Corrosion Morphology and Mechanical Behavior of Corroded Prestressing Strands

The corrosion morphology and the mechanical behavior of corroded prestressing strands are investigated in the present study. Nineteen corroded strands are obtained through controlling stress level, corrosion time and chloride ion concentration under artificial climate conditions. A total of 119 corrosion pits are counted to investigate the geometric morphology of corrosion pits. A depth-width ratio parameter is first defined to describe the distribution law of corrosion pits, which obeys the lognormal distribution. A tension test is conducted to investigate the mechanical behavior of corroded strands. The fracture morphology and micro-cracks of corroded steel wires are observed by the scanning electron microscopy. A constitutive model is proposed to predict the stress-strain curve of corroded prestressing strands and verified by the experimental results. Results show that the maximum corrosion loss of strand increases by 4.91% when the stress level changes from 45% to 75% of strand yield strength. The high stress level can promote the propagation of corrosion micro-cracks on strand surface. The propagation of corrosion micro-cracks has a significant effect on ultimate strength of strand, while has a little effect on elastic modulus. The proposed model can give an accurate prediction for the stress-strain of corroded prestressing strand.