An electrical impedance investigation into the chloride ion transport resistance of alkali silicate powder activated slag concretes

The chloride transport resistance of alkali silicate powder activated slag concretes is evaluated. Two different Na2O-to-source material ratios (n) and two SiO2-to-Na2O ratios of the activator (Ms) are used on concretes proportioned using two slag contents (300 kg/m3 and 400 kg/m3). Rapid chloride permeability (RCP) and non-steady state migration (NSSM) tests are used to evaluate the chloride transport behavior. Alkali silicate powder activated concretes demonstrate comparable or better chloride transport resistance than OPC concretes when evaluated using RCP and NSSM tests. The relationships between the activator parameter, n·Ms, and the critical pore sizes (dc) or the RCP and NSSM values demonstrate similar trends showing the influence of dc in determining the ionic transport response. Electrical impedance spectroscopy (EIS) is used to relate the material response before and after the transport tests, and equivalent circuit models are used to extract the parameters that relate to the pore structure. EIS coupled with circuit modeling clearly brings out the differences between the RCP and NSSM test on their influences in the microstructure of alkali activated slag concretes.