Figure 70. Batten-protected creosoted-pile tops, Lighthouse Point Marina, Pompano Beach, 

 Florida. 



In areas where timber is scarce or costly, reinforced concrete construction is frequently 

 used for fixed-level berthing systems. The structural design criteria are similar to timber 

 construction except that connections and fastening devices are different and the dead load 

 to be supported is greater. However, lightweight concretes are sometimes used in stringers 

 and decking to reduce the dead load. If enough concrete cover on the reinforcing steel is not 

 provided, cracking and spalling from rust swells may result. As for bulkhead construction, 

 all concrete in a saltwater environment should have 3 inches of concrete covering all steel 

 reinforcement. This amount of cover may be insufficient if care is not exercised in placing 

 and vibrating the concrete. With a properly designed mix and careful placement, a good 

 dense concrete can be obtained to outlast almost any type of construction. 



The lasting quality of concrete was demonstrated in an experiment started in 1905 by 

 the U.S. Army, Corps of Engineers. Eighteen large test blocks of concrete were placed on a 

 shelf just below the waterline on the seaward side of the Los Angeles Harbor breakwater at 

 San Pedro, California. The concrete was varied from block to block both in the mix and 

 type of cement used (several commercial brands were available at the time). Seventeen 

 blocks were recovered, core-drilled and returned to the shelf in 1932; six were again 

 recovered, core-drilled, and replaced in 1972. Cores from the 1932 operation tested from 

 2,180 to 6,010 pounds per square inch and those from the 1972 operation tested from 



119 



