Cement is one of the most widely used construction materials with one billion tonnes used annually. From an engineering point of view, it is essential that cement sets and hardens in a correct manner, indeed, modification of the setting and hardening characteristics of cement by the use of admixtures is becoming widespread in the construction industry. The reaction between cement clinker and water is a complicated chemical process which results in a rigid matrix capable of sustaining load. The increase in strength of the cement matrix is the consequence of hydration and crystal formation within the paste. Understanding the mechanisms of hydration and how they can be modified could result in new cement blends and admixtures tailor-made to suit any particular set of design criteria. In this paper it is shown that the temporal change in electrical response can be used to monitor the progress of hydration, and give an insight into mechanisms of hydration. Data are presented for several cement paste consistencies over the frequency range 20 Hz to 300 kHz. © 1988 Chapman and Hall Ltd.