Influence of carbon nano fibers (CNF) on the performance of high strength concrete exposed to elevated temperatures

Abstract

Carbon nano fibers (CNFs) were added into high strength concrete (HSC) to evaluate the fire endurance of incumbent matrix. The residual mechanical performance was evaluated by conducting material property tests namely compressive strength, tensile strength, stress-strain response, elastic modulus, compressive toughness and mass loss made with 0.1% CNF and 0.2% CNF as cement replacement in the temperature range of 23 °C to 800 °C. The internal structure damage on exposure to fire was analyzed by ultrasonic pulse velocity (UPV) in macro-phase while scanning electron microscopy (SEM) is used for micro and nano forensics. Being exceptionally conductive and resilient, these fibers reduce spalling potential via low thermal inertia and crack bridging action as established in forensic analysis. The test results revealed better retention in mechanical and physical properties of high strength concrete containing CNFs. Mathematical relationships based on statistical analysis have been proposed for predicting mechanical, durability and energy related properties of HSC modified with varying percentages of CNFs at elevated temperatures.