The many adverse effects of ice on concrete marine structures have 
been described (Peyton, 1968). These effects have been experienced at 
oil drilling platforms (Cloyd, 1969) and concrete piers in Alaska where 
it has been demonstrated that the magnitude of forces due to ice flows 
must be carefully provided for if the structures are to successfully 
meet operational requirements. 
The Posey Tube, a two-lane subway nearly one mile long under the 
estuary between Alameda and Oakland, California, is another significant 
concrete maritime structure. Constructed in 1927, and in continual 
use to the present, it included 12 precast reinforced concrete tubes, 
each 203 feet long, which were fabricated at Hunter's Point near San 
Francisco and then floated across the Bay, sunk in place, and joined 
underwater (Horwege, 1929). 
Precast reinforced concrete units for wharves exposed to seawater 
were used in constructing harbor facilities at Aberdeen, England and 
at Tanga, East Africa during the period 1908 to 1912 (Billig, 1955). 
These structures are probably the earliest examples of precasting methods 
necessitated by economic reasons (e. g., excessive cost of hauling raw 
materials to the construction site or shortage of skilled labor or both). 
A more recent example of precast concrete is found in the San Mateo- 
Hayward Bridge, constructed in 1928 and 1929, in San Francisco Bay. The 
total length, including approaches, is nearly 12 miles, of which, 7 
miles consists of the concrete trestle portion. The concrete deck slabs 
were precast on shore, barged to the site, and installed over precast 
piles. Within 8 years serious cracking was evident (Gewertz, 1958) and 
repairs were made intermittently until 1951, when the California State 
Highway Division purchased the bridge. Repairs have been continued to 
the present; portions previously restored have undergone more recent 
restoration. Extensive investigations of the structure indicate that 
rupture and spalling of the concrete were caused by the reinforcing 
steel suffering from corrosion promoted by the chemical action of sodium 
chloride and sea mist (Temper and Bright, 1958). 
Many of the cast-in-situ reinforced concrete structures built during 
the early decades of the 20th century now appear rather ponderous when 
compared with currently built structures which are comprised of slender 
precast members made of higher strength concrete. 
During 1946 and 1947, a 3800 feet long by 26 feet wide causeway and 
a 3500 feet long by 120 feet wide wharf, both of reinforced concrete, 
were constructed in San Francisco Bay at Richmond (Gerwick, 1948). Pre- 
cast deck slabs and precast piles were transported to the site by barge. 
Pile caps were cast in place using precast concrete forms designed to 
slip over the precast piles. This construction job typified most of 
the principles of precast concrete for maritime use. The central casting 
yard, suitably located relative to transportation facilities, was: (a) 
level, yet drained readily; (b) did not settle under extremely heavy 
loads; (c) equipped with slabs for precasting operations; (d) had 
facilities for unloading and installing reinforcing steel, moving the 
forms, placing freshly mixed concrete, lifting and storing completed 
Delh 
