(4) Sulfur Cement Concrete and Grout . With the increased production 

 of sulfur, as a result of refining more sour crude, larger quantities of 

 sulfur become available. This makes sulfur cement concrete and grout more 

 economically competitive for many special uses. Ongoing research and testing 

 is aimed at improving sulfur-asphalt materials by developing additives to 

 improve physical properties, such as those that allow mixing at temperatures 

 above 160° Celsius to prevent dehydrogenation. In sulfur concrete develop- 

 ment, the discovery of other plasticizers to improve its physical properties 

 and upgrade its heat resistance is an important activity. 



e. Structural and Sheet Metals . 



(1) Steel . Much of the effort in the research and development of 

 steel and steel products for coastal construction is devoted to the metal- 

 lurgy in steelmaking, in order to develop products that are more corrosion 

 resistant when exposed to the marine environment. Progress has been made 

 with recent development of ASTM grades A242 and A588, using small amounts of 

 vanadium, zirconium, columbium and titanium. These alloys exhibit improved 

 strength and yield values; however, the cost of these products is high and, 

 with the improved protective systems available (both coatings and cathodic 

 protection), very little of these steel alloys is produced. Studies in the 

 application and control of cathodic protection are ongoing to improve the 

 understanding of hydrogen imbrittlement and stress corrosion cracking of 

 metals, that may lead to greater use of structural steel in future coastal 

 structures. 



(2) Aluminum and Copper . The studies and investigations of aluminum 

 and copper, as well as other metals, are similar to those of steel. Much of 

 the research work is concerned with a better understanding of the physical- 

 chemistry of the oxide films that are responsible for the passivity and 

 corrosion resistance of these metals. These studies may lead to new alloys 

 and resulting allotropic modifications that might improve corrosion re- 

 sistance as well as enhance some physical properties of the metals, in- 

 cluding resistance to halogen and acidic ions. 



There is so much research in progress that it is difficult to estimate 

 at this time what new knowledge may contribute to the improved use of metals 

 in a marine environment. 



f . Wood. Because wood is produced by nature under various uncontrolled 

 environmental conditions, the product is highly variable. Also, the fact 

 that the tree is alive and produces wood of different properties at different 

 ages complicates the analysis of properties of wood. Recent investigations 

 on the strength properties to determine the material variability of clear 

 wood are based on the statistical probability of sampling. 



(1) Elastic Parameters . Present design often involves curved 

 members and three dimensional stress distributions. Therefore, recent 

 emphasis has been directed toward the determination of strength and elastic 

 characteristics of wood in all the principal directions. Prediction equations 

 have been developed recently which allow the estimation of all the elastic 

 parameter values of wood (Bodig and Goodman, 1973). Also, there is consider- 

 able interest in predicting the elastic and strength characteristics of wood 

 at any arbitrary ring and grain angle. 



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