Civil MDC

Report on Corrosion of Prestressing Steels 2

Report on Corrosion of Prestressing Steels

Description

Several attempts were made to prestress concrete in the 1800s, but modern development of prestressed concrete began in 1928 and is credited to E. Freyssinet of France (Lin and Burns 1981). Freyssinet understood the importance of prestressing using high-strength steel to avoid prestressing losses that significantly reduce the applied prestressing force. Use of prestressed concrete began in the United States with circular-wrapped prestressed tanks in 1941 (Schupack 1964). The first prestressed segmental concrete bridge in the United States was constructed in Madison County, TN, and opened to the public on October 28, 1950 (Bennett et al. 2002). The Walnut Lane Memorial Bridge, located in Penn-sylvania, was completed in the fall of 1950 (Manning 1988). Applications of prestressing in bridge and building construc-tion then spread rapidly and have proven to be a successful construction method.

Prestressed concrete construction enhances structural efficiency, improves control of flexural cracking, and allows for structural members with reduced dimensions.Although corrosion is not as well documented in prestressed concrete structures as in nonprestressed concrete structures, prestressed concrete members have a number of advan-tages regarding corrosion performance over conventional nonprestressed concrete elements. In general, prestressed concrete construction follows higher-quality control prac-tices and material standards than conventional nonpre-stressed construction.

These practices result in improved concrete properties that limit diffusion of chloride, which is further reduced in prestressed concrete members due to absence or reduced-level cracking. Corrosion of prestressed concrete structures appears to be restricted to specific circumstances, including improper design, construction details, and construction practices. The potential for accel-erated corrosion still exists in environments contaminated with chloride ions and hydrogen sulfide and it is impera-tive to protect prestressing steel. Corrosion of prestressing steel in bridges and buildings may not display outward signs of corrosion. Because failure of prestressing tendons could compromise the integrity of the structure, structures subjected to corrosive conditions should be periodically inspected with specific attention focused on the condition of the prestressing system.


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