Effects of basalt fiber reinforced polymer minibars on the flexural behavior of pre-cracked UHPC after chloride induced corrosion

Ultra-high performance concrete (UHPC) exhibits high shrinkage, which results in a severe risk of cracking in practice, leading to the risk of long-term mechanical performance degradation caused by steel fiber corrosion in harsh environment. This study aims to use basalt fiber reinforced polymer (BFRP) minibars to improve the long-term flexural behavior of UHPC. UHPC reinforced with 3 % BFRP minibars and 3 % steel fibers were pretreated for initial crack and cured in chloride solution for various dry-wet cycles, respectively. The long-term tensile behavior of BFRP minibar and steel fiber, and long-term flexural behavior of UHPC with BFRP minibars and steel fibers were systematically tested and evaluated before and after corrosion, respectively. Ac-cording to the test results, compared to steel fiber, BFRP minibar showed a much better chloride resistance, leading to a great improvement in long-term flexural behavior of UHPC after chloride induced corrosion. When the initial crack width was less than 0.1 mm, two kinds of UHPC showed the ideal residual flexural behavior rate after a 150-cycle corrosion, which exceeded 95 %, owing to the self-healing of initial crack caused by the further hydration of unreacted binders in UHPC matrix. When the initial crack width was near 0.2 mm and 0.3 mm, after a 150-cycle corrosion, the flexural strength of UHPC with BFRP minibars was decreased by 10.94 % and 12.99 %, the decrease rate was 59.72 % and 52.24 % lower than UHPC with steel fibers in same environment, respectively. The similar changes in toughness and stiffness were found too. It indicated that using BFRP minibars to reinforce UHPC effectively alleviated the risk of decrease in mechanical properties of pre-cracked UHPC caused by steel fiber corrosion under harsh environment.