Influence of salt freeze-thaw cycles on the damage and the following electrical and self-sensing performance of carbon nanofibers concrete

This paper aimed to study the damage of carbon nanofibers (CNFs) concrete during salt freeze-thaw cycles. The evolution of weigh, relative dynamic elasticity modulus and electrical resistance of the specimens were determined to evaluate the freeze-thaw damage. Moreover, the self-sensing performance of CNFs concrete under monotonic compressive loading, cyclic compressive loading and three-point flexural loading was studied. Water and 3.0% NaCl solution were selected as freeze-thaw mediums, while the freeze-thaw temperature cycles were conducted at -10 degrees C similar to 10 degrees C. Results indicated that the mass, the relative dynamic elasticity modulus decreased and the resistance increased with the increasing freeze-thaw cycles. The dried specimens exhibited the best piezoresistive performance. Additionally, the sensitivity and linearity of piezoresistivity deteriorated after 300 freeze-thaw cycles (The deterioration of piezoresistivity after 300 salt freeze-thaw cycles was more obvious). The resistance of all specimens (except the specimens after 300 freeze-thaw cycles in NaCl solution) increased during the flexural loading. The water-saturated specimens showed the highest flexural self-sensing sensibility while the drying specimens presented the lowest flexural self-sensing sensibility. However, the resistance of NaCl freeze-thaw specimens decreased firstly before destruction during three-point flexural loading. When the concrete was destroyed, the resistance of all groups increased to a maximum value rapidly. As a result, CNFs concrete can be a kind of self-sensing material.