Anomalous Electromechanical Behavior of Portland Cement: Electro‐osmotically‐lnduced Shape Changes

Abstract

The electromechanical behavior of hardened portland cement paste has been investigated as a function of measurement frequency and dc electrical bias, using an inter‐ferometric technique. Large field‐induced shape changes on the order of 100 A have been found in millimeter‐thick specimens exposed to moisture. In addition, strong hysteresis effects were found on cycling a large ac field. Dry samples were found to exhibit no field‐induced deformations. The mechanism underlying this anomalous behavior is believed to be an electro‐osmotically induced swelling of the pore structures. Evidence in support of this hypothesis was found by corresponding investigations of porous silica gels.