Tensile performance of pre-cracked UHPC under the coupled actions of sustained loading and corrosive media

This study investigated the tensile performance of pre-cracked ultra-high performance concrete (UHPC) subjected to sustained loading and various environmental conditions, including air, water, and 3 % NaCl solution. The findings indicated that prolonged tensile loading significantly reduced the tensile properties of UHPC, particularly at higher stress levels. Interestingly, the presence of water and NaCl solution facilitated recovery and, in some instances, even enhanced the mechanical properties of the cracked UHPC specimens beyond their original values. Microstructural analyses using SEM and EDS revealed that hydration products, predominantly C-S-H gel and CaCO₃, improved the bonding between steel fibers and the UHPC matrix. These products effectively filled the cracks and refined the overall microstructure. The results underscored the significant influence of stress levels and environmental exposure on the performance of UHPC in service, highlighting the necessity of considering these factors in the design and application of UHPC to ensure long-term structural integrity and durability.