Precast prestressed concrete has become the favorite solution for many owners and specifiers seeking durable parking structures. The precaster should take an active part in building the owner's awareness on the importance of continuing maintenance. Despite quality control measures taken by precast producers, such as tight control of reinforcing steel placement, and use of strong dense concrete, precast structures face the same threats as other structural systems. This can include scaling caused by freezing and thawing in the presence of deicers, corrosion of reinforcement by chlorides and moisture, and lack of maintenance.
One advantage of precast structures is that the prestressed reinforcement is mostly near the bottom of the section. Water and chlorides on the driving surface are far above the strands as long as the top surface--the top flange, topping or fill, and joints--are watertight. If water and chlorides pass through the top barrier, the prestressed reinforcement is threatened.
Durability depends on the concrete quality and plant practices. Field conditions also are important. Careful handling during placement is essential to prevent damage. Special connections, joint widths, or joint sealants may be needed to make strong, tough connections. Maintenance is an integral part of ensuring long structure life. Joint seals must be checked and maintained on a routine basis.