Investigation and evaluation on early-age crack resistance of ultra-high performance seawater sea-sand concrete with non-metallic fiber

Ultra-high performance seawater sea-sand concrete (UHP-SSC) exhibits outstanding mechanical properties, but the high cracking potential of UHP-SSC under restrained conditions should not be neglected. As steel fibers pose a corrosion risk when used in UHP-SSC, this study investigated and assessed the crack resistance of UHP-SSCs reinforced with non-metallic fibers. Cracking experiments were conducted employing a slab test, and the influencing mechanism was investigated based on macro-fiber pullout testing, pore structure determination, autogenous shrinkage (AS) monitoring, and uniaxial tensile testing. Results revealed that both the twisted texture of macro-fibers and micro-fiber incorporation into the matrix can enhance bonding. Adding fibers increased the macroporosity, except for the basalt fiber. The fiber's mechanical properties were positively related to the reduction in AS, and increase in tensile performance, crack resistance. Meanwhile, with a partial replacement of macro-fibers with micro-fibers, multi-scale hybrid non-metallic fibers exhibited better anti-cracking ability than UHP-SSC reinforced with straight steel fibers.