of animal growth of mostly snail tubes is found. The maximum depth for 

 snail tubes growth is not known at this time but existing concrete plat- 

 forms in 450-foot depth will yield this data for the North Sea in the 

 future. Growth of this magnitude will decrease buoyancy and significantly 

 increase mooring forces. The Civil Engineering Laboratory (CEL) has pioneered 

 in the development of an antifouling concrete. L 37 J Toxic chemicals are 

 incorporated into concrete by first impregnating porous expanded shale 

 aggregate with the chemicals and then mixing this aggregate with the 

 other concrete ingredients. The antifouling concrete has successfully 

 prevented marine growth for up to 4 years (limit of test) in surface 

 waters and at a depth of 120 feet. 



Coatings have been an age-old technique for short-term prevention of 

 marine growth. New products, such as dense-polyurethane and dense-epoxies 

 which contain no solvent to evaporate, have appeared on the market and hold promise 

 for long-term prevention. The dense-polyurethanes and epoxies exhibit 

 highly smooth surfaces which may prove easy to clean. However, coatings 

 may lead to intensified galvanic cell corrosion by creating locations of 

 differential electrical potential, because some concrete sections are wet 

 and others are relatively dry. 



Recent Developments . New materials and techniques have been researched 

 over the last 10 years that may have application to ocean structures. 

 Fiber-reinforced concrete is beginning to have field acceptance. Fibers 

 of steel, glass, or synthetics are incorporated in the concrete as it is 

 mixed .L J The notable improvements in engineering properties are an in- 

 creased tensile strength, increased ductility, and improved crack control. 



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