like the coastline af the Gulf of Mexico, the southeastern United States or 

 parts of the shorelines of the Great Lakes may be the only protective 

 material immediately available. Sources of salvaged concrete for use in 

 revetment are broken highway or landing strip paving, foundations for 

 structures, broken piles or light standards, manholes, large sewer or water 

 pipe. Thin slabs, particularly those reinforced with wire mesh, should not 

 be used as they tend to form flat planes upon which other materials slide 

 into deeper water and the exposed mesh is hazardous to recreationalists and 

 the rusting of the mesh causes rapid deterioration. 



(2) Groins . The application of salvaged concrete is the same for 

 groins as revetment but as groins are usually located in recreational areas 

 the concrete is much less desirable from an esthetic and safety point of 

 view. 



(3) Jetties . Concrete rubble is generally not desirable as armor 

 material for jetties unless the jetties are located in small bays or lakes 

 where waves are of limited height. The several thousand pieces of armor 

 material required are usually not available in design size from broken 

 concrete. Jetties are also usually designed for a long life and the concrete 

 blocks tend to wear rapidly or disintegrate. Concrete rubble may, however, 

 be used as graded core material. 



(4) Breakwaters . Concrete rubble is generally undesirable for the 

 armor or underlayers of a breakwater unless it is in a small bay or lake. 

 Wave action may be too severe and it is not feasible to obtain an adequate 

 quantity of design size pieces. Concrete rubble is acceptable as a filler 

 within the core section, as long as it is well mixed with the remaining 

 core material to avoid excessive voids. 



c. Crushed Concrete . Equipment is available now to economically crush 

 unreinforced concrete to most any size and gradation desired. Because of 

 the need to completely rebuild miles of old highways, crushed concrete will, 

 in some areas, compete with the cost of crushed stone. 



(1) Protective Structures . The principal use for crushed concrete 

 in breakwaters, groins, and jetties would be for the core and bedding 

 layer. Density is not so important here as for the cover layers but the 

 crushed concrete should satisfy the same size, gradation and durability 

 requirements as those established in the SPM {U.S. Army, Corps of Engineers, 

 Coastal Engineering Research Center (CERC), 1977} for stone. The same 

 criteria apply to the use of crushed concrete for use as filter layers in 

 revetments, seawalls and bulkheads, and special measures may be required to 

 control the amount of dirt in a crushed concrete mix. 



(2) Roads and Parking Lots and Storage Areas . Crushed concrete is 

 frequently used as a base course for roads, parking, or storage areas, 

 particularly in commercial harbors. Properly graded, it is as effective as 

 crushed stone and in urban areas may be less costly. 



d. Unbroken Concrete . Unbroken concrete would normally be so large as 

 to be a supplement to cover stone. It would consist of foundation blocks, 

 light standards, concrete piles, manholes and other reasonably compact 

 concrete structures weighing between 0.44 and 88 kilonewtons (100 and 20 000 



310 



