Investigation of specimen size, geometry and temperature effects on resistivity of electrically conductive concretes

In ECON research, it is important to determine a suitable size-geometry of specimen for resistivity measurement. In this study, specimens of three different geometries (cube, cylinder and prismatic) were produced in three different sizes using a mixture of normal concrete and ECON. In the ECON mixture, 0.8 vol% carbon fiber was used as conductivity increasing additive and carboxymethyl cellulose was used as fiber distributor agent. Resistivity (rho) values were obtained once by applying different voltages and once directly measuring resistance (R) by ohm meters. It has shown that the resistivity values decrease with increasing voltage, according to the results obtained by the voltage application method, for both normal and ECON samples. In ECON specimens, it has been specified that the resistivity value increases with increasing cross section area (A)/length (L) ratio. Since the A/L ratios among the cylinder specimens were lower than the others, the resistivity difference of these samples was less. To determine the temperature-resistivity relationship in ECONs, the resistivity of 10 cm diameter, 20 cm long cylinder specimen was examined between -10 and room temperature. According to the results of temperature-resistivity relationship research, as the temperature increased from similar to 10 degrees C to about 15 degrees C, the resistivity decreased, then the resistivity was fixed with increasing temperature. (C) 2020 Elsevier Ltd. All rights reserved.