mined by weighing to be 9.05 mg/cm. Controls from a previous untreated 
set were deployed at both sites along with five replicates of each 
candidate antifouling concrete. 
Set no. 5 was prepared by wrapping and cementing a proprietary 
TBTO-impregnated elastomer about untreated cylinders. No controls were 
prepared in this case. Five samples were placed at each of the exposure 
sites. 
Ocean Exposure 
Design Setup. Candidate antifouling concrete specimens were prepared 
as 3-in.-diam x 6-in.-long cylinders so that compressive strengths could 
be determined (Ref 10). To prepare the cylinders for exposure in the 
ocean, two small rectangular connector rings were threaded onto each of 
two nylon cable ties. One cable tie was tightly fastened about the 
circumference at each end of a cylinder with the connector rings on each 
tie located 180 degrees apart and in line with one another at opposite 
ends of the cylinder (see Figure 1). Finally, an identifying number was 
melted into each nylon cable tie with a soldering pencil. Cylinders 
prepared for exposure by this method were attached to one another by 
placing still other nylon straps through the connector rings of adjacent 
specimens loosely enough that they hung at a distance from each other, 
forming what could be described as rungs of a ladder. Such groups of 
cylinders, each suspended horizontally, were hung from docks so that the 
topmost cylinder was beneath water during an extreme low tide. Four 
cylinders were typically deployed in each group. At Port Hueneme, their 
position relative to one another in the group was changed periodically 
when they were weighed to eliminate the effect of the depth variable. 
Also, the place from which each group was suspended from the dock was 
changed to prevent the entrance of effects of other variables into the 
results. 
Sites. Port Hueneme was chosen as an exposure site because the 
Civil Engineering Laboratory is close by. Specimens were exposed in the 
channel to this deep-water port where a good exchange of water from the 
ocean is made daily — semi-diurnal tides range from 4 to 9 feet. The 
temperature extremes of the surface water range from 9° to 222 Cm (Re tam) 
Key Biscayne, Fla., was chosen as a second exposure site because of 
its warmer water and the availability of qualified personnel at the 
University of Miami to monitor the antifouling properties of the specimens. 
At Key Biscayne, the specimens were exposed in shallower water than at 
Port Hueneme, but they were placed in a location where a 5-knot current 
flowed about them. It is felt that this relatively high flow rate would 
at least approach simulation of flow conditions one might encounter in 
the cold water pipe of an OTEC platform. The tidal extremes at Key 
Biscayne are less than 2 feet, and the water temperature extremes in 
1977 ranged from 15° to 32°C (Ref 12). 
Corrosion of Simulated Reinforcing Rod 
The effect on the corrosion rate of simulated reinforcing rods by 
toxicants employed in antifouling concrete set no. 2 and 3 was investi- 
gated. One cylinder from each set was crushed and the pieces placed in 
