Electrical conductivity based microstructure and strength prediction of plain and modified concretes

摘要

Electrical response of cementitious systems can be used to understand the evolving microstructure, and thus to provide indications of the mechanical and durability performance of such systems. This paper deals with the use of a generalized effective medium (GEM) theory to predict the porosity of cement pastes and concretes containing several cement replacement materials. Methodologies to obtain the pore solution conductivities and an equivalent soild phase conductivity in the case of concretes are outlined. The predicted porosities are found to match well with the experimental values obtained from a vacuum saturation method. It is shown in this paper that the critical exponent in the GEM equation influences the predicted porosities and a universal value for this exponent cannot be used in continuum percolating systems such as cement pastes and concretes. The thermal signature of hydrating cementitious systems, represented using the equivalent age maturity index, is related to a microstructural parameter obtained from electrical impedance. A unique relationship is observed between the equivalent age and the micro-structural parameter irrespective of the mixture design parameters thereby providing a crucial link between maturity and microstructure development.