Abstract:
A steel reinforced concrete protector in an anode cavity such as a cored hole, drilled hole or cut chase is disclosed. The protector includes a sacrificial anode assembly and a separate backfill. The sacrificial anode assembly includes a sacrificial metal element and an activator to maintain an activity of the sacrificial metal element and at least one spacer. The spacer prevents the sacrificial metal element and the activator from contacting the surface of the anode cavity. The spacer and the sacrificial metal element have a coupling mechanism which facilitates connection of the sacrificial metal element to the spacer. The backfill is a pliable and viscous material which contains an electrolyte and fills the spaces between the sacrificial anode assembly and the anode cavity wall. The invention also relates to a pre-packaged sacrificial anode assembly to increase the shelf life of the assembly.

Description:
FIELD OF THE INVENTION 
     This invention concerns the protection of steel in concrete using one or more sacrificial anode assemblies where the one or more sacrificial anode assemblies are embedded within cavities formed in the concrete and, more specifically, where the cavities are mechanically formed for the purposes of accommodating the one or more sacrificial anode assemblies. 
     BACKGROUND OF THE INVENTION 
     Reinforced concrete structures sometimes suffer deterioration because the reinforcing steel eventually corrodes. This is often caused by chloride contamination or carbonation of the concrete. Sacrificial anodes are used to inhibit the corrosion of steel in concrete. Sacrificial anode assemblies, embedded within cavities formed in concrete, typically comprise a sacrificial metal that is less noble than steel (i.e., electrochemically more negative than steel) such as zinc, an activator for maintaining an activity of the sacrificial metal element, a backfill for accommodating the products of the sacrificial metal dissolution and a ductile elongate metal conductor for interconnecting the sacrificial metal element with the steel or to a power supply. 
     In some cases-typically the case when a consumed activator is used, the backfill and the activator will be assembled with the sacrificial metal and the conductor in a factory and this assembly will then be installed on site by embedding the assembly in a cementitious mortar in a cavity formed within the concrete. In cavities formed as the result of corrosion damage, the sacrificial anode assembly will be “tied” or otherwise electrically coupled or connected to the steel before substantially filling the cavity with a concrete repair material in order to restore the exterior profile and properties of the concrete substantially back to its original state. In other cases, an anode cavity (for example, a drilled hole) may be mechanically formed for the purpose of installing a sacrificial anode assembly and, in this case, the anode cavity will be substantially filled with the assembly (see Repair Application Procedure 8 published by the American Concrete Institute at www.concrete.org/generall/RAP-8.pdf). 
     More recent developments include assembling the components of a sacrificial anode assembly within an anode cavity. For example, a sacrificial metal element may be embedded directly in a backfill located in the anode cavity, as disclosed in U.S. Pat. No. 8,002,964. The anode cavity may also open into a larger cavity formed as the result of corrosion damage to protect the steel in the adjacent undamaged concrete. 
     It is to be appreciated that the embedded sacrificial anodes, for reinforced concrete structures, need to be activated if they are to provide the desired protection to the reinforcing steel. Activators for sacrificial anodes may be described as a consumed activator or a catalytic activator. An example of an activator that is consumed is hydroxyl ions. The hydroxyl ions react with the sacrificial metal element to produce a soluble species. It is to be appreciated that with this form of activation, the functional life of the sacrificial anode assembly depends on the quantity of the activator present. Such activators are generally pre-assembled as an anode-backfill assembly. It is to be appreciated that such activators may also be aggressive to the parent concrete by, for example, causing an adverse alkali silica reaction to occur within the parent concrete. 
     Examples of catalytic activators—which include halide ions and sulphate ions—are found in, for example, U.S. Pat. No. 7,749,362. The halide ions render passive films on a sacrificial metal element unstable. One problem associated with this form of activation is that such activators also tend to be aggressive with respect to the reinforcing steel and this can cause corrosion problems. 
     Another problem with sacrificial anode assemblies containing activators is that they may, when located in contact with the air, gradually deteriorate because an active metal in contact with an activator normally suffers from atmospheric corrosion. As a result, this phenomena tends to limit the shelf life of such a sacrificial anode assembly. 
     Sacrificial anode assemblies are sometimes used in combination with a power supply to deliver an impressed current treatment, for example, as disclosed in U.S. Pat. No. 7,909,982. This arrangement can be also used to draw chloride ions, present in the concrete, to the sacrificial metal element to activate the anode assembly. In this case, an activator(s) may not be required and an increased shelf life of the assembly can be achieved. 
     When a sacrificial anode assembly is assembled from components and placed within a cavity formed in an underside or a downwardly facing opening in a reinforced concrete element another problem occurs, namely, the anode may fall out of the cavity due to the effect of gravity until such time as the backfill sufficiently hardens or a concrete repair material covers the assembly to prevent inadvertent removal thereof. 
     SUMMARY OF THE INVENTION 
     Wherefore, it is an object of the present invention to overcome the above mentioned shortcomings and drawbacks associated with the prior art assemblies and techniques. 
     An objective of the present invention is to provide a method of using a catalytic activating agent or a catalytic activator in a manner that does not place the reinforcing steel at risk of having substantial contact with the catalytic agent or activator once sacrificial anode assembly or assemblies are assembled in the anode cavities which are formed within concrete. 
     Another objective of the present invention is to retain the anode, the activator and the backfill in place following assembly within a cavity formed in the underside or downwardly facing surface of a reinforced concrete element. 
     A further objective of the present invention is to provide a method of increasing the shelf life of the sacrificial anode assembly, containing an activator, that would normally deteriorate once the sacrificial metal element and the activator are exposed to air and/or moisture. 
