pounds) . They are generally of an awkward shape to place and, if made of 

 reinforced concrete, can have severe handling and corrosion problems, 

 particularly if used in saltwater. They are generally unsightly and can Be 

 difficult to recover when no longer needed. 



Concrete barges or concrete hulled ships have, on a few occasions, been 

 used in breakwater, groin or jetty construction. They may be incorporated 

 into the mass of a breakwater or jetty, or may be used singly or in a line 

 to act as a groin. In general they have not served well because their 

 smooth sides and bottoms and large surface area compared to mass permit 

 them to slide or tip out of position. The interior of these barges or 

 ships may be difficult to fill with ballast and they are subject to the 

 same deterioration problems of these slabs of concrete. Such barge or ship 

 hulls can be extremely difficult and costly to remove or salvage. 



(1) Temporary or Emergency Protection . This is the most prevalent 

 use of unbroken concrete units and many times does more harm than good. 

 Unbroken concrete units are usually large enough that they should have an 

 underlayer, or bedding layer, of smaller rocks, as in the design of a 

 rubble-mound stone structure. Shapes such as light standards and pilings 

 are usually too long and rigid to act as flexible and effective units, and 

 in general there is little variety in size or shape to provide a well- 

 graded section such as can be done with stone. Without a bedding layer, 

 these units tend to work into the sand bottom and can be very difficult to 

 remove. However, in emergencies they may be the only medium to high 

 density material available and may be used pending later availability of 

 properly graded stones. 



(2) Supplement to Armor Stone . Generally, for rubble construction, 

 these unbroken concrete units are not available in a sufficient range of 

 sizes to be used as armor stone. However, if they fit some of the design 

 sizes for armor stone, and esthetics and the safety of recreationalists are 

 not a controlling condition, they may be used in combination with armor 

 stone to reduce costs. 



(3) Supplement to Core Stone . Unbroken concrete units are frequent- 

 ly used in conjunction with core stone to simply provide bulk and reduce 

 costs. Care must be taken to fill all voids inside and around these units 

 so that they become an effective part of the core. Problems may be en- 

 countered if their dimensions do not allow them to fit within the core 

 boundaries and they should not be placed so that large flat surfaces are 

 near horizontal thus encouraging the sliding of other stones across them. 



3. Asphalt . 



a. General. The primary types of asphalt mix used as a salvaged 

 material in shoreline structures are the asphalt and concrete mixes and the 

 asphalt and sand mixes. Both are used much in the same manner as salvaged 

 concrete; i.e., as a substitute for stone. Depending on the proportion of 

 asphalt, both the mixes tend to be of a lower specific gravity than stone 

 or concrete and for this reason are less desirable. Both are less durable 

 than stone or concrete. Because of its black to brown coloration it is 

 less desirable from an esthetic point of view than concrete or rock. 



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