Activating matrix for cathodic protection

Abstract

The galvanic cathodic protection of reinforced concrete structures such as bridges, buildings, parking structures, piers, and wharves, is enhanced by the use of an inert water absorbent solid. The absorbent solid and chemicals are mixed with a cementitious binder to form an activating matrix. This matrix surrounds a sacrificial metal anode such as zinc, or aluminum or their alloys. The metal anode is electrically connected to the ferrous reinforcing member by a metallic conductor. The water absorbent solid may be a clay such as bentonite or a hydrated mineral such as vermiculite. It is preferably in the form of discrete particles dispersed throughout the binder. The inclusion of the absorbent solid in the activating matrix serves to increase the protective current, thereby reducing corrosion of the reinforcing components of the concrete structure.

1 . An apparatus for cathodic protection of a reinforced concrete structure, comprising:
 at least one sacrificial anode member;   an ionically-conductive material into which is bound an electrochemical activating agent at least partly covering the sacrificial anode member(s);
 at least one elongated metallic conductor bonded to the sacrificial anode member(s); 
   characterized in that at least one inert water absorbent solid is dispersed into the ionically-conductive material surrounding the anode.   
   
   
       2 . The apparatus of  claim 1  wherein the sacrificial anode member is zinc or a zinc alloy. 
   
   
       3 . The apparatus of  claim 1  wherein the sacrificial anode member is a high surface area structure having an actual surface area from 3 to 6 times that of its superficial surface area. 
   
   
       4 . The apparatus of  claim 1  wherein the ionically-conductive covering material is a cementitious-based material. 
   
   
       5 . The apparatus of  claim 1  wherein the electrochemical activating agent is an alkaline hydroxide present in sufficient amount to raise the pH of the covering material above about pH 13.3. 
   
   
       6 . The apparatus of  claim 1  wherein the electrochemical activating agent is a deliquescent or hygroscopic material. 
   
   
       7 . The apparatus of  claim 6  wherein the electrochemical activating agent is lithium nitrate, lithium bromide, or combinations thereof. 
   
   
       8 . The apparatus of  claim 1  wherein the inert water absorbent solid is bentonite, vermiculite, or combinations thereof. 
   
   
       9 . The apparatus of  claim 1  wherein the inert water absorbent solid is bentonite. 
   
   
       10 . The apparatus of  claim 1  wherein the inert water absorbent solid is vermiculite. 
   
   
       11 . An method for the cathodic protection of a reinforced concrete structure, comprising:
 at least one sacrificial anode member;   an ionically-conductive covering material surrounding said sacrificial anode member(s), into which is bound an electrochemical activating agent;
 at least one elongated metallic conductor bonded to the sacrificial anode member(s) with a carbon loaded organic-based mastic; 
   and, connecting the elongated metallic conductor to the reinforcing steel of the reinforced concrete structure, thus causing protective current to flow;   characterized in that an inert water absorbent solid material is dispersed into the ionically-conductive covering material.   
   
   
       12 . The method of  claim 11  wherein the sacrificial anode member is zinc or a zinc alloy. 
   
   
       13 . The method of  claim 11  wherein the sacrificial anode member is a high surface area structure having an actual surface area from 3 to 6 times that of its superficial surface area. 
   
   
       14 . The method of  claim 11  wherein the ionically-conductive covering material is a cementitious-based material. 
   
   
       15 . The method of  claim 11  wherein the electrochemical activating agent is an alkaline hydroxide present in sufficient amount to raise the pH of the covering material above about pH 13.5. 
   
   
       16 . The method of  claim 11  wherein the electrochemical activating agent is a deliquescent of hygroscopic material. 
   
   
       17 . The method of  claim 16  wherein the electrochemical activating agent is lithium nitrate, lithium bromide, or combinations thereof. 
   
   
       18 . The method of  claim 11  wherein the inert water absorbent solid material is bentonite, vermiculite, or combinations thereof. 
   
   
       19 . The method of  claim 11  wherein the inert water absorbent solid material is bentonite. 
   
   
       20 . The method of  claim 11  wherein the inert water absorbent solid material is vermiculite.