     A still further objective of the present invention is to provide a method of protecting steel, when located in concrete, using a sacrificial metal element which comprises a metal less noble than steel, an activator, a backfill and at least one spacer, the method comprising the steps of: 
     forming an anode cavity in the concrete for the purposes of installing a sacrificial anode assembly therein, 
     locating the sacrificial metal element and the activator within the backfill contained within the cavity, the backfill being selected such that the backfill remains pliable and viscous and does not harden until after the installation process is completed, 
     using the spacer to space the sacrificial metal element and the catalytic agent or activator away from the surfaces of the cavity, and 
     supplying a current from the sacrificial metal element to the steel in the concrete to protect the steel in the concrete. 
     In one preferred embodiment the spacer is a housing spacer with a bore in which the sacrificial metal element is housed. In another embodiment, the spacer is a plurality of resilient plastic wedges or other elements that hold or retain the sacrificial metal element spaced away from the inwardly facing surface or sides of the anode cavity. The plastic wedges may be secured to the sacrificial metal element by one or more rubber bands, cable ties, or other conventional fasteners. The plastic wedges need not be secured to the sacrificial metal element and may only be located within the cavity once the sacrificial metal element is placed within the cavity. 
     The spacer is preferably a resilient member. The resilient property may be achieved by forming the spacer from either a metal or a plastic. The spacer may be a resilient plastic spacer. Examples of a plastic that may be used include acetyl and polypropylene. If a metal spacer is utilized, preferably the metal spacer is insulated or covered and this may be achieved by coating at least the exterior surface of the metal spacer with a conventional polymer. The spacer preferably substantially comprises a polymer which imparts resilience or insulates the resilient component. 
     The spacer preferably includes at least one aperture or bore into which the sacrificial metal element may be received, accommodated or otherwise housed. The spacer preferably grips, couples and captively retains the sacrificial metal element to the spacer. During use, the spacer preferably holds and maintains the sacrificial metal element in a spaced arrangement with respect to the inwardly facing surface of the cavity. The spacer preferably holds and spaces the sacrificial metal element and the catalytic agent or the activator away from the inwardly facing surface of the anode cavity. This may be achieved by sizing the anode cavity in the concrete and the spacer such that the spacer grips the sacrificial metal element and exerts a sufficient pressure against the inwardly facing surface of the anode cavity once the spacer is located in the cavity. In this example, the spacer is placed under compression in the anode cavity and the pressure between the spacer and the inwardly facing surface of the cavity results in the spacer sufficiently gripping the inwardly facing surface of the cavity so as to captively retain the sacrificial anode assembly within the cavity. 
     The anode cavity is a three dimensional space. The spacer(s) preferably locates the sacrificial metal element and the catalytic agent or the activator generally at the center of at least one dimension of the anode cavity. The spacer(s) may also locate the sacrificial metal element and the catalytic agent or the activator at the center of two dimensions of the anode cavity, e.g., both radially as well as axially along the length of the drilled or cored hole. 
     The sacrificial metal element and the activator are preferably assembled together with one another prior to being embedded within the anode cavity. The activator may be applied as a coating to the sacrificial metal element. Such a coating will typically comprise a binder and the activator. A catalytic activator may be applied as a relatively thin coating. One example of the binder is calcium sulphate which also acts as the catalytic agent or activator. Another example of the binder is an outdoor metal paint that may be thinned with an organic solvent. In this case, the binder is inert and the quantity of an inert binder is preferably maintained below 20% of the dry coating weight. Thicker coatings may be applied using hydraulic cement, as a binder, to contain a consumed activating agent. The spacer is also preferably assembled with the sacrificial metal element and the activator prior to embedding the assembly within the anode cavity. 
     In one preferred embodiment, the activator is a catalytic activator. Examples of suitable catalytic agents/activators are disclosed, for example, in U.S. Pat. Nos. 7,749,362 and 7,731,875. The quantity of the catalytic agent or activator included with the sacrificial metal element should preferably be sufficiently small such that assuming that the catalytic agent or the activator is uniformly distributed throughout the anode cavity, the catalytic agent or the activator will be diluted to a concentration that is insufficient to present any substantial corrosion risk to the steel to be protected within the concrete. Thus corrosion risk presented to the steel by the catalytic agent or the activator, once the sacrificial metal element has been totally consumed, will be negligible. 
     In another embodiment, the activator is a consumed activator. Examples of a consumed activator are potassium hydroxide or sodium hydroxide. To avoid a deleterious alkali silica reaction between such an activator and the parent concrete, it is preferable to keep the activator away from the parent concrete while the activator is consumed by reactions at the anode. 
     It is to be appreciated that combinations of both consumed and catalytic activators are also envisaged and included as part of the present invention. 
     Examples of suitable backfills, for use with the present invention, are disclosed in U.S. Pat. No. 8,002,964. The backfill may also be a powder mixed with water to produce a paste when installing the sacrificial anode assembly, an example of which would be a weak air entrained cement mortar paste. The backfill is preferably placed within the anode cavity and the sacrificial anode assembly, comprising an assembled metal element, the catalytic agent or the activator and a spacer are preferably pressed into the backfill previously located within the anode cavity. The backfill preferably retains its viscous and pliable properties for at least 48 hours and more preferably the backfill retains these properties for a longer period of time (e.g., at least one week and more preferably at least one month) as this feature renders the backfill practical for storage within a container, such as a cartridge, for an extended period of time. One example of such a preferable backfill is a lime mortar paste. 
