Computation of diffusion coefficients and prediction of corrosion initiation in concrete structures

Chloride induced reinforcement corrosion is one of the major problems in premature deterioration of several concrete structures such as bridge decks, concrete pavements and substructures in chloride laden environments. In this research, different ternary, binary and control cementitious concrete mixtures are studied for chloride induced corrosion initiation prediction of concrete structures. Diffusion coefficients are one of the primary variables that initiate chloride induced corrosion. The primary objective of the research is focused on investigation of chloride permeability of different cementitious materials and computation of reliable diffusion coefficients from the Chloride Ion Penetration Test (CIPT) and Wenner probe resistivity data using fundamentals of elctrochemistry. Several theoretical equations and methods are applied to compute improved diffusion coefficients of different ternary, binary based High Performance Cementitious (HPC) system. Correlation between the results of CIPT and the Wenner probe also measures their durability acceptance criterion for investigation of long term chlride penetration. This research also investigated electrical conductivity of different cementitius mixtures from the CIPT data and its effect on ternary cementitious systems. The other objective of this research is focused on the formulation of probabilistic corrosion initiation model with inclusion of apparent variation of previously computed HPC diffusion coefficients and the variation of surface chloride concentration with several corrosion resistant steel reinforcements. The distribution of the other governing parameters is generated from either detailed field survey or laboratory experimental investigation. This study shows the variability and sensitivity of estimation of the time to onset of corrosion using the Monte Carlo technique and Simulation Based Reliability Approach (SBRA). Results from this probabilistic analysis estimate the corrosion free service life for the design of concrete structures in harsh chloride environments with respect to methods for diffusion coefficients computation.