with the use of small quantities of cement. In good soils, 7-day compressive 

 strengths of 2 070 kilopascals (300 pounds per square inch) are obtainable. 

 Soil cement is used primarily as a base course for stabilizing and compacting 

 soils for foundations, bank protection, and subbase construction. It has 

 been used for earth dam cores, reservoir linings, and slope protection. 



(5) Sulfur Cement . Sulfur cement concrete and grouts are a rela- 

 tively recent development and as such do not have a long history of use in 

 coastal structures. Recently, the availability of large quantities of sulfur 

 has resulted in its increased use in construction projects as a binder or 

 admixture of aggregates. Molten sulfur mixed with sand and aggregates pro- 

 duces a sulfur concrete of excellent strength. 



Sulfur-asphalt binder materials have higher densities than normal asphalt 

 as sulfur is about twice as heavy as asphalt. The sulfur- asphalt binder 

 usually results in a lower void percentage than the asphalt cement without 

 the sulfur addition. Sulfur does increase resistance to gasoline, diesel 

 fuel, and similar solvents. It also improves stress fatigue characteristics. 

 The finely dispersed sulfur particles add strength to impregnated fabrics. 



Whereas sulfur cement materials reach their full strength quickly upon 

 cooling, the inherent flammability and low melting point of sulfur impose 

 some limitations on the use of sulfur cement. However, because of its 

 quick-set characteristics, it may find many uses in emergency repairs that 

 could have considerable longevity. With more experience and additional 

 development, sulfur-cement products will probably find increased use in 

 coastal construction. 



e. Structural and Sheet Metals . 



(1) Steel . Steel is the most utilized of all metals in marine 

 service and for coastal structures. Carbon steel is an alloy of iron and 

 carbon in which the carbon content is less than 2 percent. Structural steel 

 limits the carbon content to less than 0.35 percent. Adding small amounts of 

 alloying elements during the steelmaking process can improve the mechanical 

 properties of steel as well as its corrosion resistance. Small additions of 

 copper, nickel, chromium, silicon, and phosphorus have been effective in 

 improving the corrosion resistance of steel. 



In addition to its strength, the mechanical properties of steel of most 

 interest in the design of steel structures are: ductility, brittleness, 

 malleability, flexibility, hardness, resilience and toughness. Ductility is 

 defined as the ability of a material to be drawn out without change in 

 volume. Brittleness defines its lack of ability to be deformed without 

 rupture. Malleability is the opposite of brittleness and refers to its 

 ability to be forged or rolled into thin sheets. Flexibility describes its 

 ability to bend under stress and return to its original shape when the load 

 is removed. Hardness is a measure of its ability, to resist indentation when 

 subjected to impact. Resilience is its ability to absorb energy due to 

 applied loads without breaking. Toughness indicates its ability to absorb 

 large amounts of energy without rupture. Structural steel has a high degree 

 of all these properties. , 



379 