     The anode cavity is preferably a cored or drilled hole or a cut chase which is normally mechanically formed within the concrete in a conventional manner. The sacrificial metal element preferably consists of zinc or a zinc alloy. A conductor is attached to the sacrificial metal element to facilitate the flow of the galvanic electrical current from the sacrificial metal element to the steel to be protected. The conductor is preferably integrally assembled with the sacrificial metal element to form an integrated unit which is separate from the concrete. The conductor may comprise a steel or a titanium wire. The sacrificial metal element is preferably cast around at least a leading end portion of the conductor. The conductor may be attached directly to the steel to deliver a galvanic current, or may be first connected to the steel, via a power supply, to deliver an impressed current which may precede the subsequent galvanic current. When the conductor is to be connected directly to the steel, the conductor preferably is an elongate ductile conductor having a length of at least 250 mm or greater to facilitate ease of connection and avoid the need to splice conductors to complete the connection. 
     In another aspect this invention provides a steel reinforced concrete protector for use in a cored hole, a drilled hole or a cut chase in concrete comprising an anode assembly and a separate backfill wherein the sacrificial anode assembly comprises a sacrificial metal element and an agent or an activator and a spacer for locating the sacrificial metal element and the agent or the activator in a spaced relationship away from the inwardly facing surface of the cored hole, the drilled hole or the cut chase, and the sacrificial metal element comprises a metal less noble than steel and the backfill is a viscous and pliable backfill for embedding the sacrificial anode assembly in the hole. 
     In another aspect this invention provides a method of extending the shelf life of a sacrificial anode assembly comprising a sacrificial metal element less noble than steel and an activating agent or activator, wherein the sacrificial metal element and the activating agent or the activator are assembled together with one another and stored within a plastic bag or some other suitable container in which at least water vapor, oxygen and/or carbon dioxide are removed from the air storing the sacrificial anode assembly. 
     In one arrangement, the air is sucked out of or otherwise removed from the bag or the other container, under vacuum, and then the opening to the bag or the other container is sealed in a conventional manner. The preferred process for packaging and sealing is conventionally known as vacuum packing and used in the food processing industry. In the case of a bag, the bag will have at least one face that is dimpled to facilitate the flow of air out of the bag and, once the required vacuum for the interior cavity of the bag is achieved, the opening of the bag is then sealed by a conventional heating and melting process which seals the opposed surfaces of the bag, defining the opening, together. 
     The spacer and the elongate connector may be assembled with the sacrificial metal element and a catalytic agent or the activator, or assembled therewith prior to installation. It is to be appreciated that the plastic, forming the plastic bag, must be sufficiently thick and robust so as to avoid being punctured during the vacuum packing process as well as during shipment and handling thereof. If desired or necessary, it is to be appreciated that more than one layer of plastic may be used to resist the bag from being inadvertently punctured. 
     In the place of vacuum packing the anode-activator assembly or sacrificial anode assemblies, the sacrificial anode assembly may be sealed, along with an inert gas or other fluid, within the interior cavity of the plastic bag or other container. For example, oxygen, carbon dioxide and/or water vapor may be removed from the gas contained within the interior cavity or the storage compartment of the plastic bag in order to prevent deterioration and preserve the life of the sacrificial anode assembly to be stored within the bag or other container. Alternatively, an inert gas or other fluid may be added to the interior cavity or storage compartment of the plastic bag, along with the sacrificial anode assembly, to facilitate storage and resist deterioration of the sacrificial anode assembly. 
     A method of protecting steel in concrete using one or more sacrificial anode assemblies comprising a sacrificial metal element, an agent or an activator, a pliable viscous backfill and a conductor, may involve exposing the steel, at an area requiring concrete patch repair, forming an anode cavity comprising a cored or a drilled hole in the concrete adjacent to an area of patch repair for purposes of installing the sacrificial anode assembly therein, embedding the sacrificial metal element and the agent or the activator in the backfill within the anode cavity and spacing the anode and the activator away from the inwardly facing surface or sides of the anode cavity via at least one spacer, connecting the sacrificial metal element to the exposed steel located in the adjacent patch repair, via an elongate ductile conductor having a sufficient length to extend from the sacrificial metal element to the steel without the need for splicing, wherein the elongate ductile conductor is assembled with the sacrificial metal element prior to embedding the sacrificial metal element. The agent or the activator is preferably a catalytic agent or a catalytic activator and the spacer is preferably assembled with the catalytic agent or the activator and sacrificial metal element to create a space that is filled with the backfill between the activator and the inwardly facing surface or walls of the cored or drilled hole. The catalytic agent or the activator and the spacer are preferably preassembled with the sacrificial metal element prior to installation. 
     The present invention also relates to a steel reinforced concrete protector, for use in an anode cavity, comprising: a cored hole or drilled hole or cut chase in concrete comprising a sacrificial anode assembly and a separate backfill wherein the sacrificial anode assembly comprises a sacrificial metal element that is a metal less noble than steel; an activator to maintain an activity of the sacrificial metal element; at least one spacer that prevents the sacrificial metal element and the activator from contacting a surface of an anode cavity; the spacer and the sacrificial metal element have a coupling mechanism which facilitates retention of the sacrificial metal element to the spacer; and the backfill is a pliable and viscous material which contains an electrolyte, and the backfill facilitates embedding the anode assembly in the anode cavity. 
