Determination of diffusion coefficient of chloride in concrete using Warburg diffusion coefficient

Assessment of diffusion coefficient of chloride (D) using chloride profile method based on Fick's law (D-FL) is either overestimates or underestimates the time to initiation of corrosion (T-i). An alternate method for predicting 'D' using Warburg diffusion coefficient (D-WI) which is determined from Electrochemical Impedance Spectroscopy technique (EIS) is established. The results reveal that EIS being non-destructive appears a promising technique to arrive at time-dependent characteristics of D-WI in situ in concrete structures. D-WI is an intrinsic effective diffusivity measures the diffusion of free chloride through the pore solution present in the interconnected pores. Pore constriction by pozzolanic reaction and higher chloride binding capacity reduces the D-WI in PPC and PSC concrete by a factor of 1.65 and 4 times that of OPC concrete in 20 MPa concrete: 1.83 and 2.52 in 30 MPa concrete; 24 and 16 times in 40 MPa concrete respectively. (C) 2009 Elsevier Ltd. All rights reserved.