Investigations on influencing factors of resistivity measurement for graphite tailings concrete

Using graphite tailings (GT) to replace part of sand to prepare graphite tailings concrete (GTC) is an effective way to reduce the environmental hazards. At present, there is still unclear issues on the durability of GTC. Resistivity is an important index to characterize the durability of concrete, and the effect of influencing factors (e.g. applied voltage, measuring electrode) on the measurement of resistivity needs to be studied in depth. Therefore, the accurate measurement of resistivity of GTC is a topic worthy of research. In this work, four/two-electrode methods and 4 V–32 V of applied voltages are employed for measuring the resistivity of GTC with 3 days–180 days curing ages and the results are compared to those of ordinary Portland concrete (OPC). Meanwhile, the porosity of concrete was tested using MIP to explore the conductive mechanism of GTC. The results show that the applied voltage, measuring electrode and curing age all have a significant impact on the measurement results of the resistivity. For accuracy and stability, the four-electrode method with 12 V of applied voltage is preferred. For convenience, the two-electrode method with 16 V of applied voltage is also acceptable. The porosity of concrete decreases with the increase of curing age, which leads to the decrease of the hole conduction and ionic conduction, thereby increasing the resistivity of concrete. In addition, the addition of GT can reduce the porosity of GTC with the increase of curing age, thereby increasing the resistivity of GTC, which indicates that the durability of GTC has been improved.