It is possible through heat processing to melt asphalt down and reuse it 

 as a mixing agent but the cost is prohibitive and the material is of no value 

 for shoreline structures. 



b. Asphalt in Rubble Structures . Broken asphalt concrete can be used 

 in the underlayer if the same design criteria are followed as for stone. As 

 a cover layer it is not desirable as it is of low specific gravity, is not 

 as durable as stone or broken concrete, and due to its color and appearance 

 is not esthetically appealing. Asphalt-sand has little durability, a charac- 

 teristic that makes it undesirable in the cover layer. 



c. Crushed Asphalt Concrete . Crushed asphalt concrete or asphalt-sand 

 is an acceptable substitute for stone as core or bedding material in 

 coastal structures but must be used with care as filter material because of 

 the difficulty of obtaining and maintaining an adequately graded mix to 

 properly act as a filter. The most common use is as a base material for 

 roads, parking lots, and storage areas in the same manner as discussed for 

 broken concrete. Either broken or crushed asphalt concrete or asphalt-sand 

 may be used as fill material so long as the voids can be filled. 



4. Concrete Blocks and Bricks . 



a. General. Salvage material, consisting generally of hollow concrete 

 blocks, cinder blocks and bricks, may be used in random placement. These 

 materials are seldom used unless for emergency protection or of economic 

 necessity. 



b. Concrete Blocks . These are generally hollow blocks salvaged from 

 dismantled buildings or broken in production during the curing period. In 

 the western United States these blocks are made of concrete, have a specific 

 gravity of about 2.3 in seawater, and are not particularly durable. In the 

 eastern United States they are frequently fabricated using cinders or slag 

 for aggregate and are known as cinder blocks. These are even less durable 

 than the concrete block and have a very low specific gravity (about 1.5 to 

 2.0). 



(1) Rubble Structures . Concrete blocks are frequently used for 

 emergency protection because they are frequently readily available for only 

 the cost of transporting. They generally break down through handling and 

 are of no value in the armor layer or in the underlayer. They are not 

 durable nor are they esthetically acceptable. However, they can be used as 

 temporary protection during an emergency in isolated, nonrecreational areas 

 as long as it is realized that they must be covered with designed layers of 

 stone that will act as a protective material. 



(2) Crushed Concrete Block . Concrete blocks will generally crush 

 easier than broken concrete or stone and can be used in the same manner for 

 bedding layers, filter layers, or as part of a base course for roads, 

 parking lots, and storage areas. 



c. Bricks . Common building bricks have a specific gravity of about 

 1.9. They are not generally durable when subject to abrasion nor are they 

 esthetically desirable. 



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