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 (DFL) is either overestimates or underestimates the time to initiation of corrosion (Ti). An alternate method for predicting ‘D’ using Warburg diffusion coefficient (DWI) 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 DWI in situ in concrete structures. DWI 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 DWI 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.