Material and Corrosion Evaluation of Deficient PT Grout with Enhanced Sulfate Concentrations

摘要

Analysis of deficient grout in Florida post-tensioned (PT) bridges where severe corrosion developed indicated enhanced sulfate ion concentration, high pore water pH, and enhanced moisture content. However, limited information is available on the corrosion behavior of PT strand in grout materials with enhanced sulfate content. Earlier research had shown inconsistencies on the role of enhanced sulfates in the corrosion of steel in solution and embedded in hydrated cementitious material. Laboratory cast samples created to enhance grout chemical and physical deficiencies were analyzed. Verification of enhanced free sulfate ion concentrations in deficient grout is important to elucidate the role of sulfates in the corrosion process and further testing was intended to differentiate physical, electrical, and chemical parameters of the grout material. Additional testing of steel in sulfate solution was conducted to identify potential for sulfates to disrupt passive film formation. Results of research in progress indicated that grout deficiencies related to excess moisture content can allow for accumulation of sulfate ions and can create adverse grout properties related to corrosion development. Anodic polarization tests of steel in pH 13 and 20,000 ppm sulfate solution with preconditioning to large negative polarization do not indicate strong tendency to disrupt passive film formation.