Fly Ash Blended Cement Resistivity Monitoring Using Carbon Screen-Printed Electrodes

Abstract

In this paper, electrical resistivity monitoring using carbon screen-printed electrodes (SPEs) was successfully implemented to characterize the early age properties of cement and fly ash blended pastes, showing good agreement with other conventional methods (such as heat evolution and Vicat needle penetration). Resistivity changes were attributed to the material hydration physical and chemical changes, identifying four critical points in early hydration. These critical points correlate with different hydration phases, including ionic dissolution, early product formation, percolation of solid hydrates, and the final setting phase. The findings suggest that SPE can effectively track hydration evolution, providing an alternative to traditional setting time and calorimetry measurements. Limitations associated with contact resistivity methods found in macroelectrodes were addressed in this research using printed microelectrodes, in which due to their small size, the required electrical currents are very small, preventing the negative effects of ohmic drop (IR drop), noise, and temperature increase at the electrode/material interface. Through this method, sensitive measurements of the hydration process of cement pastes were carried out. Finally, As paste resistivity at early age is governed by the pore solution conductivity and the solid cementitious microstructure development, this research also includes the results of a neural network model designed to predict the early pore solution conductivity, offering researchers a practical tool to model and analyze the behavior of fly ash-blended cement mixtures, providing insights into the material’s early behavior.