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We have presented, for a white cement paste of water:cement ratio 0.5, systematic experimental measurements of the bulk dc conductivity σ and the pore fluid conductivity σo, using impedance spectroscopy, and compared them with results from computer simulations for the ratio Γ = σ / σo. Reasonable quantitative agreement is obtained in regions of porosity well above the capillary percolation threshold, conditions under which the exact conductivity assigned to the C-S-H phase in the microstructural model is not important, so long as it was small compared to the capillary pore space conductivity. Separating the bulk conductivity into the microstructural part, Γ(t), and the pore fluid part, σo(t), was crucial both for being able to compare experimental results with simulation results, and for being able to distinguish between the physical and chemical processes that determine the electrical conductivity.
Both NIST and Northwestern University would like to thank the National Science Foundation Science and Technology Center for Advanced Cement-Based Materials for financial support of this work. The use of facilities and materials of the National Cement and Ceramics Laboratories is also gratefully acknowledged.