X. RECYCLED AND OTHER MATERIALS 



1 . Introduction . 



In emergency situations or when funds are lacking and the need is 

 great, almost any material, with a specific gravity greater than water, has 

 been used either as a temporary or permanent protective device against 

 damaging waves or currents. Even for temporary protection, materials with a 

 specific gravity of less than 1.5 are of little value. Other materials 

 that may provide emergency or short-term protection may be so difficult to 

 recover, or remove, as to be undesirable. Others may be environmentally 

 undesirable due to hazards to bathers, visual or chemical pollution, or 

 there may be the possibility that waves or currents may transport the 

 material to an undesirable location or cause undue scour. 



New materials are continually being offered for coastal installations, 

 but durability and resistance to fatigue and chemical breakdown are vital 

 to the economic life of a coastal structure and, too frequently, only a 

 long period of time will determine how the untested new material will 

 function. 



2. Concrete . 



a. General . Salvaged concrete may be used as found in its original 

 form so long as lifting and transport equipment can handle it. It may be 

 of reinforced or unreinforced concrete broken into sizes more easily 

 handled, or it may be crushed and reduced to sizes ranging from sand to 

 cobbles. 



b. Concrete Rubble . Concrete broken into sizes capable of being 

 transported and handled by conventional rock-placing equipment can be used 

 in the same manner as rock rubble for the armor and underlayers of rubble- 

 mound structures. It is generally of two types- -unreinforced or reinforced 

 concrete. Unreinforced is preferred. If reinforcing steel is protruding, 

 it is unsightly and dangerous to bathers or recreationalists climbing on 

 it. If possible, protruding sections of steel should be cut off. In 

 saltwater the exposed steel will corrode rapidly and split the pieces of 

 concrete into smaller units and reduce their effectiveness to resist the 

 force of waves or currents. 



(1) Revetment . The most common use of concrete rubble is in 

 revetment. It may be used for armor stone or for the underlayer and design 

 slope and sizing should follow the same design procedure as for rock. It 

 must be kept in mind that concrete only has a specific gravity of about 2.3 

 to 2.5 and does not have the hardness of most stone so it will have a 

 limited life. In place, it generally presents a somewhat unattractive 

 appearance as compared to rock but, if in the wave wash area, will be 

 abraded into a less angular shape and appear similar to waterworn rocks. 

 It is acceptable as an underlayer beneath armor rock and near urban areas 

 may be less costly. 



The primary use of salvaged concrete or concrete rubble in revetments 

 is for emergency, low costs, or temporary revetment of an eroding bank or 

 bluff. It is generally available for the cost of hauling and in many areas 



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