     The present invention also relates to a prepackaged sacrificial anode assembly comprising: a sacrificial metal element comprising of a metal less noble than steel and including an activating agent being at least one of coated on a surface of the sacrificial metal element and integrally mixed with the sacrificial metal element; an elongate connector being connected to the sacrificial metal element; at least one spacer for preventing contact between the sacrificial metal element and a surface of an anode cavity, and a coupling mechanism for coupling the sacrificial metal element to the spacer; and the sacrificial anode assembly, following manufacture thereof, being sealed within a package which is substantially free of at least one of oxygen, water vapor and carbon dioxide. 
     The present invention also relates to a method of protecting steel in concrete using a sacrificial metal element, an activator, a backfill and at least one spacer, the method comprising the steps of: forming an anode cavity in the concrete, and the anode cavity being sized so as to be substantially filled by the sacrificial metal element, the activator and the backfill; placing the sacrificial metal element, the activator and the backfill in the anode cavity; using at least one spacer to space the sacrificial metal element and the activator away from an inwardly facing surface of the anode cavity; and passing a current from the sacrificial metal element to the steel; wherein the sacrificial metal element comprises a metal less noble than steel, and the backfill is sufficiently pliable and viscous so that the backfill does not harden until after an installation process of the sacrificial metal element, the activator and the backfill is completed. 
     The present invention also relates to a method for increasing a shelf life of a sacrificial anode assembly comprising the steps of: assembling of the sacrificial metal element less noble than steel with an activator to maintain an activity of the sacrificial metal element and form the sacrificial anode assembly; and sealing the sacrificial anode assembly within a package which is substantially free of at least one of oxygen, water vapor and carbon dioxide to increase a shelf life of the sacrificial anode assembly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described, by way of example, with reference to the accompanying drawings in which: 
         FIG. 1  is a diagrammatic cross sectional view of the sacrificial anode assembly, according to the present invention, contained within a sealed container, and  FIG. 1A  is a similar diagrammatic cross sectional view diagrammatically showing the activator intimately mixed with and dispersed within and throughout the sacrificial metal element; 
         FIG. 2  is an isometric side view of the spacer of  FIG. 1 ; 
         FIG. 3  is a top plan view of the spacer described of  FIG. 1 ; 
         FIG. 4  is a diagrammatic sectional view showing the sacrificial anode assembly of  FIG. 1  being inserted and captively retained within an overhead cavity; 
         FIG. 5  is a diagrammatic sectional view showing two, sequentially arranged spacers for supporting a longer or elongate sacrificial metal element within a cavity; 
         FIG. 6  is a diagrammatic sectional view showing the sacrificial anode assembly of  FIG. 5  inserted and captively retained within a cavity; 
         FIG. 7  is a diagrammatic sectional view showing a longer alternative arrangement of the spacer for supporting a longer sacrificial metal element within a cavity; 
         FIG. 8  is a diagrammatic sectional view showing an alternative arrangement for the retaining members for supporting the sacrificial metal element within a cavity; and 
         FIG. 9  is a diagrammatic cross sectional view of a repaired steel reinforced concrete element which illustrates use of the sacrificial anode assembly according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Turning first to  FIGS. 1 to 3 , a description concerning the various components of the present invention will now be briefly discussed. As can be seen in this embodiment,  FIG. 1  shows a sacrificial anode assembly  2  which comprises a generally cylindrical sacrificial metal element  4  which has an elongate ductile connector  6  extending from a trailing first end thereof. The sacrificial metal element  4  includes a catalytic activating agent or a catalytic activator  8  (only diagrammatically shown) and both the sacrificial metal element  4  and the catalytic activating agent or the catalytic activator  8  are at least partially received and accommodated within a central bore  10  of a generally cylindrical spacer  12 . Following completion of assembly of the sacrificial anode assembly  2 , the sacrificial anode assembly  2  is sealed within a substantially evacuated container  14  (only diagrammatically shown), as generally shown in  FIG. 1 , which is substantially free of oxygen, water vapor and/or carbon dioxide so as to inhibit the catalytic activating agent or the catalytic activator  8  from reacting with the sacrificial metal element  4  and thereby improve the storage or shelf life of the sacrificial anode assembly  2 . 
     The housing spacer  12  comprises a generally elongate cylindrical body  16  which has both a leading end  18  and a trailing end  20  and the central bore  10  facilitates insertion of the sacrificial metal element  4  in the housing spacer  12 . When the sacrificial anode assembly  2  is inserted into a cavity  22  provided with an electrolytic backfill  24 , as discussed below in further detail and generally shown in  FIG. 4 , the backfill  24  provides communication between the sacrificial metal element  4  and the adjacent concrete  26 . The housing spacer  12  is designed to surround and at least partially encase and enclose the sacrificial metal element  4  and prevent both the leading end surface as well as the perimeter side surface of the sacrificial metal element  4  from directly contacting with the concrete  26 , i.e., as generally shown in  FIG. 1 , the leading end surface of the sacrificial metal element  4  is spaced axially inwardly and away from the leading end  18  of the housing spacer  12  so as to avoid contact with the concrete  26 . 
     The exterior surface of the housing spacer  12  has a plurality of radially outwardly extending retaining members  28  which facilitate spacing and generally centering of the housing spacer  12 , and thus centering of the sacrificial anode assembly  2 , radially with respect to the walls or inwardly facing surface  30  of the cavity  22  (see  FIG. 4 ) as well as retention of the sacrificial anode assembly  2  within the cavity  22 . The interior surface  40  of the housing spacer  12  has one or more nub(s), protrusion(s) or annular member(s)  32  located for engagement with the at least one annular groove or recess  34  formed in the sacrificial metal element  4  for coupling, connecting and captively retaining the sacrificial metal element  4  to the housing spacer  12 . 
