Influence of carbon nanofiber content and sodium chloride solution on the stability of resistance and the following self-sensing performance of carbon nanofiber cement paste

This paper aimed to study the influence of carbon nanofibers (CNFs) content and sodium chloride solution on the stability of the electrical resistance and the following self-sensing performance of CNFs cement paste. CNFs content ranged from 1.5% to 3.0% by the volume of cement. The electrical resistance and capacitive reactance of specimens were tested. AC voltage was applied to the dried or NaCl immersed specimens. While, DC voltage was supplied to dried specimens as contrastive group. Additionally, the piezoresistivity of dried samples was investigated. Results indicated that the capacitive reactance of drying specimens increased obviously with the increasing CNFs dosages. However, the capacitive reactance kept stably with the increasing CNFs content after the specimens were immersed in NaCl solution. While, the resistivity of the samples decreased obviously with the increasing CNFs content both in drying state and immersion in NaCl solution. The capacitive reactance was increased and the electrical resistivity was decreased after immersing in NaCl solution. The stability of electrical resistivity of drying specimens was decreased by increasing the dosages of CNFs. Meanwhile, the stability of electrical resistivity of specimens after disposed in NaCl solution first decreased then increased with the increasing CNFs content. The resistance of specimens determined by AC voltage was more stable than that tested by DC voltage. No obvious self-sensing performance was observed, when CNFs content was less than 2.5%. Additionally, CNFs cement paste presented the highest sensitivity of self-sensing performance when CNFs content was 2.5%.