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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.

Deicing and anti-icing salts and seawater are the main sources of chloride ions that cause the corrosion of steel reinforcement embedded in reinforced concrete (RC) bridge and marine structures. This article reports on a study undertaken to evaluate the influence of the steel reinforcement surface condition on the corrosion performance. In the study, the critical chloride threshold values of five uncoated steel reinforcement types (ASTM A 706, ASTM A 615, microcomposite, stainless steel 304, and stainless steel [SS] 316LN) with as-received and polished surface conditions were quantitatively determined using the accelerated chloride threshold (ACT) test procedure. Micrographs of the surfaces (characterizing the mill scale and surface topography) for all steel reinforcement types were obtained using both optical and scanning electron microscopy (SEM). Results showed that the mean critical chloride threshold values increased with the complete removal of the as-received surface and with surface polishing for the ASTM A 706, microcomposite, and stainless steel 304 reinforcements. In addition the mean critical chloride threshold values decreased with the complete removal of the as-received surface and with surface polishing of the ASTM A 615 and SS316LN steels. The authors conclude that removal of the mill scale on the microcomposite steel reinforcement showed a significant improvement in the critical chloride threshold and removal of this mill scale may be economically justified.