The temperature of the air inside the furnace was measured by an in-built thermocouple of the furnace. The temperature at the centre of the cylinder was measured by a K-type thermocouple inserted in the specimens during casting. The thermocouples were connected to electronic data loggers that recorded the measured
temperatures. The cylinders were subjected to the peak tempera-
800
600
400
200
0
0 50 100 150 200
Time (minutes)
Furnace air
OPC
GPN
GPH
Standard fire
tures of 400, 650, 800 and 1000 oC. Once the desired peak temperature of the furnace air was achieved, it was maintained in order to raise the temperature inside the cylinder. As expected, the temperature rise at the centre of the cylinder was slower than that of the furnace air. The cylinders were heated for duration of
150 min. The temperature at the centre of the cylinders reached
Fig. 5. Temperature–time graph in concrete samples exposed to fire at 1000 oC.
70
60
50
3. Test results and discussion