Enhancing self-stress sensing ability of smart ultra-high performance concretes under compression by using nano functional fillers

Smart ultra-high performance concretes (S–UHPCs) with high self-stress sensing abilities have great application potential for monitoring the loss of prestressing stress in steel tendons to predict structural failure. This study aimed to enhance the self-stress sensing ability of compressed S–UHPCs by employing different types of electrically conductive functional fillers, including fiber type (short smooth steel fibers), particle type (fine steel slag aggregates, FSSAs; nickel aggregates, NAs; and copper aggregates, CPAs), and nano type (multiwall carbon nanotubes, MWCNTs). The S–UHPCs containing CPAs exhibited the highest electrical conductivity due to the high electrical conductivity of the CPAs. However, the S–UHPCs containing a combination of steel fibers, FSSAs, and MWCNTs produced the highest fractional change in electrical resistivity (56.8%) and stress sensitivity coefficient (0.41%/MPa).