APPLICATION OF AC IMPEDANCE TECHNIQUES IN STUDIES OF POROUS CEMENTITIOUS MATERIALS .2. RELATIONSHIP BETWEEN ACIS BEHAVIOR AND THE POROUS MICROSTRUCTURE

The relationship between A.C. impedance parameters and the structure of porous cementitious systems was investigated. Theoretical equations relating the high frequency semicircle diameter to the descriptors of ionic concentration in the pore solution have been derived from the application of electrochemical and surface chemical principles to these systems. It is apparent that there is a linear relation between the semicircle diameter and the reciprocal of the square root of ionic concentration. The semicircle diameter was also found to be inversely proportional to the product of porosity and mean pore size. These equations have been confirmed by experiment with porous cementitious systems. It is concluded that the microstructure of porous materials can be characterized by parameters determined by application of A.C impedance techniques.