     As noted above, the sacrificial metal element  4  has at least one annular groove or recess  34  formed within the exterior surface of the sacrificial metal element  4 . The at least one annular groove or recess  34  is located so as to engage with the one or more nub(s), protrusion(s) or annular member(s)  32 , supported by interior surface  40  of the housing spacer  12 , and maintain a secure engagement between the sacrificial metal element  4  and the housing spacer  12 . Generally there is sufficient play between the at least one annular groove or recess  34  and the one or more nub(s), protrusion(s) or annular member(s)  32  so as to permit some relative movement therebetween while still securely coupling the sacrificial metal element  4  to the housing spacer  12 . It is to be appreciated that a variety of other types of conventional coupling mechanisms or arrangements, for reliably coupling or connecting the sacrificial metal element  4  to the housing spacer  12 , may be utilized instead of the at least one annular groove or recess  34  and the one or more nub(s), protrusion(s) or annular member(s)  32 , as discussed above, without departing from the spirit and scope of the present invention. 
     One challenge with off site or pre-application or integration of an activating agent or an activator with the sacrificial metal element  4  is that the activating agent or the activator typically begins reacting with the sacrificial metal element  4  as soon as the activating agent or the activator is applied to or mixed with the sacrificial metal element  4  in the presence of oxygen and water vapor. Furthermore, it is to be appreciated that carbon dioxide may also react with the sacrificial metal element to form a metal carbonate passivating layer on the sacrificial metal element. In order to minimize such reaction(s), it is necessary to package the coated sacrificial metal element  4 , or the sacrificial metal element  4  with the integral activating agent or the activator, generally within an environment which is free of reactive gasses or within a container  14  shortly after combining the sacrificial metal element  4  with the catalytic activating agent or the activator, e.g., typically within  14  days after assembling or combining those components with one another. 
     A preferred method of gas free packaging of the sacrificial anode assembly  2  is a conventional vacuum packaging process in which the sacrificial anode assembly  4  is vacuum sealed within an evacuated plastic bag or container  14 , and this process is discussed below in further detail. Other methods of inert packaging of the sacrificial anode assembly  2  are envisioned and contemplated, such as packaging the sacrificial anode assembly  2  in a quantity of a non-reactive gas(es), such as nitrogen, or argon, which is sealed within the sealed container  14  along with the sacrificial anode assembly  2 . Examples of suitable containers  14  for packaging the sacrificial anode assembly  2  include sealed plastic bags, both hard or soft plastic containers, metal containers, shrink wrap packaging, etc. 
     The housing spacer  12  is preferably a material that is designed for centering and maintaining the sacrificial metal element  4  in a spaced relationship within the cavity  22 . The housing spacer  12  must be sufficiently stiff such that it will not collapse under the weight of the sacrificial metal element  4 . As described above, the housing spacer  12  is preferably assembled with the sacrificial metal element  4  and the catalytic activating agent or the catalytic activator  8 , prior to embedding or placing the sacrificial anode assembly  2  within the cavity  22 , but such assembly could be performed on site if desired or necessary. 
     The housing spacer  12  preferably is cylindrically shaped and a diameter of the central bore  10  of the housing spacer  12  is larger than a diameter of an exterior surface  36  of the sacrificial metal element  4 . It is to be appreciated that the housing spacer  12  can also be conical or venturi shaped and/or have a varying distance between the interior surface  40  of the housing spacer  12  and the exterior surface  36  of the sacrificial metal element  4 . The housing spacer  12  ideally has a cylindrical body  16 , so as to substantially match the preferably cylindrical shape of the sacrificial metal element  4 , but the housing spacer  12  may also have a cross section that is triangular, rectangular, pentagonal, hexagonal, or some other desired shape. 
     For sacrificial metal element  4  having a length of less than about 75 mm, typically only one housing spacer  12  is used, while for sacrificial metal elements  4  having a length greater than 75 mm, typically the sacrificial metal element  4  accommodates two or more sequentially arranged housing spacers  12  (see  FIGS. 5 and 6 ). When two or more sequentially arranged housing spacers  12  are utilized for the longer sacrificial metal elements  4 ′, it is to be appreciated that such longer sacrificial metal elements  4 ′ are provided with two or more sequentially arranged and spaced apart annular grooves or recesses  34 , each located for receiving and accommodating the one or more respective nub(s), protrusion(s) or annular member(s)  32  of the respective housing spacer  12 . 
     The body  16  of the housing spacer  12  is typically solid, but the body  16  may include one or more interruptions  38  such as holes, slots, windows, perforations or apertures (only shown in dashed lines in  FIG. 2 ) in order to increase ion flow and conductivity through the body  16  of the housing spacer  12 . While such interruptions  38  in the body  16  of the housing spacer  12  will generally increase the conductivity, they also will simultaneously reduce the structural integrity of the housing spacer  12 , and increase the possibility the sacrificial metal element  4  may inadvertently directly contact the reinforcing steel  35 . In view of this drawback, the number, the size, the spacing and the location of the interruptions  38  in the body  16  should be designed so as to avoid the sacrificial metal element  4  from contacting the reinforcing steel  35 . 
