet twisting tool.