Aluminum. A few bridges, including highway plate girder bridges and arch-type pedestrian bridges, have been constructed of aluminum. These bridges have generally performed well and have not required much maintenance. The plate girder bridges do not seem to have experienced problems that one might anticipate due to the difference in thermal coefficient between the aluminum girders and the concrete deck. The main reason aluminum bridges have not captured a larger share of the market is high cost. Design specifications for aluminum bridges may be found in Guide Specifications for Aluminum Highway Bridges, AASHTO, 1991.
Aluminum railings, while not having the strength or ductility of steel, do not require maintenance painting. Aluminum posts are cast, and aluminum rail elements are extruded in shapes that are convenient for bolted assembly of the railing. Bolts to anchor aluminum railings in concrete parapets are generally stainless steel.
Rubber. Rubber, sometimes natural but more often synthetic, is used in bridge bearings and expansion joint sealing devices. Reinforced rubber sheets are used to fabricate troughs to conduct storm water that is permitted to flow through open expansion joints.
Stone. Stone is used in some states to face barriers and to provide waterline protection of piers. It is sometimes also used for aesthetic reasons.
