Testing the Corrosion Rate of Prestressed Concrete Beams Under Variable Temperature and Humidity Conditions

Area of Science:

• Civil Engineering
• Materials Science
• Corrosion Science

Background:

• Existing research on temperature and humidity effects on concrete corrosion primarily focuses on ordinary steel reinforcement, with limited data on prestressed elements.
• Varied testing conditions and electrochemical methods in previous studies hinder clear conclusions regarding corrosion rates.
• Prestressed concrete structures require specific analysis due to unique reinforcement behaviors.

Purpose of the Study:

• To evaluate the impact of temperature and humidity fluctuations on corrosion development in prestressed concrete beams.
• To assess the influence of chloride ion exposure and mechanical loading on corrosion processes.
• To compare corrosion rates and structural performance under different environmental and loading conditions.

Main Methods:

• Prestressed concrete beams were exposed to controlled temperature and humidity variations in a climatic chamber.
• Chloride ion migration was accelerated using an electric field, and some beams were subjected to sustained loading causing scratching.
• Corrosion rates were measured non-destructively using the linear polarization resistance (LPR) method.
• Structural integrity was assessed through strength tests, and surface deformations were monitored using digital image correlation (DIC).

Main Results:

• Beams without chloride additives maintained a stable, low corrosion current density, indicating passive reinforcement.
• Accelerated corrosion was observed at 30% humidity and 20°C compared to 90% humidity and 30°C with chloride additives.
• Scratched beams exhibited a lower increase in corrosion current density than non-scratched beams.
• Beams with accelerated chloride migration showed significantly reduced deflection and milder surface strains during scratching.

Conclusions:

• Temperature and humidity significantly influence corrosion rates in prestressed concrete, with lower humidity and temperature potentially accelerating corrosion in certain conditions.
• Chloride ion ingress and mechanical loading (scratching) critically impair the structural performance and increase susceptibility to corrosion.
• The study highlights the need for specific research on prestressed concrete elements to understand and mitigate corrosion risks effectively.