STRENGTH LOSS CHARACTERISTICS OF FLY ASH BASED GEOPOLYMER CONCRETE SUBJECT TO HIGHER TEMPERATURES

Fly ash based geopolymer concrete, one of the environment friendly alternatives to conventional concrete, is expected to behave better at elevated temperatures. However limited information is available about its behaviour at elevated temperatures. This paper presents the engineering properties of fly ash based geopolymer concrete after exposure to elevated temperatures and compares the corresponding results with those of a conventional concrete having almost the same compressive strength of geopolymer concrete (at ambient temperature). The specimens were heated at a constant rate (5.5 °C /minute) to different set temperatures (200,400, 600 and 800 °C). They were cooled to ambient temperature by air cooling and water cooling and then tested for their strength properties. It could be observed that,the fly ash based geopolymer concrete undergoes a higher rate of strength loss during its early heating period (up to 200 ^°C) compared to OPC concrete. However, the residual strength properties of both the concrete are almost the same at 400 ^°C temperature exposure and beyond 600 ^°C, while OPC concrete loses its strength properties rapidly; geopolymer concrete improves its strength. Hence, it could be concluded that the fly ash based geopolymer concrete could be considered as a better sustainable material than conventional concrete under the situations where it may be exposed to temperatures beyond 400 °C.