In another experiment, concrete mixtures containing 0.7 to 2.9 percent 

 of a DTNSRDC-developed insoluble acrylic organometallic polymer powder, 

 which exhibited good antifouling performance in static antifouling tests, 

 were prepared and cured. The concrete showed little reduction in compres- 

 sive strength and exhibited little fouling after 8 months of exposure in 

 the Chesapeake Bay. Further investigation is necessary before this concrete 

 can be considered as a viable antifouling concrete. 



Possible New Methods 



Another possible method for providing long-term antifouling protection 

 for OTEC structures is through use of various antifouling polymer- 

 impregnated concrete. The impregnation process involves: (1) absorption 

 of a monomer or partially polymerized system about 1 in. deep in a cured 

 concrete structure, (2) subsequent evaporation of solvent, and (3) polymer- 

 ization within the concrete. Although polymeric and monomeric antifouling 

 systems have been developed by the Navy and private industry, they have not 

 been used for this specific application. 



Polymer concrete consists of aggregate mixed with monomer which is 

 poljrmerized in place. This concrete has characteristics similar to polymer- 

 impregnated concrete and could use an antifouling monomer system similar to 

 those mentioned above. Polymer concrete has a short curing time and early 

 full strength. However, one disadvantage of this material is its high 

 polymer content (.7 to 8 percent by weight); this could increase signifi- 

 cantly its costs compared to conventional concrete and could limit the 

 use of polymer concrete to a surface shell coating, similar to the 

 impregnated-shale antifouling concrete described above. 



Cost Estimates 



Table 12 presents approximate costs for various raw materials neces- 

 sary to manufacture the different antifouling concretes. 



The costs of concrete vary considerably with geographic location, 

 while the antifouling additive material costs do not. This causes the 

 amount of antifouling material used and the labor intensity of its incor- 

 poration in each method to become the critical factors in the determination 

 of the most economically advantageous system. Even though the costs of 



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