A probabilistic approach for predicting corrosion initiation time for RC Members considering effect of temperature and relative humidity

Abstract

Corrosion initiation time of steel reinforcement in partially saturated concrete member subjected to chloride ingress is investigated at five geographic locations along Indian coasts. An approximate explicit method from literature is modified to incorporate additional variables affecting diffusion rate. The method accounts for uncertainties of input parameters and predict expected time of first corrosion for the chosen risk of corrosion. Method is also utilized to study the sensitivity of the parameters to reinforcement corrosion. Previously proposed diffusion based chloride ingress model is used for the analysis of time to initiate corrosion (corrosion initiation time). Corrosion is initiated when the chloride concentration on steel reinforcement exceeds a threshold value. Considerable variation in corrosion initiation time is observed for same concrete structure at different geographic locations. Life-365 predicts the time to corrosion initiation considering full-saturated condition of concrete. Comparing the results of the analysis for partially saturated and fully saturated concrete, it was found that Life-365 underestimates the time to corrosion initiation. Corrosion initiation time in ascending order was found at places Colaba, Kanyakumari, Santacruz, Chennai and Vishakhapatnam. Knowledge of corrosion initiation time is useful for owner, designer, or to an organization to take decision about repair strategy and prioritize repair of structures for corrosion protection in order to optimize maintenance planning and budgeting, since planned maintenance at the optimum time is the safest and most cost effective approach.