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).