       FIGS. 1 and 4  shows the plurality of nub(s), protrusion(s) or annular member(s)  32 , supported by the interior surface  40  of the body  16  of the housing spacer  12 , received within the annular groove or recess  34  of the sacrificial metal element  4  so as to facilitate a reliable but a relatively loose interconnection therebetween. Since the radial inwardly length of the plurality of nub(s), protrusion(s) or annular member(s)  32  is greater than the radial depth of the annular groove or recess  34  of the sacrificial metal element  4 , an annular gap  42  is formed between the exterior surface  36  of the sacrificial metal element  4  and the interior surface  40  of the body  16  of the housing spacer  12 . This gap  42  permits the electrolytic backfill  24  to directly contact and electrochemically couple and connect the sacrificial metal element  4  with the concrete  26 . 
     The size of the gap  42 , located between the interior surface  40  of the housing spacer  12  and the exterior surface of the sacrificial metal element  4 , is preferably sufficient so that the gap  42  to be at least partially filled with a small quantity of the conductive electrolytic backfill  24 . By providing a gap  42  between the housing spacer  12  and the sacrificial metal element  4  and using a conductive electrolytic backfill  24 , which is sufficiently pliable to penetrate into the gap  42  between the housing spacer  12  and the sacrificial metal element  4 , the otherwise negative effect of the housing spacer  12 , on the current output of the sacrificial anode assembly  2 , becomes negligible. This effect is dependent on the conductivity and fineness of the backfill and the presence of the activating agent. The effect of the housing spacer  12  on current output is not significant when the gap  42  is about 1 mm and lime putty is used as a backfill  24 . The housing spacer  12  also has no significant effect on the current output when the gap is completely filled with activating agent. 
     Preferably, there are between two and eight nub(s), protrusion(s) or annular member(s)  32 . The nub(s), protrusion(s) or annular member(s)  32  may ideally have a wedge shaped profile, as generally shown in  FIG. 1 . This permits the sacrificial metal element  4  to easily be slid and snapped in place within the internal bore  10  of the spacer  12 , and be captively retained therein once the one or more nub(s), protrusion(s) or annular member(s)  32  are received within and engage with the at least one annular groove or recess  34 . The nub(s), protrusion(s) or annular member(s)  32  can be coplanar, axially spiral, or axially randomly distributed. It is to be appreciated that the size, the number and the location of nub(s), protrusion(s) or annular member(s)  32  are selected so as not to compromise the open area through which ions can flow into and out of the housing spacer  12 . In an alternative embodiment, the nub(s), protrusion(s) or annular member(s)  32  could each be coupled to or formed as an annular ring which is sized to engage with the annular groove or recess  34  formed in the sacrificial metal element  4 . 
     It is to be appreciated that in the place of, or in addition to, protrusions  32  located on the interior surface  40  of the housing spacer  12 , separate protrusions may be formed on exterior of the sacrificial metal element  4  that would engage a mating groove(s), hole(s), recess(es) or indentation(s) formed in the interior surface  40  of the housing spacer  12 . 
     The plurality of retaining members  28  of the housing spacer  12  typically extend both axially and radially from at least adjacent one trailing end  20  of the housing spacer  12 , as generally shown in  FIGS. 1-4 . The retaining members  28  each have a sufficient length so as to engage with an inwardly facing surface  30  of the cavity  22  and thereby assist with both retaining and maintaining the housing spacer  12 , and thus the sacrificial metal element  4 , centered in place, even in an overhead downwardly facing cavity  22 , as well as assists with retaining the backfill  24  within the cavity  22 . The size, the number and the spacing of the retaining members  28  are generally limited to maximize the open area through which ions can flow past the retaining members  28 . For example, the housing spacer may have between three and ten retaining members  28  integrally formed with the housing spacer  12 . Each retaining member  28  preferably has a width of between 2 and 8 mm, and a length of between 7 and 25 mm. The angle at which the retaining members  28  project away from the exterior wall of the housing spacer  12  assists with applying a desired “spring” or retaining pressure, e.g., a compression force, by which the retaining members  28  engage with the inwardly facing surface  30  of the cavity  22  and thereby retain the sacrificial anode assembly  2  and the backfill  24  in their installed position. 
     The angle formed between the retaining members  28  and the housing spacer  12  is preferably between about 30 degrees and 70 degrees. As each retaining member  28  generally tapers radially away from the housing spacer  12 , from the leading end of the sacrificial anode assembly  2  toward the trailing end of the sacrificial anode assembly  2 . Such taper facilitates ease of insertion of the sacrificial anode assembly  2  within the cavity  22 , as the retaining members  28  are each easily deflected radially inward somewhat as the outer ends or edges of the retaining members  28  engage with and slide along the inwardly facing surface  30  of the cavity  22 . Once the sacrificial anode assembly  2  is completely received within the cavity  22 , so that the leading end  18  abuts against a base of the cavity  22  as generally shown in  FIG. 4 , the outer ends or edges of the retaining members  28  have a tendency, due to the angle that they project from the exterior surface of the housing spacer  12 , to be compressed by and thus frictionally engage against the inwardly facing surface  30  of the cavity  22  and thereby facilitate a secure retention of the sacrificial anode assembly  2  within the cavity  22 . 
     During a typical installation, the sacrificial anode assembly  2  is inserted into a cavity  22 , which is typically a cored or a drilled hole or a cut chase, mechanically formed in the concrete  26  containing the steel to be protected and located adjacent to exposed steel  35  that is connected to the steel to be protected. The cavity  22  is typically cylindrical in shape and has a diameter of between 15 and 100 mm, e.g., typically approximately between 25 and 50 mm, and a depth of between 35 and 500 mm, typically approximately between 35 and 300 mm, which is sized to receive one or more desired sacrificial anode assemblies  2 . It is to be appreciated that the diameter cavity  22  must be larger than exterior surface of the housing spacer  12 , but is preferably smaller than the outer diameter D (see  FIG. 3 ) of the retaining members  28  so that the retaining members  28  can engage with and be deflected somewhat by the inwardly facing surface  30  of the cavity  22 , as the desired sacrificial anode assembly  2  is received therein, and frictionally retain the sacrificial anode assembly  2  within the cavity  22 , even in an overhead cavity  22 . Typically, the cavity  22  will have a length which is somewhat longer than a total axial length of the sacrificial anode assembly  2 . 
