Table 3. Shearing Forces Required to Remove 3-Inch-Square Panels 

 of Antifouling Concrete From Concrete Surface to Which 

 They are Bonded 



System 



Liquid 



Method for Removing Oil From 



Load 



No. 



Vehicle 



Surface of Aggregates 



(lb) 



2 



Creosote 



Rinsed with solvent not dried. 



1,700 



9 



Creosote and TBTO 



Rinsed with solvent and dried. 



1,400 



9 



Creosote and TBTO 



Rinsed with solvent and dried. 



2,200 



10 



Creosote and TBTO 



Rinsed with solvent and dried. 



1,200 



10 



Creosote and TBTO 



Rinsed with solvent and dried. 



1,500 



11 



Petroleum 



Rinsed wtih solvent and dried. 



1,000 



14 



Water 



Controls. No oil to remove. 



1,500 



14 



Water 



Controls. No oil to remove. 



2,600 



14 



Water 



Controls. No oil to remove. 



2,500 



with a mixture of creosote, tributyltin oxide (TBTO) at the lOO-ml-per- 

 liter level, malachite green, and pentachlorophenol (System 10). Control 

 panels in which the aggregate was impregnated with water (System 14) 

 were also exposed at the 600-foot site. The panels were exposed for a 

 period of 9 months. No fouling accumulated on either the test panels or 

 the control panels. Occasionally a few fouling organisms were found on 

 specimens of other material exposed at this station but the fouling was 

 scant and was slow to develop. 



One-Hundred-Twenty-Foot Depth . Fouling was somewhat heavier at the 

 shallow exposure site at a depth of 120 feet. Specimens of the antifoul- 

 ing concrete in which the aggregates were impregnated with creosote 

 mixtures containing TBTO at the 250-ml-per-liter level (System 8) and at 

 the 100-ml-per-liter level (Systems 7 and 9) and with mixtures contain- 

 ing copper naphthenate (Systems 11, 12 and 13) were exposed at the 120- 

 foot station. Untreated control panels (System 14) and untreated panels 

 which were coated with a mixture of TBTO at the 100-ml-per-liter level 

 and rubber or epoxy compound were also exposed at the 120-foot depth. 

 The specimens were all exposed at that depth for a period of 19 months. 



At the end of the exposure period, the control panels were covered 

 by a fairly heavy layer of fouling organisms. The fouling was markedly 

 heavier on the sheltered side than on the side exposed to the prevailing 

 ocean currents. 



There was very little fouling on the panels made with aggregates 

 impregnated with mixtures containing TBTO at either the 100- or 250-ml- 

 per-liter level. What little fouling there was, tended to be only on 

 the side exposed to the prevailing ocean currents. This is the reverse 

 of the fouling pattern on the control panels which was heaviest on the 



11 



