An Investigation of Degradation of Mechanical Behaviour of Prestressing Strands Subjected to Chloride Attacking

Corrosion of reinforcing and prestressing steel due to chloride contamination is one of the primary causes of deterioration of concrete structures. A review of published literatures shows that the research on the deterioration of mechanical properties of reinforcing steel is more than that on prestressing strands, even though the corrosion of prestressing strands may trigger structural collapse without warnings due to higher stress levels in the steel. This paper aims to investigate the degradation of mechanical behaviour of corroded prestressing strands. Details of a comprehensive experiment designed to examine the mechanical behaviour of corroded prestressing strands in concrete structural members are presented. A micromechanical damage model for failure mechanism of corroded prestressing strands is proposed, and a model for damage factor is derived. Based on these models, a constitutive model for corroded prestressing strands is developed and verified with test results. It is found in the paper that both the strength and ductility of corroded prestressing strands decrease with the increase of corrosion and that the hemispherical model for the pit shape is more appropriate for the prediction of strength reduction of corroded prestressing strands. The paper concludes that the constitutive model developed in the paper can be used to predict the mechanical behaviour of corroded prestressing strands accurately, paving the way for the assessment of corrosion-induced flexural failure of prestressed concrete structures.