Optimization of Self-Sensible Louisiana-Sourced Ultra-High Performance Concrete: Balancing Mechanical Strength, Piezoresistivity, and Cost with Hybrid Fiber Reinforcement

AbstractUltra-high performance concrete (UHPC) is a unique cementitious composite that shows great potential for transportation infrastructure applications, such as bridges. Steel fibers are often used in UHPC to significantly improve its tensile performance. While steel fibers improve the mechanical properties of UHPC, the self-sensing behavior is not obvious. Therefore, in this study, the use of cost-effective carbon fibers was explored to design the hybrid fibers UHPC to enable selfsensing behavior, facilitating earlier damage detection. Locally sourced raw materials were used in the design of UHPC. The UHPC incorporating various percentages of straight steel fibers, along with 0.1% and 0.5% carbon fibers was prepared. Furthermore, compressive and flexural strength tests were carried out in order to assess the mechanical properties. The changes in electrical resistivity under compression loading were measured to determine the self-sensing ability of hybrid fiber UHPC. Results showed that the compressive strength of samples with 2% and 2.5% steel fibers exceeded the Federal Highway Administration's UHPC criteria of 17.5 ksi. In addition, the samples with incorporated carbon fibers generally indicated better mechanical properties than those samples that contained only steel fibers. However, as the carbon fiber content increased, self-sensing performance improved. Among all the samples, the UHPC mixture with 2.5% steel fibers and 0.5% carbon fibers demonstrated the best piezoresistivity while retaining satisfactory mechanical properties. The results of this study show the potential for future implementation of self-sensible UHPC for transportation infrastructure.