CONCLUSIONS 



Antifouling marine concrete made from a porous expanded shale 

 aggregate impregnated with mixtures of creosote, tributyltin oxide at 

 levels of 100 to 250 ml per liter, and other toxic chemicals have remained 

 essentially free of marine fouling for at least 4 years. The antifouling 

 concrete is not as strong as concrete made from sand and gravel, but it 

 is sufficiently strong for construction in which a compressive strength 

 of 3,500 psi is acceptable. The antifouling concrete is effective at 

 Guantanamo Bay, Cuba, as well as at Port Hueneme and Point Mugu, Cali- 

 fornia. It is effective near the surface of the ocean and at a depth of 

 120 feet. Concrete made from aggregate impregnated with a 50:50 mixture 

 of creosote and copper naphthenate is fouled as readily as ordinary 

 concrete containing no toxic chemicals. Coating concrete with rubber 

 that contains tribulyltin oxide at a level of 100 ml per liter does not 

 provide long-term protection against fouling. 



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