Characterisation of lime/metakaolin paste using Impedance Spectroscopy

This paper describes the study of lime/metakaolin pastes using impedance spectroscopy during the first three weeks after mixing. Changes in the composition, structure and morphology were obtained using scanning electron microscopy, energy dispersive analysis of X-rays, differential scanning calorimetry, thermal gravimetric analysis and mercury intrusion porosimetry. The impedance data was studied with reference to changes in ac conductivity, relative permittivity and bulk resistance. Electrical behaviour was found consistent with structural and compositional changes. This study highlights the importance of impedance spectroscopy as a method for the non destructive monitoring and evaluation of lime based hydraulic binders.