Recent corrosion failures of tendons in Florida post-tensioned (PT) bridges utilizing low bleed specified grout products have shown the need for better understanding of the mechanisms that cause corrosion and to determine the extent of the problem in PT tendons with similar materials. Those deficient grouts in the tendons showed low chloride content below commonly assumed threshold limits for corrosion initiation, but they showed higher concentrations of sulfate ions, high pore water pH and higher moisture content. The role of enhanced sulfate ion concentrations in the development of steel corrosion in deficient grout has not been elucidated, but the role of sulfate ions in deficient grout with high moisture content may be comparable to the role of sulfate ions in alkaline solution.
The objectives of the research were to verify the role of sulfates but also to quantify sulfate content and introduce possible sulfate limits for corrosion development in various grout conditions. To examine the cause of corrosion failure, large-scale mockup tendons of about 15 feet long were cast using expired grout materials, an excess of 15% water mix water, and enhanced chloride and sulfate concentrations to create deficiencies and corrosion conditions in the grout environment. The tendons were cast at a 30-degree incline to produce segregated grout on the upper elevation. Steel probes were embedded in the tendons on varying heights and corrosion measurements were carried on these probes. The role of pH (12.5
