Parameters Influencing Corrosion and Tension Capacity of Post-Tensioning Strands

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Title: Parameters Influencing Corrosion and Tension Capacity of Post-Tensioning Strands

Author(s): David Trejo, Radhakrishna G. Pillai, Mary Beth D. Hueste, Kenneth F. Reinschmidt, and Paolo Gardoni

Publication: Materials Journal

Volume: 106

Issue: 2

Appears on pages(s): 144-153

Keywords: chloride; corrosion; duct; moisture; post-tensioning strand; segmental bridge; strand; stress; tendon; tensile strength; void.

Date: 3/1/2009

Abstract:
A 12-month long strand corrosion test program with 298 specimens was conducted to identify and quantify parameters influencing corrosion and tension capacity of strands in post-tensioned bridges. The parameters investigated were grout class, moisture content, chloride concentration, void type, and stress level. The test specimens were 41 in. (1041 mm) long, in unstressed or stressed conditions, partially or completely embedded in cementitious grout, and exposed to various environmental conditions representing possible field conditions. After the exposure period, the grout material was removed and the strand surfaces were cleaned and visually evaluated for corrosion damage. The tension capacities of the strands were then determined. Results indicate that the corrosion was most severe at or near the grout-air-strand (GAS) interface. Corrosion evaluation and statistical analysis of the strand tension capacity results show that orthogonal, inclined, and bleedwater void conditions caused more corrosion and tension capacity loss than parallel and no-void conditions. The change in grout class did not result in statistically significant changes in the tension capacity of the strand samples evaluated. Statistically significant changes in tension capacity were observed with changes in the GAS interface, stress level, moisture content, and chloride concentration.