Comparative Study on Performance of Corrosion Protective Systems for Post-Tensioned Concrete Members

摘要

Prestressing strands subjected to high tensile stresses are likely to become vulnerable to hydrogen embrittlement due to stress corrosion. Corrosion protection should be selected for safety and durability of the post-tensioned concrete structure. In this study, performances of corrosion protective systems used in post-tensioning construction were evaluated by the electrochemical and weight loss measurement methods. Test specimens represented the bonded strand and unbonded strand with plastic sheathing in grouted multi-strand tendons, as well as unbonded single-strand tendon and bare-strand. Corrosion tests were carried out in accordance with PTI M55.1-12 with slight modifications. Tests conducted included: corrosion by chloride ion (Cl-) solution and corrosion by chloride ion and dissolved oxygen (Cl- + DO) solution. lest results indicated that the specimens using plastic sheathing showed 0.03 to 0.07 mu A/cm(2) average corrosion current densities, which can be regarded as insignificant corrosion condition in comparison with the average value of critical corrosion current densities of 0.15 or 0.17 mu A/cm(2) for strand-corrosion testing due to only chloride ion or both chloride ion and dissolved oxygen. Therefore, the plastic sheathing had the best protective performance among the tested specimens; even significant sheath damage was considered during the installation process. The corrosion resistances of specimens protected by cement grout and grease coating, respectively, were similar to each other: This study is expected to contribute to the selection of effective corrosion protective systems fir construction of post-tensioned concrete structures requiring high durability.