     The preferred process for packaging the anode assembly  2  is vacuum packing, a process used in the food processing industry. In this case, the vacuum bags will preferably have at least one face that is dimpled to facilitate the flow of air out of the bag and, once the required vacuum is achieved, the opening of the bag is sealed by conventionally heating and melting of the overlapped plastic layers together. The plastic forming the plastic bag should be sufficiently thick and durable so as not be easily punctured during the vacuum packing process. More than one layer of plastic may be used to avoid the bag from being inadvertently punctured during the packaging, shipping, distribution or sales processes. The vacuum packaging greatly increases the shelf life of the sacrificial anode assembly  2 . 
     As noted above, a suitable backfill  24 , to be used with the anode assembly is disclosed in U.S. Pat. No. 8,002,964, and such disclosure is fully incorporated herein, as see GB 2430 938. The backfill  24  is ideally a pliable, putty-like, ionically conductive material. The backfill  24  is typically preferably first placed within the cavity  22  and then the complete sacrificial anode assembly  2  is preferably pressed directly into the backfill  24 , accommodated within the cavity  22 , which may cause some of the backfill  24  to be displaced from inside the cavity  22 . It is to be appreciated that this process may, for some applications, be reversed. The backfill  24  is selected such that the backfill  24  retains its plasticity during the installation. 
     In order to install the sacrificial anode assembly  2 , as noted above, the cavity  22  is first cored or drilled into the concrete  26 . Then a sufficient quantity of the pliable, electrolytic backfill  24  is placed within the cavity  22 . Next, the sealed, evacuated container  14 , containing the preassembled sacrificial anode assembly  2 , is opened and the sacrificial anode assembly  2  is then inserted into the backfill  24  located within the cavity  22 , the leading end  18  of the housing spacer  12  first, so that the connector  6  remains located outside of the cavity  22 . If a preassembled sacrificial anode assembly  2  is not available, then the sacrificial anode assembly  2  should preferably be assembled on site for insertion as a sacrificial anode assembly into the cavity  22 . Lastly, the connector  6  is then connected to a desired piece of the steel  35 , and located within the concrete  26 , in a conventional manner. 
     Turning now to  FIG. 5 , this Figure shows two sequentially arranged housing spacers  12  which both accommodate a portion of the longer elongate sacrificial metal element  4 ′. The two housing spacers  12  both assist with maintaining the longer elongate sacrificial metal element  4  spaced radially from the inwardly facing surface  30  of the cavity  22  during use, as shown in  FIG. 6 . Due to the sequential arrangement of the housing spacers  12  as well as the manner in which the housing spacers  12  each accommodate a portion of the longer elongate sacrificial metal element  4 ′, the backfill  24  is still readily able to flow in and around the longer elongate sacrificial metal element  4 ′, during operation of the sacrificial anode assembly  2 . 
     Turning now to  FIG. 7 , this figure shows an elongate housing spacer  12 ′ which accommodates a substantial portion of the longer elongate sacrificial metal element  4 ′. According to this embodiment, the elongate housing spacer  12 ′ is provided with two sets of spaced apart retaining members  28  which both assist with maintaining the elongate housing spacer  12 ′ generally centered within the cavity  22  and thereby space the longer elongate sacrificial metal element  4 ′ from the inwardly facing surface  30  of the cavity  22  during use, as generally shown in  FIG. 7 . In order to facilitate passage of the backfill  24  around the sacrificial metal element  4 , during operation of the sacrificial anode assembly  2 , as well as the flow of ions, one or more openings interruptions  38  may be provided within the body  16  of the elongate housing spacer  12 ′. 
     Turning now to  FIG. 8 , an alternative arrangement of the retaining members  28  of the housing spacer  12  is shown. According to this embodiment, the retaining members  28  each generally have an oval shape which extends from adjacent the leading end  18  toward the trailing end  20  of the housing spacer  12 , e.g., forms a taper profile. Such tapered profile facilitates ease of insertion of the sacrificial anode assembly  2  within the cavity  22  since the intermediate sections  28 ′ of the retaining members  28  are easily deflected radially inward somewhat as those sections of the retaining members  28  engage with and slide along the inwardly facing surface  30  of the cavity  22 . Once the sacrificial anode assembly  2  is completely received within the cavity  22 , so that the leading end  18  abuts against a base of the cavity  22 , the intermediate sections  28 ′ of the retaining members  28  are compressed by and thus frictionally engage against the inwardly facing surface  30  of the cavity  22  and thereby facilitate a secure retention of the sacrificial anode assembly  2  within the cavity  22 . 
     It is to be appreciated that a variety of other types of other retaining members  28 , e.g., wedges, etc., may be utilized for generally centering and retaining the housing spacer  12  and/or the sacrificial metal element  4  and the catalytic activating agent or the catalytic activator  8 , within the cavity  22 , without departing from the spirit and scope of the present invention. The important feature of the retaining members  28  is that they must generally frictionally engage with the inwardly facing surface  40  of the cavity  22  so as to generally center and retain at least the sacrificial metal element  4  within the cavity  22 . 
