(3) Use in Coastal Structures . Because geotextiles are relatively- 

 new as a construction material, there has not been sufficient time to develop 

 agreed upon standard testing techniques for the most important characteristics 

 a fabric should have for specific applications. However, they are finding 

 many uses in coastal structures. Different fabric specifications may be 

 required for specific uses, such as replacement of stone filters under riprap, 

 drainage control by silt retention fabrics, and road stabilization by road or 

 highway fabrics. Fabric users should seek the advice and recommendations of 

 knowledgeable sources with experience in the specific use being considered, 

 such as consultants and more than one manufacturer. 



Many forms of plastics other than geotextiles are also used in coastal 

 structures. Flexible plastics are used as mold forms for concrete and for 

 wrapping timber pile to provide protection from marine animals and for wrap- 

 ping metal piles to prevent corrosion. Molded forms have applications as 

 rubbing strips, fenders and bumpers. Plastic extrusions in the form of pipe 

 and culverts are in common use. Pipe may be reinforced or not depending on 

 the structural strength required. 



h. Recycled and Other Materials . Generally recycled materials consist 

 of a variety of materials that may be available in a given location and are 

 normally used in emergency situations as temporary (occasionally as perma- 

 nent) protective devices against damaging waves or currents. Such materials 

 should have a specific gravity greater than 1.5 to be useful unless a float- 

 ing type of structure is needed. 



Materials considered in this category are salvaged concrete, concrete 

 rubble, crushed concrete, recycled asphalt used either as rubble or crushed, 

 blocks and bricks, and salvaged steel structures. Normally, because of the 

 emergency type use of recycled materials, little consideration is given to 

 the properties of such materials other than their specific gravity. Also, 

 little concern is given to their environmental impacts; however, these im- 

 pacts would generally be different than for the materials before recycling or 

 reuse. 



Recycled or salvaged materials have been used for many years for emergen- 

 cy repairs or to construct temporary structures. In many cases these tempo- 

 rary structures have remained in place for many years. 



Salvaged concrete, either as rubble, crushed or unbroken has been used to 

 repair revetments, groins, jetties and breakwaters. These materials may not 

 have a pleasing esthetic appearance, especially if they contain reinforcing 

 steel. If located in a recreation area, the reinforcing steel may create a 

 safety hazard. Of course, exposed reinforcing bars will corrode at a rapid 

 rate causing accelerated concrete spalling and deterioration. Generally 

 these materials are used as a substitute for stone in coastal structures. 



Recycled asphalt can be used as an underlayer in coastal structures. 

 Although it is relatively hard and unflexible because of its age, it will 

 retain its broken shape for extended periods of time and further deteriora- 

 tion is not a problem. Recovered asphalt may be crushed and used as core or 

 bedding material in coastal structures, but unless well graded, it does not 

 make a satisfactory filter material. Crushed asphalt is. also finding greater 

 use as a base material for highways, roads, streets, and parking lbts. 



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