Abstract
After corrosion failure of post-tensioned tendons was identified in a Florida bridge in early 2011, laboratory tests were conducted in this study on extracted sections from the failed tendons to identify the grout properties and makeup leading to the failure and also to elucidate the mechanism of corrosion. The initial steps in identification of PT tendons with a high propensity for corrosion initiation or damaged included a detailed visual inspection and identification of voids in the grout. Voids in tendon can be a result of bleed water formation or construction problems. General characteristics of the deficient grout and corrosion behavior of steel in the affected bridge gave a first approach to assessing grout deficiency and corrosion susceptibility. However, refinements in the understanding of the mechanisms causing grout segregation and the elucidation of the role of sulfates, oxygen content, and pore water pH in corrosion development are required.
Highlights
Corrosion protection of post-tensioned (PT) tendons typically consists of embedding the strand in cementitious grout inside a high density polyethylene (HDPE) duct
After corrosion failure of post-tensioned tendons was identified in a Florida bridge in early 2011, laboratory tests were conducted in this study on extracted sections from the failed tendons to identify the grout properties and makeup leading to the failure and to elucidate the mechanism of corrosion
PT tendon failures have been associated with localized corrosion of strand at void spaces that formed in the tendon due to bleed water accumulation and reabsorption [1,2]
Summary
Corrosion protection of post-tensioned (PT) tendons typically consists of embedding the strand in cementitious grout inside a high density polyethylene (HDPE) duct. More recent corrosion failure in PT tendons constructed with grout material conforming to the low-bleed requirements has occurred as well. A corrosion failure of several PT tendons occurred in a bridge in Florida constructed with low-bleed grouts in 2011. Visual examination and electrochemical testing suggested significant anodic corrosion activity of the strand, predominantly in the presence of the deficient grout [4]. Inspection of the tendons for grout material deficiencies and corrosion development has been a challenge without the wide availability and acceptance of appropriate non-destructive testing techniques. A description of important material parameters, test methods, and initial results from a case study are presented to help characterize the conditions in the PT tendons with deficient grout materials and help identify the propensity for possible corrosion development
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