     With reference now to  FIG. 9 , this Figure shows the sacrificial metal element  4  and the housing spacer  12  embedded in a backfill  24  located within an anode cavity  22  that may be, for example, a 25 mm diameter by 40 mm deep hole which is mechanically drilled or otherwise bored or formed within a concrete  26 . The sacrificial metal element  4  may be coated with a catalytic activating agent or catalytic activator. The anode cavity  22  opens into an adjacent cavity  44  that was formed because of corrosive damage. In this adjacent cavity  44 , a steel bar  35  was exposed and cleaned, in a conventional manner. The elongate ductile connector  6  interconnects the sacrificial metal element  4  with the steel bar  35  in order to deliver a galvanic protection current from the sacrificial metal element  4  to reinforcing steel (not shown) located within the concrete  26  that is connected to the steel bar  35 , during use. 
     As described above, a first end of the elongate ductile connector  6  is formed or embedded within or otherwise connected with the sacrificial metal element  4  while the second opposite end of the elongate conductor  6  is sufficiently long so as to facilitate a secure electrical clamping or connection with the steel bar  35 , for example, via a conventional cable tie  46  which makes and maintains the electrical connection therebetween in a secure and substantially permanent manner. Steel or stainless steel tie wire may also be used to secure the connection. Once the sacrificial anode assembly  2  is installed, as generally described above and shown in  FIG. 9 , then the adjacent cavity  44  is filled with an appropriate concrete repair material  48  so that both the sacrificial anode assembly  2  and the steel bar  35  are embedded within and substantially covered by the concrete repair material  48 . During such repair, a cavity  22  is drilled typically at 500 mm intervals in the concrete  26  around the periphery of the cavity  44  and a respective sacrificial anode assembly  2  is located within each one of those cavities  22  and connected, as described above, so as to provide the desired galvanic current protection. 
     The sacrificial metal element  4  is a metal less noble that steel, and preferably comprises either zinc or a zinc alloy. The sacrificial metal element  4  is preferably cast as a cylindrical shaped body, but it is to be appreciated that the sacrificial metal element  4  may be shaped into a variety of other shapes or configurations, such as regular polygon prisms. The sacrificial metal element  4  generally has a constant cross section along its length, but the cross-sectional shape of the sacrificial metal element  4  may vary depending upon the particular application. The sacrificial metal element  4 , which is designed to fit within a 28 mm diameter by 50 mm long cavity  22 , will typically have a diameter or width of 18 mm and a length of 40 mm. 
     The elongate ductile connector  6  facilitates convenient connection of the sacrificial metal element  4  to the steel without the need to splice any additional conductor directly to the sacrificial metal element  4  during the installation process. The connector  6  may be a steel or a titanium wire. The connector  6  typically has a length of between 25 and 40 mm and a diameter of between 0.7 and 2 mm. The connector  6  is preferably at least partially embedded within the trailing end of the sacrificial metal element  4  and may extend the entire length of the sacrificial metal element  4 . More preferably, the sacrificial metal element  4  is cast around at least a portion of connector  6  with the connector  6  extending out from the trailing end of the sacrificial metal element  4  for a sufficient distance to facilitate ease of connection of the remote free end of the connector  6  with the steel  35  reinforcement in the concrete  26  to be protected. 
     As noted above, the sacrificial metal element  4  is assembled with the catalytic activating agent or catalytic activator  8 . That is, either the exterior surface  36  of the sacrificial metal element  4  is coated with the catalytic activating agent or the catalytic activator  8 , e.g., a compound(s) containing halide ions and sulphate ions, or alternatively, as diagrammatically shown in  FIG. 1A , the catalytic activating agent or catalytic activator  8  is intimately mixed with and dispersed within and throughout the sacrificial metal element  4 . 
     The quantity of the catalytic activating agent or catalytic activator  8 , to be included with the sacrificial metal element  4  should preferably be sufficient to provide the desired ion flow between the sacrificial metal element  4  and the concrete  26  but insufficient to create a significant corrosion risk by the catalytic activating agent or catalytic activator  8  to the steel  35  once the sacrificial metal element  4  has been consumed. Preferably the quantity of catalytic activating agent or catalytic activator  8  is such that if it were to be uniformly distributed within the cavity  22 , the catalytic activating agent or catalytic activator  8  would be diluted to a concentration that is insufficient to present a corrosion risk to steel embedded within the concrete  26 . For a chloride activator, this equates to a quantity of less than 1.6 kg of chloride ions per cubic meter of anode cavity. 
     As indicated above, the catalytic activating agent or catalytic activator  8  can be coated on the exterior surface  36  of the sacrificial metal element  4  or integrated into and throughout the sacrificial metal element  4 , or both, and that the same the catalytic activating agent or the catalytic activator  8  or two different the catalytic activating agent or the catalytic activator  8  may be applied to the sacrificial metal element  4 . Ideally the catalytic activating agent or the catalytic activator  8  is applied to or integrated into the sacrificial metal element  4 , prior to packaging the sacrificial anode assembly  2  for shipment and subsequent sale or installation. This allows the installation process of the sacrificial anode assembly  2  within a cavity  22 , at the installation site, to proceed at a faster rate than if the catalytic activating agent or the catalytic activator  8  was manually applied to each sacrificial metal element  4 , on site, prior to installation or was injected into a porous anode body after installation. 
     Since certain changes may be made in the above described sacrificial anode assembly, without departing from the spirit and scope of the invention herein involved, it is intended that all of the subject matter of the above description or shown in the accompanying drawings shall be interpreted merely as examples illustrating the inventive concept herein and shall not be construed as limiting the invention.