Transport Properties and Resistance Improvement of Ultra-High Performance Concrete (UHPC) after Exposure to Elevated Temperatures

Ultra-high performance concrete (UHPC) has a high self-healing capacity and is prone to bursting after exposure temperatures due its characteristics. This work evaluates the damage improvement of UHPC with coarse aggregates through mechanical properties (compressive strength ultrasonic pulse velocity), transport (water absorption chloride diffusion test), micro-properties such as X-ray diffraction (XRD), Mercury intrusion porosimetry (MIP), Scanning electronic microscopy (SEM). The result demonstrates that polypropylene (PP) fibers are more suitable for temperature tests than polyacrylonitrile (PAN) fibers. shows 400 °C critical point. With increase in temperature, hydration becomes significant, internal material phase changes accordingly. Although total pore volume increased, percentage various types pores was optimized within °C. mass loss gradually increased velocity decreased. While compressive first then decreased, occurred 25–400 As properties, migration coefficient capillary both dramatically higher sensitivity changes. results property test showed at above 800 °C, recovered by 65% 75%. In terms compared before self-healing, decreased up 59%, 89% coefficient, respect enhancement effect temperatures, environment 5% Na2SO4 solution not good clean water environment. corresponding microstructure during process can explain change pattern macroscopic precisely.