Abstract:
Graphite nano/micro platelets (GNMPs) are one of the most promising nano materials because of their pozzolanic reactivity besides the micro-pore filling effect. It is imperative to characterize their behavior under different service conditions. Fire plays vital role in varying condition of concrete structures and properties of concrete change promptly when exposed to higher temperature. Hence, the necessity to characterize properties of GNMPs at elevated temperature becomes important. An experimental program was designed to investigate the properties of high strength concrete (HSC) modified with different percentages of graphite nano/micro platelets (GNMPs) after exposure to elevated temperature. Diversion, restriction and blocking of cracks at nano and micro level, strong bonding with matrix, high surface area and unique carbon-carbon hexagonal plane structure make GNMPs to have excellent mechanical, electrical and thermal properties. Mechanical properties such as compressive strength, tensile strength, stress-strain response, elastic modulus and mass loss of concrete mixtures modified with different percentages of GNMPs have been studied at elevated temperature in 23-800°C range and discussed in detail. Heating rate of 5°C per minute was selected for the cylindrical specimens to reach target temperatures up to 800°C. Scanning electron microscopy (SEM) was used for the study of morphological changes such as crack formation, microstructural damage and the dispersions of GNMPs. Durability properties have been assessed using non-destructive testing technique such as ultrasonic pulse velocity (UPV). Two different types of cooling techniques were used to cool down the heated samples to ambient temperatures. Results showed better retention of mechanical and physical properties of high strength concrete containing GNMPs. Data obtained was utilized to formulate mathematical relationships for expressing mechanical and durability related properties of HSC modified with different percentages of GNMPs as a function of temperature.
