Observation of an electromechanical effect of hardened cement paste

A bending moment was created by an external load in a bar of hardened cement paste. Two electrodes had been attached to opposite surfaces. With this experimental set-up a stress dependent voltage could be determined between the tension and compression zone. This observation is called direct electromechanical effect. The generation of an electric field between the two electrodes results in a bending moment in the bar. The bending of the bar caused by this effect (converse effect) was recorded. Movement of adsorbed water layers, e.g. electrically charged double layers (electroosmosis), is supposed to be responsible for this behaviour.