Electric polarization in carbon fiber-reinforced cement

Electric polarization induced an increase of the measured electrical resist ivity of carbon fiber-reinforced cement paste during resistivity measuremen t. The effect was diminished by increasing the conductivity of the cement p aste through the use of carbon fibers that were more crystalline, the incre ase of the fiber content, or the use of silica fume instead of latex as an admixture. Intercalation of crystalline fibers further increased the conduc tivity of the composite, but it increased the extent of polarization. Volta ge polarity switching effects were dominated by the polarization of the sam ple itself when the four-probe method was used, but were dominated by the p olarization at the contact-sample interface when the two-probe method was u sed. Polarization reversal was faster and more complete for the latter. (C) 2001 Elsevier Science Ltd. All rights reserved.