Low-to-medium-frequency range impedance spectroscopy was used to investigate two series of dried calcium silicate hydrates with or without aluminum atoms, C–S–H and C–A–S–H. Over four decades in frequency, sample Nyquist plots were fitted by adopting an equivalent circuit using constant phase elements (CPE). Conductivity values of the order of 10−9–10−10 S/cm were obtained at 316 K. The presence of CPE characteristic of the depleted semicircle at high frequency was related to a fractal dimension ranging from 2.4 up to 2.7. Above 316 K, the impedance spectra behaved unpredictably due to the dehydration process, while below 316 K the behavior was followed by adopting the modulus loss factor. The associated peak maximum variation is of the Arrhenius-type. The entire behavior may be interpreted by ionic motion and charge accumulation in addition to dielectric polarization at the grain boundaries associated to low fractal surface.