Effects of load level, dimensional effects and temperature conditions on the pressure sensitivity of short carbon fiber cementitious composites

Abstract

Carbon fiber reinforced cementitious composites (CFRCC) are a kind of sensing materials in structural self-monitoring system. However, their performances still need to be enhanced. In this study, the effects of load level, dimensional effect, temperature and temperature cycles on the pressure sensitivity of CFRCC with hydroxyethyl cellulose (HEC) dispersant were systematically investigated. Simultaneously, the change rate of resistance was adopted to quantify the pressure and temperature sensitivity of CFRCC. It is found that the pressure sensitivity of CFRCC is stable as load level is below 50 per of the ultimate load. With the increasing size of the specimens, the compressive strength of CFRCC gradually declines whereas its change rate of resistance hikes quickly, both of which show obvious size effect. Furthermore, in the range of 5 °C to 80 °C, the resistivity of CFRCC demonstrates the effect of negative temperature coefficient (NTC), and the sensitivity coefficients of CFRCC tend to decrease with the increasing temperature. Compared with the sensitivity coefficient at 70 °C, the sensitivity coefficient of each specimen at 15 °C have increased by four times. In addition, the pressure sensitivity of CFRCC has significantly decreased after temperature cycles, and especially after 20 temperature cycles, CFRCC’s maximum change rate of resistance decreases by about 30% compared to the initial one. Therefore, CFRCC can be directly used in concrete structures to undertake the task of structural health self-monitoring.