Microstructural changes and chloride transport in cement pastes are studied under DC current and pulsed electric fields. Impedance spectroscopy and ultrasonic pulse velocity measurements have been employed for quasi-real time monitoring of changes in the cement paste microstructure. The results show that the electric resistivity and ultrasound velocity (measured at 500 kHz) are modified during the migration experiments. At the end of test, mercury intrusion porosimetry reveals an important increase in the fraction of gel pores. The experimental results show conduction enhanced through gel pores. The use of pulsed current is presented as an alternative method to minimise the negative effects produced by DC current.