Corrosion failure of post-Tensioned tendons in presence of deficient grout Conference

cited authors

  • Lau, K; Lasa, I; Paredes, M

fiu authors

abstract

  • The assessment of recently failed external post-Tensioned tendons from a bridge in Florida provided some insight on the material and environmental conditions of the tendon components leading to the failure. Segregated grout material was observed in the vicinity of the corrosion failure. The segregated grout was manifested as wet plastic grout, white chalky grout, and sedimented grout. The deficient grout material has been attributed to segregation of the grout as evidenced by differences in texture and color of the grout, high moisture content, and apparent accumulation of chloride, sulfate, and other ionic species. No evidence of significant carbonation was detected by pH measurement. Accelerated corrosion was evidently caused by macrocell coupling of local anodes in the strand embedded in segregated grout and extended cathodes throughout the tendon. Due to grout segregation, part of the upper region of the tendon contained high water content which carried higher concentrations of ionic species including sulfates and chloride ions. The segregated grout material provided poor corrosion protection due to its high porosity, enhanced sulfate concentration, and possible enhanced carbonation and their associated deleterious effects on pore water chemistry and steel passivation. Differential aeration due to easy access to oxygen at vent caps, vastly different moisture contents in localized tendon regions, and strand interstitial spaces that created crevices allowed greater extent of macrocell polarization whereby corrosion failure occurred within a short time frame. © 2013 by NACE International.

publication date

  • September 2, 2013