Self-sensing capacity of ultra-high-performance fiber-reinforced concrete containing conductive powders in tension

This study experimentally analyzed the self-sensing performance of the tensile behavior of ultra-high-performance fiber-reinforced concrete (UHPFRC) incorporating four different types of conductive powders: carbon black (CB), nickel powder (NP), graphite powder (GP), and steel slag powder (SP). The conductive powders were incorporated by weight ratios of 5% and 10% of quartz powder (QP) which is used as a mechanical filler of UHPFRC. The results showed a decrease in tensile strength with an increase in the incorporated amount of CB, NP, and GP and an increase in tensile strength according to the increase in the incorporated amount of SP from 5% to 10%. The results of microstructure analysis by EDS mapping showed that, when incorporating 5% of CB and GP, which have a lower density than QP, conductive powders were sufficiently distributed, enabling both direct contact between conductive powders and the tunneling effect. In the case of NP and SP, which have a higher density than QP, at least 10% of NP and SP must be incorporated to achieve self-sensing performance. The tensile stress/strain versus time responses of UHPFRC with conductive powders were simulated using the measured FCRs. The pre-peak tensile behaviors were also well simulated using empirical equations based on the obtained FCR by nonlinear regression analysis. The predicted pre-peak tensile behaviors had smaller errors compared to the experimentally obtained tensile behaviors. In the case of the post-peak, only tensile stress was well simulated. As a result, 10% of NP and 5% of GP had sufficient self-sensing performance for UHPFRC with conductive powders.