concrete. Seismic forces can cause structure failure by producing excessive 

 stress in the material, resulting in structural deterioration. 



n. Human Activity . Human activity has very little impact on structures 

 of these materials except where visual impact may be noticeable resulting 

 from graffiti or other defacing action. 



7. Uses In Coastal Structures , 

 a. General. 



(1) Bituminous Concrete . Bituminous concrete is used to perform 

 three basic functions in coastal construction. It is used as a binder or 

 filler to stabilize quarrystone work or soils, as a sealant to prevent the 

 migration or flow of liquids, and, in its asphaltic cement form, as a 

 wearing surface that can be easily repaired or replaced as it is eroded. 

 Bituminous materials are also used in the preservative treatment of wood as 

 discussed in Section VIII, Wood. 



(2) Preplaced Concrete . Preplaced concrete is usually used in 

 large dimension mass concrete structures when aggregate larger than can be 

 conveniently handled by ordinary mixing methods is desired. 



(3) Portland Cement Grout . Portland cement grout is used generally 

 as a filler and binder for quarrystone work and as a stabilizer for soils. 



(4) Soil Cement . Soil cement is used to strengthen foundation 

 soils and to resist erosion of selected layers of soil. 



(5) Sulfur Cement and Grout . Sulfur cement and grout are resistant 

 to many environmental attacks in the coastal zone and may become economical 

 to use due to an increasing abundance. Because of limited general use and 

 history, sulfur cement and sulfur asphalt must be considered unproven 

 materials. However, the property of reaching full strength on cooling 

 could be especially useful in making repairs to structures and embankments 

 where the cost of delay is high. In busy cargo terminals, on heavily used 

 roads or in coastal structures subject to imminent assault by storms, quick 

 repairs to structures not immersed in water could be made. No practical 

 techniques for placing sulfur concrete under water have been developed to 

 date. (Fast cooling is the problem.) 



b. Offshore Structures . 



(1) Bituminous Concrete . Bituminous concrete is used for reinforce- 

 ment or grout to fill and plug the voids in stone or rubble-mound breakwaters, 

 The binding action of the mastic tends to produce a large firm mass while 

 being flexible enough to conform to some differential settlement of the 

 structure (Fig. 44.) 



(2) Preplaced Concrete . An impermeable breakwater could be made 



by placing uniformly graded stones in layers along the contours of a rubble- 

 mound breakwater. Each layer would be bound together with tremie-placed 

 Portland cement concrete grout. The resulting mass concrete structure 

 would be accomplished by the preplaced concrete method except that no forms 

 would be used. 



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