an extended period of time may fail due to excessive expansion of the 

 steel, resulting in spalling and cracking of the concrete. 



Steel, of course, is not combustible but if exposed to high tempera- 

 tures will tend to warp and lose strength. A rigid steel structure may 

 also tend to warp and buckle due to excessive expansion of its members. 



Asphalt is vulnerable to relatively low fire-induced temperature rises 

 and is not considered fire resistant. Wood, the least fire resistant of 

 coastal construction materials, is vulnerable to fire. 



Synthetics are also vulnerable to fire and may generate dangerous toxic 

 fumes . 



4. Availability . 



The availability of both the construction materials and the construc- 

 tion equipment necessary to build the structure may limit the selection of 

 materials; e.g.,, a lack of availability of the ingredients required for 

 mixing concrete onsite might necessitate use of more readily available wood 

 or the availability of utilities during construction might limit emplacement 

 methods and thus limit materials used. Site access with respect to local 

 resources and materials must also be considered. For example, in remote 

 areas bringing in steel and concrete may be difficult, while timber is 

 readily available. In this instance, all the properties of wood and its 

 durability must be carefully considered to determine if it is a suitable 

 substitute. This is one of the most important factors influencing the 

 selection, especially when considered in conjunction with transportation 

 costs. 



a. Abundance . 



(1) Stone . Stone is generally abundant in the continental United 

 States and most outlying areas. However, along the coasts of the Gulf of 

 Mexico and the South Atlantic, sources are 240 kilometers (150 miles) or 

 more from projects so handling costs can become a major factor. In many 

 areas, particularly the volcanic areas of the Pacific Ocean, the stone may 

 be of low density or will be so badly fractured as to not be suitable for 

 armor stone. The mere presence of large stone sources does not guarantee 

 suitability or availability of the stone. Only for a very large project is 

 it feasible to develop a new quarry from virgin rock. Even when a quarry 

 exists, it may not be equipped to produce the type and size stone needed 

 for a particular coastal project. Availability of handling equipment at 

 the quarry may be a critical factor. The cost of quarrying and transporting 

 will affect the choice of stone as compared to some other construction 

 material . 



(2) Earth . In most parts of the world an adequate quantity of 

 earth material is available for fills, dikes, and beaches, with two excep- 

 tions: in some delta areas, the immediately adjacent earths may be pre- 

 dominantly silts and clays; in some rocky coast areas, beach sands may not 

 be available. 



