Impedance spectra were monitored at early ages on hydrating Portland cement pastes subjected to a sustained load. The pastes were prepared with two different water-cement ratios (0.35 and 0.50). The experiments were conducted in a controlled chamber maintained at (96 +/- 2)% relative humidity. The three ages at loading investigated were 18, 24 and 30 hrs. Real-time changes in paste microstructure due to sustained load were followed through the coupling of an AC impedance frequency analyzer with a miniature loading system. Cement paste specimens were in the form of "T-shaped" columns with a minimum thickness value (for the web and flanges) less than 1.25 mm. The impedance analysis included an assessment of the relevance of the high frequency arc depression angle to an understanding of the creep and shrinkage behavior of cement paste. Electrical models were developed in order to predict the creep coefficient of normal (w/c = 0.50) and high strength (w/c = 0.35) cement pastes from early age data. (C) 2003 Kluwer Academic Publishers.