Technological Aspects of Carbonation-induced Corrosion in Reinforced Concrete Structures of Civil Defense Facilities: Analysis, Challenges and Solutions

Carbonation-induced corrosion of reinforced concrete threatens the durability of civil defense facilities, particularly where ventilation is insufficient and humidity is high. Purpose: The aim is to assess concrete carbonation and the risk of steel corrosion in reinforced concrete structures of civil defense facilities based on field inspections. Methodology: Field inspections are conducted in three shelters in Moscow built in the 1970s–1980s. The study included measurements of the CO₂ concentration, concrete carbonation depth using a phenolphthalein indicator, reinforcement potential, and diffusion-based carbonation modeling. Research findings: The carbonation front in the inspected facilities nearly reaches the reinforcement depth (20–26 mm), indicating the risk of corrosion initiation. The main factors identified are the insufficient ventilation (CO₂ concentration up to 0.3 vol.%), high (70–90 %) relative humidity, and concrete quality. Value: Without protective measures, some of structural elements may lose their load-bearing capacity within 5–10 years. It is recommended to include improving ventilation, applying waterproofing and protective materials, and implementing regular monitoring.