Assessment of manufacturing process efficiency in the dispersion of carbon fibers in smart concrete by measuring AC impedance

Abstract

Smart concrete is a construction material designed to perform structural and self-sensing roles simultaneously. Self-sensing behavior stems from the inclusion of conductive fibers within the cementitious matrix, reducing its electrical impedance and enabling piezoresistive behavior. Good dispersion of fibers is essential to ensure good mechanical and sensing properties. This study assesses the efficiency of different mixing sequences and energies in dispersing fibers within the mortar. The efficiency is assessed with 0.1% and 0.5% carbon fiber volume, by measuring the AC impedance: those volume fractions correspond to two fiber percolation states: around the percolation threshold (0.1%), and in the saturation zone (0.5%). The study showed that the mixing sequence has a significant effect on the final impedance of the material, and that increasing mixing energy is relatively ineffective in enhancing the fiber dispersion. Differences between different mixing sequences were evident with 0.1% carbon fibers, while, to a certain extent, saturating the system with conductive fibers reduced the gaps between different mixing sequences.